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Old 02-09-2017, 03:45 PM   #1
Ian in Mississauga
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Default Mismatched brake drums

A recent question about mixing old and new brake linings got me thinking. My car had original cast iron rear brake drums. One drum had a crack at a bolt hole so I replaced it with a new cast iron drum. The new drum is much heavier than the Ford original one. Both have been turned and new shoes arced to the drums. Is this mismatch going to be a problem?
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Old 02-09-2017, 03:54 PM   #2
wmws
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Default Re: Mismatched brake drums

I would say it would be ok on the rear but not on the front.
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Old 02-09-2017, 05:04 PM   #3
J Franklin
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Default Re: Mismatched brake drums

Just don't mix cast and steel on the same axle.
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Old 02-09-2017, 06:33 PM   #4
Kevin in NJ
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Default Re: Mismatched brake drums

Maybe.

I would think you really would want to keep the metals the same side to side. I would guess there is a difference in the friction between the old and new metals. Plus there may be larger differences between the brake fade with heat between the metals. You may find some unpleasantness only after a few fast stops.

I personally would only go in pairs on the brakes.
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Old 02-10-2017, 12:34 AM   #5
H. L. Chauvin
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Default Re: Mismatched brake drums

Hi Ian,

Friction Engineering 101:

After determining if the driver is classified as heavy or light, just try to seat your heavier passengers on the side with the light drum; and allow your light passengers to sit on the side of the heavy drum.

Has lots to do with advanced mechanical engineering equations involving the weight and the square inch area of the loaded spread out inflated rubber tire tread in direct contact with the pavement below.

The coefficient of friction of a particular highway surface usually traveled has to be incorporated into this complicated mechanical engineering equation to insure that stopping energy is equal.

After all above meticulous calculations are performed in great detail, drive in a rural pasture, hit the brakes, and "see" which wheel slides the most on the grass, and adjust brakes accordingly according to Ford's simple recommendations for adjusting brakes.

Last edited by H. L. Chauvin; 02-10-2017 at 01:06 AM. Reason: typo
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Old 02-10-2017, 06:15 AM   #6
Ed Saniewski
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Default Re: Mismatched brake drums

I thought all the Model A brake drums were originally steel? When did Ford start making cast iron drums?
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Old 02-10-2017, 02:32 PM   #7
Ian in Mississauga
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Default Re: Mismatched brake drums

Thanks for the replies fellas. Ed, my understanding is Ford switched to cast iron late in 1931 and the replacements were of course also iron. The friend who did the swedging and checked the drums on a special lathe and arced the shoes also assured me the new drum was the good one.
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