I think it's possible that off-road braking is significantly different than road braking. In off-road braking, you could easily exceed the traction of the front wheel and cause it to start skidding; at that point you've certainly lost your most effective braking; sliding friction is a fraction of static friction. With a loose surface, you absolutely want to use both brakes and de-emphasize the front brake, because you need square inches on the ground to provide traction to brake with.

The same would be true on any surface where the front wheel's traction was not sufficient when braking to lift the rear wheel from the ground; gravel roads, wet pavement, snow, ice, etc. In fact, on ice and loose gravel or sand, it can be very dangerous to use the front brake at all. However, once you get to the point where you've got so much traction on the front wheel that you can flip the bike over it, I don't really get how the physics could support anything but maximum braking on the front wheel, just to the point where there's hardly any contact on the rear wheel. If I'm braking 90% front, and 10% rear, and I increase the front braking power a bit so it's 100%/0%, and I still have not started skidding the front tire, I don't believe that I'm slowing down SLOWER than I was before I increased the braking power on the front.

It certainly is not a good idea to go all the way 100%/0% in almost any situation though, since you'd have almost no control left. But if I'm anywhere near that, I'm going to let go my rear brake, because the rear wheel would skid with almost any brake pressure when that much weight had shifted forwards, and I do NOT want either of my wheels skidding in emergency situations; skidding = loss of control and much less traction.

I am not insisting that I'm right, but I can't visualize how the physics would support the partial-rear-brake balance as stopping faster. I'd like to see the study, or if someone wants to draw up the force vectors of the two situations, I'd be very interested.

Applying some pressure on the rear brake can also help maintain control of the bike if you are swerving sharply while braking. Although that seems pretty instinctual.

I would offer only statistics - as in only a fraction of the time will 100/0 braking be achieved, and an even smaller fraction where it is done safely and correctly. However, 80/20 or even 90/10 can be achieved a lot easier, repeatably, and with confidence. Therefore, training riders in keeping both wheels on the ground using mostly front braking will cause better results and shorter stopping distances as a whole.

This would not benefit those riders who are at the very edge of the bell curve who can brake and handle a lot better than most - just like the motorcycle racers demonstrate when they lift the rear wheel slowing down at speeds over a hundred miles an hour. However, asking your average middle aged Harley rider to practice a stoppie would keep the emergency rooms full all summer. The MSF (Motorcycle Safety Foundation) taught that motorcyclists were widely afraid to use the front brake. Just getting the average rider to go to 60/40 or 70/30 made them incredibly more safe than relying on the rear brake primarily. My Honda goldwing is so large (900 + pounds) that the rear brake can not be activated independently - hit the rear brake and one front brake gets squeezed as well, maximal braking requires both front and rear simultaneously by design. I have yet to see any data or references for bicycle riders, and have no idea how many apply what brake and to what extent, nor how the lighter bicycle/rider system and slower speeds affects things.

I think that the difference between 90/10 and 100/0 might not be all that large anyway, so having either skill would be considered darn good braking.

Interesting about the interlock on the Gold Wing. Do they make a point of telling you that when you buy one? (Just wondering.)

i agree with others practice and use the front brake. if possible get a buddy and an empty parking log. have them bump into you at slow speeds and higher speeds. practice making bank turns, hairpin turns, picking up water bottles and being able to bunny hop them.

in the last month i've had to make alteast 3 emergency stops. just yesterday a car almost right hooked me merging into the bike lane just 4 feet infront of me when i was going 17mph into a business parking lot. i applied my front brake and rang my bell served into part of the right lane, then shouted cause they didn't seem to notice. it wasn't a textbook emerceny monover, but i felt i did an ok job. if you want to get better practice and ride more.

and yes the front brake has twice the stoping power as the rear brake. i almost never use my rear one

David Wilson, Bicycling Science , around page 230 (I don't have my copy with me right now).

The numbers I was citing comes from Bicycling Science (referenced elsewhere) and apply to road conditions. Mountain bike conditions were used as an example of the most extreme braking situation I can think of. A sliding front wheel is just as disastrous on- or off-road. It is a situation that few, even with superior bike handling skills, can recover from.

Your comment (emphasized above) could be used for dry pavement as well. That is the absolute best braking situation you can find yourself in. Both wheels are at the maximum of adhesion and your brakes are operating at their maximum efficiency. Remove one from the equation...by not applying it...and you reduce the overall braking capacity of the system. Why would you do that?


First, I'm not saying that you should use your brakes in a 90/10 or any other kind of ratio. The maximum deceleration a bike can achieve without going over the front wheel, according to Bicycling Science, is around 0.5g to 0.56g with a seated rider. 90% of that deceleration comes from the front wheel. But 10% comes from the back wheel. Remove the rear wheel from the equation and the overall maximum deceleration has to decrease.

The maximum deceleration point of the system isn't when the rear wheel lifts off the ground and the rear wheel starts to skid. The maximum is reached when both wheels are contributing the most to the overall deceleration. That's when both wheels are in contact with the ground. That holds if the pavement is dry, wet, icy, or nonexistent - i.e. dirt

That's why mountain bikers release pressure on the front brake. Pitch over is the point where the front wheel is about to stop, i.e. skid. Releasing pressure on the front brake transfers weight back to the rear wheel, puts it back in contact with the ground and increases the overall deceleration. In other words, you stop faster.

Weight shifts also effect this weight transfer...and is, again, something that mountain bikers learn early on. A tandem, for example, has a maximum deceleration around 0.8g. All of the extra deceleration ability comes from the extra weight over the rear wheel. Moving your center of gravity back and down while braking, can increase the rear wheel's ability to stay in contact with the ground and provide more braking power. It works very well in high angle descents on a mountain bike and it's much more effective on level pavement.

Think of it this way: Two riders using identical force in identical situations braking under maximum deceleration. Neither rider is allowed to skid the rear wheel and, for safety sake, both wheels remain on the ground. Rider 1 uses only the front brake. His deceleration is around 0.5g. Rider 2 uses both brakes. His deceleration is going to be 0.5g on the front wheel and 10% of the deceleration of the front wheel on the back wheel or, overall, 0.55g. Not a huge amount of deceleration but Rider 2 will stop a little sooner than Rider 1.

Now let's let the rear wheel come off the ground. Rider 1's deceleration is the same, 0.5g. Rider 2's deceleration goes from 0.55g to 0.5g (neglecting the slight amount of friction from the sliding tire). Their deceleration is now the same and the stopping distance will be the same. If both riders, with the brakes applied, shift their weight rearward, the tires will come back in contact with the ground and Rider 2's deceleration will increase. Rider 1's will remain the same.

Now try releasing pressure on the front brake. Rider 1's bike will come back in contact with the ground but his overall deceleration will remain close to the same, minus what amount he had to give up to keep from doing a pitchover. Rider 2's bike will come back in contact with the ground minus the deceleration needed to prevent a pitchover but his rear wheel is providing deceleration again and his deceleration is higher than Rider 1's. He'll stop sooner.

I can't think of a situation where losing the rear brake's contribution, albeit minimal, to the overall deceleration of the bike is a detriment. As long as the wheel is rolling, the braking power it adds is significant enough that I'll use both brakes in all situations. I do adjust for extremely slick conditions with more bias towards the back, however

The emergency stop, quick stop, or panic stop, depending on what you want to call it, is one of the avoidance drills taught in the LAB traffic skills courses. It's a skill you need to learn and practice, because as you've apparently found out, when you need it, you need it badly ;-)

For all bikes, the braking power of a wheel is directly proportional to the amount of weight that the wheel is bearing. When you're just riding along, your weight is fairly evenly distributed between the front and rear, with maybe a little more to the rear wheel.

When you and your bike are traveling forward, due to your momentum you will slow down only if something pushes back at you from the front. The brakes cause the road surface to push back on the tires, and that push slows the bike down. Because you are up higher on your bike, and the push is down at the road surface level, while the push slows the bike, the rider’s momentum tends to keep him or her moving forward, shifting weight forward to the front wheel.

The stronger the braking force, the more weight is shifted forward. If too much braking force is applied, the weight on the rear wheel is lessened to the point that the wheel loses traction, and tries to come up instead of pushing down on the road, and since there is nothing to hold the rear wheel down, the back end of the bike comes up and the rider is launched over the handlebars.

What you want to do is to use both front and rear brakes, and keep the rear brake from losing grip and tossing you over the bars.

When you're just rolling along and need to do a panic stop, here's what you do:

Squeeze both the front and rear brake levers -- the front brake about two to three times harder than the rear. As the bike slows and your weight shifts forward, most of your braking power is going to be in that front wheel. At some point, you'll feel the back wheel start to skid, or even start to come up off the road, because it's no longer bearing much weight, and has lost traction. That's a signal to let up a little on the front brake until the back wheel no longer skids.

To help the matter. level your pedals. stand up, and thrust your butt back off the saddle and over the rear wheel to shift your weight back. This is where some experience mountain biking really helps, if for no other reason than mountain bikers find themselves needing this little trick more often than road riders. A good rider can put his belly button or his chest over the saddle and really shift that weight to the rear.

As soon as you slow down enough, unclip one foot and put it down when you stop. Depending on the situation, you might need to come to a full stop, or you may find it safer to use the panic stop to slow down significantly, and then do a quick turn to avoid whatever it was that caused you to brake in the first place.

It's a good skill to practice... get out in a vacant parking lot somewhere and practice coming to a stop as quickly (and safely) as you can from your usual cruising speed...

Tom

I have an odd but effective stopping-on-a-dime routine. I don't know exactly what I do mechanically, but I think I can explain what happens.

Basically, I nail both brakes and unclip from the pedals all at the same time. I then somehow plant both feet firmly on mother earth while locking front wheel, so nothing moves. The sass end of the bike lifts up behind me and comes to a stop when it hits me in the back.

Like I said, I have no idea how I do this; it's all automatic. It works like a champ, but I am a little concerned that I might do damage to my back or knees with this technique.

That's almost a controlled bail-out rather than a panic stop. You're just hucking the bike behind you rather than trying to leg-over. (If I'm picturing it correctly...you wind up standing on both feet, mostly off the saddle with the handlebars around your thighs/knees somewhere?)

Pretty much what everyone else said... I don't let my wheels get locked up, and I use both brakes in balance to get maximum stopping power.

A biggie that some faster riders around here don't realize tho... you need to look ahead just as far on a bike as you would in a car, or even further. You can't avoid all emergency stops that way, but it does help. Coasting a bit or using a lower cruising speed can eliminate a lot of emergencies too. Around here, some of the major arteries have light timings where the main road has long enough lights that a 15mph rider won't have to stop, and pushing to 20mph can mean a lot of sudden stops. (there are roads that are just the opposite too of course)

Yep, completely off the saddle, bars at...call it, mid-thigh.

As you can imagine, I feel a lot of impact force through my legs and thighs when I do this. I am currently working on another method which keeps my butt int the saddle, but the other day, when I E-stopped, I noticed that I went right back to my Semi-Bailout technique.

Yes, I used to do that a lot as a kid. I don't do it so much anymore as most of my current bikes have very little standover clearance. So I get hit a little lower. Ahem.

I know what you mean about the force you absorb in the legs/knees and back too. It's probably not the best technique. If ski injury rates are any indication, it's probably worse for you as you get older.

The joys of hydralic discs.

Btw, as the hydralic discs may suggest, I am a mountain biker, and was on a mountain bike, and as such can get my weight so far back I can get virtually sit behind the rear wheel. May have something to do with my my front wheel skidded, althought I don't recall going THAT far back.

Also, curiosity again, why is locking the front wheel so much worse than the back? I can understand if it gets airbourne and comes slamming back down when locked up hard, but why is skidding it so bad?

All this stuff people are saying though, I was kinda after actual stories, I'm wondering if you actually end up doing a perfect textbook stop when your about to go headlong into a stream of traffic or if something else takes over, and what generally ends up happeneing.

disaster averted by controlled skid into an embarrassing, graceless sideflop, followed by incoherent fist-shaking and then nervous frame inspection.

Locking the wheels is always a bad idea. You just switched from static friction to sliding friction, so you're getting a LOT less braking power, plus you just lost control. You're putting your feet down instinctually because you just gave up all other control of the bike. If you'd keep from locking the wheel in the first place you probably wouldn't have to put your feet down, and you'd stop faster too.

I didn't have to put my feet down. I know that a locked wheel slows you down less, but why is the front worse than the rear?

Typically I pull hard on both brakes. My rear wheel may or may not start skidding. I approach the cause of the stoppage at an angle so that if I must I can go around.

I haven't read every single word posted here,but just wanted to make sure the point was made to brake as hard as possible as early as possible. Don't wait until you realise you're not going to stop in time before you apply maximum braking. Several articles from the motorcycle world discuss this and explain that the earlier you start to brake,the lower your speed,and the more time/distance you have to maneuver.

That's probably the most useful thing I've gotten out of this thread.

Also, there's no way the OP or anybody else locked up a front wheel on dry pavement short of sticking a pump in the spokes. Might seem like that when you're skidding out of control, but it doesn't happen.

As neteon said, this is the single most important piece of advice in this thread.

To throw in my two cents, the very fastest way you can possibly stop on an upright bicycle is by sitting the furthest back on your seat and applying the front brake until the rear wheel barely begins to lift. That is putting a huge amount of normal force on the front fire due to the torque from braking, so unless there is lose ground you really aren't going to be losing traction. If you want to use the rear brake you have to let up on the front.

I've only braked like that twice, and honestly it's because I wasn't paying enough attention. The other posters have mentioned that you want to keep the rear wheel on the ground so you can brake with it and I completely agree - not because it helps you stop faster (though the difference in stop distance would be really close) but because you have more control over the bike with both wheels on the ground.

Generally, with two wheels you can either turn hard or brake hard, but not both.

Yep: Brake early and often.

This is the truth of the matter, you just have to get out there and do it. We can tell you how to kick a soccer ball but until you actually do you are still without enlightenment.

Trust me on this, the front wheel was no longer turning. I did have knobblies on though, and maybe my weight was further back than I realised.