Rear Drum Brakes Locking On (1972 Camper)

[Ben Middleton]

Well, I am still having problems.

I’ve continued to work on the brakes. I had a problem where I pressed on the pedal and it stopped halfway and required another push for it to reach the bottom. This stop would only occur for the first push. After a short break, it would return on the next first push. I assume that this was due to the brake shoes contacting at different times. I believe it improves somewhat when the handbrake is connected.

The other issue I’m having is that the shoes are rubbing, even when they are adjusted to the lowest setting. Additionally, this low setting causes the braking performance to be very bad for some reason.

I have now installed brand new brake drums. The only things that are not brand new in the rear braking system are the backing plate, the adjusters, the internal mechanism, and the left rear brake cylinder.

Does anybody have explanation for these braking issues? Here are some photos of the rear brakes:


RIGHT REAR

LEFT REAR

Any advice is appreciated!

I have double checked that the front brake discs are in satisfactory condition. The pads are fine. The left front disc looks fairly worn. Here is a photo of it:

Does that require replacement yet?

Finally, I have also realised the CV joint was clicking on the left rear drive shaft, so I have fitted two new GSK/Lobro CV joints with GSK/Lobro rubber bellows too.

That’s all for now!

[busdaddy]

Have a look at this: https://www.thesamba.com/vw/forum/viewtopic.php?p=8293061#8293061
As for the front disc health you'll have to measure it's thickness.
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[Wildthings]

Looks to me like the parking brake got tightened up before the shoes were properly adjusted. Back the P. break all the way off and then adjust your shoes up using the correct procedure.

[Ben Middleton]

[Wildthings]

[SGKent]

the rear pistons appear slightly extended as Mike said. Loosen the bleeder and see if they retract. If they do then a rubber line is swollen, or something is going on in the master. The condition of the front rotors tells me that these brakes have been down for awhile.

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[kreemoweet]

Notice the non-stock bolt and nut connecting the push bar and p.b. lever in the photo. Stock was pin #211-609-831 with
clip 211-609-833. There's a thread and photo about this clip at https://www.thesamba.com/vw/forum/viewtopic.php?p=1977134

The hitch at the brake pedal sounds like some kind of mechanical obstruction in the system somewhere.

It's been my experience that poorly adjusted rear brakes will certainly render them barely functional, but the effect on overall brake
performance is barely noticeable, because the front disk brakes do most of the braking. Therefore, "very bad brake performance"
as described would likely have more to do with the front brakes. I would be looking very closely at those very worn disks. There's
only 1.5 mm of allowable wear on those, per spec.
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[Wildthings]

This is your brake

Here are a couple of pictures taken from the Samba gallery, note the difference in how far in the lower end of the parking break lever is sitting. Yours is way too tight.

[kreemoweet]

Here's a thread that contains a photo of the 72-only pin that goes along with the clip mentioned above:
https://www.thesamba.com/vw/forum/viewtopic.php?t=509977

The p.b. lever is also a 72-only item, but one can't see what the OP has becasue the wheel hub is hiding it in
all the photos. Wildthings is right on, either the p.b. cables are inappropriately tight, or there's some
sort of interference due to non-stock parts being used.
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'71 kombi: not yet seized by the authorities

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[Ben Middleton]

Here we go again.

I went to a local scrap yard and sourced the correct pin for the spreader bar. It made no difference to the brakes rubbing after I installed it.

Every time I bled the left rear I noticed that the brake fluid was dirty, and those brake shoes were obviously rubbing so I decided to replace the brake cylinder with a new one, even though it wasn't leaking. This stopped the shoes rubbing.

I bled the rear brakes again and I adjusted them. They're still not adjusted very high, but at least they're not rubbing at the lowest setting.

During testing, I still have a major issue with the brake pedal stopping at different points in its travel and the braking performance is dangerously bad. When I pump the pedal, it does get harder and higher so that suggests there is air in the system but I've bled it so many times it's getting ridiculous now. I must have spent £30 on brake fluid alone.

The handbrake is completely disconnected at the moment. The brakes are not rubbing anymore and are completely cool after a drive, so that's progress I suppose.

Also, looking at that photo one of you showed of the '72 spreader bar - that is different from both of the spreader bars on my bus. Mine matches the drawing in the lower right of this image:

[Ben Middleton]

Since I replaced the other damaged brake cylinder, the shoes don’t rub at the lowest setting. However, to get the brakes functioning I’ve had to adjust them up so that they are rubbing. Thankfully, the drums aren’t getting too hot so I’m using the rubbing to shape the shoes correctly and I’ll readjust them when the drums are completely cool after a drive.

Hopefully this will be the end of this saga!

[Ben Middleton]

We return to the braking saga! I did an interesting experiment today and would love to hear opinions. But first, just as a note, I started a different thread regarding my parking brake which is shown here:

https://www.thesamba.com/vw/forum/viewtopic.php?t=722326&highlight=

I'll now continue any updates in this original thread instead.

I tried resetting my rear brakes many times, using all different methods suggested. To cut a long story short, they have to be adjusted so low that they're barely functional. However, the interesting thing to note is that when I adjust the brakes up, they begin to rub intermittently as I rotate the drum. It's not a continuous rubbing sound as you would expect. This suggests that the drums are warped (but they are both brand new, and I had the same problem with the previous drums which I had had professionally recut).

I tested both drums today to see if they are moving vertically under rotation. Please view the following video to see the tests being undertaken:


Link


What could be causing this amount of movement in the drums? I'm focusing on the difference between the lowest point and the highest point. As you can see, the first drum (passenger side) moves significantly more than the second drum (driver side). I did replace the CV joints on only the driver side driveshaft recently, so it is possible that the CV joints on the passenger side are worn - could this be causing the dramatic difference? I did receive one suggestion that maybe the driveshafts are bent and that is causing the movement. I'd like to hear any and all opinions you have!

Finally, I have noticed that the shoes rub more on the edges than in the centre, so in the morning I will fettle them and make sure they fit the drums perfectly.

On a final note, referencing the discussion in the parking brake thread I linked to at the beginning of this post, here is a photo of the gaps in the ends of the spreader bar for the parking brake. It was previously suggested that this gap can wear deeper and cause the parking brake to require extra tightening to work. Do these gap sizes look normal?

Thanks again guys for taking the time to read about my hell

[Abscate]

I think you are just way too loosely adjusted.

Crank the adjusters down alternately until the drum won't move. Then back each one off two clicks, no more.

Test drive.

If you drums are out of round, the brakes wont work, so check that next.
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[busdaddy]

Your video proves nothing, the outer side of the casting will always measure oddly. It's the inside surface where the shoes touch that counts, if you don't have a tool to hold them for testing then removing a backing plate and bolting them back on (including the wheel) is the only sure way to measure runout.

Severely loose brakes will be grabby and lock up, try running them tight and see how it works.
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[SGKent]

do the drums sit all the way over the central hub? There is a locating ring on the hub that centers the drum. Make sure that it isn't deformed where the drums cannot sit all the way over it. That is what centers the drum. If there is any play where the center hole in the drum is too large it can allow the drum to be off center. If so you may have to tap the drum with a plastic mallet, piece of wood with the two bolts lightly tightened until if runs true. If the center of the hub has an uneven build up of rust on it that can cause the drums to run off center too. A tire strike on a curb can bend or warp an axle. Do you own a runout gauge and a magnetic base, if so use it to determine what part is warped and has the run out.

Your front rotors look worn out and glazed, but they aren't the rear problem unless the front calipers are binding and that causes the rear drums to lock when you are stopping. A bad proportioning valve can cause the rear to get too much pressure on hard breaking but VW proportioning valves are pretty simple.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Ben Middleton]

My shoes were only rubbing on the edges, so I have now fettled them to fit the drums. The passenger side shoes were 0.73mm out of true and the driver's side shoes were 0.4mm out of true.

[Abscate]

Lets pull off the rear drums, and the shoes, and show us a picture of the shoes being held in the drums, so we can see the radii of these parts and how close they are.

You have a wrong part in there, somewhere, I think.

PS - Im even grumpier than Steve, but I admire your fortitude for sticking this out. With that attitude, you will get it done, no fear!
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[Ben Middleton]

I've currently got the shoes on the drums but I'll do that ASAP!

On another note, I looked at this rebuild kit for the drum brakes. I don't have the two small springs I've circled in the image below, does anyone know what these are for and should I be using them on my 1972 braking system (Aug 71-Dec 72)?

[busdaddy]

The tiny springs are for early wide five brakes, yours use the single larger spring across between the shoes.
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[Ben Middleton]

I'm going to give a review of the work I've done to the brakes, but first I have a question:

1972 brakes. They have only one spreader bar. The Bentley states that each shoe should be adjusted up by 3 clicks alternately until the brakes begin to rub. Then you back them off 3 to 4 clicks.

The problem is - the front shoe rubs waaaaaay before the rear one does. I could back the front-facing shoes off by the 3 clicks and then increase the rear-facing shoes by another 30 clicks before that shoe begins to rub!

What is the correct method for the 1972 brakes?

Now, regarding the things I've done to this braking system to try and solve the issue of the rear right brake rubbing (and other issues):

Replaced Parts

- Rear drums
- Rear shoes
- Rear brake backing plates
- All drum brake springs and clips
- Both rear brake cylinders
- Handbrake cables
- Most of the copper brake lines
- All of the rubber brake lines
- Front brake discs
- Front brake pads
- Brake calliper rebuild kits (front brakes)
- All wheel bearings (front and back)
- Master cylinder
- Brake servo (booster)

I have also reconditioned the rear brake pressure regulator, rebuilt the (brand new) master cylinder, dismantled and rebuilt the front brake calipers, adjusted the brake servo locating rod, and obviously changed all the brake fluid (a thousand times). And, finally, I added shims to the rear bearing housings to bring the drums further away from the new brake backing plates which notoriously rub due to bad manufacturing. It definitely helped when I added them. Maybe I just need a couple more shims on each side.

And guess what..

I just went on a long trip around the UK for five days. The bus seemed fine at first but I had a difficult moment on a hill. I needed to adjust the handbrake more. I tightened it slightly.

Over the next few days I noticed that the engine was getting very hot and so were the drum brakes (particularly the right rear). I was also losing a lot of oil (probably because it was burning off).

Despite this, the van happily flew along the motorway at 80mph. Yes, some days the ambient temperature was hot, but some days it wasn't. And yes, the engine and brakes became hot very quickly into any journey; not just after the high speed trips.

In conclusion, I'm stumped. This is why I have asked the first question. I think there is an issue with one of the shoes (probably the front) connecting with the drum way before the other shoe. That shoe is probably already rubbing and it didn't take much of an increase in the handbrake tension for the rubbing to worsen.

This would also explain why, despite the shoes rubbing, the handbrake is still ineffective on steep hills.

As always, any advice is appreciated. Thanks for all your help chaps.