Rear Brake Shoes

[JKLedbetter]

I was replacing my rear brake pads and discovered a problem.



The brake pad on the left is the inside old one I took off, the one on the right is a new inside Wagner pad, and the gold colored thing below center is the double metal shim? or backing plate? (not sure what it is called).

The problem is that the nipple in the top middle of the new pad sticks up so high it interferes with the metal shim. I noticed that whoever installed the old pad apparently resolved the problem by grinding off the nipple.

It appears that the nipple may have something to do with engaging the cross shaped groove on the face of the brake piston. However, the pattern on the metal shim indicates that even without the nipple the piston never turned during the life of the old shoe.

So, is it ok to just grind the nipple off, or should the metal shims not be used with this particular shoe? One or the other has to go. Or are you supposed to drill a hole in the shims to allow the nipple to stick through?

And how does that goofy screw in piston work? I had an awful time getting it to turn, which made me wonder if the piston was sticking, but it pushed back out fine when I mashed the brake pedal to check it. Then I had to wrestle with it to screw it back in again.

Puzzled,
Kennon

[paulo57509]

Do not grind off the nub on the backing plate of the inboard pad. Your pad set should have come with the correct shims. The shims should have a hole (or holes) that will clear the nub.

These shims are Beck-Arnley shims (why I have a spare set of shims is a sad Vatozone story):


The nub is needed in order for the self adjusting feature for the parking brake to work. One of these tools makes turning the piston back in a much easier task:

http://www.amazon.com/Lisle-28600-Di.../dp/B0002SQUFY

The shim in your photo looks like it's for the outer pad.

[sam o nela]

^ +1

If all the shims are flat like that, a drill press will fix it in 10 seconds flat!

Otherwise, a drill and a vice will also suffice

[JKLedbetter]

These are Wagner pads and they didn't come with new shims. I don't think I've ever bought pads that included new shims. I've always had to reuse the old ones.

The shims in the photo are definitely from the inside pad, you can see the imprint of the face of the brake piston. And it is a double shim with one piece having different tabs so that it can overlap the other piece.

Can someone explain how the self adjusting feature works? It looks like the nub does nothing more than prevent the piston from turning. And from the marks on the old shim, it looks like the piston never turned anyway, even without the nub.

Kennon

[paulo57509]

Refer to the FSM page below. The two things to note are the Adjusting Bolt and the Piston.



When the brakes are applied, hydraulic pressure pushes the piston out against the pad.

Because the adjusting bolt is not allowed to move with the piston, it rotates when the piston moves. Think if it as the hydraulic pressure trying to separate the adjusting bolt and piston. So when the piston moves out, it "unscrews" the adjusting bolt. This action maintains proper parking brake adjustment (provided the parking brake is adjusted correctly at the handle).

If the piston is allowed to rotate (grinding off the nub on the inboard pad) the caliper looses the ability to self-adjust.

The only time the adjusting bolt moves with the piston is when the parking brake is applied.

In your case, I would guess that this self-adjusting feature is frozen.

[pnoye2]

Originally Posted by JKLedbetter

Can someone explain how the self adjusting feature works?

Kennon

^ You the man paulo

[DrDave]

The ones that come from Acura always seem to be correct.

Dave