Brake pedal travel

[30Murray]

I know there are tons of threads on brakes but I couldn't find and answer to my specific question. I have a '39 M/Cyl with '42 brakes and a Bob Drake repro pedal assembly. All wheels are adjusted with slight drag and the pedal has about the right free play, but possibly could be tighter. The pedal travels about 4" when I apply the brakes and stops about 3" from the floor. The car stops OK from normal speeds. They don't feel spongy and pumping doesn't make any difference to pedal travel. I am a little concerned that in a hard panic stop the pedal may bottom out. Is this too much pedal travel - what is normal? Not sure if any further adjustment to freeplay will help.

 

[Kube]

I know there are tons of threads on brakes but I couldn't find and answer to my specific question. I have a '39 M/Cyl with '42 brakes and a Bob Drake repro pedal assembly. All wheels are adjusted with slight drag and the pedal has about the right free play, but possibly could be tighter. The pedal travels about 4" when I apply the brakes and stops about 3" from the floor. The car stops OK from normal speeds. They don't feel spongy and pumping doesn't make any difference to pedal travel. I am a little concerned that in a hard panic stop the pedal may bottom out. Is this too much pedal travel - what is normal? Not sure if any further adjustment to freeplay will help.

Three inches from the floor is pretty darn good.
You may be able to get a little better result by lengthening the rod at the master cylinder. However, when lengthening, do perhaps two turns, go for a drive and see how the brakes are. There is a "fine line" between that rod being okay to too long. If it's too long, the fluid can't get back into the reservoir and your brakes will lock up.
That's why I suggest two turns, go for a drive, perhaps two more turns, go for a drive.

 

[Flathead Fever]

If it's rock hard at about half pedal travel, it's pretty good. In an emergency stop the pedal is not going to go any further than it does when you're stomping on it in the driveway. You can eliminate any play in the linkage but no more than it takes to take out the play and allow the master cylinder's piston to come back all the way to the snap-ring, plus maybe a 1'16" of free play. Too tight and your brakes will lock up and stay locked up. If you done this and adjusted the brakes up that about all you can do. If you have the correct bore master cylinder and the wheel cylinders that go with it everything should work.


You can also make sure the shoes are arched to the drums, that they are making full contact otherwise it might make the brakes a little spongy until they wear in. It's only stopping on the center of the lining if it has oversized drums. The drums and shoes were originally made for one diameter. When the drums become larger new shoes don't make 100% contact until they wear into place. We used to grind the shoes to match the diameter of the drums but then the State of CA came into our shop and took away our shoe grinder because of the asbestos dust. That was probably 40-years ago that we stopped grinding the shoes to match the drums. By then it wasn't a big deal on the rears and the cars had disc brakes in the front. But on 4-wheel drum brakes everything needs to be right, or they don't' stop like they did when they were new.

I found an Ammco brake shoe grinder at a garage sale, actually two of them but one needs a new grinder drum. I haven't used it yet, I haven't ground shoes in 40-years, but I have if I need to. That's if I can remember how to use it?

I found a video of a brake shoe grinder. We used to grind the shoes to fit the drums on every brake job until they made it illegal to do so because of the asbestos dust. I keep waiting for that 40-year-old asbestos to start growing cancer in me.

https://www.youtube.com/watch?v=afuwxWqBBa8

I found another video where the guy grinds the shoes on a belt sander. What's good is he shows you how the shoes fit the drums on an oversized brake drum.

https://www.youtube.com/watch?v=0n02-GU_VYs

 

[pete rose]

I should be able to pump the brakes firmly
several times in my shop and get the brakes to lock up if the pushrod is extended too far into the master cyliner. Then back off the pushrod until the brakes release.
Is my understanding correct?
If so I will try this, get a half pedal firm brake and all should be good..
Now I can go for a drive..
Pete Rose

 

[Flathead Fever]

I should be able to pump the brakes firmly
several times in my shop and get the brakes to lock up if the pushrod is extended too far into the master cyliner. Then back off the pushrod until the brakes release.
Is my understanding correct?
If so I will try this, get a half pedal firm brake and all should be good..
Now I can go for a drive..
Pete Rose

There has to be space between the rod and master cylinder but not so much that the rod can fall out. Just a little space, maybe a 1/16". Make sure you can see that the piston has come all the way back to its stop and then adjust the linkage.