Motorcycle Tips & Techniques

Motorcycle Safety/Dynamics

Skip Repetitive Navigational Links
Safety TipsNew Rider   Tip217   Print article Print

Your Motorcycle CANNOT Fall Down
(At any speed greater than 10 MPH)

By: James R. Davis


I have recently received a number of E-mails from new riders asking me to help them figure out how to deal with the fear they feel while riding at highway speeds and having to lean their bikes during turns. Invariably they tell me that they can't take those turns as fast as other riders do because they are afraid to lean the bikes enough to allow them to do so.

Despite the fact that their comments include all the information they need to know about their problem, they honestly don't get it. (That is, they know that if they do not go as fast as others do they will not lean their bikes as far as those others do either.)

So, here is a brief and possibly eye-opening response to those people and to those of you who are experiencing the same problem.

When you are moving at a speed in excess of about 10 MPH on your motorcycle, so long as you keep your tires on the ground (without losing traction), you CANNOT FALL DOWN. It is IMPOSSIBLE!

Balance is only required by you as a rider at speeds so slow that counter-steering doesn't work. Above that speed, not only is steering virtually effortless, it is the only thing that you CAN control about your motorcycle other than its speed. You are along just for the ride when traveling at speeds in excess of 10 MPH.

Your motorcycle does not have a brain and it does not, therefore, decide to do what you want it to, or not. Instead, it is just a dumb machine that ALWAYS follows the laws (of physics), even if you don't.

And, you do NOT decide what the bike's lean angle will be when you are in a turn - the bike does that for you automatically, as a result of following those laws of physics.

The amount of centrifugal force generated in a turn is determined, exactly, and invariably, as a function of the square of your speed and the radius of the turn you are in. The greater the speed or the shorter that radius is, the steeper that lean angle will be. When the amount of centrifugal force is exactly equal to the force of gravity (discounting any effect that a side wind might have), the bike will be leaned over at exactly 45 degrees. Less centrifugal force, because gravity is constant, results in a smaller lean angle while if it is greater than gravity the lean angle will be greater than 45 degrees. *YOU* control the amount of centrifugal force by changing speed or by changing the radius of the turn you are in.

So, for example, if when you are riding at 45 MPH on a particular curve your lean angle might be 30 degrees and when you speed up to 55 MPH on that same curve that lean angle might be 35 degrees. That is the angle at which the force of gravity which is trying to pull you down is exactly offset by the centrifugal force being generated.

Why should that matter to you? Because not only is it impossible for that lean angle to be less than the one determined by the laws of physics as I just described, but because it CANNOT BE GREATER THAN THAT - in other words, IT CANNOT FALL OVER!

In order for the bike to fall over that lean angle would have to increase to well over 45 degrees at which point your pegs would scrape HARD and that, in turn, would lift your tires off the ground (which is why, then, you fall down.) But we already know that the lean angle CANNOT BE GREATER than the angle at which the centrifugal force and gravity are equally offsetting each other. In order to reach a 45 degree angle or more you have to deliberately increase your speed or shorten the radius of the turn.

Let me be very clear about the above. *YOU* can decide only the direction and the speed of travel of your motorcycle. Those things, in turn, determine what the lean angle of your bike is - not you. Once you have reached a lean angle of, say, 40 degrees, if you do not increase your speed or shorten the radius of the turn, your motorcycle (and rider) MUST maintain that lean angle - neither less than nor greater than that angle. So it CANNOT FALL DOWN.

The same is true at any lean angle. So long as your tires maintain traction and you are not dragging any parts of the bike, you CANNOT FALL DOWN.

There is something to be said about following the law, no?

Copyright ? 1992 - 2019 by The Master Strategy Group, all rights reserved.
http://www.msgroup.org

(James R. Davis is a recognized expert witness in the fields of Motorcycle Safety/Dynamics.)

     
Visitors
48,316,377
A plea for your help
Views
116,673,068