Ooops -for some reason (probably operator error) the computer did not post the formula in the same way I typed it in. So I'll try again.
235 X .80 X 2 = 376. 376 divided by 25.4 = 14.80 14.80 + 16 = 30.8 inches tire diameter.
Computer would not let me enter calculations using fractional notation, so this will have to do.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.