Emergency Braking

[Devil]

hang on.
i failed physics, BUT
if i had 500N acting downwards at the back of my bike it sure would not lift upwards as easily as if i had 0N actuing downwards?
aka only when the pillion was directly above said pivot point would my stoppie be helped by said pillion

Close, as the pillions mass progressed in an arc around the pivot point, the force would increase at an exponential rate (hopefully not until ye be fucked).

[scracha]

yes but the additional weight you have added to get the 500N is traveling forward with you towards a truck that pulled out from a driveway and now you have to reduce the speed of your very porky bike on the same tyres and brakes.Never mind cause what you cant achieve the truck will finish off for you.
increased mass = longer time to stop with an equal amount of force applied.

Gravity to make the 500N generally pushes the tyres harder on the ground giving them a greater friction co-efficient to partly offset the increased mass that has to be decellerated. Otherwise 40 tonne trucks would never come to a stop.

increased mass = longer time to stop with an equal amount of force applied.
True, but with the lard arse on your pillion you can apply the brakes (yes, I said brakes) harder before the tyres lock up.

[mossy1200]

Gravity to make the 500N generally pushes the tyres harder on the ground giving them a greater friction co-efficient to partly offset the increased mass that has to be decellerated. Otherwise 40 tonne trucks would never come to a stop.

increased mass = longer time to stop with an equal amount of force applied.
True, but with the lard arse on your pillion you can apply the brakes (yes, I said brakes) harder before the tyres lock up.

Dont have arguement with that other than the mass creating the 500N is above the axis point thus wants to revolve on that point during deceleration. Once this force gets greater than the 500N caused by gravity up and over it will want to go.By adding weight to the bike all this is doing is moving the central point of mass of the bike.Yes the point of stoppie(rotation)changes but so to does the formula of fixed mass decelaration against tractionable force(tyre) against maximum force capable of resistance induced by brake pads onto discs(drag).

I think my theory is correct therefore I will not be applying led weights to the rear of my motorcycle to reduce the stopping distance in an emergency as suggested earlier in the thread.
40 ton trucks have many large brakes and a huge contact patch.Weight in proportion to drag during decleration will give stopping distance.
I will admit having 18 wheels on your bike will reduce the time it takes to stop.

[p.dath]

Therein lies the problem, 500 were excluded, and that is without being in an emergency situation.
How many would they have got right in an emergency situation?
I also note that they excluded a front brake only pass that was extrordinary, I guess it didn't meet their predetermined outcome.

There doesn't seem any point in including lots of samples that took much longer to stop.

You are right that it was curious they did exclude the one front brake pass without a decent explanation. But that is only a single sample.

[scracha]

Yes the point of stoppie(rotation)changes but so to does the formula of fixed mass decelaration against tractionable force(tyre) against maximum force capable of resistance induced by brake pads onto discs(drag).

I wouldn't worry too much as on any modern sportsbike the maximum force of the brakes is waaay more than the tyre can cope with. Take a fat pillion out with you, you'll find you can brake VERY hard without locking up. Ignore the head-butting and crushed testicles though.

I'm not trying to ignore them - just no one has posted a link to them.

If you can tell me who did the much larger study I'll go find it on Google myself. I would be interested in any studies that were more extensive, or even of a similar size.

So what study should I search for?

I quoted you the bloodly text and gave you the name of the publication. Do you want the ISBN number too? Believe it or not, most academic studies are not published freely on the web. This lot took me all of 2 minutes to find.

Here...page 72.
http://books.google.co.nz/books?id=w...age&q=&f=false


I like this one. Especially how lane splitting is SAFER than having an arsehole driving too close to your rear tyre.

http://www.motorcyclecruiser.com/str...ort/index.html

Page 26
http://www.dmvnv.com/pdfforms/dlbookmotorcycle.pdf

Page 82
http://books.google.co.nz/books?id=d...age&q=&f=false

Some more:

http://books.google.co.nz/books?id=2...rcycle&f=false


Some good stuff in there about covering brakes when approaching junctions/intersections and flicking brake light on to tail-gators.

[Disco Dan]

ooooooh I can forsee a new episode of Mythbusters from this ! ! !

utter pap this thread is turning into...

[scracha]

Huge list of references at the bottom of this one for ya p.dath

http://www.rospa.com/roadsafety/advi...paper_2006.pdf


TRL research12 shows that the incorrect use of motorcycle brakes is considered to be a factor in many motorcycle accidents. Over a third of riders used only the rear brake and 11% used only the front brake. Even in an emergency, 19% of riders only used their rear brakes and 3% only used their front one. One study estimated that correct braking, using the full braking capability of the motorcycle, could prevent 30% of motorcycle accidents, although this study was conducted before ABS was available for motorcycles.

[The Stranger:Me]

There doesn't seem any point in including lots of samples that took much longer to stop.

Why then include 298 samples?
The 522 samples were excluded for not meeting the selection criteria i.e. the instructions given to riders weren't complied with - in a non emergency situation.
As noted, they were "experienced" riders - unlike yourself, what hope would you have th?.
You don't get to do it again once you just hit the concrete truck.

[beyond]

The GSX1400 simply will not tolerate rear braking when stopping in an emergency or braking hard.

I've learnt from several sideways excursions into the shrubbery on my earlier blue and white 1400 that they do not like rear brake under heavy braking.

As R6_Kid pointed out, when braking hard on modern bikes of the sports or sports tourer style, the rear wheel is not in contact with the ground and therefore the rear brake is useless.....in fact... totally useless.
The 1400 throws a lot of weight forward when braking hard and therefore pulls up remarkably quick with front brake alone.

I have found out the hard way that the rear brake is good for low speed conditions, wet weather braking and hill starts but no good at any other times.
I now use only the front brake as this suits the bike perfectly and this bike can brake well into a corner and maintain a lot of grip.

[boomer]

Pretty sure that they tell you this so that you dot get confused reaching for all the different leavers and knobs while that fkn car is pulling out in front of you.

EFFECTS OF DECELERATION FORCE
The mean deceleration for the group of 298 passes braking from 100 km/h to zero wa -0.898 g in a mean time
of 3.18 seconds. During these more than 3 seconds, the rider had to manage his braking while subjected to a considerable
deceleration force against his arms and hands which must in large measure support his upper body. A
simulator designed to recreate this force would have to incline the motorcycle on its front wheel at an angle of
64 degrees.

they obvoiusly used knob ends like boomer for their tests as most riders know to hold the tank with their knees

ahahhaa and you're a competent rider are you..??! how do you work that out then krasher...???! Bwahahhahahaha

[FROSTY:Me]

Heres the thing guys n gals. EVERY situation is different. EVERY emergency presents issues in a different way.
I can without pause quote situations where heavy front end brakeing made use of the rear brake totally pointless
I can think of situations where less front brake meant the rear brakes efficiency was greatly increased.
I can think of bikes where the weight biase and brake setup mean you have to use both brakes to stop.



Add to that different bikes do indeed need the brakes applied in a different way.

That said The same basic principle still applies.
If you wanna stop --USE THE LOT

and practicing emergency braking on YOUR bike to find how IT stops quickest in ideal conditions is always a great idea.

[p.dath]

...
I quoted you the bloodly text and gave you the name of the publication. Do you want the ISBN number too? Believe it or not, most academic studies are not published freely on the web. This lot took me all of 2 minutes to find.

Here...page 72.
http://books.google.co.nz/books?id=w...age&q=&f=false

...

http://www.motorcyclecruiser.com/str...ort/index.html

Page 26
http://www.dmvnv.com/pdfforms/dlbookmotorcycle.pdf

Page 82
http://books.google.co.nz/books?id=d...age&q=&f=false

Some more:

http://books.google.co.nz/books?id=2...rcycle&f=false

The DSA reference on Google only goes up to page 33.

The motorcruiser article doesn't mention anything about braking first.

The dmvnv talks about using the rear brake.

The "How to ride a motorcycle" book also talks about using the rear brake.

The last article about BMW discusses their antilock braking system.


None of these articles contain research. They don't contain a more extensive study. And they don't support your premise that you shouldn't use the front brake before the rear brake.

They just discuss emergency braking in general, and pretty have similar results to the study I posted.

[p.dath]

The GSX1400 simply will not tolerate rear braking when stopping in an emergency or braking hard.

I've learnt from several sideways excursions into the shrubbery on my earlier blue and white 1400 that they do not like rear brake under heavy braking.

As R6_Kid pointed out, when braking hard on modern bikes of the sports or sports tourer style, the rear wheel is not in contact with the ground and therefore the rear brake is useless.....in fact... totally useless.
The 1400 throws a lot of weight forward when braking hard and therefore pulls up remarkably quick with front brake alone.

I have found out the hard way that the rear brake is good for low speed conditions, wet weather braking and hill starts but no good at any other times.
I now use only the front brake as this suits the bike perfectly and this bike can brake well into a corner and maintain a lot of grip.

There is no disagreement that once the weight has transferred onto the front wheel that rear wheel braking (or changing down) has hardly any impact (especially if your rear tyre is off the ground!).

And I don't think there is any disagreement that the rear brake is only effective for a very short time as a result. I think from memory it reduced the stopping distance by another 3m to 4m from 100km/h.

The only real question is weather applying the rear brake at the beginning of the exercise produces a shorter stopping distance.
Perhaps if it is sliding sideways too much rear brake was being used?

[p.dath]

Why then include 298 samples?
The 522 samples were excluded for not meeting the selection criteria i.e. the instructions given to riders weren't complied with - in a non emergency situation.
As noted, they were "experienced" riders - unlike yourself, what hope would you have th?.
You don't get to do it again once you just hit the concrete truck.

They were trying to test stopping in the shortest distance, so obviously you want to exclude those cases where the stopping distance was much longer.

They also examined which *factors* lead to a shorter stop. So obviously once you are down to that stage it doesn't make sense to consider a stop that doesn't involve that factor.

[FROSTY:Me]

The DSA reference on Google only goes up to page 33.

The motorcruiser article doesn't mention anything about braking first.

The dmvnv talks about using the rear brake.

The "How to ride a motorcycle" book also talks about using the rear brake.

The last article about BMW discusses their antilock braking system.


None of these articles contain research. They don't contain a more extensive study. And they don't support your premise that you shouldn't use the front brake before the rear brake.

They just discuss emergency braking in general, and pretty have similar results to the study I posted.

iN A NUTSHELL DUDE THAT STUFF IS EXACTLY the issue I see with KB at times.
Quote a bunch of articles and stuff without actual personal experience.

If I can find it I will dig out a well researched article that tells you the best way to avoid an accident on a bike. It goes into detail on the best way to lay your bike down so it slows smoothly and with minimum damage on its side. And you know what Im (just) from the generation where that information was actually true.