Looking for a study... -- Emergency Stopping

[leed]

Well, this is vague, and I figured I would ask... After spending the last hour, no luck. Granted, there are tons of articles on this particular subject, but there was one I believe was posted on here..

The topic was Emergency Braking ( or panic stopping, emergency halting, something ambiguous and not direct). Regardless, the focus of the study was braking, with several bikes used (sport, sport tourer, no cruiser I don't think). The conclusion was specific, noting that clutch-in front-braking only without downshifting resulted in the shortest and quickest stop.

I've searched (not so ruthlessly, but painstakingly) through this forum and on Google, with no luck. It provided quite a few pictures as well. I don't think it was NHTSA, and I believe it was a European study (hence the ambiguity of the term for 'emergency stop' ).

If anyone knows what I'm talking about, you are awesome.

[Jinx250]

Originally Posted by leed

The conclusion was specific, noting that clutch-in front-braking only without downshifting resulted in the shortest and quickest stop.

I seriously doubt that was the conclusion.

Try searching "motorcycle stopping distance"

[Alex]

In the Riding Skills sticky at the top of that section, there are several threads dealing with rear braking. A number of studies are linked from there. I don't think any of them matched exactly with your thoughts, but they were close. The difference between using the rear brake or not using the rear brake in a panic stop, given optimal usage of both the front and rear brakes, was a difference of 5 feet at 150 feet of stopping distance.

[kaiserz]

I know there's one here in ninjette. cause I remember printing something out here and practicing in at the parking lot. It was a study made in europe or something and then they translated it in english, I'ma try to look for it and I'ma let you know.

[leed]

Originally Posted by Jinx250

I seriously doubt that was the conclusion.

Try searching "motorcycle stopping distance"

Though there is much variability in the user, this article (not what I was looking for, but came up first) says otherwise:

http://mfes.com/motorcyclebraking.html

Originally Posted by Alex

In the Riding Skills sticky at the top of that section, there are several threads dealing with rear braking. A number of studies are linked from there. I don't think any of them matched exactly with your thoughts, but they were close. The difference between using the rear brake or not using the rear brake in a panic stop, given optimal usage of both the front and rear brakes, was a difference of 5 feet at 150 feet of stopping distance.

Yeah, the thing was the person who posted it, posted it in an obscure thread not directly related. I will have to keep looking, I just figured the person who might have posted it would likely remember it.

Originally Posted by kaiserz

I know there's one here in ninjette. cause I remember printing something out here and practicing in at the parking lot. It was a study made in europe or something and then they translated it in english, I'ma try to look for it and I'ma let you know.

Yeah! See, I'm not completely crazy!

Thanks for all the help though, guys. I'm wasn't sure if this justified it's own thread, so if it does not, by all means move/merge/delete what-have-you.

[NathanF]

Originally Posted by Alex

In the Riding Skills sticky at the top of that section, there are several threads dealing with rear braking. A number of studies are linked from there. I don't think any of them matched exactly with your thoughts, but they were close. The difference between using the rear brake or not using the rear brake in a panic stop, given optimal usage of both the front and rear brakes, was a difference of 5 feet at 150 feet of stopping distance.

Wow! Why is it often said that 30 percent of your braking ability comes from the rear brake then?

[Alex]

People say alot of things.

[LazinCajun]

Originally Posted by NathanF

Wow! Why is it often said that 30 percent of your braking ability comes from the rear brake then?

The harder you brake, the more the weight of the bike shifts to the front, and the more useless your rear brake becomes. See: stoppies

Additionally, motorcycles with longer wheelbases (read: cruisers) don't transfer weight as easily to the front because the lever arm to keep the back end down is longer. TBH I'm not sure if it makes enough of a difference for 30% of the braking power to be in the rear, but it's definitely more useful than on a sportbike.

[blink]

5% is better than no percent...in any case

[Alex]

That 5% isn't a guarantee. It's an indication that getting the front brake right is most critical. And if you screw up the front brake (not hard enough, too hard and need to let it off and re-apply), then nothing you do with the rear will ever get you those feet back. All of this has been discussed in detail in those rear braking threads from the riding skills sticky.

[blink]

Front brake is most critical. If you can't front brake properly in an emergency situation, you will not stop efficiently. So yes, agreed.

[Pyro]

The reason it's not recommend to use the rear is because the lack of downforce on the back also means you can easily lock up that wheel.

Locking up the wheel can take an already hairy situation over the top even if you DON'T hit anything. That gyroscopic effect helps keep you upright, and the traction from the rear helps keep the bike in a straight line.

That said:
If you only get 5% of your breaking from the rear, it can still make a healthy difference... That extra 5% also means you stop in a distance roughly 5% shorter. That's the difference of being at the back bumper of a small car or at the front bumper of a car from 100km/h (60mph)... and the distance you have to travel through the car is MUCH harder than travelling the 40m before the car.

[RaZeDaHeLL]

Have any of you actually locked up your tires from emergency breaking? I've been in a few situation where I had to break HARD and my tires never locked up. I almost always use both breaks. The only time I only use the front break is when I'm going slow and have to be ready to stop quickly... mostly to catch my balance if I have to.

[kaiserz]

It is very easy to lock up the ninjette's rear tire, why? because the ninjette is really light.

here's what I do:

Emergency stop. I close my throttle, I gently apply the rear brake(to slow down, not to stop) while pulling the clutch in and then I use my front brake to stop. I also make sure that I'm at an upright position/straight body and looking forward. I've read this from the study that I found here on ninjette, some guy posted on some thread.

Emergency "slow down" and evade. I use the same technique as my "emergency stop" but I control the clutch and I make sure I'm at the right gear so I can speed off to safety. (I used this technique a couple of times, practicing my emergency stopping skills saved my ass a couple of times from cagers too. )

Slowing down for a turn. I use my front brakes (Like Rossi does)

Slowing down to yield. I use my rear break + clutch control + front break if I need to stop.

@ leed I'm still looking for the thing, but I can't seem to find it.

[NathanF]

Originally Posted by Alex

People say alot of things.

Well, by people I was referring to the MSF, Team Oregon, etc... In fact, looking at my Team Oregon book now, it shows a chart with braking distance at highway speed. It lists 180 feet with just rear, 130 feet with just front, and 95 feet with both.

You're saying that is incorrect, and I probably shouldn't bother with my rear brake in a panic stop? (Which, incidentally is my default tactic - I almost never use my rear brake, but I've been trying to work on using it in the hope that I would be more apt to use both in a panic stop.)

[Alex]

That chart may have some validity for a long-wheelbase heavy cruiser, but it is completely wrong for any modern short-wheelbase sportbike. If you're not bringing the front close to lockup, you're not stopping as hard as you can. If you think you're bringing the front close to lockup, yet the rear end is still weighted down enough that you can apply any significant braking pressure, you're not anywhere close to front lockup.

[alex.s]

i removed one of my front calipers the other day... it was weighing me down... plus the rear brake is cooler anyway

[Pyro]

Originally Posted by NathanF

Well, by people I was referring to the MSF, Team Oregon, etc... In fact, looking at my Team Oregon book now, it shows a chart with braking distance at highway speed. It lists 180 feet with just rear, 130 feet with just front, and 95 feet with both.

You're saying that is incorrect, and I probably shouldn't bother with my rear brake in a panic stop? (Which, incidentally is my default tactic - I almost never use my rear brake, but I've been trying to work on using it in the hope that I would be more apt to use both in a panic stop.)

That sounds closer to what I heard as well and closer to 30% rear then.

[LazinCajun]

Originally Posted by Alex

That chart may have some validity for a long-wheelbase heavy cruiser, but it is completely wrong for any modern short-wheelbase sportbike. If you're not bringing the front close to lockup, you're not stopping as hard as you can. If you think you're bringing the front close to lockup, yet the rear end is still weighted down enough that you can apply any significant braking pressure, you're not anywhere close to front lockup.

+1. Next time motogp is on, watch rear tires carefully as they brake hard. They will often lift off the ground slightly -- not much grip is available to a tire in the air.

[Pyro]

Originally Posted by LazinCajun

+1. Next time motogp is on, watch rear tires carefully as they brake hard. They will often lift off the ground slightly -- not much grip is available to a tire in the air.

That's motogp with warm super-grippy tyres on very good surfaces, but to be fair a shorter wheelbase would reduce rear grip under hard braking, yes.

[LazinCajun]

Google "ninja 250 stoppie youtube" and I'm sure you'll see it's no problem

[Pyro]

Originally Posted by LazinCajun

Google "ninja 250 stoppie youtube" and I'm sure you'll see it's no problem

Can't you sit back further to get the centre of gravity further back? This should allow you to get more force onto the road without lifting the tyre.

[Toly]

Originally Posted by RaZeDaHeLL

Have any of you actually locked up your tires from emergency breaking? I've been in a few situation where I had to break HARD and my tires never locked up. I almost always use both breaks. The only time I only use the front break is when I'm going slow and have to be ready to stop quickly... mostly to catch my balance if I have to.

Eve, if you haven't locked the rear wheel, you weren't braking hard enough. In fact, it's very easy to do. For instance, grab both brakes hard at 25mph going downhill Just be careful...

Last year I had the same idea as you in terms of approach to braking, until it started biting me hard later, at higher speeds. I now use front brake only - not having to worry about rear locking up saves precious concentration in an emergency. Now I use rear brake mostly in slow-speed turns and when coasting to a stop light... We should go for a ride soon.

[Alex]

Originally Posted by Toly

Eve, if you haven't locked the rear wheel, you weren't braking hard enough.

I'm not sure I follow here? The goal isn't to lock the rear wheel; once that happens it's foreseeable that the stop will take much long er as you have to concentrate even harder keeping the bike upright while now modulating the front. If you choose to use the rear in an emergency stop, you need to be sure that you in fact won't lock it, right?

[Pyro]

Originally Posted by Toly

Eve, if you haven't locked the rear wheel, you weren't braking hard enough. In fact, it's very easy to do. For instance, grab both brakes hard at 25mph going downhill Just be careful...

Last year I had the same idea as you in terms of approach to braking, until it started biting me hard later, at higher speeds. I now use front brake only - not having to worry about rear locking up saves precious concentration in an emergency. Now I use rear brake mostly in slow-speed turns and when coasting to a stop light... We should go for a ride soon.

Had it today again

To be fair, I was lane-splitting on broken lines. Car to the right of me changed to the left without indicating, so I got on to the brakes. Rear did an S-shake, although I suspect it hit the painted line as well.

While splitting I often have my foot on the brake and have my hand hovering on the other. Might not be much, but even a foot might be enough to make a difference.

Didn't even touch the horn, but the car to my left climbed on his as he had to get on the brakes as well and he hammered out a few notes.

[Alex]

Originally Posted by Pyro

Might not be much, but even a foot might be enough to make a difference.

But if you're locking the rear, you're not gaining a foot. Once sliding the coefficient of friction goes right back down. You need to be able to manage both brakes without locking either when trying to stop, and it sounds like you're using too much pedal.

[alex.s]

but sliding your rear looks so coooooool!!!

[Pyro]

Originally Posted by Alex

But if you're locking the rear, you're not gaining a foot. Once sliding the coefficient of friction goes right back down. You need to be able to manage both brakes without locking either when trying to stop, and it sounds like you're using too much pedal.

Without sliding I could gain about 2 feet. If the rear start sliding I could still save a foot. But yes, I'm sure I was overeager on the brakes. You only brake for slightly more than a second at that speed, so I didn't get a chance to think about things

Also - You'll lose the most of the useful gyroscopic effect at about 15mph, and that's reached in less than half a second at slow speeds.

---

Taking it in a different light, if my front touched paint, and my rear didn't, I at least would've had braking force on the rear although I might've wiped out the front

Braking with just the front wouldn't I have an even higher chance to wipe out if I lose traction on the front? Braking on the rear at least 'pulls' the back of the bike swinging the front towards the direction of motion.