The Ford Barn

Talon one · 10-10-2023, 11:53 AM

Does anyone know if there is a difference between mechanical brake drums and Hydraulic, I found two rear drums and when compared to the ones I already have on my A they Stand a little taller when placed on the floor, I have hydraulic on my car but was wondering if the ones I found may be for a mechanical system. Would they be interchangeable?

Kurt in NJ · 10-10-2023, 01:22 PM

depends on what was done to convert to hydraulic

nkaminar · 10-10-2023, 02:40 PM

Mechanical brake drums have an 11-inch inside diameter. If machined it could be a little bigger.

Talon one · 10-10-2023, 02:59 PM

Thanks I measured them and they are 11in on the nose. Appreciate the help!

rotorwrench · 10-10-2023, 03:02 PM

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Ford hydraulic brakes used 12-inch drums from 1939 through 1948. The 1939 drums were wide five design. When changing from mechanicals to hydraulics, most folks use the backing plates to fit the 12-inch Lockheed brakes and the associated drums. There are always exceptions depending on the person that did the alteration and what other components may have been utilized.

10-10-2023, 11:53 AM	#1
Talon one Junior Member Join Date: Sep 2023 Location: Indianapolis Posts: 4	Rear brake drums Does anyone know if there is a difference between mechanical brake drums and Hydraulic, I found two rear drums and when compared to the ones I already have on my A they Stand a little taller when placed on the floor, I have hydraulic on my car but was wondering if the ones I found may be for a mechanical system. Would they be interchangeable?

10-10-2023, 01:22 PM	#2
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,188	Re: Rear brake drums depends on what was done to convert to hydraulic

10-10-2023, 02:40 PM	#3
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 4,131	Re: Rear brake drums Mechanical brake drums have an 11-inch inside diameter. If machined it could be a little bigger. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

10-10-2023, 02:59 PM	#4
Talon one Junior Member Join Date: Sep 2023 Location: Indianapolis Posts: 4	Re: Rear brake drums Thanks I measured them and they are 11in on the nose. Appreciate the help!

10-10-2023, 03:02 PM	#5
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,543	Re: Rear brake drums Sponsored Links (Register now to hide all advertisements) Ford hydraulic brakes used 12-inch drums from 1939 through 1948. The 1939 drums were wide five design. When changing from mechanicals to hydraulics, most folks use the backing plates to fit the 12-inch Lockheed brakes and the associated drums. There are always exceptions depending on the person that did the alteration and what other components may have been utilized.