Does NOT Provide Stability
By: James R. Davis
Like other folklore, a popular misconception is making its round within the motorcycle community that is simply wrong - and dangerous to you should you believe it - that speed provides a motorcycle's stability.
Indeed, even the MSF teaches this inaccuracy to its students during the first day of range work. So how, do you suppose, can they explain the following fact?
If you lock your rear brake while traveling at 100 MPH your bike will fall over.
I received correspondence today from a person who wished to discuss highside avoidance techniques. He trotted out what he said an MSF instructor had told his class: if you lock your rear brake and cause a skid, all you have to do is look forward and keep your head vertical and your bike will come to a stop without falling over (if you keep your brakes applied.) He said that the instructor told the class that the rear-end of the bike would not slide out from under them, but would, instead, 'fishtail' (wander back and forth from side to side.)
That advise is entirely correct - ONLY at speeds less than about 20 MPH. (The speed at which you are instructed to be going during their rear-brake lock and skid exercise on the range.)
Speed is NOT what provides stability (or ease of balance) to a motorcycle. Rather, it is the enormous strength of the gyroscopic force generated by your spinning rear wheel. Since that spinning rear wheel is directly connected to the frame of the motorcycle (unlike your front wheel), it affects the stability and ease of balance of about 80% of the mass involved (including you.)
Should you lock your rear brake, thus stopping the rotation of the rear wheel, your bike will fall over in a matter of seconds - far less time than it takes to stop when traveling at any meaningful speed!!! This is what causes your rear-end to slide out from under you, and cannot explain or support a fishtailing - once it starts to fall to one side or the other there is nothing the direction you are looking at can do to cause the bike to change gravity and try to fall UP rather than DOWN.
There is NEVER a time when it makes sense to aggressively use your rear brake - NEVER - WITHOUT EXCEPTION. Not even during an MSF range exercise. Refuse to do it - it is not mandatory (at least if you have some form of integrated brakes.) I wonder why.
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