forester tire rotation

Correct. What I meant and could have said is ... Thus making the spare unsuitable for putting on the car [as a permanent replacement] (if you give any credence at all to the 1/4 inch rule).

I reread my post. I think my comment about using a well worn tire as a permanent spare covered that issue (not afraid to use an off-sized tire for short periods of time).

Nice to know some body is actually reading this stuff ;-)

Tom

Agreed. So, the only incentive is economic --- extending the life of the tires. But, including the spare in the rotation is a one-time savings. You can't do this with the second set of tires you have on the car, since the new tires will have much more tread than the spare --- even if you buy the Geolanders again. If you buy 5 tires, then you negate the savings achieved from including the spare in the rotation.

I'm guessing that Subaru and others think this one-time savings is not significant enough for them to have to print 2 sets of instructions for tire rotation --- one set on instructions for when the spare is new and another set for when the spare is worn down. (Supposing that a worn down spare is OK to use during an emergency. Otherwise, you would have to buy

5 tires each time.)

Richard

I agree that the primary reason I elected to include the spare in the rotation was for economic reasons. The economic predicament that that this fellow has is the one I hope to avoid.

Posted to:

couple of days ago. Subject: 1 dead tire means replace all 4???

"2002 Subaru Forrester 5 spd withlimited slip diff. 17k miles. I hit a pothole and the right rear Geolandar bought it. I go to tire shop and they say i need to replace all 4 because even a tiny mismatch in circumnference front to back introduced a bind on the transfer case (or whatever they call it). I've read that only a variance of 1/4" in circumference is allowed. This translates to about 1/32" tread wear difference. Hard to beleive."

Now you could argue that he did not need to buy 4 new tires (or even three if the spare was a match). But it would still go against the 1/4 inch rule, and at 17k miles (per the example) the difference may be worth the risk. But what if it was 20K, 25K, 30K? (rhetorical question).

Tom

Suppose that a tire lasts 40,000 miles. (The argument below works equally well for any other number you prefer.)

After a 4-tire rotation, at 40,000 miles those tires are used up. If new tires can be bought to match the unused spare, then only three have to be bought and one of the four used ones becomes the spare. Thereafter four tires must be bought every 40,000 miles.

With a five-tire rotation, the originals will last 50,000 vehicle miles, after which four tires must be bought (no longer constrained to match the original equipment), and four more at each 40,000 miles thereafter.

SO:

_______Number of tires purchased_______ Vehicle miles 4-wheel rotation 5-wheel rotation Total Total 40,000 3 0 50,000 0 3 4 80,000 4 7 0 4 90,000 0 7 4 8

120,000 4 11 0 8 130,000 0 11 4 12

Which way is cheapest depends on how long you plan to keep the car. Note that if the replacement at 40,000 miles is 4 tires instead of three, either because tires to match the spare can't be found or because the buyer just wants something different, then the 4-wheel rotation is never better than the

5-wheel rotation.

HOWEVER: the 5-tire rotation has the advantage that, if one of the tires is destroyed by a road hazard during the first 50,000 miles, only one, not four, new tires must be bought. After that, it doesn't matter because either way the spare won't match the road tires.

It might not be a bad idea to rotate 5 tires and buy 5 new ones each time. Here's the above table expanded to show the 5-tire repurchase:

________________Number of tires purchased_______________ Vehicle miles 4-wheel rotation 5-wheel rotation 5-tire repurchase Total Total Total 40,000 3 0 50,000 0 3 4 5 80,000 4 7 0 4 0 5 90,000 0 7 4 8 0 5

100,000 0 7 0 8 5 10 120,000 4 11 0 8 0 10 130,000 0 11 4 12 0 10

It looks like if you plan to run the car until it falls apart you're better off rotating and buying 5 tires every time. This has the advantage that if a tire is destroyed, only one new one is needed, regardless of mileage.

Anyway, the cost of printing two sets of instructions should hardly be a deciding factor.

Yes, that's an alternative, but you can only do that if they can match brand, model, and size of the tires on the car, and even if so you'll pay 100% of the price of a tire that has only a fraction of its tread life left. The decision on whether to do this would depend on how much life is left in the three good tires. If they're almost new, buy the shaved replacement, but if they are near their end of life, better to replace them rather than ruin a new tire. And if your tires are intermediate, neither new nor at end of life, flip a coin?