1967 Front Shoe Sizes

[cancow]

I went to the auto parts store to get front drum shoes for my 67' F250 CS and they said there are 2 sizes. I think the said 2 1/2" wide and 2 1/8" wide. Can one use the 2 1/2 if the existing shoes were 2 1/8"? Why the 2 sizes?

[fordman]

the wider size is for heavy duty brakes. if your truck is rated higher than 7500 pounds it would be a heavy duty brake system used on your truck. you cant use the wide shoe in a narrow drum.

[cancow]

Thanks. The front pads look like they have alot of material left, but the wear that i do see is only on the top edge fo the shoe. Is this normal or is something wrong? Also is there a way to tell if the shoe material has crystalized?

[fordman]

that wear on top of the shoe may be caused from not arching the brake shoes. but i am guessing on that. if the matieral is crystalized it will look liek diamond dust on them. lots of shiny flakes in the material. my rear brakes on my 4wd look like that. but since i havent driven it yet. im not worried about the brakes right now. but they are so easy to change in just a few minutes. mine is a f100 so the drum comes off alot easier than the f250.

[cancow]

How do you arch a brake shoe?

[70_F100]

1) The wear only at the top indicates you may have brakes that are out of adjustment. The wheel cylinders push the brakes out at the top, and if they are out of adjustment, the top of the primary (front) shoe makes contact first. That could also come from not arching the linings to fit the drum (as fordman said) if the drums have been turned significantly.

2) Crystallization of the linings should show up as a "spider web" pattern. Fordman, shiny flakes in the material are normal because of the composition of the linings. They are a "composite" material, including some metal flakes. Years ago, there was no metal in the linings so "flakes" may have been one of the indicators on the older linings. Another way to check for crystallization is to take a small file and see how difficult is is to "score" the linings. If they are extremely hard, they're probably crystallized. That's more prevalent with bonded linings than with riveted.

[cancow]

Interesting... Maybe the out of adjustment explains the massive leg press' I need to do in order to stop.

[fordman]

yes what was i thinking. i guess becasue mine were degraded (rotten) they were showing more shiny flakes than usual.

[70_F100]

If you have manual brakes, it takes a "leg press" to stop some of these trucks.

If they are out of adjustment, you should have a low pedal.

When adjusting, there's one thing that people usually don't take into consideration on the rear. The parking brake adjustment affects the adjustment of the shoes. You can actually have the shoes tight against the drum and have a low pedal because of this. The shoes are against the drum, but the wheel cylinder has a long way to travel before reaching the point of applying hydraulic pressure.

To adjust the parking brake, you tighten the cables going to the rear brakes. This affects the parking brake lever inside the brake drum. Sometimes mechanics just tighten up the adjustment on the cable to make the parking brake work properly, without making sure the brakes are adjusted first.

To properly adjust the rear brakes, the parking brake adjustment should be loosened so that there is ABSOLUTELY no tension applied to this mechanism.

Adjust the star wheel with the parking brake loose, then go back and adjust the parking brake.

I've seen vehicles that, when the rear brake shoes were replaced, the drums wouldn't go back on, even though the star wheel adjuster was completely collapsed. The parking brake was holding the shoes in an extended position.

Check that and make sure your rear brakes are adjusted properly.

[cancow]

"If they are out of adjustment, you should have a low pedal." Why would that be?

[70_F100]

If they are not adjusted properly, the wheel cylinder pistons have to travel an excessive distance to push the shoes out.

[cancow]

The part of the shoe that is wearing is at the top near the piston. If the adjuster is moved so the bottom of the shoe moves out then wont more surface area of the shoe be in play? I do not see why there would be a difference in piston travel if this is the case.

If they are not adjusted properly, the wheel cylinder pistons have to travel an excessive distance to push the shoes out.

[fordman]

when the brake is applied the whole shoe tries to move out even though the top is the only part being pushed. i didnt word that right but let me try again. the piston pushes out the top of the brake shoe. if the bottom of the shoe isnt out far enough or close enough to the drum it may not rub the drum to stop when the piston pushes the brakes out. so you would get uneven wear on the shoes. the bottom wouldnt be close enough for the brake shoe bottoms to rub the brake drum butthe top would becuae the piston is pushing it out. since the bottom isnt very close. the piston keeps pushing until it gets a stopping place to make the fluid stop pushing the piston. well thats the best i can tell it. but i understand it. i hope you can also.