Most medium truck drums can go up to .090" above their nominal diameter, so if it's got 11" drums, for instance, the maximum oversize would be 11.090". As a practical limit on a big drum like a 1-ton, you could probably get away with a .125" (1/8") oversize, but that would only work if you weren't planning to ever run with a maximum gross weight. The bigger the drum diameter is machined, the less material there is to dissipate heat.
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!