DRUM SIZE
- Thread starter nodemon
- Start date
-
Drum diameter is measured on the inside (the braking surface area). Drum width is measured the same way — the width of the inside braking surface, which is roughly the width of the shoe, though there is always a little extra width on the drum. So you need to remove the drum, or interpolate/guesstimate.
72 Demon
cudamark
Well-Known Member
If it's factory, you could have 9" or 10" brakes. The front would be either 9 X 2 1/2", or 10 X 2 1/4". The rears would be 9" X 2" or 10" X 1 3/4". Usually the 6 cyl cars came with 9" brakes and the V8 cars came with the 10". If your car came with disc brakes in the front, they would have had 10" brakes in the rear. As mentioned, the diameter is measured on the inside of the drum surface....where the shoes ride. Measuring the width of the drum can be tricky as there were several different manufacturers of drums and they didn't all have the same width shoe surface. Assuming the exiting shoes are correct, just measure the width of the shoe to get a replacement.
The drum size will either be cast/stamped into the outer edge of the drums along with the maximum oversize depending on the brand and age of the drums.
Not always a good idea to just buy what came off. The wrong parts could have been installed the last time.
Always refer to the Factory Service Manual.
Not always a good idea to just buy what came off. The wrong parts could have been installed the last time.
Always refer to the Factory Service Manual.
cudamark
Well-Known Member
Most of the early drums were not stamped, and have .060 as the maximum you can take off. Most aftermarket drums are stamped, and have .090 as the limit.
67Dart273
Well-Known Member
A few other things. If buying used drums use a jaundiced eye. Find someone or figure a way to "mike" them to be sure they are not worn oversize, and if used they will NEED to be turned. Drums wear different ways, "belled", "keg" and just plain irregular, as well as being beyond spec
The larger the drums are worn, the worst the shoes fit, because now the shoe dia and the drum dia are much different, and pretty soon the shoes only contact the drum "in the center" area of the shoe. This puts more stress on what little lining is in contact, and glazes/ overheats the lining.
The larger the drums are worn, the worst the shoes fit, because now the shoe dia and the drum dia are much different, and pretty soon the shoes only contact the drum "in the center" area of the shoe. This puts more stress on what little lining is in contact, and glazes/ overheats the lining.
cudamark
Well-Known Member
After staking new drums onto the front hubs, it's a good idea to check the run-out, and turn them on a lathe if needed. Most of the time they won't need much, just a light cut to true them up, but, sometimes they need a lot more. I've run across brand new drums that were so warped, they couldn't be used.
Brake drums are so inexpensive there is really no sense in buying used ones. Replace them all. The braking system is the one area where you want everything to be in top condition.
Safety first. Car is 50 years old. Things wear out, corrode, rust etc... Disc brakes ? Brake lines, hoses, bearings, seals, hardware kits, wheel cylinders ? master cylinder, flush complete system. Get out the Service Manual.
Service Manuals – MyMopar
Safety first. Car is 50 years old. Things wear out, corrode, rust etc... Disc brakes ? Brake lines, hoses, bearings, seals, hardware kits, wheel cylinders ? master cylinder, flush complete system. Get out the Service Manual.
Service Manuals – MyMopar
-
