Because of AWD, I figured when one of the tires (front left) was damaged beyond repair that I would have to replace both. That is, due to difference in diameter for an old and new tire, I would have to replace both tires on each end of the axle. That was also the recommendation from my favorite car shop and I thought that is what the Subaru dealer said.
Just got an oil change and that car shop said that I also need to replace the rear tires. They are older and more worn but far from needing replacement due to tread wear (probably more than half life left on them). Like the idea that both tires on the same axle need to be the same diameter, the guy at this shop says that I also should have new tires put on the back. He sells tires but not the brand on the front so he knows he wouldn't get my business to put them on the back, and even mentioned that. So it wasn't like he was trying to drum up a sale and he said the fronts are brand new and there would be no reason to replace them to get a full set of 4 and instead go back to where I got the fronts and get the same for the rears. He claims the tranmission would blow due to the rears spinning faster than the front because of their reduced diameter from being much more worn, and that the tranny would see that as slippage on the rear.
So, is it true that if you lose one tire that you end up having to buy a whole new set of 4 tires so they all are the same starting diameter?