Replacing less than all four tires at once

Does anyone have any experience with replacing one tire at a time on our AWD cars? I know that it's not a good idea to have different size tires due to the problems it can cause with our diffs, but it's pretty painful to think that blowing one tire means replacing all four.

I've been riding on BF Goodrich Super Sport A/S tires for the last 30,000 miles or so. My car is lowered with no camber kit (Ion Springs) so shops can typically get the alignment close but not perfect. I curbed the tire at speed pretty badly a week after getting the tires, so I replaced one tire after about 2,000 miles. About 25,000 miles in, I replaced another tire when it picked up a nail. After being pretty tardy about rotating my tires, and getting an alignment (hadn't had it aligned since the initial mounting, and didn't do it after curbing the tire) I finally got it aligned - and found that the new tire that had replaced the curbed one was unevenly worn. Badly. Down to the cords. I've been driving with it on the back passenger side for about 5k miles since then, waiting for it to blow out on me.

So why didn't I replace it when I was doing the all wheel alignment? I tried to. The guy at the tire store refused to sell me one tire. He said it was an AWD car and it would wreck my diff to have a new tire with three old ones. I pointed out that only two of the tires on the car had the same mileage. He said he'd replace three. I counter offered with two. He said he'd think about it. I then realized I was bargaining about how much money he would let me pay him and decided I'd take my business elsewhere.

I haven't had any problems with having tires with different mileages on them so far. I'm planning on replacing the two most worn ones and making sure things are properly aligned this time, but I wanted to hear if anyone else had experiences, like catastrophic failure of the blinker fluid or something for doing something similar.

The guy is correct... Listen to him!!!

Mismatched tires do cause unnecessary wear on you diffs.

Subaru advises against it in general, but there's something in the manual about how much circumference difference is acceptable. I don't remember it offhand. From that you could do some math to figure out how many rotations per minute Subaru feels the center diff can absorb.

If I was in your place I'd put matched tires up front, matched tires in the rear, and see how long the center diff lasts, just in the name of science. But first I'd do some more math to see how many rotations per minute the center diff will have to absorb with that setup, and see how it compares to Subaru's recommendation.

Then there's the issue of how different tires front and rear will affect handling. If your car understeers now, put the new tires on the front.

Several people on this site will go absolutely apeshit after reading the above. Watch:

it the treads for all 4 tires are with in 3/32" of each other then ur fine. so u can have 3 tires with 8/32" and get a new one with 10/32 and be ok.

3/32" is from discount tire which they have a sheet from each car company telling them when u need to replace all tires on just one.

Search. I made a detailed thread about this that has not been stickied that will answer the questions and correct the wrong info in this thread.

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http://www.legacygt.com/forums/showthread.php?t=105336&highlight=replace+tires