Wheel Alighment

I bought new tires for my 2007 Volvo C70 about 15,000 miles ago and have had them rotated twice since then. I took the car into the tire shop yesterday for a slow leak in one of the back tires. When they pulled the tire off the car the inside of the tire was badly worn. The tires were just rotated less than 6 months ago by the same company. The service man checked the alignment for me and game me a printout indicating that both the front and the back tires were out of alignment. My questions: How does this happen in just 6 months with about 4,000 miles of driving, and does the back end get out of alignment? I thought just the front needed alignment, but may be living in the past before all wheel drive cars. The original tires on the car lasted over 35,000 miles by the way

Independent rear suspension (like yours) can get out of alignment just like the front. When was your last alignment? You might have hit a pothole any time since then and thrown both front and rear out of alignment. Until the wear was extreme it might not have been apparent.

Time for new tires and a 4-wheel alignment, it seems.

Many vehicles today require a 4 wheel alignment, especially if they have 4 wheel independent suspension. Your alignment shop should tell you when your model is one that needs the 4 wheel alignment.

As for the inside tread wear, because you rotate your tires so often, the wear pattern could have come from another position on the car, not necessarily where the tire is now. Do all 4 tires show the same inside wear? If so, it is possible that the front is just toed out too much and the inside wear occurred when the tires were on the front.

Do you regularly carry heavy loads in this vehicle? If so, when it is loaded, look at the back tires, do they tilt in? Do they tilt in even when unloaded? This would indicate worn struts and springs more than an alignment problem.

Can you post the specs the serviceman gave you? This would be a big help for us to use to help you.