Author Topic: Rear brake shoes  (Read 345 times)

Offline Cheyenne1010

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Rear brake shoes
« on: June 10, 2018, 08:43:20 PM »
I got a 1973 chevy C10 and I'm doing the rear brake shoes
I notice the shoes are not exactly alike,one shoe has more brake material then the other one,why is that?

Offline Big Chip

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Re: Rear brake shoes
« Reply #1 on: June 11, 2018, 09:18:56 AM »
Are you saying itís thicker or longer?  The longer one goes toward the front I believe.

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Online bd

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Re: Rear brake shoes
« Reply #2 on: June 11, 2018, 12:20:34 PM »
The 73-87(91) GM trucks use a duo-servo brake system.  The primary (forward or leading) shoe on both sides typically has shorter friction lining than the secondary (rearward or trailing) shoe.  Duo-servo brakes are self-energizing, meaning that as the shoes are forced outward against the drum by pressure applied via the wheel cylinders, the forward movement of the vehicle and rotation direction of the drum rotates the primary shoe toward the secondary shoe through the automatic star adjuster located at the bottom of the backing plate.  Since the automatic star adjuster is not anchored to the backing plate the rotational force of the primary shoe forces the secondary shoe into the heavy anchor pin that is fixed in position at the top of the backing plate, amplifying the outward force of the secondary shoe against the drum.  Because of the self-energizing effect of duo-servo brakes, the secondary shoe presses outward against the drum with greater force than the primary shoe.  Hence, the secondary shoe has more friction material (the lining has greater surface area) than the primary shoe to help equalize the wear on the shoes.

When backing up, the same principle applies except the drum rotates in the opposite direction.  When backing up, the primary shoe presses against the drum with greater force than the secondary shoe (the roles are reversed).  However, since so little time is expended braking while backing up, accelerated wear of the primary shoe is not an important consideration.

So, the important point to remember is that the secondary shoe has longer friction lining than the primary shoe and mounts in the trailing or rearward position.
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Offline Captain Swampy

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Re: Rear brake shoes
« Reply #3 on: June 11, 2018, 03:47:46 PM »
Thanks for taking time to explain all of that.
1987  350TBI 700R4  4X4  4.56 gears  33" BFG All Terrain