So, I figure I should get some more opinions on running oversized drums. The ones I have should clean up around 12.080 -12.100. My local shoe reliner is willing to turn them and fit oversized shoes. I know this was common practice before new was available. New drums are pricey @ 125each. I know with brakes that's still cheap when you are betting on you life. I am just wondering what is "safe" or "acceptable".
Check your state law and see what is the maximum (ask at a brake shop). If you are over that and involved in an accident a clever lawyer could clean you out (and in this case I would agree with them). Charlie Stephens
is it 12.60 or 12.060? I know it's one of those numbers. I've seen both of those referenced as Max Turn but I'm not sure which and there is a big difference. Also I have seen 12.90/ 12.090 as discard. You are probably correct. But I'm not asking for legal advice.I'm sure a clever lawyer would get me on the fact that the brakes aren't original to the car either or the fact that it's built out of parts from like nine different years of vehicles. I guess I should have written a better original post. My shoe reliner says it's pretty common to oversize. I'm just curious how common it is/was and what others have done. He knows I am trying to build it cheap. But I don't want to be stupid. I do plan to drive this thing and I don't want to wish I'd gone another route later. or have problems with overheating brakes. regardless, I don't think I'm going to run them. I'll use them for mock up. It will be awhile before I need brakes anyways I think it makes more sense to save for Lincoln self-energizers than just drums for this mine.
My brake guy went a little too far getting rid of some pitting. With new shoes they still stopped really good. I don't have the exact measurement, lets just say I would have liked him to stop cutting a feww passes sooner!
A lot depends on the car weight ,under 2000 12.100 would be fine. I've been in the auto trades 50 years and before the Feds stuck their nose in shops that I worked in would go .090 on a regular basis. You have to have a base line for OS and the Feds decided .060 was going to be it and of course you also have to allow for further wear say another .030 or so. Again common sense should be your guide.
12.060...(60 thousandths) is max on '39-'48 ford drums. I'd go 12.080 on the rears but the fronts I'd max at 12.060...The "new" drums you can go 12.090.....
My truck drums were around 12.090 or so, ive been driving it for 7 years, they are not warped and the brakes work awsome. usually 12.090 is what i go to. JEFF
dont go over .060 over. thats the general stopping point. but i know guys that have gone more than that and have been fine.....
Are there specs available on the max oversize permitted? I know the old drums didn't have the info cast into them like drums of the 1960's and up. I think you'll be ok at .100 over, but use all new hardware and quality shoes and let them break in. Take a rasp and bevel the leading and trailing edge of the shoes a little to expedite the break in process. I always kept front drums turned within .010 of each other. So, go easy on them for the first 500 miles and if you don't end up with any hot spots in the drums, you should be ok. Bob
Just FWIW: A drum (or disc) operates by turning the friction from the shoes into heat. Simple enough. The factor that is less well understood is the heat retention of the drum. Said drum must dissipate said heat into the air, but, must also allow for multiple stops. So, the drum must be able to retain a certain amount of heat to work properly. And the only method any drum (or disc) has to retain heat is the mass of the drum. In other words, it's weight. Cut down any on the mass of the drum, and you lose heat retention. Lose heat retention, and you will experience fade. Once you experience fade, you WILL become religious (as in "Oh, GOD, PLEASE make this thing STOP, NOW!!!!!"). Turning drums most definitely cuts out mass, and will reduce heat retention. Cut more at your own, and, sadly, others', risk. Cosmo
I would watch the area that 440 roadrunner mentions. I had one drum that had been cut to spec crack along that perimeter area.
One thing that will help eliminate the abovementioned situation is to have the brake shoes ground on an arcing machine, if you can find anyone that still does it. Arcing the shoes matches them to the circumfrence of the drum, and makes for more complete shoe to drum contact. It's worthwhile, especially when using a non self energizing system such as the '39-'48 Ford setup.
Hey Hitchhiker, Durms have a camphered edge around the outside of the shoe bearing surface. Rule of thumb was if the campher was too thin to allow the drum to be turned down smooth again, it had to be replaced. Hope this helps. SAFU
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