Another example: Fot the same car (same max rpm, same final gear ratio) What gearing do I need to get to 70mph if I''ve already found bigger foamies (larger radius->more top speed), let''s say with 4cm radius (the ones that miami guys use)??? (searching for the T1/T2 ratio)

Solution:
We have to calculate backwards. With easy modifications I rebuild the equation: Vmax[mph]=0.62*Vmax[km/h] => Vmax[km/h] = 70mph/0.62 = 112.9km/h

(T1/T2) = (Vmax*Tf2)/(0.003768*(rpm)e*Tf1*Rw) => (T1/T2) = (112.9*38)/(0.003768*38000*13*4) => (T1/T2) = 0.57621

So for the current T1 pinion gear (23T) I need T2=39.916T wich means that using the HPI 39T spur gear will boost the car above 70mph!!!

FEAR TRAXXAS!!!