The coefficient of friction on a given surface is a constant. Its the braking effectiveness which varies with weight . It's a long time since I did A level physics, but I do remember the formula: F=uR, where F= retarding force, u= coefficient of friction, R= weight on tyre. Increase the applied weight and you increase the retarding force.
Last edited by 777fly; 9th Oct 2012 at 19:44.