Spec Racer Ford Speed Versus RPM

Here is a plot of speed versus rpm in each gear for the Spec Racer Ford. The results vary slightly depending on tire pressure and the amount of tread on the tire since the tire radius changes, but for BFG tires with shaved and slightly worn tread at 28 psi hot these numbers should be pretty close:

speed.gif (8922 bytes)

First gear is about 191 rpm per mph.
Second gear is about 103 rpm per mph.
Third gear is about 72 rpm per mph.
Fourth gear is about 54 rpm per mph.
Fifth gear is about 41 rpm per mph.

Transmission Gear ratios:
First         3.42:1
Second    1.84:1
Third        1.29:1
Fourth      0.97:1
Fifth         0.73:1

Final Drive ratio:
3.62:1

Typical loaded tire radius:
10.9"

For an on-line Speed versus RPM Calculator, as well as an explanation of the equations, see my on-line calculator page at:

Speed versus RPM Calculator

Richard Shelquist
Longmont, Colorado