Drum Brake Adjustment Issue

[SS317]

Ok guys. Ever since I bought my truck it has pulled to the right. I've adjusted it half assed a few times and today I just got sick of it. I jacked up the truck and pulled both front tires. I adjusted the wheels on the drums until both wheels turned with just a little but of rubbing.

I pulled out of the driveway and they seem to be fixed. Truck stops even. I drive the truck around and try to heat up the old girl and once warm, it reverts back to the old pull to the right. Pretty bad pull, it will turn the steering wheel out of your hand if you're not careful.

This is my first drum brake vehicle. What else should I be looking at?

Thanks!

[markeb01]

First thing I’d check is to make sure the shoes on all four brake assemblies are installed correctly. It is not uncommon for one or more pairs of shoes to be installed backwards, especially by people that are not experienced with drum brakes.

On each pair of shoes, there is a primary (short) shoe, and a secondary (longer) shoe. The primary short shoe always mounts in the forward position. If one or more of these sets of shoes are reversed (which is easy to do), the vehicle will always pull in one direction or the other when the brakes are applied. I've even seen installations with two primaries on one side and two secondary shoes on the other side of the vehicle.

While you have the drums off, inspect them for checks, cracks, deep scoring, or blue spots on the friction surface. If they show blue spots, they have been overheated and are probably warped – needing replacement. If they have any of the other problems they probably need to be resurfaced.

2. Check each brake assembly for leaks. Any hydraulic fluid on the linings will prevent that brake from gripping the drum.

3. If the shoes are installed correctly, check to see if each of the wheel cylinders is actually working by pulling the drum (one at a time) and having someone step gently on the brake pedal. You should see movement at the shoes. Don’t have them stomp on the brakes or they can force the shoes beyond their normal operating range and cause leaks. If one of the brakes does not move, you have a stuck wheel cylinder.

4. If all the wheel cylinders are working, and there is no fluid leakage, inspect the general area for crud build up between the shoes and where they ride against the backing plates. If too much debris collects, this can block movement of the shoes. If filthy, they should be cleaned with brake cleaner. Do not blow the crud off with an air compressor since this can cause ingestion of old asbestos dust and residue. Once clean, apply a small smear of white lubricant on the backing plate where the shoes ride.

5. Last thing – the best method I’ve found to adjust the shoes is too run the adjusters up until they can no longer be turned (completely locking the brake assembly). This centers the brakes within the drum. Then back off the adjuster until a slight drag is achieved. Count the number of notches. As you do each wheel, adjust to the same exact number of notches from full lock. If one wheel needs more or less notches to achieve correct drag, make sure the other side matches the same count when you are done.

If none of these steps fix the problem, it’s probably time to measure the drums. You may have one or more that is beyond tolerance. When they get too old (thin) they will no longer provide friction properties within specification. And of course the same goes for the shoes. If one is thin, or they don't match you will have problems. Some shoe assemblies are glued (bonded) to the backing while others are riveted in place. All four sets should be the same type, but most importantly they must match side for side.

[S-31]

You wouldn't think it matters, but, check the adjustment on the rear brakes also. If they are out of adjustment it can also cause the same problem.

[SS317]

Thanks guys. I'll tear it apart again. I just bled the brakes again for air bubbles and it fixed it until I got a little ways down the road again. I also just pulled off the rear tires and made sure the rear brakes were set even, they weren't. The rear adjustment didn't help with the pulling to the right.

It may be just me, but it seems like my left front of the truck dips down when I brake and the truck turns to the right.

[blackedoutharley]

Be very, very careful applying brake pressure when the drums are removed!!!!!!!!!!!!

Another thing to look at is to see if the contact points on the backing plates are grooved where the shoes ride. If they are grooved it can cause the shoes to hang up causing issues.

In the old days we used to "arc" the shoes to the drums on a grinding machine made for this but you can thank the EPA and the treehuggers for outlawing this useful tool.

[Wrenchbender Ret]

The guys have brought up some really good points to look at. You mentioned the front end. Bad front end parts & alignment can also effect brakes pulling. Adjustment does not cause pulling on hyd. brakes unless it is way off.

[SS317]

I got it fixed. I printed out this thread (thanks Markieb01) and used it as a checklist. Turned out being the brake cylinder. I replaced it and now I'm pulling a heck of a lot straighter than before. I do have to work a little more air out of the system but I have good brakes now.
THANK YOU for the help!!

[aerotruk63]

I pressure bleed my brakes now. It was recommended in the Chevrolet Shop Manual for my big truck I had and now I do my light duty's as well this way. Pumping the pedal and not watching the fluid level in the master can re-introduce air into the system. The pressure system maintains an amount of brake fluid and pressurizes the master at the same time. It is a one man job ( sorry ladies ) this way. Very quick way to effectively bleed the system. There was no other way of bleeding the Big Truck system as many experienced mechanics found out.

[bama63]

or you can use the poor mans bleed system...take a 20oz drink bottle,pour it half full of brake fluid,pick up a 20 inch length of 3/16 rubber or clear vinyl hose, now push the hose onto the barb of the bleeder screw and place the other end into the 20oz bottle all the way to the bottom, now crack the bleeder screw and pump the brake pedal slowly,you will be able to see the bubbles in the bottle as you push the pedal down, when all bubbles are gone close the bleeder screw. this will bleed the air out and only takes one person to do it, i have used this method for many years and works really good.

[Woogeroo]

reassembly instructions for rear drum brakes

the main difference is the park brake parts.

-W