Determining Brake Drum Inside Diameter

[Joe Flanagan]

Does anyone know of a way to do this in the absence of the AMMCO tool or a dial indicator? Right now I have my brake shoes flat and even all the way around using a homemade gauge. They are in light contact with the drum all the way around but I'd like to do this right and determine the actual diameter of the drum. Thanks.

 

[55 Fargo]

yes this can be tough without the tool, or most importantly a brake shoe arcing.

Get it close, or set anchors to factory, and allow to wear, and do minor adjustments as needed, that worked extremely well for me.

If you slip over the drums, and make slight contact, with both shoes, then use your brake tool, and get even contact, back off just slightly if too tight.........

Take drums into a shop for accurate measurement, you can be as oversized as 10.060, with machining total drum 30 over

Edited March 24, 2013 by C38Spitfire6

[TodFitch]

If you can get a rod, preferably metal, cut to the exact length of the standard size drum then you could use that and feeler gauges to measure the drum ID.

[greg g]

Make an interior gauge from a piece of dowel.  cut it about 2 inches shorter then the distance across the drum.  Drill the end to accept a small diameter round headed screw.  glue an appropriate sized nut over the hole insert the screw and use it to find the inside measurement of your drum/s.

 

take the measurement at 90 degree angles at the same depth.  You can round off the end of the dowel to get a smaller and more accurate measurement.

[Joe Flanagan]

Thanks, Tod. I was thinking about something along those lines a well. I'll toy around with a few things and see what I can do.

 

Thanks, Greg. I was typing at the same time you were. I'll give that a try.

Edited March 24, 2013 by Joe Flanagan

[_shel_ny]

 ...

Edited March 24, 2013 by shel_bizzy_48

[55 Fargo]

If your looking for an accurate measurement. The shop that undertakes the DMV Vehicle Safety, will measure the drums will they not?

Or are you trying to determine the mesurement to set-up the brakes.

Dodgeb4ya, has provided the best advice in this area, #1 choice, arcing the shoes to fit drums, difficult to find a shop to provide this service. The Miller or Ammco brake tool, get get yopu close, but if you need arcing, you may need some miles to wear the shoes in.

How about set-up the brakes real close, get all lines, hoses and fittings hooked up to MC. Bleed brakes, and see what you have.

On my 47, had not bad brakes, when all was brand new, then followed Bob Hs advice, set Majors to factory position, let shoes wear in, adjusted minors periodicaly, and brakes seem very good. I just inspected the brakes and shoes, shoes have all even wear....

[Joe Flanagan]

Fred, I'm installing re-lined shoes on my rear brakes. I set them inside the drums and they're perfectly arced. I got one shoe in scuffing contact at the toe, determined what that was on the gauge, then adjusted the other toe and the two heels to match. I used powdered dry guide on the shoes to get some idea of how they're making contact and it looks like it's even throughout. Once I'm ready to actually drive the car, I'll use Don C.'s sharpie idea and see what I have, then adjust accordingly. 

[55 Fargo]

Fred, I'm installing re-lined shoes on my rear brakes. I set them inside the drums and they're perfectly arced. I got one shoe in scuffing contact at the toe, determined what that was on the gauge, then adjusted the other toe and the two heels to match. I used powdered dry guide on the shoes to get some idea of how they're making contact and it looks like it's even throughout. Once I'm ready to actually drive the car, I'll use Don C.'s sharpie idea and see what I have, then adjust accordingly. 

Oh, sounds good, thought you were trying to determine drum sizing for a DMV safety. Most likely you will have good brakes, and if not immediately, after some miles, and adjustments......