Originally posted by Dave Severson
My calculators shows the difference to be:

4500 RPM, 30" Dia. Tire, 3.89:1 gear =103.28 mph

4500 RPM, 30" Dia. Tire, 4.11:1 gear = 97.75 mph

Hope that helps ya out.
It helps, will be able to use all information, so doing some of the building allow for bigger tires