The Stovebolt Site Forums The Shop Area Driveline Uneven Braking

I have drum brakes, all four wheels. Brake lines are original except for the line going over the rear axle. Rubber front hoses are new along with wheel cylinders and master cylinder.
The problem is that the front right wheel brakes substantially harder than the left and also the rear left braking harder if I have to brake hard ( a bit scary and I have to compensate steering left a bit.). Working the brakes while cruising helps just slightly. I checked the left front wheel, spinning and hearing just a slight touching of the brake linings.

Could the new master cylinder be faulty? Anyone try installing a proportioning valve?

Check to see if some of the brake shoes are installed backwards. The front lining should be shorter than the rear. I've seen that mistake made very frequently.
Jerry

If your shoes are installed correctly and your wheel cylinders aren't leaking, you need to do a proper, by-the-book adjustment on all four wheels.

Don't guess by spinning the wheels. Take them apart and look at all the parts and adjust them according to the manual.

By the way, the right front brake is probably working correctly. The left front brake is probably the problem child.

You don't need a proportioning valve. That's for front to back, anyway, not side to side.

Adjustment has nothing to do with brake pull. None of the brakes do any stopping until ALL of the linings are firmly contacting the drums. The only thing an improperly adjusted brake affects is pedal height.
Jerry

If both sides of the front brakes aren't adjusted equally one will make contact with the drum first and pull the car in that direction.

Nevertheless, both sides need to be inspected for sticking or leaking wheel cylinders.

Pull the drums and inspect for brake fluid leaks, inspect the rest of the components also. Adjustment following the inspection/repair.

The reason why unevenly tightened shoes from one wheel to the next does not cause uneven braking is because when the tighter one receives enough fluid to move the shoes to the drum, there will be no braking action until the rest of the wheel cylinders receive enough fluid to move their shoes to their drums.
Most pulling while braking is caused by worn front steering components in my experience, but gets blamed on the brakes until a brake job is done and the pulling problem still remains.
Bottom line: Don't look for the magic bullet. Inspect and repair everything.

"working the brake helps..."

I had similar issue. Normal braking seemed OK, but under hard braking the truck pulled to the left. Problem was incomplete bleeding; there was still a little bit of air in the line to the front right brake. It's OK now.

Thanks for all the excellent suggestions. I checked the front linings. Short lining is in front on both. I did not see any fluid leaks. Pedal height is good. I believe I did a thorough bleeding when I installed new components a year or so ago. I only put about 500 miles on the new brakes. So the new master cylinder would not be at fault, maybe? The steering components are original to the truck with the exception of a new tie rod. I had an alignment done. It steers quite well.
It does pull rather extreme right on hard braking initially driving but improves slightly(still not good) while regular driving and braking. I use dot5 brake fluid. I don't have any "system" for bleeding. I just get the wife to step on the pedal. Would there be any benefit of a shop doing the bleeding?

DOT 5- - - - -that can be a real problem, since it's silicone-based and can cause compatibility problems with the style of rubber compounds found in older brake systems. Chances are you have the beginnings of a sticky wheel cylinder on one side, caused by the rubber cylinder cups swelling. Unfortunately, once the silicone is there, it's virtually impossible to flush out- - - -it contaminates every rubber part it contacts. DOT 3 or 4 should be used in older vehicles like stovebolts.
Jerry

I use DOT5 too. I also used the wife (Fran) to do the pedal work. I know DOT5 is expensive, so you don't want to waste too much with seemingly excessive bleeding, but ...

We follow the procedure used by Rusted Nut: Bleeding Brakes

Communication is the key here. Make sure she knows what to do: Hold the pedal and do not release it until you say so.

JoeDude, the master cylinder is not the issue at this point although it may become one if the DOT 5 brake fluid deforms the rubber components within. Also with the new description, possibly the drums became rusty while sitting through the winter and now the shoes are grabby until the rust is polished off, one side being worse.

DOT 5 brake fluid is silicone based and not compatible with DOT 3, 4, or 5.1; which is glycol based. Unless you completely flushed all the old glycol based fluid out of the system, or preferably installed all new parts, the DOT 5 may be gelling up and not flowing like it should; which could cause your issues.

I have had DOT5 for 27 years in my truck, nothing has deformed yet and I am still waiting for the brakes to explode and fall off.

Go to a parking lot and give the truck three or four good hard stops from 30 to 40 mph. It will help set the shoes to the drums and wear off any edge or rust that maybe grabbing, this will also give you a better idea what may or may not be happening. Take along a thermo heat gun and check drum temps just to see what all four are. Everyone should do this just so you know what the truck is going to do in case you really need to stop. A true problem will repeat itself time after time.

Use a short section of clear bleeder hose, maybe 3" long, just long enough so it points straight up. Open each bleeder just enough to allow fluid out, but not let air enter around the threads, if there is any air, it will be at the top and come out, if no air, all you will get is a little bit of fluid. No need for waisting fluid, a full system will dribble fluid as soon as the bleeder is open. You may need a helper to apply a little pressure since the master cylinder is low mounted. Firewall mounted MC will gravity bleed easy enough. If you feel you need to fully bleed them again, just reuse the fluid if its clean, run it through a paint filter if it makes you feel better, I just dump it back in the master and go on.

Second quick test is to check the toe-in adjustment. Roll the truck forward on smooth ground at least one tire revolution without hitting the brakes. You want it to be in as driving position. Have helper hold one side of the tape measure, pick a tread groove or outer edge, or better yet a scribbled line down the center, and a high up as possible. I know the exhaust or something else will not permit using the half way point, but the higher you can measure, the more accurate it will be. Start at the rear of the tire, then move to the front and use the same points to measure from. 1/8" smaller at the front. This adjustment can cause all kinds of weird driving if its not right.

Tie-rod end adjustment, if they are loose, under hard braking, the spring gets collapsed moving the toe-in to toe-out real fast causing the one side to pull off center. Fully seat the adjusting screw to bottom out the spring, then back off 1/2 to 1 full turn. I went the closest hole that allowed the cotter pin to go through.

Be sure the steering wheel is center to the steering box, and the steering box is dead ahead straight when the tires are straight ahead, the tight spot of the gear box helps hold the steering tight. If the gear box has free play in the gears, it can cause stopping issues as well.

You can always swap tires left and right just to rule them out, it's unlikely they are the issue, but it can't hurt.

My truck will momentarially pull right but self centers and stops OK. I have tried to eliminate it, but it always does it under extreme stopping. My 40 mph jam on the brake test lets me know what to expect, and every so often I repeat it just so I'm reminded of it. Mine stops fine and I don't worry about the quick pull, what I do think about is the rear tires locking up, I have a regulator on the rear brake line to limit the pressure and prevent total lock up. It's set for the worst case stop, its on the edge of total lock up, tires just leave black marks but still roll. I can get total rear lock if I try. My truck has soft leaf springs and nose dives more then a stock spring did, so not much weight on the rear tires when braking. I do have disk brakes up front.

With the rear also acting up, a readjustment sounds like is what you need. Do the parking lot test first so the shoes are seated good, then readjust all four wheels. My method is to adjust till the tire won't turn, then back off 5 or 6 clicks of the star wheel on modern brakes. The '38 manual said to adjust to a slight drag, then back off 4 clicks. Your idea, GM's idea, and mine will differ on what a slight drag is, going to lock up then backing off eliminates the feel aspect.

Joe

Joe, have you changed the Dot5 in those 27 years? Asking for a friend who has same in a couple rigs.

RonR

Nope, still the same fluid. My truck see about 1000 to 1500 miles a year, some years more, some less, and is always in a garage that's not to cold or to hot. I probably should look at the fluid but never think about while under the truck.

My Dad had fully restored '67 GTO in his garage along with his race car. For some reason he was working on the race cars front brakes and managed to get brake fluid on the GTO's hoods. He didn't see it till the next day, brake fluid and lacquer paint did not like each other! From then one we both switched to DOT5.