Subaru AWD tires

I recently destroyed one of my tires on my 1998 subaru legacy GT wagon(AWD). I went to the mechanic thinking I could easily get it replaced until he told me the bad news…with AWD tires, you really should get all 4 replaced at once so that all 4 tires are the same pressure otherwise it would affect the transmission later on. I was wondering if anyone had input on this? Could I just get 2 changed and be okay? Should I get all 4? The tires are about 2 years old I believe (with <30,000miles on them). Could I also look around for a USED tired to replace just that one busted one?

Your mechanic is correct, although you misheard part of his message. It is not a matter of pressure in the tires, but instead is a matter of the amount of tread wear on the tires. After all–it is very easy to adjust the pressure in your tires, and hopefully you do this routinely anyway.

A new tire will have a larger circumference than the 3 old tires. If you drive more than a few hundred miles with mismatched tires, you will do severe damage to the moderately expensive center viscous coupling, and in sort of a falling domino effect, you can also wind up damaging the very expensive transmission.

In other words, it is FAR cheaper to replace all 4 tires.

However, a good tire shop can “shave” a new tire, so that it has the same circumference as your three old, worn tires–thus avoiding the mechanical damage that would result from mismatched tires. Make a few phone calls to find a tire shop that can do this, and you will save a lot of money for the present. However, bear in mind that the 30k mile tires that are on the car will likely need to be replaced in another year or so anyway, so this is a judgment call on your part.

As to a used tire, that is a possibility, as long as it is the same brand, same size, and has essentially the same circumference as the other three tires. While you are driving around looking for that needle in a haystack tire, you could wind up doing the type of damage that I described above–thus making this a questionable choice. Also–with a used tire you have no way of knowing how many times it may have hit a curb and suffered internal damage. Personally, I would avoid a used tire unless you have no other financial options.

Incidentally, this topic is discussed in your Owner’s Manual, albeit in much less detail.
You might want to take the time to read that manual since you are unfamiliar with this topic and possibly other important topics that relate to your car.

This a common question with Subaru owner’s, you can use the search feature for more posts and answers.

If you can find a used tire it should be the same brand, tread design, and have very close to the same tread depth remaining as the current tires. This isn’t likely that you will find such a tire, but if you live in an area with some good used tire reseller’s it is worth a try.

The other option is to buy an new tire, again same brand, size, and tread design. Have the tire “shaved” so that it has the same tread remaining as the other 3 tires. Shaving a tire is not something every tire shop will want to do, so you’ll have to shop around for both the tire and someone to shave it.

This makes the easiest option to get 4 new tires.

Now your car is a '98 and perhaps you don’t plan to keep it long, or want to put much money into it. You could buy a used tire, same size and approximate tread depth but it will likely be a different brand and tread design than the current tires. This might work, but you are risking an expensive repair to the transfer case if it doesn’t. The transfer case repair would likely exceed the value of the car. If you are at the “run it into the ground” stage you might be OK taking that kind of risk.

Either 4 tires new or a used tire that has circumference(distance around) within 1/4" of the average of the 3 others.

Downside to owning a Subaru and many other brand AWD vehicles.

AWD…I’m trying to come up with a word associaton for the letters.

When you buy an AWD vehicle, you buy into the knowledge that if a mid-wear tire must be replaced, it’s going to be big money.

The tire price is minimal compared to the co$t to replace any part of the AWD drive train.

Liability issues with the mechanic. If you wanted 1 replaced, and he failed to mention this to you about the AWD system, THEN had your AWD system crap out on you because the tires were mismatched, he’d be liable to pay for the damaged AWD system because he knew about it but didn’t inform you about it. So, to cover himself, he tells you about it, but several people think the mechanic is just trying to make a boat payment(if you do a search for “AWD tire replacement”, you’d find out several people think that way.

The only other way you could get around it is if your Subaru is an automatic, and you have the fuse in the dash that when removed, puts the car into FWD Only mode, and activates a yellow AWD warning light on the dash.

You would then have a FWD Subaru until your next set of tires, but you wouldn’t have to replace all 4 at the same time anymore.

This is what has to be done when the spare tire is used, and I doubt anyone actually remembers to do so.