Cast iron drums and other brake questions

AA Ford Discussion Group relating to the repair and restoration of your AA Ford.
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RustydoubleA
Posts: 108
Joined: June 18th, 2014, 10:22 pm
Body Type: express
Model Year: 1930
Location: N. Calif.

Cast iron drums and other brake questions

Post by RustydoubleA »

I just acquired a pair of cast iron AA brake drums mounted on front hubs. I measured the drums and they are 1/16th" SMALLER than 14" I.D. The inside stud nuts were peened using a center punch. I suppose that someone took some brand new drums and placed them on the hubs and did not have the units turned true. No scoring or wear! To have maximum braking efficiency, I will have the units turned true. One axle will retain the stamped steel drums, at least until I find another pair of cast iron ones. Question 1) which axle should I put these drums on, front or rear? I will probably never drive it very often loaded up. Question 2) shall I use bonded or woven shoes with cast iron drums? Question 3) I have a couple of small roadster pickups that I installed 32-34 12" cast iron drums on the front and shortened the lever on the front brake operating shaft 3/8" so instead of 60/40 it is more like 55/45 and the trucks stop GREAT!!!!!! Has anyone shortened or put car levers on an AA truck? Thanks, Steve.
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tiredtruckrestorer
Posts: 338
Joined: April 20th, 2003, 7:09 pm
Model Year: 1931
Location: Orwigsburg, PA

Re: Cast iron drums and other brake questions

Post by tiredtruckrestorer »

The rule was to use woven lining on the steel drums and the molded lining on the cast drums, although the woven could be used on the cast drums also, but not visa versa. The molded lining sends the heat out to the drums, but the cast drums don't expand like a steel drum would. The woven lining usually has brass in it and this helps dissipate some of the heat into the brake shoes and the rest out to the steel drums. I'd put the cast drums on the front first. When braking, the weight transfers to the front axle so the front brakes are working harder the rear ones. I don't think you'd experience brake fade as quick with cast drums on the front.

Keith
RustydoubleA
Posts: 108
Joined: June 18th, 2014, 10:22 pm
Body Type: express
Model Year: 1930
Location: N. Calif.

Re: Cast iron drums and other brake questions

Post by RustydoubleA »

Thanks for your reply Keith, I always learn something new when I read this forum and also learn more when I ask questions! I did not realize that the brass wire in the woven shoes absorbed heat, then in turn it would also expand the shoe to conform to the expanded drum. I know that on my WWII Dodge army trucks that the woven lining tends to wear the cast iron drums quicker, but they do stop better in using them together. So, just like my little Model A trucks, the better brakes will go on the front. Incidently, last year I test drove a Model AA truck with 7:50 tires, 351 V-8, and 1937 ford 1 1/2 ton axles/mechanical brakes; that truck stopped great, just as good as a hydrovac/hydraulic system. I did not care for the V-8 though. Thanks, Steve.
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