How fast can you stop. Have you tried?

[Dean]

does the GN250RR go to 60 ??

the gn250rr which i proudly own can go up to 140 mate

[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:Me]

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:Me]

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:Me]

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? (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.