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Emergency Braking for Motorcyclists

Very little causes more confusion in my beginner motorcycle classes than the subject of braking. Topics we frequently discuss:

Weight shift and the effect on traction

Let's try an experiment. Picture a motorcycle tire on the pavement. Not the wheel, not the entire bike, just the tire standing upright. Take hold of it and try to slide it across the pavement. It slides pretty easily. Now ask your assistant to stand on the tire, and then try to slide it. Much harder to slide, right? In other words, the tire has a lot more traction now. If you add the weight of two or three people, it gets harder yet.

So what we've seen is that there's a relationship between weight and traction, and it is this: More weight, more traction.

A motorcycle in operation has a certain weight distribution, as designed by its makers. Suppose now some BDC (BDC is a technical term used by motorcyclists; it stands for "brain-dead cager") jumps out in front of that bike and rider, and the rider gets on the brakes. What happens to the weight of the bike? It shifts forward, toward the front tire. And in keeping with our earlier discovery of the relationship between weight and traction, the traction at the front tire increases and that at the rear decreases. So the result is that the rider can now use more front brake than he could an instant before, before the weight had transferred. If he does use more front brake, then still more weight shifts forward, raising the traction at the front still more, which enables still more front brake to be used.

Now you can see why the front brake is so much more powerful than the rear, why my Bandit has two large disks on the front and a single small disk on the rear. It's simply a response to the fact that matter has inertia, that is, that when you try to stop something, weight shifts forward.

Why use both brakes?

Ok, so the front brake is more powerful than the rear due to laws of physics. How much more? The Motorcycle Safety Foundation's student class materials say that about 70% of a motorcycle's braking power is at the front brake. I think that's a gross underestimate. Have you ever seen a sportbike stopping so fast that the rear tire is in the air (a "stoppie")? How much of that motorcycle's braking power is in the front? Right, 100%.

Now that's not a reason to ignore the rear brake for several reasons. In the first place, only a short and light motorcycle will loft the rear tire; a cruiser, for instance, is too heavy and too long to do that. The rear tire will always be on the ground with some weight, and hence some traction, on it. Furthermore, even on a short light sportbike, it takes significant skill to do it. Contrary to what a lot of my students think, just grabbing the front brake will not cause the rear tire to rise; it'll cause the front tire to skid and dump you.

Still, though, the front brake has far more power than the rear, so why use the rear at all? That's pretty simple: In an emergency, are you going to be satisfied with 70%, or even 95%, of your braking power? Not a chance. If both tires are on the pavement then they both have some traction. In an emergency, use it all.

Ok, I will, in an emergency. How about that routine stop at the traffic light? I don't need 100% of my braking power there; maybe more like 5%. Do I need to use both brakes there?

Yes, you do. It's a matter of habit, of being prepared for the emergency. If you routinely use just one brake, when the BDC stops in front of you, what are you going to do? You're going to do what you always do, that's what. So I insist that my students always make flawless stops: Both brakes. Right foot stays on the brake all the way to a stop, with no paddling at the end. Be in first gear by the time you stop. Do it right every time, so you'll do it right when it counts.

Shifting too?

Yes, shifting during the stop too. Consider: The same light weight that makes your motorcycle accelerate faster than other vehicles on the road, allows it to stop faster than other vehicles also. So in that emergency, you'll be able to stop much more quickly than you would in a car, and thus avoid hitting the BDC. Good deal — until you hear the squeal of the sliding tires behind you. Now you have another emergency, and this one requires you to get out quickly. No problem — IF you're in first gear. So BE in first gear. Do not be caught dead in second gear. Shift to first gear during the stop, every stop.

How many times to downshift? 13 should be enough. Seriously, if you think you're in third gear, don't be satisfied with two downshifts. You might have lost track and be in fourth gear. You might not hit the shifter hard enough and go to neutral. Keep shifting down until you know you're in first gear (because it didn't shift again at that last press), and then shift down twice more. Do not be caught dead in second gear.

I'll just use engine braking so I'll stop even faster!

Everyone knows that just getting off the throttle will cause you to slow down. Anyone who's driven a vehicle with a manual transmission knows you can get a greater effect by downshifting first. But I didn't say anything about it in my emergency braking discussion because it isn't effective. Consider that engine braking works on the rear wheel. If you want more braking from the rear wheel, then just press on the rear brake pedal a little more. That's simpler, smoother, and more precise than pausing in your shifting to first gear (because you aren't going to be caught dead in second) and releasing the clutch. And simple, smooth, and precise are things you want in motorcycling.

I'm not going to tell you I never use engine braking. If I need to downshift for a turn, it may be true that just easing out the clutch will give me all the braking I need for the turn. But in general, I use the brakes for braking, and I use the engine to go.

Emergency Stop!

So let's put all this together. How do you stop in the shortest possible distance? You use both brakes. You use progressively increasing pressure on the front brake, to use the increasing traction at the front as the weight shifts forward. You use light pressure on the rear brake; there isn't much traction back there because so much of the weight has shifted forward, but there's some, so use it. You squeeze the clutch and you tap on the shifter, without counting the taps, until your left foot has to go down just before you stop.

And how does this differ from a routine stop? Only in the amount of pressure used on the brakes. Everything else is the same, must be the same, because you want it to be automatic in an emergency. The only way to make it happen automatically is to do it the same way every time.

In the ultimate emergency, I'll just lay it down.

You mean you'll crash? Why? Wouldn't you rather avoid crashing? Do you think motorcycles stop faster on their sides than on their tires? This makes no sense. Tires have better traction than plastic and chrome. Keep the motorcycle upright and use the brakes, or swerve around the problem.

What about braking in a curve?

The problem with braking in a curve is that some of your traction is being used in turning the motorcycle. That part of the traction hasn't disappeared, but it's unavailable to you for braking. One option is to brake, but more gently than you could if the motorcycle were straight. This is what you'd do on a curving off-ramp with a stop sign at the end. Just use the brakes gently to come to a perfectly routine stop at the end of the ramp.

The problem comes when you need to brake hard while you're turning; maybe there's a dead deer in the middle of the road part way through the turn, and when you see it you're leaned over, going fast, and using up much of your traction keeping the motorcycle turning. Your best option might be to get the motorcycle upright as quickly as possible, which will make that turning traction available to you again, and then use it in a maximum straight-line stop.

By the way, if you can't get stopped before you hit the dead deer, then you made another mistake before you entered the turn: You entered too fast. If you can't stop in the distance you can see, you should seriously consider slowing down until you can.

Swerving and braking

The discussion on braking in curves applies to swerving also. A swerve is just a hard turn to avoid something, like a shovel that fell out of the truck in front of you, followed by another hard turn to straighten up again. In those two hard turns, your traction may be used to the limit; don't ask for yet more traction from the tires by braking also. Brake first, then get off the brakes before you swerve; or swerve, and then get on the brakes after you're straight.