I bought a used XC90, '04 with 16,000 miles on it a few months ago. I didn't look close enough at the tires. They were worn on the inside and outside 1" and I didn't notice it. The tread in the middle looked ok. The tires are Michelin MXM4 235/60 18. The wheels are the standard Volvo 18" wheels that came on the car new. Now I have 30,000 miles and the tires are shot. They have been for the last 5-10K miles. About 10K miles ago I had the tires rotated at Discount Tire and they told me the two rear wheels were bent and that was causing the poor wear on the tires. Only problem is all 4 tires are wearing out on the outer edges. I do check preesure regularly and have had no problems with the presure dropping much between checks. I took the car to the dealer about 4K miles ago and they said that the wheels were only slightly bent and the tire wear looked normal. Maybe normal is 20K maximun. I am unhappy about this tire wear isssue and have another appointment with the dealer in a couple of days. If this is normal, 20K and new tires are needed, I may get rid of the car.