Directional tires generally are performance tires. Performance tires have a softer compound than other tires. This means that they grab the road better. BUT it also means that they wear out much faster than regular passenger tires. Also, any suspension issue will be magnified with preformance tires.(Race cars have a type of performance tire on them - that is why they change them every pit stop)
Even if your suspension was perfect (which it does not seem to be) performance tires will wear out way before regular tires. Now to the issue with the cupping. By cupping on the inside -- do you mean wearing out evenly - or actually cupping which looks like there are chunks of tread "cupped" off the tire.
Cupping is almost always a shock and/or strut problem. However, it is could also be a tire out of ballance. Being that you say that you remove the tires from the rims when you rotate them -- make sure that the tires and ALWAYS high speed ballanced every time that they are removed from the rim.
BTW -- cupping is the result of the tire "bouncing" beyond the control or without the control of the suspension.
Friday, November 27th, 2009 AT 9:05 PM