I am being told by Tire Warehouse that if I have all wheel drive, they won’t mount tires unless all 4 tires match exactly and vary in tread depth by no more than 1/32 of an inch. They especially seem to stress it for a Suburu. Is this really necessary? They say they got many complaints about transaxles going when the tires aren’t matched. Does this mean that if you have one tire blow for some reason you have to buy 4 new tires unless you have only used 1/32 of the tread? What if you have two on the front that match and two on the back that match but not front to back? Does matching mean brand name or just size and usage type like summer vs. winter?
I have to assume that you have never read your Owner’s Manual. This topic is covered in that book, and I would strongly suggest that you read it, as it will verify what the tire retailer told you.
We recently had a more detailed discussion about this topic. See here: http://community.cartalk.com/posts/list/1024809.page. It appears that Subarus are indeed affected by mismatched tire sizes, or so it is believed.
This is extremely important for AWD vehicles, and especially so for a Subaru. You bought a vehicle with a very sophisticated AWD system, and variations in tire diameter and wear can do significant damage the system.
As VDCdriver suggested, the owner’s manual will provide the necessary information. You want all four tires to be as closely matched as possible.
An $800 transmission repair made a believer out of me, Steve. The transfer valve and clutch pack in a Subaru automatic transmission will wear rapidly when there are mismatched tires on the vehicle, and when the valve and clutch pack wear out the drivetrain will bind in turns, resulting in a very annoying shudder. If you ignore this problem long enough the transmission case itself can be damaged.
As for tread remaining, read carefully the instructions on how to measure the tire circumference of the remaining tires, to determine if you need to replace all four. If the other three are within the allowed tolerance, purchasing one exact replacement tire would do. My personal experience is that you are OK to around 20K miles or so, and after that you are out of the allowed circumference tolerance. Also note that tread depth, while informative, is not how Subaru measures the allowable tolerance – they specify tire circumference.
Tire Warehouse is safe-siding themselves, because the Subaru instructions do allow for replacement of only one (exact brand/model/tread style replacement) if the circumference tolerance is met on the other three.
Effectively, since I hated the OEM tires, I always use my first destroyed tire opportunity to replace all four tires, to a tire I chose.
“Effectively, since I hated the OEM tires, I always use my first destroyed tire opportunity to replace all four tires, to a tire I chose.”
Good point! If the Subaru in question came equipped with Bridgestone Potenza RE-92 tires, the OP should consider this to be an opportunity to rid himself of those crappy tires! Those Potenzas feature relatively fast tread wear and once a bit of wear has taken place, their wet traction is poor and their snow traction is non-existent!
Try tirerack.com for a replacement. They can shave a new tire to match the other three for a small fee(~$20).
See here for Subaru stance ->>> http://www.subaru.com/common/faq/tech_info.jsp#4
I will state that manual transmission AWD’s are less finicky about this than the automatic ones which an expensive repair happens if you ignore the warning.
Keep the faith and heed what has been said…we got nearly !00k out of rotating summer winter tires and staying with the manual suggestions. I would argue that properly maintained, AWD may even be superior in tire wear dept. than FWD alone. Do what they say.
You may find other local tyre dealers who will also shave the tyre as needed. It may not be the best choice, but it may well be an option. (BTW I do recommend tirerack)
I’ve seen the reviews of those tires and seen that most summer tires get better traction in the rain than these tires, and I imagine they’d get better snow traction as well(even though summer tires aren’t tested for winter conditions)
http://www.tirerack.com/tires/tires.jsp?tireMake=Bridgestone&tireModel=Potenza+RE92
http://www.tirerack.com/tires/tires.jsp?tireMake=Bridgestone&tireModel=Potenza+RE-01R <-- even their extreme summer tires are better