Adjusting the brakes

Posted on by December 4, 2023
I have had no time since I modified the Ammco 1750 to try it out. Time to fix that. I only have about three hours to work on it but it should not take long (this is where the ominous music kicks in!).
It only took a few minutes to peel off the tire and brake drum. The wheel cylinder I put in back in 2020 is holding up well. In fact everything in here looks great.
But I did spot this. It is a bit hard to see but there is a big loogie of goop leaking out of the shock absorber. I will have to figure this out but that is a tomorrow problem. Whatever this is, it is really sticky, almost like Permatex #2.
Just to review, these brakes are neither self-centering nor self-adjusting. To center and adjust them the central pin at the bottom and the two pins on either side are on eccentrics. In this older picture with the shoes off you can see the eccentrics on the side pins clearly. The anchor pin at the bottom is less obvious but trust me, it is there. The point of this exercise is to get the shoes as centered as possible and to match the drum diameter as best we can.
Now for the Ammco. I put my custom drum measuring pin in and fitted it to the brake drum. Once in, just turn the dial until it hits the brake drum and you have measured the drum.
As you can see here the drum is about .064″ oversized. Cool!
We just measured diameter at 9.064″. But to adjust the brakes we need to use radius. So I set the dial to .032″ and locked it down.
With the tool adjusted I put my custom sleeve on the pin. Now we are ready to adjust.

Here is how it works. The bearing fits over the axle. We can then spin the tool around, adjusting the tool to try and get the shoes to just about touch all the way around.

Here you can see the gap we are trying to close. I quickly realized this can’t be perfect. The shoes are not arced to match the drum perfectly so there is in way they are going to match exactly. But I got it as close as I could. The modified tool worked great!

Once the shoes were adjusted, I retracted the shoes using the side pins to allow me to get the drum back on.

With the axle nut tightened I adjusted the brake shoes so the were just barely not touching. Then the trouble started. Just to check I applied the brakes using the brake pedal. The drum was locked up such that I could barely turn it. I re-adjusted and tried again. Same result.

Setting this problem aside, I went and did the other front brake. That one worked perfectly and does not have the lockup problem. WTF? So I returned to the passenger side and took the drum off again, recentered the shoes, and re-assembled. No change.

My next thought was maybe a hydraulic problem. Maybe a defective brake hose or something is holding pressure on the wheel cylinder. I hit the brakes to lock up the wheel and opened the bleeder screw. No pressure. So I am back to mechanical problem. But I was out of time and I needed to put another car on the lift so I just put it together.

Then the second problem arose. Somehow in taking the wheel off I boogered up the thread on one of the wheel studs. I could not get the wheel nut to start without cross-threading. I was really pissed with myself and a little panicked since changing a wheel stud is no small matter in these cars. Fortunately, it was on the passenger side so the stud had right-hand threads. I carefully cleaned up the threads with a small file. After several tries, I got a die to start on the stud then I used that to chase the threads. It all worked out, but it was not my finest moment. I also did not take any pictures, sorry.

Right now I have three theories about the brake problem:

  • The return spring is weak and not pulling the shoes back. If it is really weak I should be able to tell just removing it. If it is just a little weak I can swap it to the other side and see if the problem moves. I may have used springs in my parts stash too. I replaced these springs in 2006 but that was 17 years ago…
  • Something about the shoes is binding. When I have the spring off I will make sure the shoes move smoothly and don’t bind.
  • When I center the shoes I am somehow putting a shoe in a position where it wedges somehow against the drum. This seems highly unlikely. But I may try shifting the shoes up or down a bit to see if anything changes.

I will get this guy on the lift again soon and start working this problem.


Comments

Adjusting the brakes — 1 Comment

  1. Pingback: Brake centering and adjustment part deux | 1941 Studebaker Champion

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