Do original drums have a marking of max dia. 11.090 or would that be a replacement part? What is the original GM part numbers and then the superceding numbers?
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Dino Lanno -
Re: 64 Drum Brakes
Dino-----
The service limit for brake drums should be the same for original or replacement brake drums, pretty much regardless of manufacturer. For parts like brakes which have significant SAFETY implications, very tight and industry-wide standards are generally adhered to.
The original brake drums for your car, assuming that it was not equipped with heavy duty or metallic brakes, are GM PART #3830166, front and GM #3868801, rear. The last available GM parts were GM PART #3872326, front and GM #3985944, rear. Both are GM-discontinued.
Be advised that the numbers that I provided are PART NUMBERS and NOT CASTING NUMBERS. The casting numbers found on GM brake drums are usually different from part numbers. However, if you find a 7 digit number cast into the drum which begins with "37", "38", or "39", you likely have a GM-sourced drum, original or replacement.
If your drums exceed the maximum diameter cast onto the drum by law, then the drums are scrap for road use, regardless of how original they might be.In Appreciation of John Hinckley
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