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Park Brake Clearance Adjust Impossible?

george.underwood

By george.underwood
in Ask A GM Technician

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george.underwood Enthusiast

george.underwood

Posted
Posted

Need help with 2002 Sub 1500 parking brake adjustment. (125K miles or so)

 

I installed new rear parking brake shoes while doing pads and rotor resurface. Machine shop did not touch parking brake surface on rotor/drum. Parking brakes were not working when removed. (the lever went to floor with little resistance). I had NO problem removing the rear rotor/drums.

 

Haynes manual calls for 0.026 inch (0.66mm) clearance between shoes and drum. I had no way to measure this so I adjusted new shoes out out as much as i could and still get the drum/rotor on. When all back together the park brakes worked just like they did before - NOT AT ALL. But i did not do a cable adjustment procedure.

 

So i ordered the special tool (shoe clearance gauge) recommended to set the brakes and pulled a rotor/drum off today to set them correctly. Also found a more detailed adjustment procedure on internet that agrees with the Haynes spec.

 

Here are the important steps (quoted):

--------------------------------

20. Set a drum to shoe clearance gauge so that it contacts the inside diameter of the rotor.

21. Position the gauge over the shoe and the lining at the widest point.

Important:

a. The parking brake adjustment screw threads should not exceed 5 mm (0.2 in) of exposed thread.

b. The clearance between the park brake shoe and the rotor is 0.6604 mm (0.026 in).

----------------------------------

 

The problem is the inner surface of the drum is 216mm dia and the lip at the edge is 211mm dia. (using the gauge i ordered) There is no way to get 0.66mm clearance with a 5mm smaller hole that the shoe has to fit thru! At min, i can have 5mm/2 = 2.5mm clearance.

 

Am i missing something? Are they talking about clearance to the lip, not the inner braking surface? Is there supposed to be a lip on the rotor/drum at all? Has the lip been worn in by previous (factory) set of parking shoes? I dont think this is likely because I had no problem removing the rear rotor/drums.

 

I have NOT done the cable adjustment procedure yet. I will put them back on tonite and do that and see if they work with about 2.5mm clearance.

Zembonez Senior Enthusiast

Zembonez

Posted
Posted

It sounds like the old park brake shoes have worn the inner surface beyond spec. There should be no lip on the edge (just like a traditional drum brake). You may be able to adjust them further out and tighten the cable under the driver's side and have a functional parking brake. You'll just have to do the old adjust until you hear friction and back off a bit. It worked for decades on old cars. :cheers:

george.underwood Enthusiast

george.underwood

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Posted
It sounds like the old park brake shoes have worn the inner surface beyond spec. There should be no lip on the edge (just like a traditional drum brake). You may be able to adjust them further out and tighten the cable under the driver's side and have a functional parking brake. You'll just have to do the old adjust until you hear friction and back off a bit. It worked for decades on old cars. :D

 

I guess I'll do that as the rotors are in fine shape- this was thier first resurface. On this vintage (2002), the only adjustment that can be done after the rotor/drum is on is the cable adjuster. There is no ratchet adjuster access from the back side like in the good old days. Unfortunately, my cable adjuster is already at max tight. Looks like it came from the factory that way as i have not adjusted it before.

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