Brake drum wear tolerance

[don58van]

I have started to recondition a pair of rear brakes on a 1968 model. One drum is junk. The other seems good and I would like to retain it because it is a MOWOG item.
Can someone please enlighten me on the initial internal diameter of a rear brake drum? Is there a factory-recommended amount of wear that is considered the threshold for replacement?

Don

[svenedin]

I don't know the measurements but in practical terms, when the drums can no longer be locked by using the adjusters, the drums are worn out. I have a pair of such rear drums that have worn out during my ownership. For worn front drums (8"), oversized adjusters can be purchased which can also be used for drums that have been scored and have required skimming. At the rear, I am not aware of oversized adjusters being made and if you tried to use the front 8" adjusters at the rear I think this would be too much of a jump up in size. Some owners have had trouble with brake shoes that are undersize and will not adjust up enough to lock the drum. Their solution has been to make a shim to fit under the adjuster. Obviously there are limits to this and if the drum wall is too thin it must be replaced.

Stephen

[Mervin]

"Some owners have had trouble with brake shoes that are undersize and will not adjust up enough to lock the drum."
Not particularly relevant, but I have experienced the opposite of that with a set of new front shoes. I had to remove some material from the ends of the shoes for them to clear the drum sufficiently when at the minimum adjustment.

[Bill_qaz]

I have started to recondition a pair of rear brakes on a 1968 model. One drum is junk. The other seems good and I would like to retain it because it is a MOWOG item.
Can someone please enlighten me on the initial internal diameter of a rear brake drum? Is there a factory-recommended amount of wear that is considered the threshold for replacement?

Don

The manual doesn't give a wear figure, only original sizes of 7" and 8"
As a guide only! classic mini recommends max 1/16" skim