Posted by John Waak [99.53.150.180] on Sunday, November 03, 2013 at 04:26:06 :
In Reply to: wheel cylinder question posted by chris [67.82.251.179] on Sunday, November 03, 2013 at 01:02:40 :
In your mind, picture the brake shoes mounted on the backing plate. They are anchored at the bottom. When the truck is in forward motion and brake pressure is applied from the brake pedal and master cylinder, hydraulic pressure in the wheel cylinder pushes the tops of the brake shoes outward against the drum.
As the brake drum turns in a forward direction and brake pressure is applied, the drum has a grabbing motion on the upper edge of the front, or leading, shoe. The rear shoe, however, experiences a sliding motion of the drum's surface moves across it. In terms of braking force applied, the front shoe is doing more work than the rear, or trailing shoe. Therefore the brake system engineers increased the braking capacity to the rear shoe by increasing the bore of the rearmost wheel cylinder bore. The result is equal pressure against the forward moving drum by both front and rear brake shoes.
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