Sliding Rear Wheel
Brake NOT
Locked
It has been
said here (exhaustively) that I consider there never to be a time
when aggressively using the rear brake makes sense. I have used as
my argument the high likelihood that should you do so you will
probably lock the rear brake and, if you then release that brake
(and sometimes without releasing it), potentially cause a highside.
That your
rear wheel, if spinning, provides gyroscopic stability for about
80% of your motorcycle has also been repeated several times. Thus,
if you lock your rear wheel you have by definition made your bike
essentially unstable.
But what I
have failed to discuss is how to handle a rear-wheel slide if you
have not stopped its spin. For example, assume you are in a curve
and you encounter some sand that causes your rear tire to break
away. What do you do about that? Is all lost? Must you end up
riding the ground instead of your motorcycle as a result?
First, I
want to make a few comments that might seem out of place in this
discussion.
Your motorcycle, more times than not, attempts to correct
instability by itself requiring NO INPUT WHATEVER from the
rider.
Virtually
all riders know that if a bike begins to slide in a turn you
should turn your front wheel in the direction of the slide. What
too few riders seem to know is that *YOU* don't have to do
anything and the bike will, of its own accord, turn the front
wheel in the direction of a slide. Your only real job is to not
inhibit that self-correcting effort by the bike.
Should you
try to 'steer into the slide' and either over- or under-shoot the
amount of turn required to offset the slide you place the bike
into an even less stable configuration. In other words,
over-controlling is dangerous.
Similarly,
over-reacting to a bit of instability almost invariably makes
things worse. When you ride over rain grooves and your front-end
becomes squirrely, if you put a death-grip on your handlebars you
merely cause the instability of the front-end to be broadcast
through your arms into the rest of the motorcycle. If your
rear-end squirts briefly to the side (slides) while in a curve,
corrective action on your part can turn it into a disaster just as
easily as it might 'cure' the problem.
While the
rear wheel continues to spin there is essentially no danger that
your bike is going to fall down - gyroscopic forces are
tremendously strong. Further, unless your slide is the result of
hitting an oil slick or ice, you have not LOST traction, just
diminished it. You are still able to accelerate (or VERY MODESTLY
decelerate) while in a slide.
And though
it certainly feels like centrifugal force is attempting to push
you away from the center of a curve, in fact what it does is
attempt to make you go in a straight line tangential to that
curve.
Thus, as
your slide progresses there is less and less centrifugal force at
play. That means that more and more traction is becoming available
to the tire. In other words, if you do NOTHING (other than allow
your front-end to steer itself in the direction of the slide), the
odds are overwhelming that the slide will end of its own accord.
There are
three things that you could do:
Slow down - WRONG, WRONG, WRONG - this causes weight transfer to
reduce what traction you have left and the bike will almost
certainly end up on its side.
Nothing but allow the front-end to steer itself into the slide -
works most of the time and requires no skill whatever.
Modestly accelerate - increases rear-wheel traction and shortens
the slide - but requires a gentle touch (skill).
Honest! The
best course of action for almost anybody is to let it slide.
Look at any
motorcycle race film and you will observe that 100% of the turns
are negotiated with the rear wheel sliding! Nothing magic about
that, now that you know what's going on. Right?
Aren't you
glad, now, that your motorcycle generally has oversteer rather
than understeer
built in? There is essentially no 'fix' if your front-end slides
out from under you while in a curve. But if the rear wheel
continues to spin, it can slide a little and you can continue your
ride, a little more 'puckered' but none the worse for it.
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