Can you replace a single tire on Forester or have to replace all 4?

Hi,

I would recommend replacing the tyre with one that is as close as possible to a match for the other ones. If there is a significant diameter difference (ie tread depth) the 4wd can get a bit wound up. This is why your meant to put subarus into 2wd when using a spare/space saver. But as long as the tyre is close to the others it should be fine (ie same size & similar tread depth).

luke

Tire manufacturers usually list the outside diameter of the tire in their detailed specifications. I found it quote interesting that tires of similar "official" size could vary by more than 1 inch in outside diameter. If the outside diameter of the new tire matches the old one, then he should have no problem. However, if the old tire is used, then he will have trouble matching the diameter with a new tire.

-- Vic Roberts

1" difference in diameter for same nominal size? That's huge. You sure about that Vic? Can you guve some examples?

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

Bullshit, total crap. This is a Forester it is all wheel drive all the time, you cannot put it into 2WD unless you remove the drive shafts. Wind up ???? It has a diffon each end and one in the middle, it can't wind up, not possible.

You can put an automatic Outback into 2WD just by pulling a fuse in the engine compartment.

Different pressures in the same type of tire will also change the diameter.

-DanD

On Wed, 06 Aug 2003 12:44:57 GMT, "Losiho" wrote in news:dL6Ya.17739$ snipped-for-privacy@news-server.bigpond.net.au:

You add the fuse.

Some tire resellers will "shave" your new tire to match your other three. They measure the circumference of each tire and shave them all to match. You lose a little in mileage. Beats having to buy a complete set or damaging your xmission.

Al

Hmmm - tirerack.com's sheets show the Michelin Symmetry at 26.1, but even with that, it does indeed indicate 1/2" difference in diameter. That's about 2% difference, but still more than I would have thought. Thanks for pointing that out.

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

Different pressures make very little to no difference to the rolling circumference to a tire. The circumference of a tire changes little as it is a fixed value. The only difference pressure makes (when there is less pressure in that particular tire) is to drop the side wall of that tire so that the axle is now lower. This gives the feeling of pulling to that side. Pressure difference makes little difference to the AWD set up, although I would recomend having your pressures correct all round.

There has been some discussion as to the circumference difference to tires used on Subaru AWD's. There has been suggestion, I think from Subaru, that it should be a max 4% difference between tires. This is actually quite a lot of difference when you calculate it out. If you take a tire of 215/60 16, which I think is fitted to a Forester, its overall diameter is 664.4mm (we will stick to diameters as it is easier to show and Pi is a constant so it makes the same comparison as circumference). If you calculate 4% less than 664.4mm you get 637.8mm. This is a difference of 26.6mm or 13.3mm on each side of the rim (remember there is tire on each side of the rim diameter). Now, an original tire is has about 8mm of tread, so therefore, even if you wear it out to nil tread (not recomended) you only take off 16mm (8mm x 2 per side of diameter). I think you are supposed to renew a tire when it gets to 1.5mm tread left by law, which means you will end up with 13mm of tread wear overall and by this time you will need to replace all tires!

So, you should be able to replace one tire with no worries as long as all the others are not near their end of tread life of 1.5mm.

But the poster asked about a Forester.

Ed:

I suppose that 1/4" "would" be ideal, but, we're talking "real world" here. After you had a few hundred miles on your car, you would probably find that the

1/4" difference in circumfrence is exceeded by the tires on the front vs. the rears; just by normal wear. And probably, the circumfrence between the same model tire made on different moulds would be close to that. 1/4" circ. is just .08" in diameter and that could easily pass by QC. Just my two cents.

-Steve

bit of a discussion over here:

ken

5+%!? For a nominal reference of Ø26", that would mean a diameter variation of >1.3"! Possible, but I find it hard to believe.

Perhaps you saw the discussion recently in this same thread between myself and Victor Roberts when he said that the diameter in same-size tires between mfgrs. can vary as much as an inch. With the examples he came up with, the biggest difference was actually 1/2" according to the diameters in Tire Rack's spec tables. Accepting that I certainly could be proven wrong on this, I make the same challenge to you to provide examples (if we can agree that the Tire Rack spec. sheets will be the source of the numbers used).

Bill Putney (to reply by e-mail, replace the last letter of the alphabet >

0.8" according to data published on the tire manufacturer's Web sites. (And just five or so manufacturers.)

-- Vic Roberts

Three bald tires and one new. Not good. No tires wear identical. Would suggest new tire go on back to keep you from having steering drift.