Motorcycle Brakes Their Real Job Is NOT To Stop - it is to SLOW the bike
By: James R. Davis
For some reason most motorcyclists seem to think that the job of brakes is to stop their motorcycles. Wrong!
If all the brakes had to do was stop you then all they would have to do is lock your wheels when you applied them - clearly not an optimum use of their enormous power. Indeed, from a safety point of view more often than not your challenge when using your brakes, particularly the rear brake, is to prevent the wheel from stopping (locking)!
By far the most important job of your brakes is to SLOW you down. In other words, your brakes are a negative accelerator. Unlike your throttle, you can vary your speed all the way from the bike's top speed to zero without having to shift gears - in less time than it took to get from zero to that top speed. This demonstrates pretty easily that they are far more powerful than your engine. Yet if used properly, they can be just as subtle in controlling speed as your throttle and clutch lever combined.
Since you can generate nearly 100% of your stopping power with the front brake on almost any contemporary motorcycle (meaning that you can reduce traction of the rear wheel to zero via load shifting), there is a pretty strong argument that can be made that you should focus your entire braking attention to the task of using it and ignoring the fact that you even have a rear brake. I would not go that far, however.
The use of both brakes together will invariably slow you down more quickly than using just one of them.
The use of both brakes together results in LESS weight transfer than does using just the front one. (Assuming equal total braking force applied.)
Use of both brakes tends to lengthen the life of your front brakes.
If you need to stop or slow down on slick or gravel surfaces, the rear brake is just the ticket (in combination with a very gentle hand on the front one.)
If you are going less than 20 MPH then both brakes are effective (and relatively safe.)
In very slow maneuvers, the use of the rear brake alone often provides added stability and control of your motorcycle.
The most dangerous control you have on your motorcycle is your rear brake! This, because it is easy to STOP (your rear wheel) with it. The Restoring force produced by a moving motorcycle's front-end trail reacting to a change in steering angle is what provides the majority of your bike's stability. However, the gyroscopic effect of a spinning rear wheel is imposed on the frame of the motorcycle and substantially determines the attitude/stability of the entire bike except for its relatively insignificant front-end. To lock the rear wheel is, by definition, to remove a substantial amount of its attitude control and stability.
For this reason I am amazed that the MSF continues to provide a field exercise ('Controlling a rear wheel skid') to its students that invites them to harshly activate their rear brake only and skid to a stop. [Any bike that has integrated braking in any form is not required to do this exercise at all.] Surviving a rear brake lock at the modest speeds used in the exercise (less than 20 MPH) may well lead some students to the mistaken conclusion that they can recover from same at any speed. Still, the MSF goes out of its way to tell their students that use of the rear brake only is NOT a normal or recommended stopping procedure - but they fail to explain why not.
Yet another exercise they have the students perform is to stop (without locking the wheel) by using only their rear brake. This is one of three exercises designed to demonstrate that the use of both brakes at the same time is more efficient than using either one alone. It would be entirely sufficient to show how using both brakes together is more efficient than using the front brake alone. The first part of the exercise, which has the students apply their rear brakes only (but not so aggressively that they lock them), is simply too easy for a newbie to misunderstand to be just one more reasonable habit to develop - after all, "the MSF showed us how to do it."
During a panic situation your attention must be directed to the aggressive use of your front brake and at that time heavy application of the rear brake will almost certainly result in loss of control.
There is NEVER a time while riding a motorcycle that harsh use of the rear brake is anything but dangerous and wrong-headed.
And while harsh use of the rear brake, ever, is dangerous, there is one thing that is dumber still - using your engine to 'assist' during a panic stop. Your engine is NOT A BRAKE! Further, it only affects the rear wheel which we have already seen is easily stopped (locked) with even modest rear brake usage by itself. (In other words, during a panic stop situation you want your clutch lever pulled all the way to the grip. In no way is this to be taken as a suggestion not to use normal engine braking resulting from throttle roll-off.)
Use of the rear brake requires a gentle, controlled touch - EVERY TIME!
Copyright © 1992 - 2012 by The Master Strategy Group, all rights reserved.
(James R. Davis is a recognized expert witness in the fields of Motorcycle Safety/Dynamics.)
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