CMP brake question

[Jacques Reed]

Originally Posted by Phil Waterman

Hi Lynn. Grant, Rob

Thanks for the input, you've added to the list of things I want to check.

1. The idea of the spring having lost tension, fits in with the earlier observation that this adjuster turns easier than the others. Next step will be to put a torque wrench on it and see if it really is turning easier.

2. The thought that the spring itself might be winding up as the adjustment is being made, had not occurred to me.

3. Confirming that the adjustment cam is not loose on the bolt is a big thing to rule out. If it is I can not think of the damage that it could do if it dropped off in side the drum. So I suspect that pulling the drum will be a necessity.

4. A broken or weaken spring from crack, rust, age, is I suspect the most likely cause. But what is the fix? Replace spring, or put a spacer under it to increase tension?

5. Replacing the backing plate is probably the hardest, as I have no spare and a used one is just as likely to have the same problem.

Cheers Phil

PS - While I was typing Harry provided a source for NOS replace part. Thanks Harry will follow up if that is the cause.

Hi Phil,

Just looking at a brake adjuster cam that I removed a long time ago from a F15-A rear backing plate. I doubt if the cam is turning on the bolt as the elongated hole on the cam would prevent that.

A broken spring could well be the problem as that is the reason I removed this adjuster cam. The spring in the picture is a new one I had made up. In the end I found two NOS rear backing plates and never proceeded with replacing this cam's spring and another cam than had a broken spring.

If the spring is not broken then the thought occurred to me, what if the cam is resting on the shoe just past the highest point, and the return spring is enough force to rotate the cam back towards the low point on the cam that has a weakened spring?

If the linings have substantial wear it is possible the cam would be close to the top of the cam at the contact point with the shoe.

If you have to remove the cam to replace a spring a method that worked for me was to carefully grind down the side of the flat on the bolt where it is splayed to hold it to the cam. I used a Dremel cut off disk to do it. Was going to then weld the cam back on to the top of the bolt but never had to do it thanks to finding the NOS plates.

Will look forward to hearing the solution to the problem.

Cheers,