Brake Drum Thickness

johnr9q@yahoo.com

johnr9q@yahoo.com

Senior Member
Lee Andrews Book says the minimum wall thickness is .120 (If I have the original drums, which I don't know). I look online how to measure this and find People measuring the entire diameter but I don't know what the entire diameter is so how do I measure the thickness? I also don't have a micrometer that measures 11"
 

Attachments

  • IMG_0517.jpg
    IMG_0517.jpg
    54.8 KB · Views: 65
Your drum looks to be a stamped steel drum.

To determine the wall thickness you would need a micrometer to measure the inside diameter and then measure the outside diameter and take the difference of the two measurements and divide by 2 to get the wall thickness.

This only needs to be done to the area where the brake shoe hits the drum.
 
Use a ball bearing ball between the inside of the drum and the micrometer, subtract the ball diameter from the micrometer reading.
 
Cut a slice out of it to measure the thickness. Then throw it away and buy cast iron drums. Have them installed on the hubs by Randy Gross.
 
it would be nice if you took a picture from the front side to see if it is steel or cast. because some cast drums have a fat lip. what you need is a drum gauge. that will tell you the over size. and measure the drum in three different spots to make sure it is not out of round,


if you end up needing drums Randy is the best way to go by far
 
Last edited:
"Ball anvil micrometer."

The classic digital can probably do it approximately - if you can get the blades past the "curve" at the edge. (I.e. frame is "notched" where the two gauge parts slide on each other.)

The advice on Randy Gross is probably the best money you could spend.

It was possible in a past age to buy "reinforcing bands" and have them pressed on the drums - but the effect was improvement - but not great improvement.

Many in that era would seek out Ford Pinto flywheels - cut out the center and use the ring created as a reinforcing band.

Randy Gross is the better scheme. Cast iron drums is where Ford went for the Model A late in 1931 - and retained the cast iron for the next 40 years of Ford drum brake production.

Joe K
 
Your drums appear to be the original stamped steel. I would not even think of turning them, no matter how thick they are. It only takes once when your brakes fade and you end up in the middle of a busy intersection to convince you!! Luckily the traffic was light and we didn't hit anyone/anything!!

My co-pilot would not even get in my Town Sedan again after that incident.

A call to Randy Gross fixed that.
 
Stamped steel drums have a profile on the lip edge that very identifiable., cast iron drums when struck with a hammer have a dull sound compared to a ring sound of a steel one. Taking a welding grinder to the back surface and observing the spark- to a welder or person who know metal working will shows a definite spark that tells if cast or steel. Best advise - throw away the steel ones and get the cast iron drums , again Randy Gross is the go to guy for the brakes on a Model A
 
katy said:
Use a ball bearing ball between the inside of the drum and the micrometer, subtract the ball diameter from the micrometer reading.
Click to expand...
You need the bearing on the inside due to the radius. You'll also need a block on the outside thicker than the flange.
Or just get the right micrometer with a spherical anvil
 

Attachments

  • 115-215_01_1222.jpg
    115-215_01_1222.jpg
    10.9 KB · Views: 13
The original stamped steel drums are not one of Fords better ideas. Even when brand new they could not absorb as much heat as cast iron. If you're doing a brake job, take this opportunity to switch to cast iron drums. They look original-ish, but they can absorb so much more heat before you get brake fade. You will be glad you spent the money on a potentially life-saving investment.
 
Is knowing the thickness for any specific reason? The wear is measured with an inside micrometer. I think the limit to cut a drum is .060 from 11" for a Model A drum. It is not recommended to turn a steel drum.
 
In regard to Katy comment above: The Model T brakes were a joke. It was best to coast to a stop and then apply the brakes. The service brake was in the transmission, so any problem with the differential or axle meant NO brakes. The parking brakes were steel shoes on steel drums. No linings. I put disk brakes on my Model T, but only on the rear. I rigged it so that the service brake in the transmission was a backup in case the hydraulic system for the disk brakes failed.
 
That looks like a band on that drum,although I've never seen one like that.I've put a few on,but that one looks to be the best I've ever seen.I always found them to work fine.Not as good as cast iron,but new steel drums are not as good as cast iron either.I had a set on a car that were ring gears.The guy told me they were from a slant six flywheel.They worked fine too.I've cut steel A drums before,just a little,and you don't get a powder,you get a long steel strip,looks like excelscior packing material.I still have a few brake bands around,I got a lot of them from an old garage years ago.They came in a wooden barrel,and I think it is marked Funk Bros MFG.
 
You must log in or register to reply here.
Back
Top