The Stovebolt Site Forums The Shop Area Driveline Don't forget to check the spec on your brake drums

I'll save you all the long, gory details: the rear brakes kept hanging up on my '62 Suburban. The shoes would come out too far, and couldn't retract because they fell off their mounts or they fell off the little slider pads on the backing plate.

I bought a set of new drums from my local Car Quest.

With my fancy-shmancy drum caliper, this is what I found: factory spec is 11.00 inches, plus a .030-inch cut. Shop manual says that if you go to .060-inch, you'll need to get special oversized shoes.
I was at .287-inch. For those of us that are fractionally inclined, that's 1/32 and just under 2/32 respectively. I was at a tick over 7/32. YIKES.

I've got dual a dual reservoir, power booster conversion, and added self-adjust mechanisms. The rear drums hanging is from two things. The new drums should fix one, and a heat shield to protect the brake lines from the exhaust manifold will solve the other.
-Brad

Reading one of the old manuals, they interchange the depth of cut .030 with the actual diameter change, .060. My impression is that the smaller drums from the old days , 12" and under were good for .060. the larger drums were good for .125.

Generally speaking, .030" is the max machining on most passenger car and light truck drums, regardless of overall diameter, with .060" being the discard dimension. Usually, this is either cast or stamped on the drum, though not always. Unfortunatly, many "brake mechanics" have a tendacy to cut drums until they are true, regardles of how much has to come out to do it. Couple that on top of the fact that many shops brake lathes are in dire need of having the arbor zeroed out, that can take quite a bit of material out to true things up. Personally, if I have a drum that's taking more than .025" to clean up, I replace them. Same goes for rotors, depending on what the min spec is.