Brake drums

M

modelacarman

Junior Member
I have new cast iron brake drums that are out of round. I've had them turned down twice at different shops and they are still out of round, to the point my front end shimmys when I stop. What is wrong? Any help would be appreciated!
 
modelacarman said:
I have new cast iron brake drums that are out of round. I've had them turned down twice at different shops and they are still out of round, to the point my front end shimmys when I stop. What is wrong? Any help would be appreciated!
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How do you know they are out of round? Did the shops that turned them say they could not be trued? There are plenty of other reasons why an A front end will shimmy while stopping.
 
Most commercial shops can turn the front Model A drums as they are not any different than later cars. They use tapered cones to center on the taper of the bearing races. However, the rear drums are a different story. To turn the rear drums a tapered shaft is need to center the drum on the lathe. Since a commercial shop does not have such a device they try to center the drum with their cones and the drum ends up out of round.

A good rule of thumb is never take a Model A project to a shop that does not speak Model A.

Tom Endy
 
Back to modelacarman's original question. As I understand, centering the shoes will make the shoes contact the drum evenly all around the drum. If the shoes are not centered, they will still contact the drum, but maybe not on the entire drum, but he still should have constant contact somewhere, shouldn't he? If this is the case, then why does he have a shimmy? I would think something is not perfectly round.
Marty
 
marty in Ohio said:
Back to modelacarman's original question. As I understand, centering the shoes will make the shoes contact the drum evenly all around the drum. If the shoes are not centered, they will still contact the drum, but maybe not on the entire drum, but he still should have constant contact somewhere, shouldn't he? If this is the case, then why does he have a shimmy? I would think something is not perfectly round.
Marty
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You're right, and I would start by driving slowly on a smooth surface and lightly apply the brakes. If the drums are out of round you should feel a pulsating pedal.
 
Mitch//pa said:
Most modern shops have the AAMCO brake lathe... All that is needed to turn the rear drums is the VW arbor kit
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You beat me to it, my AAMCO, 2000 lathe had a skinny arbor that popped on & could turn ANYTHING.
I made LOTS of $$$$'s, turning "dropped off" rotors & drums, had a sign above the lathe, "ONLY IF THEY'RE TOTALLY SHINING CLEAN"!!!
Dad
 
marty in Ohio said:
Back to modelacarman's original question. As I understand, centering the shoes will make the shoes contact the drum evenly all around the drum. If the shoes are not centered, they will still contact the drum, but maybe not on the entire drum, but he still should have constant contact somewhere, shouldn't he? If this is the case, then why does he have a shimmy? I would think something is not perfectly round.
Marty
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You're right Marty. My bad. The shimmy could be due to a variety of things, but the lack of constant contact of the shoes/drum would not be caused by shoes not centered.
 
Are you using original A wheels?

Are the surfaces of the wheel that touch the drum level and smooth?
I powder coated my wheels and had uneven coverage on the surface that touched the drums. This warped the drums quite a bit.

I checked my drums for roundness after cutting them, did you check yours?
 
Hi Carman,

Just one thought:

With respect to your mentioned "front" brake problems, (as correctly suggested above), if your brake bands are not concentric to the axles, your service brake linings, (brake shoes) will also not be centered; hence your problem condition occurs as you correctly state in your reply no. 3:

"When I adjust them, the wheel turns free half way around then is hard to turn."

Different Suggested Choices:

1. You could keep returning to different brake shops paying for brake turning services until your "new" drums are paper thin; or,

2. You could end your "unknown" misery by getting a brake shoe measuring & "centering" tool offered by one of the parts suppliers to try to verify "if" the cause of your service brake lining binding is caused by non-centered front brake shoes.

3. Lots of time, if worn front roller tracks were either replaced with new rivets, or welded and ground smooth, they were not "always" positioned correctly to insure that the brake shoes are centered; hence, if this is the case, they must be removed and replaced or adjusted ............ or ...... if not too much off center, (which happens very often), the service brake linings can be ground down, especially at "ends" of brake linings such that they are centered and will not cause binding.

Like anything else in life, if one does not recognize the "real" problem, one can spend years trying thousands of recommended solutions that never resolved the problem.

Like in this mornings Fox Website News concerning Global Warming, Cow Farts in California will now be regulated ..... we are surrounded and they are closing in.

Wishing the best.
 
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Brake Drums

When I installed my AR wheels (1" deep in centre as opposed to 1 1/4 for regular A wheels) there is a gap between the AR wheel and the supposedly AR new drums. Will this compromise the wheel strength ? My only other solution I think would be to replace all four drums with a new AR hub (if available) swedged onto proper AR drums. This is a 700 plus option per wheel in Canada for the regular A hub/drums OR is there a spacer of some sort I should put between the drum and wheel?

We have virtually no one in our area who knows how to swedge these together so I rely solely on the expertise from this forum or speaking to someone from other sources on the internet re this and other issues with my AR.
 
I have the same problem with my new cast iron drums (not that I'm saying it's the drums at all). The rears will spin freely for 180 degrees and drag for 180. I just assumed it was the backing plates since I never touched them. Was I correct in assuming that?
 
If the backing plate had a high spot and the drum, hub, bearing, axle and bearing races were true, it would drag all the way around. It's not the backing plate. It is one of the elements of the rotating assembly.
 
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