Gear ratio vs speed calculation help

[jhhaas]

Assuming a 915 with a 7/31 ring and pinion and a 26/26 5th gear running 335/30/18 rear tires, what would the wheel speed be at 7000 rpms?

Thanks in advance.

[Huh]

try this calculator:

http://www.scirocco.org/gears/

[imcarthur]

Just type your numbers in:

Transmission Calculator

Ian

[Bill Verburg]

I prefer to go back to first princpals and do the calc myself. You can get a more accurate result by inputting the actual dynamic loaded radius rather than the static unloaded radius that most of the calculators use.

The dynamic loaded diameter of a 335/30x18 tire is 25.1 - 25.4" depending on the tire
the formula is
MPH = (RPM*DLR*0.002975)/(TR*DR)
RPM - revolutions per minute
DLR - dynamic loaded diameter
TR - transmission ratio
DR - differential ratio


For your example, using an average of 25.25" for DLR
MPH = ~119mph