Brake drum tolerences

Casey B · #1 09-09-11, 18:11

I was wondering if any one knew what the max tolerences were for the brake drums on an M38A1 with 9inch drums?
i measured with calipers and mine are 9 inches inside dia...so when are they too thin or too large a dia. to use safely...

I have Provincial inspection coming up for licencing and so it will undergo the scrutiny of the Gov. Once again!

Thanks Casey

BCA · #2 09-09-11, 18:55

Jeep brake drums were nominally 9" (except for M38A1CDN3 of course; @ 10"). While most modern drums are marked with the allowable tolerances, most old jeep brake drums are not marked so inspectors don't know what is allowable. I believe 0.060 is the limit but I can't recall seeing this spec in any military jeep manuals. You'll have to sweet talk the inspector that 0.060 is tolerable.
........ Brian

Casey B · #3 09-09-11, 20:45

Okay thanks Brian! he seems pretty reasonable as he is giving me the heads up on what i need to have done to it.

chris vickery · #4 09-09-11, 23:55

Casey, I just did my CDN3 and it has 10", they are stamped 10.060" dia max. I would agree with Brian that 9s are most likely the same. The most important thing is that they are not overly warped. I was fortunate enough to be able to have mine machined around .020 a side (.040" overall)
With brand new shoes I would not sweat it too much. As a sidenote, your CDN2 will require regular brake shoe adjustments anyhow considering that they are manual adjusters.
If you have any issues or are not comfortable, 9" drums are common and very inexpensive.

Casey B · #5 10-09-11, 14:42

Hi Chris yes will have the shoes relined at a place near home and the e brake as well...and drums probably turned as well thanks for the good advice Casey