Re: Brakes

Posted by Owen_Dyneto On 2010/2/18 16:42:59

Can't address your particular brakes (though I do have a 56 Packard), but typically the rear shoe, the secondary shoe, has the longer lining because it does more work. Often with OEM shoes it also had a different lining material with a different coefficient of friction, though this distinction is pretty much disregarded today. The front (primary) shoe, with the shorter lining, is intended to engage the drum first - this happens because it typically (but not always) has the weaker return spring, thus allowing the front shoe to engage first. As the front shoe contacts the drum, it attempts to turn with the drum in the direction of wheel rotation, and thus "cams" or jams the rear shoe into the drum, kind of a mechanical advantage to increase braking force.

Hope this helps, it not the whole story.