Re: brakes (still)
Post by luckypabst on Sept 7, 2006, 10:24pm

The basic principle of the self energizing brakes is that when the shoes expand to touch the drum, friction against the drum causes the shoes to rotate a bit with the drum rotation and "wedge" themselves, or create more pressure than what just the wheel cylinder can provide. The short lining aids in the leading shoe's "digging in" action.

This is the reason the shoes are not rigidly attached at the adjuster or the retainers - it allows them to float inside the drum.

Here's something I found quickly but you'll get a lot of responses related to bicycles if you google it:
http://www.raybestos.com/OnLineTraining/cpt-007.htm

From that link:
On a self-energizing brake, the secondary shoe does approximately 70% of the braking. It has a longer lining than the primary shoe.

Chris