Itinerant Air-Cooled

For quite some time now, my rear brakes have had two issues:

1. Under hard braking, the Bus slewed left and under really heavy braking or in the wet, the driver's side rear wheel locked.
2. No matter how tight I adjusted the parking brake cable on the driver's side, I got no significant brake force (I could turn the wheel by hand.)

I pulled the drums and found things looking fairly normal on the passenger side - plenty of shoe material left with even wear over nearly the entire length of one shoe and over half of the other shoe. The area of the drum where the shoes ride did not have much if any step between it and the area not touched by the shoes.

The driver's side showed shoes with significantly more wear near the top than the bottom and some ridges across the width of the braking area. There is also a noticeable step between the braking surface and the untouched area of the drum. If I placed the loose shoes in the drum, they did not mate nicely with the drum but would rock with either one end or the other not touching the drum.

I just replaced the shoes and this has cured the parking brake actuation issue, but the uneven braking remains. In fact it seems more pronounced with the new shoes.

What next? New wheel cylinders? New drums? All of rubber brake hoses were replaced about 2 years ago.

vwlover77 wrote:For quite some time now, the Bus slewed left

I just replaced the shoes and the uneven braking remains.

That's cuz your right brake is the culprit, just loafing along hardly using its shoes.
Colin

Amskeptic wrote:That's cuz your right brake is the culprit, just loafing along hardly using its shoes.

But why, Why, WHY??? (I'm guessing a bad wheel cylinder.)

OK, thinking I had a "lazy" passenger-side wheel cylinder, I replaced it. No difference.

OK, thinks I, maybe the driver's side wheel cylinder is sticky or something. I replaced it with the one I removed from the passenger side. Still no difference.

Now what? Restriction in the steel brake line running from the rear tee to the passenger side brake hose, or in the steel line to the wheel cylinder itself? (Both hoses are nearly new.)

Or is it somehow due to the driver's side drum being more worn than the passenger side?

vwlover77 wrote:OK, thinking I had a "lazy" passenger-side wheel cylinder, I replaced it. No difference.

OK, thinks I, maybe the driver's side wheel cylinder is sticky or something. I replaced it with the one I removed from the passenger side. Still no difference.

Now what? Restriction in the steel brake line running from the rear tee to the passenger side brake hose, or in the steel line to the wheel cylinder itself? (Both hoses are nearly new.)

Or is it somehow due to the driver's side drum being more worn than the passenger side?

Is there a difference or similarity with ebrake application only? If ebrake applied at 10 mph shares the same "laziness" on the same side, you can focus on mechanical reasons, including shoe material differences, different lengths of linings (people have been known to accidentally put both shorter trailing shoes inside one drum) ebrake linkage hanging up, etc.
If ebrake slows the car evenly, look closer at your aforementioned guesses.
Colin

I will try the e-brake test and report back.

It was clear prior to replacing the shoes that the e-brake on the driver's side had little holding force, the passenger side was doing all the work. With the new shoes (all 4), I have similar holding power from both sides (and as a result, much more overall holding power).

The new shoes had no leading / trailing shoe difference - the linings on all 4 are the same length.

Thank you!

The braking with the parking brake is even. No pull.

I will now focus on the steel lines to the passenger side brake.

vwlover77 wrote:The braking with the parking brake is even. No pull.

I will now focus on the steel lines to the passenger side brake.

And we are so sure the front is not involved in this . . .

Hmmmmm... The symptoms involve the lockup of only the driver's side rear wheel under hard braking, and different lining and drum wear on each side. There is no pull on the steering wheel, but a definite need to steer right under hard braking to hold a sraight line.

I can certainly check pad wear and general condition of the front brakes for any clues!

vwlover77 wrote:Hmmmmm... The symptoms involve the lockup of only the driver's side rear wheel under hard braking, and different lining and drum wear on each side. There is no pull on the steering wheel, but a definite need to steer right under hard braking to hold a sraight line.

I can certainly check pad wear and general condition of the front brakes for any clues!

Well, it seems pretty clear that it is in the rear. Drum surfaces have equal glaze?
What I would do, as the fresh-air mad scientist under sunny skies, is swap the shoes from side to side. I want to know if you have an accidental difference in friction coefficent. If the lining materials are from different batches, the problem will migrate over to the right. You then would replace both sets of shoes.
Colin

In an attempt to solve the issue, I replaced the shoes on both sides. The behavior is the same with the new shoes as the old ones.

vwlover77 wrote:In an attempt to solve the issue, I replaced the shoes on both sides. The behavior is the same with the new shoes as the old ones.

Don, this remarkable. Hydraulic fluid is HYDRAULIC - pressure is same across all surfaces. You have removed all variables save . . . shock absorber reaction? torsion bars? tire pressure?

Colin?

Two things I've been considering....

1. Could there be gunk in the brake lines that run from the tee to the passenger side clogging things up?

2. The driver's side drum is much more worn than the passenger side. Could the inside diameter of the drum be so large that the shoe circle diameter is mismatched to the drum ID? Could that result in the shoe pressure being concentrated in too small an area instead of spread out over the length of the shoe causing the wheel to lock? Does this make any sense? I'm tempted to swap the drums and see if anything changes.

vwlover77 wrote:Two things I've been considering....

1. Could there be gunk in the brake lines that run from the tee to the passenger side clogging things up?

2. The driver's side drum is much more worn than the passenger side. Could the inside diameter of the drum be so large that the shoe circle diameter is mismatched to the drum ID? Could that result in the shoe pressure being concentrated in too small an area instead of spread out over the length of the shoe causing the wheel to lock? Does this make any sense? I'm tempted to swap the drums and see if anything changes.

Swap drums but understand that your new shoes are attempting to break in to the drum they have to live with. And no, the radius difference between a grooved drum and a fresh drum is not all that great, BUT, like with the Road Warrior, I had weird braking when my new pads had to figure out the weird hourglass cross section of my 419,000 mile disks. Once they had worn into compliance, things were peachy. But your symptom, you say, is consistent from old linings to new . . . ? Do you see noticeable wear marks with the new shoes trying to ride a drum ridge or anything obviously glaringly dumb?

As for gunk in the hydraulic line, ask yourself if the gunk can resist in any way 785-1,000 lbs of pressure?
ColinMystifiedButHey

OK, today I verified that the steel lines from the tee to the passenger side rear brake are free and clear.

To summarize:
1. Driver's side rear brake locks much sooner than passenger side under very hard braking.
2. After a normal drive, the driver's side drum is significantly hotter than the passenger side.
3. Shoes properly adjusted with no sound of shoe/drum contact on the driver's side, and a slight rub for part of a wheel revolution on the passenger side.
4. Driver's side drum is nearly new (the old one showed significantly more wear than the passenger side).
5. Wheel cylinders on both sides nearly new.
6. Brake shoes on both sides nearly new (but have plenty of miles to be broken in).
7. Rubber hoses on both sides nearly new.
8. Braking action with the parking brake is equal on both sides.

What gives? Thanks!