Motorcycle
Riding Techniques
©
2002 - 2008, Raymond Wood
Tyres and Lean Angle
Question:
You are approaching a bend which is severe enough to crank the bike
over at an angle of 45 degrees. You neither roll off or roll on the
power - you keep the throttle position constant throughout the turn.
What will happen to your speed?
Answer:
The speed will DECREASE - you will slow down!
Why? Because of the profile of your bike tyre. Have a look at the diagrams below and notice that as the tyre is leaned over the actual radius of the wheel gets smaller because of the curvature of the tyre. This makes the tyre that is leaned over a (temporary) smaller wheel. As the actual spinning of the wheel doesn't change (it rotates at the same rate as in the vertical position) then the speed of the bike has to decrease to accommodate the smaller circumference.
Why? Because of the profile of your bike tyre. Have a look at the diagrams below and notice that as the tyre is leaned over the actual radius of the wheel gets smaller because of the curvature of the tyre. This makes the tyre that is leaned over a (temporary) smaller wheel. As the actual spinning of the wheel doesn't change (it rotates at the same rate as in the vertical position) then the speed of the bike has to decrease to accommodate the smaller circumference.
Why should this concern us?
Well, we have already decided that the best geometry for the bike in a turn is to have the weight distributed toward the rear of the bike (over the rear / power wheel) rather than the front wheel.
We also know that rolling off the power, braking or slowing causes a weight shift to the front of the bike:
What does this mean we should do to the power while in a turn?
In the Controls and Cornering Techniques sections of this presentation we talked of accelerating (or at least maintaining power) while in a turn.