The specification for 3100 brakes is 11 inches. I'm assuming that would be inside diameter of the drums. There may be a maximum diameter (11.0X for instance) cast into the drum somewhere near the rim. That's usually seen on more modern brake drums.


Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.