Re: Brake Drum Thickness

Posted by Joe on April 29, 1998 at 11:07:02

In Reply to: Brake Drum Thickness
posted by Roger Dean on April 29, 1998 at 08:57:26

: Can anyone tell me what the real minimum for brake drum thickness is?I've read in various places that the drums are junk if the wall thickness is less than .120", .130", .110", etc.
Roger
Yes, I've noted that several numbers are floating around for minimum brake drum thickness.My drums are currently worn to an average of the mid .120's depending upon where you measure as they are quite grooved and it is difficult to get a good measure. Some of the grooves are significantly below .120.
Note, however that the grooves are parallel to the "hoop stress" which the drums undergo during braking.Also, I consider my brakes to be "severely worn" and are probably unsafe for anything beyond an occasional parade.
My Snyder's catalog indicates .130 is the minimum.Some of the "How to Restore Your Model A" books indicate .120.I can't recall having seen .110 anywhere but I'm sure it exists.
The problem with generating a "minimum" number for this is that it is entirely in the judgement of the person doing the turning.If your are determined to stay with your pressed drums, I suggest to consult with this person since they do it all the time and they may have seen a similar circumstance.Being myself at the average mid .120's with somewhat successful (or at least usable) brakes, I would assume you could go to at least this amount.
But, once you get the work done, assuming it can be done, you still have the pressed steel drums and their fade problems.You also will likely end up with the "brake shims" on your front push rods and be near limit of adjustment on the rears.
I advise if you have the chance (and the wallet) consider seriously a change over to cast iron drums.Even Ford, once stocks of the pressed steel drum brakes were exhausted, changed over to a cast iron drum for replacement service on the Model A.Despite today's high level of competition in the judging crowd, cast iron drums are not disallowed or cause for a downgrade.This is done this way in the interest of safety.
Ultimately, you (and your car) will be the bearer of the largest element of risk.I am inclined to advocate that the brakes are one area where "no compromises" are advised and even the use of reinforcing bands was a stopgap of the era which improved greatly but did not bring up to standards of the time the Model A brakes.
I know my "A" future includes a set of cast iron drums.
Drive safely.Best regards,
Joe

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