Replace 2 or 4 tires?

2008 SpecB with Kumho Ecsta ASX 225/40R18 tires with 7/32 tread remaining. This tire has 9.5/32 tread depth when new.

Original tire size was 215/45Z18, but were hard to find and expensive at the time I replaced them. Not sure if running a different size effects the need to replace 2 vs 4 at the same time either?

Front passenger tire is damaged. I would like to know if I can safely replace just the 2 front tires, or if I should replace all 4 tires.

Thank you!

Not really understanding what your saying,

Did you replace the damaged tire with a 225/40/18 and keep the rest 215/45/18?

With AWD all four tires have to be the same size/model, If not you are risking damaging your differentials.

You could get away with just replacing the damaged tire, Just have it shaved so the tread depth matches the rest.

Not really understanding what your saying,

 

Did you replace the damaged tire with a 225/40/18 and keep the rest 215/45/18?

 

With AWD all four tires have to be the same size/model, If not you are risking damaging your differentials.

 

You could get away with just replacing the damaged tire, Just have it shaved so the tread depth matches the rest.

Sorry for the confusion. 1.5 years ago I replaced summer 215/45 tires with 225/40 all season tires.

Now I have one damaged tire and just wanted to know if I could replace 2 instead of 4. I would be replacing with same exact tire Kumho Ecsta ASX 225/40R18. New they have 9.5/32 tread depth. My 1.5 year old tires are at 7/32. Subaru recommends 2/32 or less difference, so I would have .5 over that. I don't see how that little amount can matter, but wanted to check.

I mentioned the size difference only because I wasn't sure if that would make it more important to replace all 4. Don't have a clue about tires I guess..

As said on NE Subaru (bspec), if only one tire is damaged, buy a replacement from tirerack.com. Make sure it is the exact same tire. Then have them shave it to 7/32. No need to buy 2 if only 1 is damaged. If you don't go with shaving, you'll have to buy all 4.

See tirerack's article: http://blog.tirerack.com/blog/buy-tire/0/0/replacing-one-tire-on-an-awd-vehicle

In that case, With one tire damaged, I would do exactly what Spec.B Dream said.

Buy a single matching tire, and have it shaved down to 7/32 by a reputable shop.

Tire shaving is generally very cheap as well ($20-30 a tire)

good luck!

Subaru recommends 2/32 or less difference, so I would have .5 over that. I don't see how that little amount can matter, but wanted to check.

 

The size difference results in the tires rotating at different speeds, which puts a small amount of stress on the AWD system. Due to the open differential in front, it might be ok in front. As soon as you rotated your tires, you'd start putting significant wear on the rear differential. Best option is to have the tire shaved.