GotQuestions? Wheel End

Q. With my parking brakes applied I can roll the truck forward. What's the problem?

Also, it doesn't move when I tried to reverse. The brake adjustment and brake system condition appear to be okay with 1.25 pushrod travel, 75% of the brake shoe is still there, and the drum are not damaged from heat glazing.

April 21, 2014

SHARING TOOLS        | Print Subscribe

A. With 75% lining left on the shoes and the stroke at 1.25”, I question whether the drum is within spec or the s-cam bushings are worn out. With the wheels jacked up in its current state, check to see if the wheel will rotate in the forward direction with the park brake released. This confirms whether the s-cam bushing are worn or not.

What is the pressure being used to get the 1.25” stroke measurement?

Using a pry bar the adjuster should only move 1/2”. If it goes beyond that it is an indication that you have foundation component issues.

I am thinking that the reason why the brakes lockup backing up is because of reverse cam rotation. With a bad s-cam bushing with reverse cam rotation the top shoe becomes the lead shoe and because there is too much clearance between the shoe and drum, the cam block locks in the drum.

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Comments

  1. 1. Duane [ April 28, 2014 @ 10:43AM ]

    I have found broken springs in some of my park brake cans. They have enough spring to apply the brake but not enough force to hold the truck. Change the park brake cans their cheap compared to having a parked truck role way.

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Jeff Geist

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STEMCO
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