40 Ford Drums

Does anyone have a spec on the maximum useable diameter of a drum off the front of a 40 Ford?

Thanks,
Phil

 

I think 12.080" is the recommended limit. I have heard of some people using them at 12.120" on lighter cars. I have some on the higher side of the range and plan to use them on my car.

 

12.060 is the maximum size. I have a 40 Ford and know that to be the max. dia. although lots of folks go to 12.090.

 

We never turned drums "back in the day", mainly because we were too dumb to and couldn't afford it anyway. We figured the lining (bonded shoes are best) would wear into the hills and valleys on the drums and provide more lining area. I don't remember ever having a problem with any of them.

 

I wonder if they wore out any faster using that method.

 

What can happen when you exceed the limits when turning drums? Can they fail or do you lose braking power because of them distorting from being thin? Has anyone ever had one come apart?

 

ALL of the above. Unless the car is always trailered and never sees normal road use, it's foolish to run drums that exceed their design size, and .060" is and has been the standard max oversize on most car/lt.truck drums. If the max diameter spec cannot be seen on the drum or found anywhere, stay with .060".

 

Drums turned over spec can easily egg-out in a panic stop (T hotrod roadster, don't ask how I know that).
Really excessive over turning can actually allow the cylinder to shoe pin/rod to drop out thus causing failure of the cylinder and total loss of brake son an old single reservoir stock master cylinder ( 57 Chevy 2door, again, don't ask).

This applies to almost all brake drums for p***enger cars and light pickups no matter the age.

 

Good info, thanks guys. I'll start looking for better parts than what I have.