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| From the Desk of the Chapter EducatorIntegrated
Braking By
James R. Davis, Master Strategy Group If,
when you apply your rear brake, your motorcycle also applies front braking for
you,then you have some form of 'integrated braking.' In the case of the Honda
GoldWing, there aretwo front disc brakes and one rear disc brake. One of the
front brakes is independently controlled by the front brake lever while the
other front brake and the rear brake are bothactivated by the rear brake pedal. Some
people do not understand why integrated braking exists and are of the opinion
that they are unsafe. There are some who actually disable (or want to) this
function and tie the two front brakes together so that they are both activated
at the same time and exclusively by the front brake lever. The reason they do
this is NOT in order to increase the amount of braking force they can employ on
the front wheel, but in order to prevent using any front brake force at all
under certain braking conditions. In other words, they want the ability to
selectively use either their front or rear brakes, or both. This, because they
fear that integrated braking increases the odds that on slippery roadways they
will lock the front wheel with the resulting dumping of their bike. This is a
common concern by those that have had no experience with integrated braking
systems, but is, in my opinion, an exaggerated concern. Let's
get something out of the way right up front - there is NEVER a time to
aggressively use your REAR brake. It is the most dangerous control on your
motorcycle because it is so easy to abuse. Under severe braking weight transfer
results in far more load on the front tire than on the rear one. What that means
is that it takes far less braking force to lock the rear wheel. Let's say, for
arguments sake, that 70 percent of the bike's weight is on the front tire and 30
percent on the back one during a severe braking event, and let's also
assume that your bike weights 1,000 pounds with you on it. In this case if you
applied about 300 pounds of braking force to the rear wheel it would be close to
sliding. Your
integrated braking system (at least in the case of a GoldWing) is setup up such
that when you apply 300 pounds to the rear brake something between 200 and 250
pounds of braking force is applied to one of your front brakes. (This is because
the size of the piston in the integrated front brake is smaller than the piston
in either of the other two brakes as well as the pistons in the master
cylinders.) Since there is 700 pounds of load on the front tire, it is clear
that the integrated braking system cannot cause the front wheel to lock by
itself. On the other hand, if you didn't use the front brake lever at all in
this condition, you have applied only a total of less than 550 pounds of braking
force (300 + up to 250) and that is not enough to have caused a weight shift
resulting in 70% being on the front tire. In other words, you had to use the
front brake as well in order to be in a 'severe braking' condition. Let
me review for a second: Braking causes a weight transfer towards the front. If
you do not lock the rear brake, you CANNOT lock the front brake unless you also
aggressively use the front brake lever. So, if you lock the front wheel you do
so with the front brake lever, not the rear one. If
you agree that it is NEVER appropriate to aggressively use the rear brake, it
becomes only marginally important when stopping aggressively. (Though that
margin could be the difference between life and death). So,
integrated braking should be viewed as providing an added safety margin when you
need to stop aggressively. Whether the surface is dry or wet, the relationship
between the two integrated brakes is the same and what has been said so far
remains true.
What if,
however, you overuse the front brake while using less rear brake than would
cause the rear wheel to lock? Then it is entirely possible to lock the front
wheel. This possibility is apparently what concerns inexperienced users the
most. I assume, because virtually all motorcycle riders know better, that you do
not employ 'severe braking' while your bike is leaned over in a curve. That is,
you straighten the bike up before you grab the binders. If that is the case,
then what is the consequence of locking the front brake? A slide that you can
abort by simply releasing some of the front brake pressure. Since your SPINNING
rear wheel provides gyroscopic stability for the majority of your motorcycle,
(meaning you have not locked the rear wheel, just the front one), then your
sliding front tire will not immediately dump you to the ground as it would if it
were sliding in a turn. In other words, you have time to release the front brake
to recover. Most people, once they learn that the rear brake must never be used aggressively, are far better off having integrated braking than not because of the marginal increase in stopping power it provides. But there is a time when they can get in the way. If you are driving at slow speeds on slippery surfaces (such as on a gravel covered parking lot), then the combination of both front brakes being used can cause the front wheel to lock easily. That is, since we are not talking about 'severe braking', then there is minimal weight on the front tire at this time and it is easier to lock that wheel. If going in a straight line you can save the situation by simply releasing the front brake, just as before. But when you are driving on a parking lot it is not unthinkable that you are making a turn or two, and if you lock that front wheel when it is not dead center, you will dump the bike. So,
should you disconnect the integrated brakes to prevent a parking lot dump? NO!
Just don't use your front brake lever in this case. As we discussed, your rear
brake lever always applies more braking force to your rear brake than it does to
the integrated front brake. If you do not lock the rear wheel with it, you will
not lock the front wheel either. Finally,
it is NOT true that just because you have integrated braking it is impossible to
apply rear-wheel braking without getting some front-wheel braking. How so? Just
use engine braking rather than your rear-brake pedal.
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