In the above equation we assume that xf and xr are angular
velocity of the front and rear wheels; and rf
d and rr
d are
dynamic radiuses of front and rear wheels.
From the Eq. (4) we can see that a 4WD tractor will not
be submitted to slip of wheels when the ratio between
deformations of rear and front tires is equal to the ratio
between angular speeds of rear and front wheels. The following
relationship may be written as follows: