Causes of rear brake pulsation other than drums?

[zuhandenheit]

I'm troubleshooting my brakes, yet again. I've had some pulsation from my rear brakes for as long as I have owned the van (many years). I tried two sets of drums, one of which I had turned. I also replaced the shoes and hardware, a long time ago. The hub faces are clean. One set of drums seems better than the other. When I had a set turned it seemed a little better, but it didn't fix the problem.

I am giving it another go and just put on some Zimmerman drums. There may be an improvement but it didn't solve the problem.

On both sides, after I adjusted the shoes, if I pull the parking brake one notch and turn the wheels by hand I can feel it catch and release unevenly. When I pull the brake while driving it catches and releases. I feel a now slight (improved) pulse in the pedal.

My friend claims it could be the shoes or hardware. I'm having trouble imagining HOW.

If it's the hubs, it is weird that it is on both sides!

I would at this point gladly replace the shoes and hardware if I thought that could fix it.

Thoughts?

[MarkWard]

You are probably not going to want to hear this. Had a vanagon in the shop for rear brakes. It got new drums, maybe Zimmerman or ATE. I don't recall. Machined them using the drum shell adapters for a pulastion. Hardly any improvement. Ended up pulling the drive hubs and torqing the drums to the drive hub. Then machined the drums with the drive hub installed. Totally fixed the pulastion problem.

Not saying this is your problem, but probally need to be sure the drive hub mounting surface is clean and free of dust to start and that you use a torque wrench to tighten the lugs. From memory, steel wheels are torqued to 110 foot pound. I've seen lower numbers for aftermarket alloys in the low 90 foot pounds.

Also your sure its the rear brakes that are pulsing the pedal?

[zuhandenheit]

Phew, yeah -- not my ideal solution!

But: yes I have spent a lot of time making sure the hub surface is clean. I think I even put paint on it or damn plastigauge at one point to check for even contact with the face of the hub.

I do use a torque wrench, and am careful about it.

I can feel the drums catch and release when I turn by hand with the parking brake up one click. And I feel and hear it when I'm driving, if I pull the break.

A friend swears I should try replacing hardware and shoes but I can't imagine that making any difference. Who's right?

Anyway as always thanks for the advice!

[tdivan82]

[zuhandenheit]

My mother's ex husband was retired from oil rig mechanic work and gave me a big beam type snap on torque wrench that i've been using for this - I set it to 120. I tried torquing with the wheels on the ground and off the ground and etc etc it doesn't really matter.

[MarkWard]

Do you know someone with a lathe with a 3 jaw chuck and a dial indicator? You wouldn’t even need to run the lathe. Chuck up the drum on the center of the drum shell with the drum facing out. Set the dial indicator against the face and zero it. Now turn the chuck by hand and you will see any out of round.

Brake lathe could do the same measurement, but I haven’t seen a brake lathe that wasn’t beat to death in a long time.

[Jeffrey Lee]

[Jeffrey Lee]

[tdivan82]

[MarkWard]

[bobbyblack]

I have been under the impression that all new drums come warped, or warp within the first heat cycle anyway. Sadly, I keep my old stuff (well, not worn out shoes) around for an eventual machining and replacing of the new ones that have been warped since the second day after I installed them. There really isn't a way to know the process that was used to produce the "new" drums. The actual solution would be to do the heat treatment yourself with a proper furnace, temperature controls, and proper cooling, then proper machining. It's just not done these days, since drum brakes are a thing of the past that companies only make to have something to sell, and steer you in the direction of disk brake upgrades.
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'87 Westy 'Flossie','86 Westy 'R1','86 tintop GL - Subi2.2 'J2','83.5 stock tintop L 'ZoomBus','74 Karmann Ghia, '63 Notch

[tdivan82]

[zuhandenheit]

Thanks for the replies!

Again, the big question is: can anything other than the drums be a cause? I know hubs are a possibility, and maybe some sort of hub-drum mismatch (thanks Mark).

There are some machine shops around here (Ridgewood, Queens). I could get someone to check my drums.

I don't have a great place to work, and I figured it would be easier to just try a new set (everyone's favorite, Zimmerman) first, and I crossed my fingers. Oh well -- there seems to be a slight improvement.

The uneven contact, which I can feel when I turn the wheels by hand, is so distinctive, so similar across three sets of drums, and so similar from side to the other, that I am wondering if there's something else going on (other than non-round drums).

I've inspected and disassembled and reassembled the shoes and hardware a few times and studied the Bentley diagrams and I am pretty sure everything is right.

I have never replaced the backing plates.

Is there any sense to trying a new set of shoes / hardware / anything else?

(I also discovered when I was swapping drums that the cylinders are leaking so that is next either way.)

[zuhandenheit]

Okay, I have an idea for my next step. I may have tried this once before but i'm not sure, and not with the new drums.

I'm going to take one side apart and tape plastigauge to the hubs, then reassemble and torque the lugs. At least that will let me rule out one possibility.

[ALIKA T3]

[Backtotheeightiesagain]

Try blocking off (clamping) each flex hose in turn and driving on a private deserted road. See if it goes away? Find exactly where problem is?
T3 notorious for the play in rear wheel bearings, housing wear, wether the angle of the drum changing can cause the feeling who knows..

[skemems]

I had rear pulsating brakes as well. I had a good set of OE drums on the shelf and had them turned, I wanted to make sure it was the drums....after having them turned this made my pulsating go away completely.......


for a while....several hundred miles later pulsating returned.


Probably due to heat cycle, maybe after turning they were out of spec to be used and they ended up warping.

I'm driving as-is for now(its not too bad) but I'm considering eventually purchasing new drums or upgrading to disk brakes.
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87 VW Westfalia - EJ25
86 VW Westfalia - EJ22
85 VW Westfalia - WBX 2.1 project

[Gnarlodious]

I recently put on a new set of T3Technique polyurethane radius rod bushings lo and behold a shimmy while braking magically went away.
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Vanagon ’83 diesel AAZ w/Giles injection, 5spd 4.57R&P+TBD and a '78 diesel Rabbit

[zuhandenheit]

I am back on this.

I replaced all the hardware, the shoes, the drums -- just at least to rule all that out. Everything is in the right place.

Not only is pulsation still there but I can feel uneven contact between drums and shoes when I turn the wheels by hand.

I don't feel play in the wheel bearings and anyway if that was the culprit, I don't think I'd feel it when I turn the wheel or drum by hand.

The whole time i have owned the van (17 years) I've had this issue, now with two sets of hardware, two sets of shoes, three sets of drums!

Re the isolation of the issue: I am convinced it is BOTH rear wheels, because it varies depending on the relative positions of the two wheels. If I am not feeling it at all and I take a 90 degree turn, it will get worse, and vice versa.

Verified in the rear with hand-brake. Verified by turning wheels by hand. Does it with every set of drums. One set I had turned by a machinist. Each set was new when I bought them.

I'm at the point of wondering if I should try replacing the entire hub assembly ...

Or maybe first I get my drums machined once more?

[Wildthings]

I am trying to remember what I had to do to get rid of the brake pulsation on my Syncro 30ish years ago. I know it had something to do with the rear hub, I believe is was that the hub wouldn't center accurately in the lathe, so I just had the drum turned without having it mounted to the hub.