2003 Subaru Legacy

I recently had to replace a rear damaged tire in order to pass the state’s inspection. The tire dealer said I had to replace both rear tires because of a rear alignment issue on this model. Is this BS?

You should replace ALL FOUR tires at the same time on a Subaru.

Installing one or two can cause significant, expensive damage to the AWD system.

The other option is to have the new tire shaved to match the other three.

Consult the owner’s manual for information about tires.

The tire dealer is wrong, but he is wrong for the wrong reason–if you can follow my logic.

As mcparadise corrected stated or implied, all four of your tires must be very closely matched in terms of tread wear and size. This has absolutely nothing to do with rear wheel alignment, and everything to do with the car’s very sensitive AWD mechanism.

Essentially, you have two options:

Replace all 4 tires
Buy just one tire and have it shaved so that its circumference matches that of the other 3 tires. Not every tire shop can do this, so you may have to shop around to find a shop with the proper equipment.

Actually, there is a third option. You can drive the car with 1 or 2 new tires and then wind up replacing the center viscous clutch…perhaps in about 300 miles…for a cost of about $600. However, I really don’t recommend option #3, because you will then still need to have 4 matched tires or you will burn out the new center viscous clutch also.

Incidentally, you should not just take the word of random strangers like us.
Instead, you should seek the opinion of the folks who designed and built the car.
Fortunately that information is contained in your Owner’s Manual.

Edited to add:
Liquid Wrench did not tell us whether he replaced just one tire, or if he replaced two tires.
In either event, the tire(s) that you bought will need to be shaved to match the “old” tires on the car.
And, I would suggest that you avoid that particular tire shop in the future. If they give out bogus advice on one topic, who knows how much other bogus information they are spreading!

Transfer valve and clutch pack for my automatic Legacy were $750. Tires are cheaper.

You may have to replace the front tires also. If your front tires average circumference(distance around tire) difference is greater than 1/2" from your new rear set replace the front too.

You’ll cook your viscous coupling(Manual transmission) or ruin your clutch pack if automatic.