My 06 OBW has just over 22,000 miles on it. Over the last three service trips to the subaru dealership they have noted that the tires are "cupping". they have tried to fix and adjust this with an alignment and rotation under warranty. The service manager claims that the tires must go because of severe cupping. He says that SOA will pay for 2 of the tires under warranty but I have to pay for the other two. Is this fair? Should they not pick up the cost of all 4?

cupping is almost always caused by loss of contact with road which is normally attributed to shock/strut malfunction!

I don't think it's any secret that new cars usually come from the factory with just barely adequate tires. Frequently, tires have their own warranties and are not covered under the new car bumper-to-bumper warranty.

I know it seems cheap, but you got about half the life that you could expect from a good set of tires. Subaru is offering to make you whole by replacing two tires without charge. From Subaru's perspective why should you benefit from 22,000 miles of free tire use?

In fact it's to your benefit to replace the tires asap. Because, if the new set starts wearing abnormally you can be almost certain that it's a mechanical roblem with your car. And you will have found the problem while the car is still under warrranty.