How fast can you stop. Have you tried?

[rocketman1]

Many of us can tell many stories of how fast we can accelerate, and how fast the bike can go but, I feel that we should as much be concentrating on how fast we can stop.
The best riders ( and racers) amongst us I suspect can stop a fast moving bike alot quicker and safer than those that have never really had to stop in an emergency.

I was riding by myself on a road without traffic a few months ago, and decided to stop fast from 120km hr, I did it several times and got better at it after about the 4th go, any stranger watching would have wondered!!!, but what I gained was some idea of stopping distances, I only locked the rear once, I do not how I would react in a real emergency, would I have the sense to be able to stop calmly without locking up everything up and losing it?
I suspect not. I have reminded myself to practice again next time Im out.
The more you practice the better you must become
Any others out there that have tried out this tyre wearing past-time

[skidMark]

Yeah i have done a fair bit of practise with this, i could haul the zxr250 to a stop from 60kph in 2 metres.

that was hard hauling em though, and front starts to skitter, but still controllable, beats being a hood ornament.

[Katman]

Yeah i have done a fair bit of practise with this, i could haul the zxr250 to a stop from 60kph in 2 metres.



It's a pity to see you back to your old bullshit stories Mark.

[skidMark]

It's a pity to see you back to your old bullshit stories Mark.


I never lie i was raised better than that.

it just comes down to practise and clocking up 60,000 k's on zxr's.

[Jantar]

I never lie i was raised better than that.

it just comes down to practise and clocking up 60,000 k's on zxr's.

And to having that amazing ability to defy the laws of physics. ;)

[cave weta]

I find that on narrow single trails I can lose speed quickly by riding about a metre either side of the usual line.

however even at 30kph pine trees really hurt:Oops:

[Virago]

...I could haul the zxr250 to a stop from 60kph in 2 metres...

Wow, those sort of G-forces would cause a fighter pilot to black out...

[jrandom]

Yeah i have done a fair bit of practise with this, i could haul the zxr250 to a stop from 60kph in 2 metres.

Mark, there are no motorcycle tyres on the market that can maintain grip under the G-forces that such deceleration would create. You may think that you measured your stop over two metres, but you simply cocked it up. It would've been further than that.

[Ixion]

Mark, my mechanics is rusty, but 2 mtrs from 60kph would require over 6g deceleration. T'ain't physically possible dude. Not without a rack and pinion down the road.

[Brooke]

I have just started practicing emergency breaking (still a learner all together so trying to pace myself). I have been gradually increasing my speed.

Reminds me, I must get out and do it again.

[swbarnett]

Fast enough to have a friend (now wife) on her less than 24hr old brand new CB250 run in to the back of me.

Make sure you know what's behind you before you try this.

[slofox]

My general answer would be "quicker than I usually expect" - based on real life experiences of having to stop suddenly. I haven't measured anything, but when the chips are down, I usually overestimate how much braking distance I need....last "twang" moment rounding a corner to find all the traffic stopped, I had more room left than I thought...

[skidMark]

you lot can say what you want they had cones layed out at wednesday night ride and i did it on morcs rvf400 as well...

Its called skill...

Something no other kb member has.

[1vanvan1]

Yeah i have done a fair bit of practise with this, i could haul the zxr250 to a stop from 60kph in 2 metres.

that was hard hauling em though, and front starts to skitter, but still controllable, beats being a hood ornament.

Hard to believe

[FlyingDutchMan]

I dunno exactly how fast I can stop, but I'm scared shitless of any cage behind that can't stop fast enough - I've heard squealing tyres a few times. On my worst day in traffic I pulled of 3 stoppies in 20 mins because of people pulling out in front of me.

Stoppie practice can be hazardous, but you know exactly just how hard to pull the brakes when need be.

[CB ARGH]

I gave this a go when I first got the bike. I was very suprised at how quickly it stopped from 60km/h. I have yet to try it at 60km/h in the rain though, now that would be interesting.

[McDuck]

you lot can say what you want they had cones layed out at wednesday night ride and i did it on morcs rvf400 as well...

Its called skill...

Something no other kb member has.

Are you sure they were not 2-3m apart? I could belive 5-6m fomr a real top rider......

[Jantar]

Are you sure they were not 2-3m apart? I could belive 5-6m fomr a real top rider......

Not even that. Do the math and at 1 G (the current limit of tyre design) it would take 14.5 m. At a more resonable 0.9 G it works out at 18 m. 2 m is 9 G, so at that he would black out as the human body can only take 5 G of horizontal acceleration.

[Rodney007]

Yeah i have done a fair bit of practise with this, i could haul the zxr250 to a stop from 60kph in 2 metres.

that was hard hauling em though, and front starts to skitter, but still controllable, beats being a hood ornament.

2 meters?, muhahahahah HAHAHAHAHAHAH

HEEHAHAHAHAHHEHEHE AHAHAHEHEHE (breathe) hehehahahahehehehahaheheah MUAHAHAHEEAEA

[McDuck]

Not even that. Do the math and at 1 G (the current limit of tyre design) it would take 14.5 m. At a more resonable 0.9 G it works out at 18 m. 2 m is 9 G, so at that he would black out as the human body can only take 5 G of horizontal acceleration.

you would appear to be better at maths than me...

[Rodney007]

now i understand what you guys mean about mark..

[McJim]

now i understand what you guys mean about mark..

Not only that - the poor fella quotes people out of context and makes himself look like a right idiot.

He also crashes barbeques uninvited......:mad:

[BMWST?]

any way get out there and practise...pull on the brakes relatively gently at first increasing pressure as the speed drops.Be ready to release the brake if the wheel locks up(esp the front),but reapply immediately.Be sure its safe,some kind of carpark or something or quiet country road

[racefactory]

you lot can say what you want they had cones layed out at wednesday night ride and i did it on morcs rvf400 as well...

Its called skill...

Something no other kb member has.

Now i see what the hype about this chap is.

Tell you this, the only thing you're stopping from 60kph that quick around here is a fist through yer fuckin' gob mate. Who are you kidding?

Back to topic: Very good thread! Absolutely, stopping is where a lot of fun is to be had to. On my NC30 i went out practicing and learnt to get it to maximum braking force in the rain by learning at what point the front wheel locks up rather than trying to regulate rear brake to save a 1/100 of braking distance.

After that the dry is not a problem and you can feel the impending lock up qutie easilly.

No need to even touch the rear as all the weight is on the front. I reckon it feels best to concentrate all effort into feeling the impending front wheel lock up.

Though i can't seem to brake as quickly as in my car in the rain before i lock the front. Probably doesnt help with warped discs though.

However I learnt there is still a shitload of braking force in the rain... On my Bt090 tyres, I had the rear wheel lifting off of the ground in the rain before coming to a dead stop- quite a lot of grip. I found as long as you don't slam the brakes on immediately and you make sure to load the front for a split second.

A good practice!!

[98tls]

any way get out there and practise...pull on the brakes relatively gently at first increasing pressure as the speed drops.Be ready to release the brake if the wheel locks up(esp the front),but reapply immediately.Be sure its safe,some kind of carpark or something or quiet country road
Good advice,sadly when confronted with an emergency stop many A freeze and do nothing B jump on everything

[gatch]

whaaaaaaat, you guys cant stop in 2m ?

shitt its a piece of cake, did you see me on mission inmpossible ? did an endo, spun around while pulling my pistol out, shot some mother fuckers, kept spinning whilst holstering my 9, and continued on to the pub for a quadruple absynthe.

get some skills :calm:

[Speedracer]

V=at +Vinitial
d=integral of v.t
d=at^2/2 +Vinitial*t
Vinital = Vkmh /3.6
t = Vinitial / G where G = 9.8m/s/s for '1G'
a = -G

Thus
d=-G(Vinitial/G)^2/2 + Vinitial*Vinitial/G
simplified:
d=-G(V^2/G^2)/2 + V^2/G
d=-V^2/2G + V^2/G
d=V^2/2G

finalise for real numbers
d=(Vkmh/3.6)^2 /(2*9.8G)
d=Vkmh^2/12.96 / (19.6 G)
d=Vkmh^2/254G where G=1 is now 1G

60kmh^2 / (254 *1G) = 14.2m
60kmh@0.9G=14.2 / 0.9G = 15.8m
.....
Assumes no reaction time, no progressive braking blah blah blah which would increase the distance.

[racefactory]

Not even that. Do the math and at 1 G (the current limit of tyre design) it would take 14.5 m. At a more resonable 0.9 G it works out at 18 m. 2 m is 9 G, so at that he would black out as the human body can only take 5 G of horizontal acceleration.

Hey that's interesting... but are you sure you don't mean that 'friction coefficient' of 1?

Reason I say that is because any light bike with good tyres can pull 1g of force in cornering on the skid pad test. I suspect braking would yield far more force right?

F1 car can pull just over 5g in braking force. From watchin both motogp and f1 i'm guessing a motogp bike can surely pull about 2.5g on the brakes?

interesting.

[Jantar]

V=at +Vinitial
d=integral of v.t
d=at^2/2 +Vinitial*t
Vinital = Vkmh /3.6
t = Vinitial / G where G = 9.8m/s/s for '1G'
a = -G

Thus
d=-G(Vinitial/G)^2/2 + Vinitial*Vinitial/G
simplified:
d=-G(V^2/G^2)/2 + V^2/G
d=-V^2/2G + V^2/G
d=V^2/2G

finalise for real numbers
d=(Vkmh/3.6)^2 /(2*9.8G)
d=Vkmh^2/12.96 / (19.6 G)
d=Vkmh^2/254G where G=1 is now 1G

60kmh^2 / (254 *1G) = 14.2m
60kmh@0.9G=14.2 / 0.9G = 15.8m
.....
Assumes no reaction time, no progressive braking blah blah blah which would increase the distance.

Simpler is V^2 = 2*a*d

[Rodney007]

so basicaly skid mark can out brake a f1 car and motogp bike?

[racefactory]

V=at +Vinitial
d=integral of v.t
d=at^2/2 +Vinitial*t
Vinital = Vkmh /3.6
t = Vinitial / G where G = 9.8m/s/s for '1G'
a = -G

Thus
d=-G(Vinitial/G)^2/2 + Vinitial*Vinitial/G
simplified:
d=-G(V^2/G^2)/2 + V^2/G
d=-V^2/2G + V^2/G
d=V^2/2G

finalise for real numbers
d=(Vkmh/3.6)^2 /(2*9.8G)
d=Vkmh^2/12.96 / (19.6 G)
d=Vkmh^2/254G where G=1 is now 1G

60kmh^2 / (254 *1G) = 14.2m
60kmh@0.9G=14.2 / 0.9G = 15.8m
.....
Assumes no reaction time, no progressive braking blah blah blah which would increase the distance.

That's cool. Where does weight come in here though? Surely weight has a big effect.

[racefactory]

so basicaly skid mark can out brake a f1 car and motogp bike?

Yeah, it looks like skidmark with his ZXR and dunlop GPR100's can out brake michael schumacher in the Shell Ferrari. the Fiat yamaha of course doesn't even make the equation here...

[Rodney007]

yeah well hes pretty talented young boy..
he was damn serious about it too..

[FzerozeroT]

Rocketman, this will be relevant to your interests.

My fastest logged lap at Puke on my SV1000S (1:07.934)

285.6 Metres from 233kph to 44kph with a maximum decelleration of -1.03 Gs coming into the hairpin. Thats the point where forks are fully compressed and it's a choice between washout and stoppie, SV has a high centre of gravity

A 600 getting a 1 minute lap can get 1.3 Gs into the hairpin (pilot climbing back onto the pillion seat)

SV wheelies at 0.83 Gs, an R1 manages 0.95 before it lifts. Both of these are in 'regular' position, climbing on the tank improves the figure

[Jantar]

Hey that's interesting... but are you sure you don't mean that 'friction coefficient' of 1?

Reason I say that is because any light bike with good tyres can pull 1g of force in cornering on the skid pad test. I suspect braking would yield far more force right?

F1 car can pull just over 5g in braking force. From watchin both motogp and f1 i'm guessing a motogp bike can surely pull about 2.5g on the brakes?

interesting.

No, I mean G force where 1 G = 9.81 m/s/s. Coefficient of friction is a factor that varies according to the tyre compound and the road surface. It is most obvious when, as you say, you are cornering. That is because the forces are all balanced and working through the Center of Gravity and the contact point of the tyres. Under braking the forces are unbalanced, and instead of working through the contact point the forward vector is some distance away and above. (This is why it is possible for bikes to perform stoppies.)

F1 cars can decellerate at almost 5 G, but then look at the contact area compared with a bike and also consider that their lower CoG puts the forward vector much closer to the multiple contact points.


That's cool. Where does weight come in here though? Surely weight has a big effect.

Weight does have an effect on the maximum force that will be exerted on the tyres, but has no effect on the calculations of stopping distance vs G force. A 1 G stop from 60 kmh will take the same distance for 100 kg as for 1000 kg. Galileo proved this concept some 520 years ago.

[Jantar]

Rocketman, this will be relevant to your interests.

My fastest logged lap at Puke on my SV1000S (1:07.934)

285.6 Metres from 233kph to 44kph with a maximum decelleration of -1.03 Gs coming into the hairpin. Thats the point where forks are fully compressed and it's a choice between washout and stoppie, SV has a high centre of gravity

A 600 getting a 1 minute lap can get 1.3 Gs into the hairpin (pilot climbing back onto the pillion seat)

SV wheelies at 0.83 Gs, an R1 manages 0.95 before it lifts. Both of these are in 'regular' position, climbing on the tank improves the figure

Thanks for that data Fzerozero. That confirms what we have been saying. You figures of 233 down to 44 in 285.6 m works out to an average decelleration of -0.73 G. There will be peaks and troughs and your maximum of -1.03G is around what I would expect, but the average is lower than I would expect.

It just goest to show that average decelleration of -9 G just isn't possible.

[GaZBur]

....I suspect not. I have reminded myself to practice again next time Im out.
The more you practice the better you must become
Any others out there that have tried out this tyre wearing past-time

Yes I have but to be honest didn't measure distances. Good topic question, more passing is done in racing under brakes than cornering but more bragging is done about corner speed. When you practice think of other things than just distance. Type of surface and temp and condition. You will be amazed at the difference in braking ability of a warm tyre compared to a cold one, different compounds and tread etc etc. Do you use back or just front.(that old arguement again) When practicing be careful and ease into it - I have found locking up the front can result in a very fast dumping and trip for x-rays.
I don't know the "officialy sanctioned technique" is but I like this technique, slam on both brakes reasonably hard then immediately ease the back and harden the front until the front just starts skuffing. This use of the back brake seems to drop the centre of gravity, reduce the weight transferance loading on the front and reduces the tendancy for the back end to try overtake the front while increasing the bite on the front tyre. Thats what I find best from seat of the pants but willing to try other styles if some else got good advice.
Stoppies are showy but not good for slowing you down, and I am crap at them so will dis them anyway.
I also have stopped from 60kph in under 2 metres. Made a fecking mess of the car I stopped against though.

[WuZards-Eugene]

It is a proven fact that one can stop in a miraculous 2 meters, from 60 kmh. I for one have the ability to come to a complete stop from 100 kmh in 2 meters, which I am pretty sure many others have successfully done.

Mark should get this on video, as I have not seen much footage of bike and rider, vs solid concrete wall, and I do not have the balls/stupidity to practice that particular feat. Sort of being like a suicide bomber instructor. "Ok everyone, Im only going to show you this once"

[racefactory]

Thanks for that data Fzerozero. That confirms what we have been saying. You figures of 233 down to 44 in 285.6 m works out to an average decelleration of -0.73 G. There will be peaks and troughs and your maximum of -1.03G is around what I would expect, but the average is lower than I would expect.

It just goest to show that average decelleration of -9 G just isn't possible.

interesting data Fzerozero. Thanks.

Assuming the surface stays the same.... Is the only reason that the maximum force figure of 1.03 can't be held constant for the braking because at high speeds even though you may be using all of your front tyre force, the air resistance is slowing you down on top of that?

Is the average lower than expected partially because at the end he may have been turning and braking at the same time into the bend? Fzerozero- that 44kph is including turn in whilst still on brakes right?

If so we can probably say that 0.8 is a good figure for working out rough braking distances for road machines eh?

In this case using 254@1g= 203.2@0.8g

100kmh^2 /203.2 = 49.26m ----motorway stopping distance.

55kmh^2 /203.2= 14.8m -----suburbian speeds.

Wet grip assuming 75% of dry grip (what most people seem to agree on)

100kmh^2 /152.4 = 65.6m ----motorway stopping distance.

55kmh^2 /152.4 =19.8m -----suburbian speeds.

Seems about right eh? Maybe the suburbian speeds would have slightly poorer figures because of no help from air resistance?

[Jantar]

Fucking interesting data Fzerozero. Thanks.

Assuming the surface stays the same.... Is the only reason that the maximum force figure of 1.03 can't be held constant for the braking because at high speeds even though you may be using all of your front tyre force, the air resistance is slowing you down on top of that?

Its more likely that the maximum figure is achieved late in the braking rather than early. As the weight transfers forward and the tyres load up the braking effect will be maximised. If the rear wheel starts to lose contact (start of a stoppie) then it will fall off again.

You are right about air resistance, that aids in decelleration, and is more effective at higher speeds.

[McDuck]

so basicaly skid mark can out brake a f1 car and motogp bike?

Well he is never really moving is he?

[SARGE]

Mark, my mechanics is rusty, but 2 mtrs from 60kph would require over 6g deceleration. T'ain't physically possible dude. Not without a rack and pinion down the road.

or a tailhook...





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[SARGE]

Not only that - the poor fella quotes people out of context and makes himself look like a right idiot.

He also crashes barbeques uninvited......:mad:

bwhahahaha..

lonely boy

[FzerozeroT]

The horizontal scale on that is distance so if you try to translate that into forces per second on the bike it is (parabolic/hyperbolic/logarithmic?), I'll post it vs time when I get home, the first patch is loading the front wheel, at 200+ you do cover a bit of ground before getting max braking, then once you do hit max decelleration you start to judge how far short of the corner you are going to stop and ease it off again to make sure that you keep decent speed up to the corner, the margin for error on any given corner for perfect speed is the width of the track, how fast do cover 8 metres? I probably have some laps where I got better braking there but the rest of the lap didn't stack up to be faster.

[Badjelly]

F1 car can pull just over 5g in braking force. From watchin both motogp and f1 i'm guessing a motogp bike can surely pull about 2.5g on the brakes?

F1 cars have wings that generate downforce. That's why they can achieve lateral accelerations much larger than 1 g and that's why an F1 car is 20 s a lap faster round a track than a MotoGP bike.

Without wings you're limited to something in the vicinity of 1 g. But I'm not sure what "in the vicinity of" means exactly; there are some interesting numbers on other posts on this thread. A MotoGP bike pulling 2.5 g? No. I might believe 1.3 g.

When doing calculations, a conversion factor I find useful is 1 g = 9.8 m/s/s = 35 km/h/s. So from 0 to 100 km/h (or vice versa) at 1 g would take 100/35 = 2.9 s. Assuming constant acceleration during that 2.9 s, your average speed is 50 km/h = 13.9 m/s so you would travel 40 m. Some modern cars can brake from 100 km/h in 35 m, so that's a bit more than 1 g.

Last year watching the Taupo A1GP on TV, they showed the instrument readout on a car braking at the end of the main straight. By my reckoning that car dropped from 270 km/h to 70 km/h in 2 s. So that's 100 km/h/s, or 2.9 g. Changing your speed by 100 km/h in a second--bloody hell!

[vifferman]

How fast can you stop? Have you tried?
Dunno. Yes.
Last year, I was momentarily distracted and when the traffic in front of me stopped, I stopped about 75mm too late. Scratched/cracked the front mudguard, and bent under the rear plastic bumper on the Peugeot in front, but it popped out, so no 'real' damage. Could've been worse.
Really shook me up, so I started practicing emergency stopping, which was nearly as scary as the incident that provoked it, as it's quite violent (though admittedly not as violent as a crash).

I have just started practicing emergency breaking
Reminds me, I must get out and do it again.
It's not a good - bike parts are expensive. Best you practice emergency braking so you don't break anything in an emergency.

[mowgli]

I don't think it's sensible discussing emergency braking without also discussing safe following. Safe following involves leaving space in front, scanning well ahead for hazards and most importantly being constantly aware of your best escape route.

Rule #1: Be prepared. As soon as you detect any hint of a hazard, throttle off a little and cover the front brake.

Rule #2: Slow down early. Slowing early will increase the space between you and the vehicle in front. Space translates to time to react for both you and the drivers behind you.

Rule #3: Emergency braking. Keep your eyes up and look through your escape route - your bike will follow your eyes even under brakes. Don't stare at the hazard.

Rule #4: Escape. In the event that braking wont be enough then escape. If you were looking to your escape while braking then chances are you're already headed this way. Don't forget to release the brakes before manoeuvring.

Rule #5: Get the hell out of the way! Bikes are invisible. Once you've got your speed under control get to the side of your lane. Don't become a hood ornament simply because the driver behind wasn't concentrating.

Rule #6: Stay focussed. While following in traffic regularly ask yourself 'what if' questions. Which way would you go? How close is that vehicle behind?

[Jantar]

So, I think we have successfully demolished Skiddies myth about stopping in 2 m from 60 kmh. Whether we can manage 1 G or only 0.7 G in an emergency stop is a matter of type of tyres, braking ability of the bike and road surface and will vary dramatically. The main point of th OP as I see it is "are we aware of just how much room we need to stop?"

Obviously some of us are and some aren't. That is to be expected.

Yesterday I went for a wee pootle around the block (Home - Ranfurly - Outram - Waipori Falls - Lawrence - Home), and while cruising the lovely sweeping twisties on the Hyde hill I got to thinking about where emergency braking is most likely to be needed. I figured that if we are looking 9 to 12 seconds ahead for hazards that emergency braking is most likely needed in those places where we can't see 9 - 12 seconds ahead. Many of those bends marked at 75 kmh that I was cruising through at 100 kmh, I could only see 5 - 6 seconds ahead. So I asked myself "can I react and stop in 5 seconds from 100 kmh while cranked over in a left hand bend?" Including the reaction time (I allowed one second) I could do it on the straight, but when cranked over I couldn't. Through a 75 kmh left hand bend from 100 kmh to 0 took me 6 full seconds while staying on my side of the road. That's 0.56 G. If I straightened up then I could stop in the 5 seconds I allowed, but that put me on the wrong side of the road.

So how many have tried emergency braking while heeled over in a bend?

[The Stranger]

So, I think we have successfully demolished Skiddies myth about stopping in 2 m from 60 kmh.

Don't be so sure. Skidmark exists in a very different reality to the rest of us.

[nodrog]

.... i could haul the zxr250 to a stop from 60kph in 2 metres.

so the speedo was fucked on that bike? explains your other bullshit story about 140kph around 45kph corners.:scooter::rockon:

[NordieBoy]

Not only that - the poor fella quotes people out of context and makes himself look like a right idiot.

He also crashes barbeques uninvited......:mad:

At what speed does he crash said bbq's?

Video footage?

[slowpoke]

I did a track day with Brian Bernard organised by the Wanganui Ulysses club and I was struck by two things.

1. For a mostly older group that spent a lot of time covering a lot of miles I was dumb founded at the lack of knowledge some riders had regarding the use of front and/or rear brake for emergency braking. These men/women ride a lot of miles, so how much worse is the average rider?

2. ABS and linked braking systems are the schizz! The BMW's and Pan Europeans etc shat all over everything when it came to stopping in a hurry. Unless you are Andrew Stroud good, forget thinking you will be able to brake better using your own judgement....believe it. If you aren't going to go on the track, and get the opportunity, go with ABS you can't beat it.

[jrandom]

For a mostly older group that spent a lot of time covering a lot of miles I was dumb founded at the lack of knowledge some riders had regarding the use of front and/or rear brake for emergency braking. These men/women ride a lot of miles, so how much worse is the average rider?

Those men and women probably are the 'average rider'.

Doing the same easy stuff over and over again teaches you nothing.

Many riders never explore their bike's handling capabilities or expand their understanding of its control beyond what's required to ride around the block or up and down the motorway.


If you aren't going to go on the track...

With the prevalence of accessible and well-run trackdays now, nobody has any good excuse for not training on the track.

:niceone:

[GaZBur]

....1. For a mostly older group that spent a lot of time covering a lot of miles I was dumb founded at the lack of knowledge some riders had regarding the use of front and/or rear brake for emergency braking. These men/women ride a lot of miles, so how much worse is the average rider? ...
I helped out at the Brass Monkey sign in that was on a slight slope. There were riders with dozens of rally badges on thier jackets that were incapable of co-ordinating brake throttle and clutch for a simple slope start, dont expect them to not run up your arse if you brake hard in front of them. The experience put me off riding in groups of others of unknown abilities.

[DMNTD]

I successfully came to a full stop from 40kmph in 10cm a couple of weekends ago. However it wasn't the mighty power of my Brembo's or the 20+ years worth of riding that helped me...it was a truck.
So surely Skiddy can't be BS'n...surely! :oi-grr:

[vifferman]

I successfully came to a full stop from 40kmph in 10cm a couple of weekends ago.
Huh.. is THAT all?!?
When I was 17, I successfully brought my bike to a stop from 40mph (that's 70km/h) in the same distance.
However, I wasn't holding on tight enough and continued on, somersaulting elegantly on the dismount (9.5) but losing points (and skin) on the landing (-12.3).
I suspect I also lost points for non-approved gymnastic attire, in the form of jandalled feet.



What does this prove? :confused:
You can't make a fool of Professor Fizzicks. Conservation of momentum (http://en.wikipedia.org/wiki/Momentum), and like that there....

[DMNTD]

I suspect I also lost points for non-approved gymnastic attire, in the form of jandalled feet.

I hobble here in pure n00bness, sir!
You sir were jandelled!

[Spyke]

The calculations fly from most that haven't gone out and tried in the true world. 1 up to the guys analysing their real world data they got from actually going out there and doing it.

[Badjelly]

The calculations fly from most that haven't gone out and tried in the true world. 1 up to the guys analysing their real world data they got from actually going out there and doing it.
The most effective way to gain knowledge is to use a combination of both.

[Jantar]

I would agree with Badjelly. I am probably the one person on KB who uses maths more than anyone. But then I go and put it into practice.

Theory (and math) is great to work out what is possible. Putting it into practice is where it really counts.

The riders who make rediculous claims are the ones who don't bother even seeing if what they claim is possible with today's technology.

[Mully]

The riders who make rediculous claims are the ones who don't bother even seeing if what they claim is possible with today's technology.

Well, I'll have you know that my RF stops with enough force to change the rotation of the Earth, and make rips in the Space Time Continuum.

[Badjelly]

I would agree with Badjelly. I am probably the one person on KB who uses maths more than anyone. But then I go and put it into practice. Theory (and math) is great to work out what is possible. Putting it into practice is where it really counts.

Yes. Your emergency-braking-on-a-bend experiments are particularly commendable!

[rocketman1]

I will go with a buddy to lonely piece of road with a tape and mark white line across with a bit of pumice or something then at varying speeds mark where I finish up and see if I can better the distance. Why not

I see worn tyres coming up, but it hopefully will prove something, and give some appreciation of following distances.
I will let you know the distances.

[BMWST?]

I will go with a buddy to lonely piece of road with a tape and mark white line across with a bit of pumice or something then at varying speeds mark where I finish up and see if I can better the distance. Why not

I see worn tyres coming up, but it hopefully will prove something, and give some appreciation of following distances.
I will let you know the distances.
you dont have to make 50 tyre shredding stops....all you have to do is make a few stops gradually increasing the force that you use on the (mostly) front brake...dont put it on hard at first increase the pressure as ou slow down.I am betting that you will decrease your stopping distance by lots....its really good practise!

[racefactory]

[QUOTE=rocketman1;1904154]I will go with a buddy to lonely piece of road with a tape and mark white line across with a bit of pumice or something then at varying speeds mark where I finish up and see if I can better the distance. Why not

I see worn tyres coming up, but it hopefully will prove something, and give some appreciation of following distances.
I will let you know the distances.[/QUOTE

I'll give you some bench marks.

I was reading an article by some government safety people in some country that made some findings upon motorcycle emergency braking and braking performance.

They took a Honda GL1500 and a Honda CBR929 and made hundreds of braking attempts.

Basicallly, they did stops from 100kph. Amazingly the CBR929 and the GL were very similar and there was no real difference between the 2 in stopping distance.

They got 38m as an average for the good runs.

I then looked up some braking stats from 100kph and i found that cars like Honda Integra type R do 38m from 100. There was a porsche 911 GT3 cup car that could do 32m!! Cars with really big sporty tyres like the 911 turbo and GT2 did 35m. I'm not sure if bikes could touch those distances. Family cars with tyres under 200 in size did 40- 42m generally.

Try see what you can get against 38m and report back?

[fatzx10r]

i had a head on with a car once, at a low speed of corse.... and i stoped real quick. wouldnt want to repeat it again :Oops:

[Jantar]

.....They got 38m as an average for the good runs.

I then looked up some braking stats from 100kph and i found that cars like Honda Integra type R do 38m from 100. There was a porsche 911 GT3 cup car that could do 32m!! Cars with really big sporty tyres like the 911 turbo and GT2 did 35m. I'm not sure if bikes could touch those distances. Family cars with tyres under 200 in size did 40- 42m generally.


This equates with the best data I have seen. Proffessional riders on a perfect surface and 38 m is 1.03 G.

Most riders on a typical road surface 0.9 G would be a satisfactory target to aim for. That's 44 m as a good stopping target.

[hmmmnz]

stopping??? not very fast, drums front and rear arnt really there to stop you, just to pass the wof, i'd stop faster if i put my feet down :D

[Ixion]

Y' reckon? Fastest stopping I ever heard of was the Vincent. 20 foot from 30 mph. Double side front admittedly.

In fact drum brakes from lowish speeds stop faster (tyres being equal) than disks. Greater friction area, and there's not time enough for the heat bukild up to stuff them

[racefactory]

Y' reckon? Fastest stopping I ever heard of was the Vincent. 20 foot from 30 mph. Double side front admittedly.

In fact drum brakes from lowish speeds stop faster (tyres being equal) than disks. Greater friction area, and there's not time enough for the heat bukild up to stuff them

But it's not about brakes, it's about tyres and weight isn't it? Any properly maintained brakes can provide enough to skid the front wheel, so isn't it about how much of that force the tyre can take?

[Jantar]

...Any brake can provide enough force to lock the front wheel, so isn't it about how much of that force the tyre can take?

Oh boy! Have you got a lot to learn. If any brake can lock up the front wheel, then why do manufacturers go to the expense of multi caliper, floating disks, etc? An old single leading edge drum would do just fine.

[racefactory]

Oh boy! Have you got a lot to learn. If any brake can lock up the front wheel, then why do manufacturers go to the expense of multi caliper, floating disks, etc? An old single leading edge drum would do just fine.

To improve feel and control... doesnt determine outright stopping distance. :2thumbsup

[doc]

Oh boy! Have you got a lot to learn. If any brake can lock up the front wheel, then why do manufacturers go to the expense of multi caliper, floating disks, etc? An old single leading edge drum would do just fine.

You forgot about USD forks. Thats what gives SM his advantage. :bash:

[discotex]

To improve feel and control... doesnt determine outright stopping distance. :2thumbsup

I think you'll find "feel and control" makes a huge difference.

If you can't feel the front about to wash out you're going to crash or brake less hard.

[Dean]

im being taught emergency braking by a mate he makes me speed as fast as i could (which aint that fast considering ive got a gn250 lol).and then visualize a little girl or boy ran infront of the road im getting there i gotta practise practise.my mate once raced in the isle of man and he made me do another excercise where i have to get my tyre nearly touching his like an mm away from his out in waipu.hes crazy whenever i dont do it right or i bump into him we have to do it again. im only on ma dam learners !!!!

[Jantar]

im being taught emergency braking by a mate he makes me speed as fast as i could (which aint that fast considering ive got a gn250 lol).and then visualize a little girl or boy ran infront of the road im getting there i gotta practise practise.my mate once raced in the isle of man and he made me do another excercise where i have to get my tyre nearly touching his like an mm away from his out in waipu.hes crazy whenever i dont do it right or i bump into him we have to do it again. im only on ma dam learners !!!!
For christ sake young man. DO NOT LEARN ANYTHING FROM YOUR MATE. You are learning to ride, not to race. Never ride that close to another bike unless you are on the race track and slipstreaming. On the road keep your distance.

Even on the track riding close behind another rider can be a risky manouver. Just ask K14 what happened when another rider touched his rear wheel. I know I have put another rider down at Ruapuna when his front wheel touched my rear. That is just dangerous, far too dangerous to be something you'd practice on the road.

Get yourself a mentor asap.

[R6_kid]

Funny how skidmark has shut the fuck up now that the maths and physics came out and got involved - hard to talk shit against cold hard facts... and to think that he could clock up 60,000km on ZXR250's alone. He's only owned one or two and they spent most of their lives time in pieces.

[marty]

But it's not about brakes, it's about tyres and weight isn't it? Any properly maintained brakes can provide enough to skid the front wheel, so isn't it about how much of that force the tyre can take?

hmmm. you've never ridden a CX500 in the rain have you (or in the dry for that matter!)

[racefactory]

im being taught emergency braking by a mate he makes me speed as fast as i could (which aint that fast considering ive got a gn250 lol).and then visualize a little girl or boy ran infront of the road im getting there i gotta practise practise.my mate once raced in the isle of man and he made me do another excercise where i have to get my tyre nearly touching his like an mm away from his out in waipu.hes crazy whenever i dont do it right or i bump into him we have to do it again. im only on ma dam learners !!!!

Just watch out for when your front wheel skids eh mate... Those Gn's got shit tyres if they are stock man.

[StatX]

Not fast enough...

Managed to land my front wheel in the rear bumper of a toyota (or something small, bubbly and blue) a few days ago... Drum Brakes Front and Back + Speed + Split second of looking down = Cars stop and you have a sore groin for a week...Fun ++

I think my back breaks are glazed, the squeaking and the lack of resistance from them might indicate that...

[Ixion]

Oh boy! Have you got a lot to learn. If any brake can lock up the front wheel, then why do manufacturers go to the expense of multi caliper, floating disks, etc? An old single leading edge drum would do just fine.


Repeatability. Drum bakes were fine for stopping quickly, once, from moderate speeds. But they fell off fast as speeds went up, and faster still if you wanted to stop several times hard in a short time. Heat build up.

Not really that much of an issue on the road (I try to seldom use my front brake at all), but definately so on the racetrack. And modern bikes are totally based around race bikes. Ergo , "the expense of multi caliper, floating disks", largely unjestified as it is.

[Jantar]

Repeatability. Drum bakes were fine for stopping quickly, once, from moderate speeds. But they fell off fast as speeds went up, and faster still if you wanted to stop several times hard in a short time. Heat build up. .....

Exactly. From moderate speeds. However I have ridden many bikes that even with disk brakes wouldn't lock the front wheel until speeds were very low. Many dirt bikes were engineered so that that they wouldn't lock the front wheel at anything much more than walking pace (Jawa cocky anyone?).

[kiwi cowboy]

skidmark were are ya DEFEND YA SELF if ya can NOT lmfao

[rocketman1]

you dont have to make 50 tyre shredding stops....all you have to do is make a few stops gradually increasing the force that you use on the (mostly) front brake...dont put it on hard at first increase the pressure as ou slow down.I am betting that you will decrease your stopping distance by lots....its really good practise!

I didnt measure on my last ride, but what I did do was stop hard from 100kmph about six times, interesting, I checked no one was behind and slapped the brakes on hard the harder as I was slowing.
The bike held the line very well, a good amount of G-force on the handle bars
To my surprise the bike scrubbed alot of speed off quickly in the first say 30m? but then when not going very fast it continued on for longer then I would thought.Maybe thats where I have to squeeze the brake a bit harder, almost felt like a bit of brake fade, very interesting, I would have thought I'd stopped quicker. What I did do was that I felt better at gauging the stopping distance, which is a benefit from all this carry on, I felt that as I was getting better and I repeated the exercise.I guess its the last few metres that count isnt it.
I will keep it going and yes will do some measurements.
Now I know the approx 40 meter stopping distance is benchmark to achieve, I will mark two marks on the road 40m apart, I guess if I can get under 40m from 100km/hr I am doing OK, Right

[Dean]

For christ sake young man. DO NOT LEARN ANYTHING FROM YOUR MATE. You are learning to ride, not to race. Never ride that close to another bike unless you are on the race track and slipstreaming. On the road keep your distance.

Even on the track riding close behind another rider can be a risky manouver. Just ask K14 what happened when another rider touched his rear wheel. I know I have put another rider down at Ruapuna when his front wheel touched my rear. That is just dangerous, far too dangerous to be something you'd practice on the road.

Get yourself a mentor asap.

hi jantar yes i am thinking about getting a mentor i think my mate just wants me to be like him yano teach me the stuff he learnt when he was my age.im pretty sure he wants me to go on the track and eventually race,he told me he started riding on the road at the age of 14 and all this hard out skills he learnt and whatnot.it seems like he wants me to be the next rossi but i dont think i will be.any mentors round the northshore whangaparaoa in particular

[BMWST?]

discs are bloody cheap to make too.Twin leading shoe drom brakes....sigh

[Ixion]

Four leading shoe brakes. Sigh

[Mikkel]

F1 car can pull just over 5g in braking force. From watchin both motogp and f1 i'm guessing a motogp bike can surely pull about 2.5g on the brakes?

It's a Jedi mind-trick - they're down with the force ya know.


That's cool. Where does weight come in here though? Surely weight has a big effect.

Weight and forces are not considered if you're only discussing kinematics (http://en.wikipedia.org/wiki/Kinematics).


But it's not about brakes, it's about tyres and weight isn't it? Any properly maintained brakes can provide enough to skid the front wheel, so isn't it about how much of that force the tyre can take?

Well, the weakest link in the chain and all that. The most powerful brakes in the world wouldn't save you if they just came with an on/off switch (I guess they could if they had ABS... :scratch:). A poorly set up suspension system can dramatically increase your braking distance as well - braking only works when the wheels are touching the ground after all.
And feel and control are imperative in that regard.


My fastest logged lap at Puke on my SV1000S (1:07.934)

285.6 Metres from 233kph to 44kph with a maximum decelleration of -1.03 Gs coming into the hairpin. Thats the point where forks are fully compressed and it's a choice between washout and stoppie, SV has a high centre of gravity

A 600 getting a 1 minute lap can get 1.3 Gs into the hairpin (pilot climbing back onto the pillion seat)

SV wheelies at 0.83 Gs, an R1 manages 0.95 before it lifts. Both of these are in 'regular' position, climbing on the tank improves the figure

I notice that the data has been obtained using GPS. Do you know how well calibrated the unit is and how often the position is updated? Real world data - real world imperfections as well...
And also, how much does such a unit cost? I want one dammit!

At high speeds you'll be able to exceed 1g - airbraking is not restricted by the friction between tyres and tarmac. This is especially true for bikes since they are about as aerodynamical as a tree. Try and sit up at 200 km/h (don't let go of the handlebars btw.) and see how quickly your speed falls off - do it again at 50 km/h and notice the difference.

As for practicing emergency braking - all good, but do ease into it or you might repeat my embarrasing incident. :whistle:

[Badjelly]

At high speeds you'll be able to exceed 1g - airbraking is not restricted by the friction between tyres and tarmac. This is especially true for bikes since they are about as aerodynamical as a tree. Try and sit up at 200 km/h (don't let go of the handlebars btw.) and see how quickly your speed falls off - do it again at 50 km/h and notice the difference.

That's a very good point that I hadn't considered. I don't have a bike that will do 200 km/h, so I can't do any tests on this. How much deceleration do you think is achievable by a rider sitting up at 200 km/h? As much as 0.3 g?

Oh, never mind, I'm sure I can calculate the answer. Let's see rhoa = 1.25 kg/m3, Cd = 0.8, A = ... :laugh:

[Jantar]

...Oh, never mind, I'm sure I can calculate the answer. Let's see rhoa = 1.25 kg/m3, Cd = 0.8, A = ... :laugh:

Come on now, out with it. What is your A? :innocent:

And Cd = 0.8? With some of the bike/rider/gear combinations I've seen it could be as low as 0.4. Then I'd probably touch a bit more than 0.8. :laugh:

So I didn't bother trying to factor drag into the calcs, but lets just accept that it is a factor at higher speeds.

[Badjelly]

Fastest stopping I ever heard of was the Vincent. 20 foot from 30 mph.

Hm, s = 20 ft = 6.1 m, v = 30 mph = 48 km/h = 13.4 m/s, a = v^2/2s = 14.7 m/s^2 = 1.5 g. Higher than I expected. Possibly higher than I believe!

[Badjelly]

Come on now, out with it. What is your A? :innocent:
I'm working on it.

[davebullet]

Fast enough to have a friend (now wife) on her less than 24hr old brand new CB250 run in to the back of me.

Guys are always inventing new ways to pick up a chick :bleh:

[Mikkel]

That's a very good point that I hadn't considered. I don't have a bike that will do 200 km/h, so I can't do any tests on this. How much deceleration do you think is achievable by a rider sitting up at 200 km/h? As much as 0.3 g?

It's hard to measure - but one of my mates has a naked bike he's had up to ridiculous speeds (excess of 250 km/h) and at that point he is hardly able keep his head level due to the forces.

And I can assure you that even at 150 km/h it makes a huge difference whether I sit upright or lean down over the tank on my motard.


Oh, never mind, I'm sure I can calculate the answer. Let's see rhoa = 1.25 kg/m3, Cd = 0.8, A = ... :laugh:

Thou should know better than to dabble in the dark arts of fluid mechanics! ;)


In the end, if you're going fast enough - no matter Cd, A, rho_air, or any other constant (as long as P>0) - you will be able to exceed 1 g through airbraking.

[davebullet]

Guys, Maths aside, I hate to tell you a 2 metre stop from 60 kph velocity is perfectly possible. You just have to have a concrete wall at the 2 metre mark (pun not intended).

[Dean]

Guys, Maths aside, I hate to tell you a 2 metre stop from 60 kph velocity is perfectly possible. You just have to have a concrete wall at the 2 metre mark (pun not intended).

i could do that easy ive done 70 kph and stopped from 2 meters on ma gn250 i dont wanna brag but i can also do endos

[HenryDorsetCase]

You guys are dreaming if you think you can stop a motorcycle in 2m from 60kph. If you can, prove it, video on youtube and I will pay you $500.

and by stop I mean controlled, upright and without hitting anything.

Anyone can stop from 60 kph in 2m, say you hit a parked car, or the concrete wall thats been mentioned.

Otherwise you are just showing how little you know, and how dangerous to yourselves and others you really are.

[Ixion]

Hm, s = 20 ft = 6.1 m, v = 30 mph = 48 km/h = 13.4 m/s, a = v^2/2s = 14.7 m/s^2 = 1.5 g. Higher than I expected. Possibly higher than I believe!

22.5 ft from 30mph. So say the expert testers of the (then) VERY respected 'Motorcycling'. (http://www.vincent-hrd.co.uk/story.html)

I've managed 8mtrs odd with ABS. Never had the opportunity to put the Vincent to the test personally. Very happy to do so if someone can oblige with a Black Shadow.

[Badjelly]

22.5 ft from 30mph.

The article you cite says "22 1/2 ft", not "22.5 ft". That's quite enough of your trying to bamboozle us with that new-fangled decimal notation, young lad!

And 22.5 ft is more than 20 ft, to the tune of one GST.

Still pretty impressive, though.

[HenryDorsetCase]

22.5 ft from 30mph. So say the expert testers of the (then) VERY respected 'Motorcycling'. (http://www.vincent-hrd.co.uk/story.html)

I've managed 8mtrs odd with ABS. Never had the opportunity to put the Vincent to the test personally. Very happy to do so if someone can oblige with a Black Shadow.

If someone was to lend me a black shadow there is no way I would be stopping till I got to about Westport. Then only for gas. Got to get it good and warmed up before practising the old braking drills y'know.

[NighthawkNZ]

Yeah i have done a fair bit of practise with this, i could haul the zxr250 to a stop from 60kph in 2 metres.

Awwee fuck Al u so cool to break the law... the laws of physics (but not as we know it Jim) ... awwe gee you are good rider al to mecky for me...

[Dean]

You guys are dreaming if you think you can stop a motorcycle in 2m from 60kph. If you can, prove it, video on youtube and I will pay you $500.

and by stop I mean controlled, upright and without hitting anything.

Anyone can stop from 60 kph in 2m, say you hit a parked car, or the concrete wall thats been mentioned.

Otherwise you are just showing how little you know, and how dangerous to yourselves and others you really are.

fine then ill put up a vid of me going 70kph stopping at 2meters

nah im such a noob im my dreams more like

[HenryDorsetCase]

Lets just exercise our brain cell shall we?

Assume your bike has a 17 inch diameter wheel and is running say a 110/80 front tyre.

The diameter of the wheel is thus 17 x 25.4 plus 2 x (110 x .8) 431.8 + 88 +88 == 607mm.

circumference of a circle is pi x D

so 3.1415962 x 607 gives a rolling diameter of 1906mm.

So the statement here (I can stop in 2m from 60kph) equates to: "I can stop in ONE and a little bit wheel rotations from 60kph"

Someone who had never ridden a motorbike before might think that was possible, but anyone with any knowledge whatsoever would see the statement is completely flawed.

My $500 (which is real money by the way) is COMPLETELY SAFE.

[Dean]

Lets just exercise our brain cell shall we?

Assume your bike has a 17 inch diameter wheel and is running say a 110/80 front tyre.

The diameter of the wheel is thus 17 x 25.4 plus 2 x (110 x .8) 431.8 + 88 +88 == 607mm.

circumference of a circle is pi x D

so 3.1415962 x 607 gives a rolling diameter of 1906mm.

So the statement here (I can stop in 2m from 60kph) equates to: "I can stop in ONE and a little bit wheel rotations from 60kph"

Someone who had never ridden a motorbike before might think that was possible, but anyone with any knowledge whatsoever would see the statement is completely flawed.

My $500 (which is real money by the way) is COMPLETELY SAFE.

actually no im gonna take that 500 dollars from you .im making a vid

[RC1]

actually no im gonna take that 500 dollars from you .im making a vid

does the GN250RR go to 60 ?? :shutup:

[Dean]

does the GN250RR go to 60 ?? :shutup:

the gn250rr which i proudly own can go up to 140 mate:headbang::clap::banana:

[AlBundy]

Tried an emergency stop the other night... before I knew it, I was doing a stoppie....

How fortunate then I've been practicing them, so didn't panic....

Pretty spectacular but doesn't help for slowing much...

[NighthawkNZ]

Pretty spectacular but doesn't help for slowing much...

mainly because you have less rubber on the ground

[Mikkel]

mainly because you have less rubber on the ground

Incorrect. You will stop faster if you keep your rear-wheel down, but it has nothing to do with the amount of rubber touching the ground.

[NZJONESY]

Went out this arvo on the 250R and tried this out on a almost empty LSZ near welly. Started in small steps then got up to doing 100kmph in a straight line and stopping dead as fast as I could. I didn't have a tape measure but braking with about 90%F 10%R from 100k's took around about 15 meters to stop dead, I could be wrong as I was just eyeballing it. Does that seem right?

Its interesting how the bike feels when your doing this, a few times the back lifted about 2-3 inches, when I started getting it bang on I only had a bit of rear end wobble which feels really neat.

[Badjelly]

Went out this arvo on the 250R and tried this out on a almost empty LSZ near welly. Started in small steps then got up to doing 100kmph in a straight line and stopping dead as fast as I could. I didn't have a tape measure but braking with about 90%F 10%R from 100k's took around about 15 meters to stop dead, I could be wrong as I was just eyeballing it. Does that seem right?

No. Way too short. The deceleration required to do this is 2.7 g. Simply not possible.

If you don't want to go to the bother of marking out the road and measuring it, try estimating how much time you take to stop. (Count 0 pause 1 pause 2 ... with the 0 as you hit the brakes.) Stopping at 1 g from 100 km/h would take 2.9 s, during which you would move 40 m. If you really did stop in 15 m it would have taken you 1.1 seconds. (This assumes deceleration is constant, which is obviously not exactly right, but close enough, I think.)

[NZJONESY]

No. Way too short. The deceleration required to do this is 2.7 g. Simply not possible.

If you don't want to go to the bother of marking out the road and measuring it, try estimating how much time you take to stop. (Count 0 pause 1 pause 2 ... with the 0 as you hit the brakes.) Stopping at 1 g from 100 km/h would take 2.9 s, during which you would move 40 m. If you really did stop in 15 m it would have taken you 1.1 seconds. (This assumes deceleration is constant, which is obviously not exactly right, but close enough, I think.)

Cool, thanks for that. Next time I'm out I'll give it a try. Its raining like a mofo now, otherwise I would be out there testing it :(
I'll get off and pace it out too.

[NighthawkNZ]

Incorrect. You will stop faster if you keep your rear-wheel down, but it has nothing to do with the amount of rubber touching the ground.

incorrect... main reason cars can out brake bikes... you will stop even quicker with both on the ground... 75% of your braking in up front... 25% from the rear... both together... stops you quicker and if I had to choose on wheel to stop it would be my front...

[quickbuck]

I did a track day with Brian Bernard organised by the Wanganui Ulysses club and I was struck by two things.

1. For a mostly older group that spent a lot of time covering a lot of miles I was dumb founded at the lack of knowledge some riders had regarding the use of front and/or rear brake for emergency braking. These men/women ride a lot of miles, so how much worse is the average rider?

2. ABS and linked braking systems are the schizz! The BMW's and Pan Europeans etc shat all over everything when it came to stopping in a hurry. Unless you are Andrew Stroud good, forget thinking you will be able to brake better using your own judgement....believe it. If you aren't going to go on the track, and get the opportunity, go with ABS you can't beat it.

Ummm,
Actually, My CBR600 hauls up in 16 metres from 70km/hr as opposed to the Police issue BMW that does 18 with the ABS chattering away in my ear at the same time......
Yes, all distences and speeds measured with Police issue tape measure and Laser gun......

I dare say the ST1100 would be a better bike for stopping...

[quickbuck]

incorrect... main reason cars can out brake bikes... you will stop even quicker with both on the ground... 75% of your braking in up front... 25% from the rear... both together... stops you quicker and if I had to choose on wheel to stop it would be my front...

Heard it was 90/10... but who am I to argue?

[Mikkel]

incorrect... main reason cars can out brake bikes... you will stop even quicker with both on the ground... 75% of your braking in up front... 25% from the rear... both together... stops you quicker and if I had to choose on wheel to stop it would be my front...

No, you are wrong - my post was 100% correct. The reason that you do not stop faster pulling a stoppie is not because you have less rubber on the road.

If you are pulling a stoppie your front wheel is doing 100% of your braking since it's your only contact point with the road. However, those 100% constitute less braking power than the combined 100% of your front and rear tyre if you keep your tail down.
And this has nothing to do with the amount of rubber touching the ground, the stopping power of your brakes, god or the corriolis effect. It has all to do with geometry.

This is of course keeping everything else equal - same bike, same tyres, same surface, same temperatures, same humidity, etc, etc.


Heard it was 90/10... but who am I to argue?

The weight distribution between front and rear tyre, and consequently the amount of braking they can supply, depends on a number of factors, the two main factors being 1) how hard you are braking (e.g. weight transfer from rear to front) and 2) the geometry of the bike.

If we're talking emergency braking only 2) really matters since we're trying to maximise 1) anyway.

This is of course keeping everything else equal - same tyres, same surface, same temperatures, same humidity, etc, etc.

[NZJONESY]

If your stopping as hard as you can possibly do so, shouldn't the G forces be like 2G or more?? I'm just remembering a Top Gear episode where they were testing the new corvette and its got a G-meter in it, Clarkson was getting it up to 1.2-1.6 just going around corners

[NighthawkNZ]

No, you are wrong - my post was 100% correct. The reason that you do not stop faster pulling a stoppie is not because you have less rubber on the road.

If you are pulling a stoppie your front wheel is doing 100% of your braking since it's your only contact point with the road. However, those 100% constitute less braking power than the combined 100% of your front and rear tyre if you keep your tail down.

I am not talking about pulling a stoppie, thats why I said more rubber on the road (terminology for have wthe wheel on the road... it ain gonna stop you if it is in th eair is it???)... and what you are saying is basically what I said...???? having both wheels on the ground... you will stop faster... (more rubber on the road I wasn't actually saying the rubber stops you... though it helps when you are in full lock and you have smoke coming from that rubber on both tyres...) The rubber does have some to do with your stopping power as well... ride round on your rims at 100kph do snap brake you will be in a skid before you know it...

[EJK]

I am not talking about pulling a stoppie, thats why I said more rubber on the road ... and what you are saying is basically what I said...???? having both wheels on the ground... (more rubber on the road) you will stop faster...

Your post got me thinking (I'm not judging you so don't be harmed, It's just a question).


Would a Harley stop faster than a sports bike? :laugh: (More rubber on the ground)

[Badjelly]

If your stopping as hard as you can possibly do so, shouldn't the G forces be like 2G or more?? I'm just remembering a Top Gear episode where they were testing the new corvette and its got a G-meter in it, Clarkson was getting it up to 1.2-1.6 just going around corners

For the moment, let's put aside the fact that Jeremy Clarkson is very amusing and provocative but not very...shall we say...reliable. (And I will tell him so if I get an opportunity during the Top Gear show in a few weeks time.) I'm curious why you think you should be able to get much more acceleration out of rubber tyres on asphalt in braking than in cornering.

Anyway, I think it's pretty clear from published figures that some vehicles can brake at something more than 1 G, say 1.2-1.3 G, but I have never seen any evidence that any rubber-tyred vehicle can brake at 2G without substantial aerodynamic downforce.

[Mikkel]

I am not talking about pulling a stoppie, thats why I said more rubber on the road (terminology for have wthe wheel on the road... it ain gonna stop you if it is in th eair is it???)... and what you are saying is basically what I said...???? having both wheels on the ground... you will stop faster... (more rubber on the road I wasn't actually saying the rubber stops you... though it helps when you are in full lock and you have smoke coming from that rubber on both tyres...)

What you said, in relation to not stopping as efficiently doing a wheelie was this:
mainly because you have less rubber on the ground

I read that as you saying that the amount of rubber on the ground is the main factor in determining how fast you can stop.
But then, I am not certain I am reading what you write in the right way.


The rubber does have some to do with your stopping power as well... ride round on your rims at 100kph do snap brake you will be in a skid before you know it...

...or for that matter trying to brake with a flat tyre.

Yes, the rubber is crucial when talking stopping power. It is however not how much of it that is touching the ground which is important. And that is all I am saying.

[imdying]

Hey that's interesting... but are you sure you don't mean that 'friction coefficient' of 1?

Reason I say that is because any light bike with good tyres can pull 1g of force in cornering on the skid pad test. I suspect braking would yield far more force right?

F1 car can pull just over 5g in braking force. From watchin both motogp and f1 i'm guessing a motogp bike can surely pull about 2.5g on the brakes?

interesting.

I'm sure in a reasonably recent PB mag, they did some bolt on upgrades to a GSXR600, which included using iron discs. Took it from 0.9g deaccelerative force to 1.6g. I'll try to remember to look it up. (So it'd be interesting to see what the max a slicked up MotoGP bike with Rossi on board can pull, plenty I'm guessing...). Having said that, doesn't help skiddy's fairytale fantasy.

[Jantar]

Some very interesting scientific test results at: http://www.msf-usa.org/imsc/proceedings/a-Green-ComparisonofStoppingDistance.pdf

Have a look at the table on page 6.

[Badjelly]

Some very interesting scientific test results at: http://www.msf-usa.org/imsc/proceedings/a-Green-ComparisonofStoppingDistance.pdf

Have a look at the table on page 6.

Thanks. I was just about to do some sums on them.

Caution: the high-speed results from the BMW F650 look very impressive compared to the others, until you read the fine print: it was tested at 118 km/h, whereas the others were tested at 129 km/h.

[mikeey01]

[QUOTE=rocketman1;1904154]

They took a Honda GL1500 and a Honda CBR929 and made hundreds of braking attempts. Basicallly, they did stops from 100kph. Amazingly the CBR929 and the GL were very similar and there was no real difference between the 2 in stopping distance. They got 38m as an average for the good runs.


Hey I'm not a maths guru, nor am I a word smith and I am certainly not a doubter when it comes to the years of knowledge u fellas have collectively got, but bear with me for a shake...
Lets apply some pure logic to the above for a second... something to me doesn't gell!

Honda GL1500 specs..
792 pounds dry (360 kg)
Front brakes Dual full-floating 296mm discs with LBS three-piston calipers

Honda CBR929 specs..
374.8 pounds dry (170 kg)
Front brake Dual 320mm discs with 4-piston calipers

So the GL weights twice as much, has less braking effort and stops in near the same distance as something that's half it's weight and has a greater braking effort? :scratch: I'm lost!

I'm not as clever as most of guys on here so I'm thinking like a big train takes years to stop and a car takes bugga all, yeah no real comparison but something doesn't gell with what you said...

Don't shoot me down as I'm really finding it hard to come to terms with how this all works.

[Jantar]

[QUOTE=trademe900;1904588] ...Don't shoot me down as I'm really finding it hard to come to terms with how this all works.

Like most tests, there isn't enough information here to explain exactly why, but the results are not surprising. Just giving the number of pistons per caliper and the disk diameter doesn't give the swept area which does affect braking performance. I also wouldn't be suprised to find that there is more allaoy in a sports bike disk and more iron in a tourer's disk whiach again will affect the braking performace. Also there is the amount of rubber in contact with the road, the air resistance etc. etc.

There are so many factors that affect braking performance that it isn't possible to calculate to the meter what any bike will achieve. It is possible to tell when claims are fancifull, or to tell when improvements could be made, but is about the limit.

[The Stranger]

Some very interesting scientific test results at: http://www.msf-usa.org/imsc/proceedings/a-Green-ComparisonofStoppingDistance.pdf

Have a look at the table on page 6.


Interesting why?

[Jantar]

Interesting why?
Mainly because the test results are exactly in line with the theoretical results we have been discussing in this thread. The stopping distances are all in the 0.7 - 0.9 G range.

[Mikkel]

So the GL weights twice as much, has less braking effort and stops in near the same distance as something that's half it's weight and has a greater braking effort? :scratch: I'm lost!

I'm not as clever as most of guys on here so I'm thinking like a big train takes years to stop and a car takes bugga all, yeah no real comparison but something doesn't gell with what you said...

The over-the-top brakes on sportsbikes are there to allow hard braking into each and every corner at very high speeds for hours on end, while maintaining consistent high performance and feel. For any imaginable single braking action such brakes are overkill and so are the ones on the GL1500 as well. After all, the GL1500 would have to be able to drive down a steep mountain pass without the brakes overheating and fading.
So, for a single braking action you shouldn't see too dramatic a difference.

The reason that trains take a long time to stop has more to do with the fact that it is steel-on-steel not rubber-on-tarmac that provides the friction that facilitate the stopping. Also, for some freight trains only the locomotive is braking, which makes a huge difference. But the steel-on-steel factor is also the reason why you only see fairly mild gradients on railroads - on the other hand, the fact that the steel wheels doesn't really deform during rotation is what makes railways so efficient.

[racefactory]

The over-the-top brakes on sportsbikes are there to allow hard braking into each and every corner at very high speeds for hours on end, while maintaining consistent high performance and feel. For any imaginable single braking action such brakes are overkill and so are the ones on the GL1500 as well. After all, the GL1500 would have to be able to drive down a steep mountain pass without the brakes overheating and fading.
So, for a single braking action you shouldn't see too dramatic a difference.

The reason that trains take a long time to stop has more to do with the fact that it is steel-on-steel not rubber-on-tarmac that provides the friction that facilitate the stopping. Also, for some freight trains only the locomotive is braking, which makes a huge difference. But the steel-on-steel factor is also the reason why you only see fairly mild gradients on railroads - on the other hand, the fact that the steel wheels doesn't really deform during rotation is what makes railways so efficient.

thats exactly how i would want to put it- thanks dude. The reason why those GL1500 and CBR were nearly the same stopping distance was mainly because there is no advantage of having those overkill brakes on the sports bike from those relatively low speeds. The CBR brakes would be designed for caning it around a track lap and lap again with minimal damage and fading.

Like i said before, limiting factor for these single runs is not the brake system but the tyre and in some cases- the CG.
Most brakes in proper spec and looked after will be able to lock the front wheel at these speeds (and that is all that is needed for this) therefore it is nothing to do with the brakes but how much friction the tyre can provide before it skids.

Lastly, on the average sporty bike, when trying to get best stopping distancem, rear contributes absolutely NOTHING except from the very first instant in the braking where the load is still on the rear wheel. If you are using rear brake whilst doing this stuff then you are clearly not applying front brake as hard as it can go.... because if you were, your rear wheel will literally be floating above/skimming the ground- providing no stopping power whatsoever.

Of course this assumes conditions are dry, good surface, reasonably good tyres.

Cool thread!

[racefactory]

Also about the car stuff that was said earlier and rear brakes.

Cars set up for track and very sporty cars will have a brake balance set of around 67% front brake bias. In real life that equates to driving at highspeed and applying brakes to the point where front will lock just before the rear does.

Compare that to a bike... it's 100% front brake bias. except the very first instant where the weight is on the front tyre.

That's how the racers say they do it don't they... rear brake first, load the front, take off the rear and 100% front brake.

Reason is because the car has better CG rear weight bias under brakes so can still put good force on rear tyres.

But then, bikes have a lot more aerodynamic force to help them.

You'd be surprised, a sports road car and bike will brake nearly about the same distances... there is so much aerodynamic help from braking on a bike at high speed. Sitting up on the bike is something like putting a great big bloody airbrake on top of the car. In the end, i think it balances out.... At least from the stats they are near the same. Until you have the super road cars like Ferraris and Lambos..extremely low to the ground with rear mounted engines.....


...but only until you start putting on great big fecking wings/extremely low cgs/mammoth sized tyres would there be any massive difference I reckon.


Bikes:

+tons of aero force

sporty car:

+ cg rear weight bias meaning more weight on the rear
+ slightly bigger contact patch vs weight.



race car:

+ big aero forces

+ massively big tyres

+ perfect CG rear weight bias.

[racefactory]

One more-

Is there formulae that can be used in conjunction to calculate braking distances and forces including the important aerodynamic effects at high speed???

[Mikkel]

sporty car:

+ low and well placed CG meaning more weight on the rear
+ slightly bigger contact patch vs weight.


Bullshit, that has nothing to do with braking. The contact patch depends upon the tyre's pressure and the load it is carrying. You can achieve exactly the same contact patch vs weight on a bike compared to a car. That still won't change a thing. The size of the contact patch has a lot more to do with feel, stability and handling than actual grip (that is while keeping the pressure within the recommended range for the given application of course).

By CG I suppose you're meaning the centre of mass (or gravity as some errant folks like to put it). It is true that the CoM is important in relation to all of this - however, it has nothing to do with how much weight it puts on the rear wheel. It has everything to do with the vertical height of the CoM compared to the centre of your front wheel. If the CoM is higher, or a lot higher, than the centre of the wheel you will be, very, limited in how much braking force you can apply at the front tyre before making a somersault.


Is there formulae that can be used in conjunction to calculate braking distances and forces including the important aerodynamic effects at high speed???

Yes, but it is a 2nd order non-linear differential equation and as such it is very difficult to work with:

m*d^2x/dt^2 - k*(dx/dt)^2 = F - F_fric

m is of course the mass.

d^2x/dt^2 is the acceleration, a.

k is a constant given by the cross-sectional aerodynamical profile of your vehicle times the drag coefficient and the atmospheric density.

dx/dt is the velocity, v - it is squared in this case because for systems on the scale of motorcycles travelling at considerable speeds the Reynolds number indicate that we are in the turbulent flow regime and thus the drag scales with the square of the velocity.

F is the applies force at the rearwheel and F_fric is the constant rolling resistance due to bearings, deformation of tyres, etc.

You asked for it ;)

Note - this is the simple case of a body travelling in a straight line on a completely flat surface in a completely still atmosphere. Fluid mechanics are in the larger field of black magic as far as I am concerned.

[racefactory]

http://www.youtube.com/watch?v=wWCAtS_Mr-g

watch this video of motogp bike stopping from 291kph...

let's see how much force he's pulling and what distance he stops in.

I downloaded the video off youtube and he goes from 291 to 146 in 3 seconds...

He loses 145kmh in 3 seconds...

So.. what are the figures here then?

[Badjelly]

Is there formulae that can be used in conjunction to calculate braking distances and forces including the important aerodynamic effects at high speed???

The aerodynamic drag force can be quantified with a simple equation, see

http://en.wikipedia.org/wiki/Drag_equation

The tricky part is coming up with good numbers for Cd (the drag coefficient) and A (the cross-section area).

Jantar suggested a good rider on a faired bike could get to Cd = 0.4, which seems reasonable. A has to be in the vicinity of 0.5-1 m^2. When the rider sits up, both Cd and A will increase, especially Cd.

I threatened earlier on this thread to do some calculations and report the results, but I haven't got around to it. I thought I'd start to try to get a handle on CdA by relating top speed to power on a few bikes.

[racefactory]

By CG I suppose you're meaning the centre of mass (or gravity as some errant folks like to put it). It is true that the CoM is important in relation to all of this - however, it has nothing to do with how much weight it puts on the rear wheel. It has everything to do with the vertical height of the CoM compared to the centre of your front wheel. If the CoM is higher, or a lot higher, than the centre of the wheel you will be, very, limited in how much braking force you can apply at the front tyre before making a somersault.


I meant CG rear weight bias. With the weigt further back i'm guessing it's an advantage under brakes right?

[Mikkel]

I meant CG rear weight bias.

So what does CG stand for?

[racefactory]

what's the formula for figuring out distance, given time? I think it's on this thread somewhere but can't find it!

If it's 145kmh lost in 3 seconds what's the distance and force?

Thanks!

don't worry- done it.

looks like the motogp bike was stopping at roughly 13.4ms^2 which is 1.37g!

[Jantar]

...looks like the motogp bike was stopping at roughly 13.4ms^2 which is 1.37g!
Correct. And at those speeds air resistance would play a reasonable part.

[Badjelly]

looks like the motogp bike was stopping at roughly 13.4ms^2 which is 1.37g!


Correct. And at those speeds air resistance would play a reasonable part.

Come on, how much then? :whistle:

A post on this page has some numbers:

http://www.msgroup.org/forums/mtt/topic.asp?TOPIC_ID=955

The relevant bits...


This is a great link that compares a Hayabusa and a Kawi ZX-12r in a wind tunnel, here is some of their figures. The link has a graph and more details.
A lower figure means less drag, and the Hayabusa recorded a Cda of
3.37 ft2 (0.313 m2), about 8 percent less than the ZX-12R's figure of
3.67 ft2 (0.341 m2).

To achieve 187.5 mph, the Hayabusa needs 147.6 horsepower to
overcome drag alone; the 12R needs 161.3 horsepower for the
same speed. However, using the wind tunnel data, test weights,
our road-test dyno figures for horsepower and a rolling-resistance
figure, Cooper calculated that the ZX-12R would have a maximum
speed of 187.0 mph and the Hayabusa 187.7 mph. The effect of wind
can vary the result, usually decreasing speed unless it's a tailwind.
Sidewinds during a test can decrease top speed as a result of the higherdrag at yaw. This calculation doesn't include any ram-air effect, butessentially, the bikes have similar speed potential, although the Suzuki has the edge.

In order to measure the frontal area, we photographed the Hayabusa and
ZX-12R from the front, using a long lens to minimize parallax distortion,with a measuring stick beside each bike as a reference point. Later wescanned the photographs, enlarged them to an identical scale and close-cropped them. Using Adobe Photoshop, the pixels in the images wereadjusted to a scaled half-inch-square size and then counted, which gaveus an accurate measurement of the frontal area of each bike, confirmingour impressions. The ZX-12R has a frontal area of 6.09 ft2 (0.566 m2),physically larger than the Hayabusa, which is 6.01 ft2 (0.558 m2). Butthe advantage for the Suzuki is not just in frontal area. With figuresfor both drag and frontal area, it's possible to calculate the coefficientof drag, which is 0.603 for the 12R and 0.561 for the Hayabusa. The winner of this wind tunnel shootout is the Suzuki.

Unfortunately the link he refers to is broken.

[Badjelly]

And then there's this from Google book search (Motorcycle Dynamics,
by Vittore Cossalter):

http://tinyurl.com/ckp3w8

From p 75:


The value of the product CdA can vary from 0.18 m2 for speed record contenders that are completely faired to 0.7 m2 for motorcycles with no fairing and the rider in an erect position. A typical value for "super bike" motorcycles is 0.30 to 0.35 m2, while "Grand Prix" motorcycles reach 0.22 m2 or even smaller values. Touring and/or sporting motorcycles with a small front fairing have values around 0.4 to 0.5 m2. The change from an erect riding position to a prone riding position leads to a reduction in the value of the product CdA that varies from 5 to 20%, depending on the type of motorcycle and the rider's body structure.

On p 76 there's a chart of drag vs speed for various values of CdA. Taking CdA = 0.3 m2 ("super bike" motorcycles with rider prone) the drag at 200 km/h is ~ 600 N. If we assume a bike + rider weight of 250 kg (180 kg bike + 70 kg rider), the deceleration is 2.4 m/s2 = 0.25 G.

PS: the power required at the back wheel to push the bike along at 200 km/h against a drag force of 600 N is 33.3 kW. This sounds about right.

[gatch]

backtracking a little..

in the goldwing / cbr comparo, would the weight distribution/wheelbase of the goldwing work to its advantage too ? ie, the goldwing is longer and i imagine the weight closer to the ground then the cbr..

would it make a difference ?

[HenryDorsetCase]

nobody looks as if they will be taking my five hundy any time soon.

[Dean]

id think again henry ive put up the vid .check youtube gn 60kph stop in 2 meters . prepare 2 b amazed

[Mikkel]

Unfortunately the link he refers to is broken.

It doesn't sound like they used anything to simulate a rider on these bikes... Granted, on a busa or a zx12, it might not make too much difference since they have "comprehensive" fairings.

The reported Cds of 0.55-0.6 sounds plausible, considering that those two machines are about as close as we get to mass-produced streamliners.

A naked bike with a rider would be a very different kettle of fish I am sure.

[rastuscat]

id think again henry ive put up the vid .check youtube gn 60kph stop in 2 meters . prepare 2 b amazed

Please, I gotta see this, where is the link?

[Tank]

hi jantar yes i am thinking about getting a mentor i think my mate just wants me to be like him yano teach me the stuff he learnt when he was my age.im pretty sure he wants me to go on the track and eventually race,he told me he started riding on the road at the age of 14 and all this hard out skills he learnt and whatnot.it seems like he wants me to be the next rossi but i dont think i will be.any mentors round the northshore whangaparaoa in particular

See the guys at the NSSS They meet Albany car-park between Farmers and Burger King Wednesday nights 7.30 pm.

Well worth while - nice people who can really help.

Then - I'd recommend English lessons.

[mikeey01]

The over-the-top brakes on sportsbikes are there to allow hard braking into each and every corner at very high speeds for hours on end, while maintaining consistent high performance and feel. For any imaginable single braking action such brakes are overkill and so are the ones on the GL1500 as well. After all, the GL1500 would have to be able to drive down a steep mountain pass without the brakes overheating and fading.
So, for a single braking action you shouldn't see too dramatic a difference.

The reason that trains take a long time to stop has more to do with the fact that it is steel-on-steel not rubber-on-tarmac that provides the friction that facilitate the stopping. Also, for some freight trains only the locomotive is braking, which makes a huge difference. But the steel-on-steel factor is also the reason why you only see fairly mild gradients on railroads - on the other hand, the fact that the steel wheels doesn't really deform during rotation is what makes railways so efficient.


Arr see I knew u clever fellas would explain that in a way I could get it! nice one now I sort of get it.
I was thinking about it after I asked that qustion "Does weight matter" and wondered if the transfer of those kilos onto front wheel of GL would allow a tad more stopping thingie.

[slofox]

http://www.kiwibiker.co.nz/forums/showthread.php?t=91326

Interesting how much faster you can stop in an emergency than when you "practice" emergency stopping.......

[rocketman1]

http://www.kiwibiker.co.nz/forums/showthread.php?t=91326

Interesting how much faster you can stop in an emergency than when you "practice" emergency stopping.......

I'm glad your practice saved you from an accident.
It is now something that I will continue to practice, I guess the only bikers that practice stopping hard are seasoned racers, not road riders, good to see it working

[Tank]

Funniest quote so far in 2009.

"I can stop a bike in 2 meters from 60km" - our very own skidmark.

[Iggy]

Funniest quote so far in 2009.

"I can stop a bike in 2 meters from 60km" - our very own skidmark.

This is what Skidmark looks like after the ''stopping his bike in 2 metres from 60km'' :shit:.....:thud:.....::doh:

[Swoop]

Funniest quote so far in 2009.

"I can stop a bike in 2 meters from 60km" - our very own skidmark.
Quite possible...
If a brick wall is involved in the process.

[McJim]

Quite possible...
If a brick wall is involved in the process.

We need to find a fast bricklayer........

[skidMark]

Funniest quote so far in 2009.

"I can stop a bike in 2 meters from 60km" - our very own skidmark.


and i can....

wanna see?

It's called a 250 and skill.

[wbks]

and i can....

wanna see?

It's called a 250 and skill.lol...


There must be something wrong with your measuring, or the speedo is way off. That would pull roughly 6G forces, and motogp 125 riders would be lucky to pull 2.5 under heavy braking, and I think somewhere after that jet fighter pilots start blacking out...
Think you can do that on a 20 year old road bike with road tires on and about 70 more kilo's onboard the bike?:yawn:

[skidMark]

lol...


There must be something wrong with your measuring, or the speedo is way off. That would pull roughly 6G forces, and motogp 125 riders would be lucky to pull 2.5 under heavy braking, and I think somewhere after that jet fighter pilots start blacking out...
Think you can do that on a 20 year old road bike with road tires on and about 70 more kilo's onboard the bike?:yawn:

210 KG all up bike with rider.... stopping in 2 metres....

I dont see the problem....

Cars can stop that fast with decent brakes and a big footprint, and its alot more mass to stop.

[Tank]

and i can....

wanna see?

It's called a 250 and skill.

Happy to set up a wee bet? How much you willing to back this up?

[McJim]

210 KG all up bike with rider.... stopping in 2 metres....

I dont see the problem....

Cars can stop that fast with decent brakes and a big footprint, and its alot more mass to stop.

Hi Skiddy - after all these years your real problem has just occurred to me. You're not actually bright enough to realise that you're an idiot are you?

[piston broke]

210 KG all up bike with rider.... stopping in 2 metres....

I dont see the problem....

Cars can stop that fast with decent brakes and a big footprint, and its alot more mass to stop.

don't.....
but show us a vid with a 2m mark from a big brick wall.
then we'd believe:eek:

[skidMark]

don't.....
but show us a vid with a 2m mark from a big brick wall.
then we'd believe:eek:


Yeah and if something lets go on the bike, real intelligent buddy.

[wbks]

A car like the atom could just about do it... But then it has four times the contact patch and only about 100kilo's or so more... Actually I'm pretty sure a formula 1 car couldn't do it.

[piston broke]

Yeah and if something lets go on the bike, real intelligent buddy.

oh well,
make a silly statement,
you will get silly replies:Playnice:

[TOTO]

On my organised 250 ride..."Toto, you can be sure it is tully a 250 ride, coz I've seen 250....km/h" :killingme

[wbks]

We need to find a fast bricklayer........Can I put that in as my signature quote?:clap:

[pritch]

Cars can stop that fast with decent brakes and a big footprint, and its alot more mass to stop.

OK I'll play this game... What bloody cars?

Links or reputable references required of course.

[skidMark]

oh well,
make a silly statement,
you will get silly replies:Playnice:


Yeah but i didn't make a silly statement so like...

Why the fuck are you still here?

[wbks]

OK I'll say it. It's not humanly possible to pull 6G's (forces needed to stop in 2 meters from 60km/h) without blacking out and suffering internal injuries. You talk so much shit I'm not surprised people talk to you like you're one

[piston broke]

Yeah but i didn't make a silly statement so like...

Why the fuck are you still here?

lol.show us some proof then.
i only met you the once.
i think maybe you reached 2 or 3 g's when you were thrown over the fence at mt welli:Playnice:
oh and you weren't even on a bike.

why am i still here?
for a good time

[racefactory]

Can't believe this skidmark dude just keeps on going!!

As i said before, the only thing that's stopping from 60kph that fast is a fucking fist through your gob mate. That is it.

60^2/254(1G stop right near front lock up) = 14.17m

-14m flat in perfect conditions and surface is the fastest you are ever gonna stop on your dunlop gpra10's dude.

-Motogp bike will do it in 10m.

ya have to be pulling exactly 7G to stop from 60k's in 2m. An F1 car can pull 3.5g from high speeds (300kmh) where aerodynamic forces help it brake. So having said this, you're not seriously fucking persisting you can do it?

[wbks]

7? Shit I thought it was 6... probably good I'm not going NCEA3 maths then. Just out of interest: What G's do motogp bikes pull max?

[MIXONE]

7? Shit I thought it was 6... probably good I'm not going NCEA3 maths then. Just out of interest: What G's do motogp bikes pull max?

I don't know about G's but I bet they pull heaps of birds.;)

[wbks]

I'm sure. They'd have to, all the riders are 5'4" 45kilo guys that probably need a barstool or a segway to talk face to face... hehehee

[1vanvan1]

and i can....

wanna see?

It's called a 250 and skill.

Fucking oath. I would love to see it.

[gatch]

and i can....

wanna see?

It's called a 250 and skill.

man you have to be taking the piss, the magnitude of your piss taking is very high, what your saying equals to me stating that me on my spada out-drag any nitro crotch rocket, out handle any moto-gp machine, and is more reliable than any 24hr racer.. AAAAAAAAAAHAHAHAHAHAHAHAHA

mug

[mikeey01]

Shouldn't this have been moved to the jokes and humour section by now?

[racefactory]

7? Shit I thought it was 6... probably good I'm not going NCEA3 maths then. Just out of interest: What G's do motogp bikes pull max?

Good question, I just had to find it out eh.

I've been watching quite a few motogp onboard videos quite closely and i came up with some figures from taking speed and time measurements to calculate forces and shit...

Basically, I look at the REALLY long straights and big braking points that are quite level such as Sepang start/finish straight into turn 1 and Shanghai's back straight which is a fucking monster. I also looked at Catalunya's main straight although i think that is on a bit of a downhill and some other tracks.

What i found was hard out braking between 13.5 and 13.9 meters a sec decceleration which turns out to be from something like 1.39g to 1.43g (got the exact figures down somewhere)

Using the same methods i calculated some other stuff:

F1 cars at around 3.5g.

Japanese JGTC race cars (calsonic skyline, castrol supra, mugen NSX etc) at nearly 2g

[EJK]

Look what I found


Resistance to "negative" (In this case, braking) or upward gees, which drive blood to the head, is much less. This limit is typically in the -2 to -3 g (-20 m/s² to -30 m/s²) range. The vision goes red and is also referred to as a red out. This is probably due to capillaries in the eyes swelling or bursting under the increased blood pressure

Translation: Your eyes will pop. Soon. Maybe.

P.S. Theres gotta be a video of some sort of a military G Force deceleration test that can prove how -2g looks like...

[skidMark]

I'm sure. They'd have to, all the riders are 5'4" 45kilo guys that probably need a barstool or a segway to talk face to face... hehehee

I'm only 62 kg...
:banana:

man you have to be taking the piss, the magnitude of your piss taking is very high, what your saying equals to me stating that me on my spada out-drag any nitro crotch rocket, out handle any moto-gp machine, and is more reliable than any 24hr racer.. AAAAAAAAAAHAHAHAHAHAHAHAHA

mug


No because you have a crappy honda.

[R6_kid]

Its ok, before he told me he could stop from 240kmh in 80m on a ZX10R. When i started going through the maths he then changed it to 180kmh in 80m which is still a hard ask. Seems he's been smoking the buds again.

[R6_kid]

Look what I found



Translation: Your eyes will pop. Soon. Maybe.

P.S. Theres gotta be a video of some sort of a military G Force deceleration test that can prove how -2g looks like...

Its similar to blacking out when you do positive G, expect that instead of seeing black, you're vision goes red. It also hurts really bad, like your head is going to explode - think of a migraine but on steroids.

[HenryDorsetCase]

Its similar to blacking out when you do positive G, expect that instead of seeing black, you're vision goes red. It also hurts really bad, like your head is going to explode - think of a migraine but on steroids.

I've watched a lot of space and spaceflight documentaries over the years. In one of them Chuck Yeager volunteers to test either ejection seats or mockup of the first Mach 1 plus aircraft. Cant remember which. He got about (IIRC) plus 6 G accellerating and -3 or 4 decel. (wired up like a christmas tree). Major damage was the mini blackout from accel and burst bloodvessels from decel.

I think they adapted those "grip your extremities" flightsuits as a result.

More G than we're talking about here though.

and no one has claimed the money yet.

[Mikkel]

Look what I found

I must assume that the (In this case, braking) is something you added.
When they are discussing negative Gs in this manner they mean negative - vertical Gs. What you experience during acceleration or braking on a motorcycle or in a car/plane/etc are lateral Gs. You are much more resistant to lateral forces than vertical forces - mainly due to how your blood vessels are laid out.

This is also why astronauts are lying on their backs facing the direction of travel of their spacecraft.

When it comes to vertical Gs fighterpilots use a combination of muscle-tensioning techniques and their G-suit to prevent the blood from draining from their head during high positive G maneuvers. However, neither of that helps very much against the negative Gs since you got no muscles in your brain that you can use to squeeze the blood out and neither does a helmet do much for you in this regard.


I've watched a lot of space and spaceflight documentaries over the years. In one of them Chuck Yeager volunteers to test either ejection seats or mockup of the first Mach 1 plus aircraft. Cant remember which. He got about (IIRC) plus 6 G accellerating and -3 or 4 decel. (wired up like a christmas tree). Major damage was the mini blackout from accel and burst bloodvessels from decel.

Yeah, talk about balls being the first man ever to test a prototype for a supersonic ejection seat :eek5:

There was one guy who was subjected to a braking force of 15g on that crazy rocketsled (http://en.wikipedia.org/wiki/Rocket_sled) of theirs. He was in a poor shape afterwards, but recovered perfectly. One injury he sustain in being subjected to these forces was that his retina delaminated from the back of his eyeballs - crazy shit. At least it grew back together.

[icekiwi]

Well I had a halfwitt cager brake hard to make an un-indicated lh turn yesterday..
Two up and we stopped on a Dime...beat that!!
Oh an did I mention my eyes pooped out...and me ringpiece...

[Tank]

I was trying to work out how fast 'ol skiddy had to stop in order to make his 2 meters claim.

60km =
60000 m per hour =
1000m per min =
16m per second.

So Skidmark had to stop in 0.125 seconds for his two meter claim.

I'd bet his pocket isn't willing to back up his (pruddy) mouth.

[samgab]

show us a vid with a 2m mark from a big brick wall.
then we'd believe:eek:

I agree, this would be a good acid test.