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Discussion Starter #1
Hi everybody,

i would greatly appreciate your input on a brake related problem that is driving me nuts.

My passenger side rear drum brake has some kind of drag. By some kind i mean, that it gets kind of hot when driving (after 20 miles, driver side is still almost cold, passender almost too hot to touch).

When i put the car on the lift and try to turn the wheel by hand i notice, that it's not a constant drag. Instead, when turning 360° it's only 1/4 that actually drags, the other 3/4 are without a drag.

Here comes the tricky part: when i remove the wheel, but drum still on, the drag is gone. Of course when removing the drum, there is also no drag. When i start mounting the wheel (also tested with a wheel spacer) and begin to tighten the lug nuts it starts to drag again in the same way. This is reproducable.

What i did:

- Rebuild the brakes twice (all new parts) - double checked with driver side, everything moves
- New wheel cylinder, rods are moving (can push them back)
- Checked restriction in brake line -> opening bleeder valve does not release the drag
- Changed brake drums passenger and driver -> no changes, still drag on passenger side
- Put on an old brake drum i had lying arround -> still drags
- Unhooked emergency brake, no change

If it helps: it's a typical 9,5 gm drum setup on a moser 12 bolt (new).

I hope you can help me finding the problem.

Thank you very much in advance.

Best regards
Alex
 

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Sounds like the axle is bent or the end is just slightly off or there is something wrong with one of the pads. I know you said the axle housing is new. Does that mean new axles as well?
Double check (if you haven't already) and make sure the wheel studs are seated properly.
Can you tighten the lug nuts to drum with the spacer or something on the drum but without the rim to eliminate the rim as a source of the problem?
You have already checked off most of the troubleshooting ideas that I had. Hopefully it is something simple!
 

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Discussion Starter #4
did the shoes get arched to drum??
Not sure what exaclty you mean. What i did was painting with chalk along the pads, put the drum on and turned the drum once. This showed that both pads make slight contact on the top only (with no brakes engaged of course).

Is that what you mean?
 

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Discussion Starter #5
How can i make sure the axle is fine/ not bend?

Axles are also new, though. Complete rear end from moser but without the brakes.

I will double check the studs, but already did.

I can and did tighten the nuts with the spacer only (without rim), so yes, rim is out of the game. Also switched the spacer from passenger to driver to make sure it's not the spacer.



Sounds like the axle is bent or the end is just slightly off or there is something wrong with one of the pads. I know you said the axle housing is new. Does that mean new axles as well?
Double check (if you haven't already) and make sure the wheel studs are seated properly.
Can you tighten the lug nuts to drum with the spacer or something on the drum but without the rim to eliminate the rim as a source of the problem?
You have already checked off most of the troubleshooting ideas that I had. Hopefully it is something simple!
 

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arching brake shoes is a lost art but when all cars had drum brakes it was a common part of doing a drum brake job. Basically you match the new shoes to the new or turned brake drum so the shoe contact to drum is uniform...not just in a small part of the shoe. Typically brake shoes would make contact top & bottom or center only because the "arch" of the shoe and the "radius" of drum were not the same. A machine would grind the shoe to conform equally to the drum. Back in the day auto part stores would do this when you bought shoes & drums but that stopped many years ago

When drum gets hot from brake use variances in contact between pad & drum get tighter and you will get brake drag

IDK why in your case why the rim off you don't have the problem but do when wheel is on other than one or more of the axle studs are crocked or the rim is bent in the hub face which when tightened will distort the drum pushing it onto the sides of the shoe
 

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Al - Waterloo, Iowa
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Alex, A few things come to mind. If you can post pics of the brakes with the drum(s)
removed it would help greatly. You may have mismatched shoes and drums. Are both
shoes resting against the top pivot pin? A frozen or partially frozen parking brake cable
can cause the tops of the shoes to be held away from the pivot pin. The backing plate
pads could be grooved and causing the shoes to not seat properly. It may just be incorrect
assembly. There is a short shoe (primary-forward) and a long shoe (secondary-rearward)
on each side. I've seen people install both primary shoes on one side and then the secondary
shoes on the other side. I've also seen the springs installed incorrectly.

 

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Discussion Starter #8
Thanks for sharing your knowledge concerning arching - sounds very locial and very much like something todays society "just don't care about".

You say that the maybe disorted drum may push into the side of the shoe: this should cause grinds on the side of the shoe and also the drum, right? I checked that and cannot see anything...

Anyway, how to best check if the studs are crocked? At least by visual inspection, they look fine.

arching brake shoes is a lost art but when all cars had drum brakes it was a common part of doing a drum brake job. Basically you match the new shoes to the new or turned brake drum so the shoe contact to drum is uniform...not just in a small part of the shoe. Typically brake shoes would make contact top & bottom or center only because the "arch" of the shoe and the "radius" of drum were not the same. A machine would grind the shoe to conform equally to the drum. Back in the day auto part stores would do this when you bought shoes & drums but that stopped many years ago

When drum gets hot from brake use variances in contact between pad & drum get tighter and you will get brake drag

IDK why in your case why the rim off you don't have the problem but do when wheel is on other than one or more of the axle studs are crocked or the rim is bent in the hub face which when tightened will distort the drum pushing it onto the sides of the shoe
 

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Discussion Starter #9
@allanjs: thanks for the input. I attached two pictures. First one is fine (driver), second is the problem side (passenger).

Actually both sides do not perfectly touch the pin on the top, but it rather seems to be a little push from the wheel cylinder rod than the parking brake cable.

The shoes are the same left and right (i mean, all new, same parts). I took care on the primary, secondary shoe thing. Bigger (secondary) is facing to end of car, smaller shoe (primary) is facing to engine.

Do you think an old backing plate can cause this issue, that it only drags partially when pressure applied (lug nuts and rim tightened)? Is there a conenction? The backing plate is actually the only old part on that rear end.
 

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Al - Waterloo, Iowa
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The shoes should be against the top pivot pin. Have you released the parking brake cables
from the main cable so you can work the inner cable ensuring it is totally free and not binding?
It doesn't take much for them to bind up. Did you sand or otherwise smooth the backing plate
pads where the shoes slide, and lube them? It's important. You've already proven the shoes are
dragging at the top so that's what I'm going on at this point. The return springs will overcome
whatever slight pressure the wheel cylinders are exerting unless you've got a hydraulic problem
causing pressure when at rest.
 

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Discussion Starter #13
Ok i will check what prevents the shoes to not be completely flush on the top pivot point. I installed new parking brake cables and the problem also existed with the old ones, but nevertheless, i will check.

I can also try to put on some old schoes and when i do that also sand and lube the backing plate pads.


I will do those checks tomorrow.


But until then: assuming the problem is, that the shoes do no completely meet on the pivot point and the drum drags on the top of the shoes:

How the heck does this lead to only become a problem once i tighten the drum and even more heck - how it only occours 1/4 of a complete 360° spin?


The shoes should be against the top pivot pin. Have you released the parking brake cables
from the main cable so you can work the inner cable ensuring it is totally free and not binding?
It doesn't take much for them to bind up. Did you sand or otherwise smooth the backing plate
pads where the shoes slide, and lube them? It's important. You've already proven the shoes are
dragging at the top so that's what I'm going on at this point. The return springs will overcome
whatever slight pressure the wheel cylinders are exerting unless you've got a hydraulic problem
causing pressure when at rest.
 

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Al - Waterloo, Iowa
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Alex, Try this. With the wheel removed install the lug nuts reversed so the nuts flat side is
up against the drum. Snug up the nuts. They don't have to be torqued. Rotate the drum
and mark it at the the point the drag occurs. I would mark it at 12 o'clock for simplicity.
Now remove the drum and relocate (rotate) it on the axle 2 studs from previous location.
Tighten nuts again and turn the drum. Note the location of the drum when the drag occurs.
If the mark is at 12 o'clock then the problem is with the drum or brakes. If it's not at 12 o'clock
then the problem is with the axle.
 

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Discussion Starter #15
Allanjs, thats a very good idea.

I was thinking it through and i come to the conclusion that if the mark is at 12 in the second run, the drum has to be the problem.

But then it cannot be the brakes according to my logic, because the brakes are not moving.

This means that if in the second run, the mark is not at 12, its either brakes or axle, but the drum is fine.

Am i right or wrong?
 

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I like Al's idea. Maybe try lightly dusting the drum with some sort of dry powder (flour, baking soda, baking powder, graphite ?, etc) that would easily come off with a blast of air. Spin it one rotation and it should be blatantly obvious where the rubbing is happening. It will be missing from the drum and be on the pad or a certain part of the pad, or who know where else.
 

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Al - Waterloo, Iowa
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What this is checking is the concentricity between the drum and the axle.
If the drum stops at the same point then the drum is out of round. If not
the axle has run out. If it was easy to do I would suggest swapping the axles
side to side. You said the same problem occurs with an old drum so I'm leaning
towards an axle problem. Just trying to systematically diagnose.
 

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Discussion Starter #18
Thank you both for your further explanations.

I did what you propposed, Al and Robert, marking the drum inside and outside. On the second run, it did not drag at the 12 mark, but "later". It also showed marks on the top of the shoes. Same thing with different drums.

And i discovered another thing and it's related to the shoes not being perfectly flush to the upper pivot point (as stated before): Actually the shoes sit flush horizontally, but not vertically. They are pushing a little upwards (towards quarter panel), can be pushed down, but will come up again. When mounting the drum without tightening, i can push the drum a tiny bit downwards. It feels that i move this vertical offset of the shoes a bit down with the drum. After tightening, the drag occured again. Now i ASSUME, that this vertical offset of the shoes causes the drum not being centered properly and if i then tighten it down, it's dragging.

This made me rework the whole brake once again, but this time i used old shoes that i had laying arround. The vertical offset got better with the old shoes and after using an old drum, there is now no more drag. On the other side (driver), i still have the new components (shoes and drum) and it's working fine - no drag at all.

So i'm currently not sure if this will persist after driving it and after the brakes adjusted themselves, but it seems that somehow the shoes do not perfectly fit to the application. Don't ask me why this problem only occurs on one side.

So far, I'd say "fixed" until i took it for a testride... I'll report if the problem occurs again.

Anyhow, very strange problem in my opinion! Thank you all a lot for your input!!!
 

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I had a similar problem after doing rear brakes, the drums would get hot so much as you could not touch them. You could see where the shoes were hitting on the top and bottom of shoe, nothing in the center. I tried to find someone to arc the shoes, no luck, so i adjusted the brakes loose enough to where the drums did not get hot, and as the shoes wore in to match the drum i adjusted them to where they need to be. No more hot drums. Yours should wear in the same way. I never thought about axle problems, but my brakes are fine now.
 

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Al - Waterloo, Iowa
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Alex, Explain what you mean by "after the brakes adjusted themselves" please.
You must manually adjust them to start with. If you haven't that may explain
why the shoes aren't contacting the pivot pin as they should. When you adjust
them the shoe arc (radius) is actually changing due to the adjuster moves the
bottom of the shoes outward. This action also causes pressure on the upper
portion of the shoe moving it towards the pivot pin. Backing up and stopping
or activating the parking brake causes the self adjuster to activate but it's very
slight increments and should not be relied upon for initial adjustment. As you
adjust the shoes rotate the drum. You want a slight drag but not tight. I think
you'll be surprised how far you have to turn the adjuster to get contact as the
arc is changing. Not knowing your experience level makes it difficult to instruct
so if you're aware of all of this just disregard my info.
 
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