im trying to decide how much of a differance that makes, I know what the acceptable differances are in front/rear diff step offs,

the problem is, as you drive down the road you dont want the VC to do anyting at all. If you start heating it up then you will lose drive and overheat the VC and the transfer oil.

them two divided comes at 0.986 differance front/rear, small amoun compared to 1.0 but it is still a differance.

what i would do is get the measurement of two identical make tyres, one being brand new, and one worn to the legal limit, this will then give you the max speed differance the vc should ever see.

hth
mark