Are these brake drums still usuable ??? - Team Camaro Tech
Brakes, Suspension & Steering Conversion questions, Steering & Handling

 
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post #1 of 8 (permalink) Old Mar 7th, 18, 06:12 PM Thread Starter
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Are these brake drums still usuable ???

I had asked in another thread if my '68 rear brake drums looked original and it was thought that they were.

Now, I am not sure if there is enough material on them to turn them and still get a reasonable amount of use out of them.

I took to them to a shop today and had the inside diameters measured. They measured 9.524" and 9.523".

A new drum would be 9.500" diameter. Looking at information from different sources, it looks like the maximum dia. they can be turned to is 9.560".....and the discard diameter is 9.590".

This would tell me I have plenty of material left but this is what is confusing me. The 1968 Chassis Service Manual says, "If a drum has to be re-bored more than .020 over the standard diameter, it should be re-bored to .060 diameter oversize and the brake facing should be replaced with .030 oversize facings."

Since my drums are already more than .020 past the standard diameter, the service manual is saying I would have to turn them to 9.560 and use oversized shoes. I'm not saying they aren't out there but I've never noticed anyone offering .030 over brake shoes.

So I'm not sure now that if I have these drums turned just enough to put a fresh surface on them, they will still be usable with the standard shoes that everyone offers.

Thanks.....Dave

1968, 327 210 HP, Power Steering, Power Disc Brakes, Custom Interior, 4 Speed, Console, Gauges, Tilt Wheel, Speed Warning, Fiber Optics, 10 Bolt 3.55 Posi Rear end......Owned since 1978.
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post #2 of 8 (permalink) Old Mar 7th, 18, 07:03 PM
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Re: Are these brake drums still usuable ???

In a perfect world, like it was in 1968, that would be the case. At that time oversize shoes were readily available. Now they're not. I say just turn the drums so that they're round and still within the .060 cut off, not even worrying if many of the grooves still show. Throw a new set of shoes on it and call it good.

For the record, I have turned literally thousands of drums. I have also refused to turn at least twice that or more. Your machinist knows best, if you can find one that is experienced, that is.

Jon N

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post #3 of 8 (permalink) Old Mar 8th, 18, 12:24 AM
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Re: Are these brake drums still usuable ???

Jon, why would the chassis manual make that recommendation (in bold type in the OP) ? I've never heard of that. Shouldn't be any problem adjusting the brakes if the drums were say .030-.040 over (9.530-9.540), with standard linings (shoes)...

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post #4 of 8 (permalink) Old Mar 8th, 18, 02:45 AM
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Re: Are these brake drums still usuable ???

IF, IF the drums can be just skim cut to clean up, AND still be in specs, I would go with them. (IF this was just a weekend cruiser)

But with that said.....

NOW IF, you plan to drive hard, go fast, get a new pair. (less worries/troubles)

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1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #5 of 8 (permalink) Old Mar 8th, 18, 05:30 AM
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Re: Are these brake drums still usuable ???

Brake drums are considered consumable like oil and filters and being original adds nothing to the value of the car.

If not in specs after turning then toss them and get new ones. They aren't that expensive
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post #6 of 8 (permalink) Old Mar 8th, 18, 07:27 AM
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Re: Are these brake drums still usuable ???

Quote:
Originally Posted by Garfields Maro View Post
Jon, why would the chassis manual make that recommendation (in bold type in the OP) ? I've never heard of that. Shouldn't be any problem adjusting the brakes if the drums were say .030-.040 over (9.530-9.540), with standard linings (shoes)...
GM probably didn't want to be sued. It's even worse now than it was in 68. More lawyers looking to make a name for themself and get a paycheck at the same time. That's just my opinion. Your mileage may vary.

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post #7 of 8 (permalink) Old Mar 8th, 18, 06:29 PM Thread Starter
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Re: Are these brake drums still usuable ???

Thanks for all of the replies.

Weighing all of the opinions here plus the fact that these drums are pretty rust pitted on the outside I went ahead and ordered new ones today.

Thanks again......Dave

1968, 327 210 HP, Power Steering, Power Disc Brakes, Custom Interior, 4 Speed, Console, Gauges, Tilt Wheel, Speed Warning, Fiber Optics, 10 Bolt 3.55 Posi Rear end......Owned since 1978.
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post #8 of 8 (permalink) Old Mar 11th, 18, 06:09 PM
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Re: Are these brake drums still usuable ???

Due to Asbestos exposure, I haven't heard of any shops doing brake shoe arcing anymore. It used to be common practice to re-arc the linings to match a turned drum. Even though Asbestos is no longer used, there are still exposure risks I guess. If the lining arc does not match the drum, the brakes will be terrible.

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