.060" for passenger car drums, and .090" for most light trucks was the rule of thumb back when I was making a living doing brakes. You can get by with slightly larger dimensions if you grind the linings to match the radius of the drums, but don't make it a habit of hauling heavy loads if you do that. Since most brake shops refuse to grind linings any more, a shade tree method that works well is to glue a piece of coarse sandpaper inside a drum and scuff the linings to a good fit. Using water-soluble glue on the sandpaper makes it easier to remove with boiling water when you're done with the fitting job.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!