With 20psi my 26x10's have a rollout of about 85 1/2 inches. Converting that to diameter, that works out to about 27 1/4. I really wouldnt want to speculate on how much a 28 or 30 inch tire rolls out, but if you could find out we could do the math.
When I selected my gear ratio I knew what MPH I needed to run, and what RPM (10% above peak power)I needed to run through the traps at. Knowing the rollout, the numbers calcaluate out to within 200 rpm of what I actually run.
Andy
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88 coupe
91 LX NMRA Pure Street 5120
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