I own a 2006 Subaru Outback and one of the tires went flat on us. When we brought it to one of those tire center places they told us that since it was an AWD vehicle we needed to replace all 4 tires and not just the one that went flat. They said without placing all 4 we risk damaging the transmission… Never heard of such a thing.
As with most issues that arise with a car, it is always a good idea to read the Owner’s Manual. The Subaru manual definitely speaks to this issue, and it will give you specifics regarding the acceptable difference in circumference between tires.
What you will find is that, if the 3 remaining tires are fairly new, you can probably buy just one tire. But, the circumference figures in the manual should be used for reference when checking the tires just to be sure. Failure to follow the advice in the manual will lead to damage to your center differential, and that would not be covered by warranty if you damage it by mounting differently sized tires.
Hopefully you will luck out, and your 3 remaining tires will fall within the acceptable specifications. Otherwise, you could have the tread “shaved” on one new tire in order to comply with the size difference. If your tire dealer is not able to perform tread shaving, then you need to find a dealer who will do this, as it would save you from buying 3 additional tires.
Even if you have never read the Owner’s Manual previously, this would be an excellent time to start to learn about your car from this valuable reference source.
VDC’s advice was, as usual, excellent and thorough. I agree totally.
I haven’t seen a tire shaving machine since the '70’s! Do shops still do that?
This is good advice on the need for four new tires…However I do not recommend having a new tire shaved…first off you’re voiding the warranty and secondly you’re depending on a tire shop guy to determine the shaved tire’s circumference as compared to the other three tires (which probably are not the same anyway).
Perhaps the tire dealer will give you a deal for the three replaced tires or you can take them home and sell them on ebay.
Since it is important to get a tire that is the approximate same diameter as the ones that are already on the vehicle I would use a tire depth gage on the three remaining tires and buy a used tire with the same average tread depth and same make of tire.
Here is the faq’s from Subaru:
http://www.subaru.com/common/faq/tech_info.jsp#4
You can mail order the OEM tire from tirerack.com and have them shave it down to the same rolling circumference.
Here’s another thought on the topic. If you live in an area that is subject to ice & snow conditions, you might want to use this situation as an excuse to replace the original equipment Potenza Re-92 tires with something else. I have to assume that Subaru selected those tires for price, or for ride quality, or for fuel economy, because they certainly didn’t choose them for good winter traction or for tread life!
The difference in winter traction with B.F. Goodrich Touring T/A tires is dramatically better than with those Potenzas. And, I believe that their dry road traction and traction in the rain are also superior to those Potenzas. Plus the Potenzas usually wear out in about 35,000 miles, while I currently have over 40k on the BF Goodies with plenty of tread remaining.
The BF Goodies are merely a suggestion. In reality, there are undoubtedly scores of tires better than the Potenza Re-92.
Easy and accurate way to measure tire circumference is with a simple metal tape measure. Hold the tape with the convex side in to prevent wrinkles in the tape.
I had one tire go on my 99 Outback a couple years ago. It was quite a surprise to hear one tire dealer (Sears) say I need four! They refused to even consider replacing just one.
Anyway, the local Subaru dealer replaced just the one tire – I guess the three good tires must have been “close enough” to replace just one and not all four.
Good luck!
Subaru requires no greaterthan 1/4" difference in overall tire height … that’s 1/8" of tread wear. Any more than that and you WILL toast the clutch pack in the AWD system. Figure on $800-$1,200 to fix that little jewel. Even running with one tire underinflated can wreck the AWD.
The sysmptom is ‘torque bind’. Take you 'roo to a dry paved area and turn as tight as you can in both directions and in both forward and reverse. If the car feels like it’s grabbing (don’t worry, you’ll know it when you feel it), ot in extreme cases crow-hopping, you have damaged the AWD. In some cases a total tranny flush and fluid replacement can help for a while. Don’t go to any of the nationals or local tranny joints for this, take it to Subaru.
For more info visit the Ultimate Subaru Message Board and search ‘torque bind’.