Turning Brake Drum Specs

[AUSMHLY]

1964 BJ8.
I believe the right rear drum is out of round.
I brought it to a machine shop that turns brake drums.
He said the drum should have specs that let him know how much he can grind them.
We could not find that information on the drum.
The book says the drum is 11 inches across, however didn't find any information about turning them.

Any help with information I can provide to the machinest?
I'm assuming he needs to know the thinest he can go from what ever number the number is now, (hopefully 11"

How important is balancing the drums?
I've read when a drum is out of balance that could cause the 50-60 scuttle shake?
I don't have the shake, and wondering if I have my drums turned, I may get scuttle shake.
If it ain't broken, don't fix it...

Thank you in advance

 

[Rob Glasgow]

Roger, my BT7 never had scuttle shake but I always had a bit of vibration when driving. No amount of balancing of the tires/wheels eliminated the vibration . I sent the drums to Hendrix Wheel and was surprised at the amount of weight required to balance them. Ever since, the vibration is gone and the car rides beautifully. In my opinion, it’s well worth the effort and money.

 

[Bob_Spidell]

My BJ8 has balanced drums and driveshaft and still has a bit of scuttle shake which varies depending on which wheel is on which corner. My BN2 had really nasty scuttle shake until Tom Monaco mounted 4 new Vredesteins on new MWS wheels for me; shake completely gone (until I hit a bad pothole anyways). 'Scuttle shake' is endemic on some/many convertibles; my dad was a factory rep for Ford and told me early Mustang convertibles all had it (convertible chassis usually aren't as rigid as sedans). Ford eventually put some underside bracing on the Mustangs; dunno if that helped or not. Some Healey owners reinforce the transmission tunnel area; results seem to vary.

p. 27:

"It is also recommended that an older drum not identified with a maximum drum diameter should not be machined to exceed 0.060 inches inside diameter over its original size."

Many shops, however, won't turn a drum without a max I.D. stamped on the drum (but I haven't presented this to any shops).