a very slight amount of rubber is removed from the respective points on the respective axially outer ribs during each revolution of the tire the above described procedure therefore is repeated for a multiplicity of rotations of the tire until the lateral force variation is reduced to the pre selected maximum force variation or the maximum allowable grind limit on either the upper or lower rib has been obtained the lateral force variation may be reduced to the pre set limit in just a few rotations of the tire or it can require as much as 10 to 20 grind cycles or more the lateral force variation curve of a tire which has been brought within the specified lateral force variation limits may appear similar to curve c 39 in fig4 and the amount of grind equal to the curves g 1 and g 2 of fig5 it will be appreciated that the average lateral force represented by the curve a may be below the zero reference line and the maximum lateral force may be exerted in a downward direction in this case the bottom rib would be ground at the point of maximum lateral force and the top rib would be ground at the point of maximum.