Drum Brakes not Working Properly

[fasttback]

On my ’66 I recently switch the rearend out to upgrade to a 9” with 2-1/4”x11” drum brakes (came with the Currie kit). The fronts are still stock drums (for right now). The car ran and stopped with no problems right after the install. Front brake pads have not been replaced...yet.

After driving around for a few months, I’m noticing the brakes when applied (slight pedal pressure) they tend to grab than not grab, like something is out-of-round. This problem is getting worse as time goes on and is most noticeable just before coming to a complete stop. I felt this brake problem before with some of our work trucks over the years, so it might be a common problem??? I just want some other opinions before I start to tear into things. Thanks.

 

[mustangdave]

If any fluid is on the brakes or drums, they will grab. Check for leaking wheel cylinder or grease leaking from the rearend into the brake system.

 

[2nd Mustang]

Did you put some grease on the backing plates where the shoes contact the backing plates?

 

[dennis112]

Your big brakes may now be "seating" in. Do the rear brakes lock up before the front?

Perhaps you need to install a proportional valve to limit the fluid to the rear wheels. You did increase the rear's braking capability. Fronts should always lock first.

Otherwise it is time to check both the front and rear brakes. Remove the drums and look for obvious problems such as a leaking wheel cylinder, shoe bind, or improperly installed parts. Check the parking brake alignment as it can dictate where the shoes are. If it is too loose, you can get a funny wedging affect.

 

[dennis112]

It is time to check both the front and rear brakes, unless you are sure the problem is in the rear. Remove the drums and look for obvious problems such as a leaking wheel cylinder, shoe bind, or improperly installed parts. Check the parking brake alignment as it can dictate where the shoes are. If it is too loose, you can get a funny wedging affect.

Probably not associated with the problem, but did you install a proportional valve for the rear brakes? I would think that the rear would need one to keep from locking up earlier.

 

[fasttback]

Change of events this weekend (had to work on the home instead of the car...not by choice).

"Did you put some grease on the backing plates where the shoes contact the backing plates?"

Yes, I followed some generic directions which talked about applying grease in this contact area = use high temp bearing grease.

"Do the rear brakes lock up before the front?"

I can't recall, the only time they were tested (locking up that is) is when someone cut me off, so my mind was not on the brakes.

There is not a proportioning valve on the car yet. I have some disk brakes on my bench that will be installed later this spring. A proportioning valve will be installed.

The parking brake works great! It will actually stop the car relatively fast in forward or reverse. The adjustment on the parking brake has not changed since the original install. It's the best parking brake I had on a Mustang to date!

What's weird is the brakes worked fine and progressively got worse, so I'm thinking some of these causes would have been noticed right away. In addition our work trucks (non-modified) have a very similar problem.

I agree, it time to check all drums for the more likely causes (e.g. leaking brake fluid on the pads). Also, it would be a good time to get off my a** and put those disk brakes on.

 

[fasttback]

I always screw that one up "disk", better known as "disc"...It will happen again.