Q. The tire shop is telling me I need 4 new tires, is this true even when I technically only need one?

A. Depending on the situation this may in fact be true, if you own an AWD Subaru all four tires must have have like tread depth and type. So if you have three used tires that are worn down to below 8/32 of tread life remaining, and the new tire comes new with 12/32 that would in fact be too much tread depth difference to allow, and it could cause damage to the AWD portion of your Subaru transmission. A good rule of thumb is not to allow more than 2/32 of tread difference right to left, and no more than 3/32 front to rear.  The reason for this is the tire that has more tread will also have a greater circumference than the other three tires and spin at a different rate of speed this over time can both “confuse” the AWD system as well as cause damage.  Next it is imperative that the tires have the same type of tread design, so if you have had a blowout and you tire is no longer offered or not available locally you will also need to buy 4 tires in this instance as well.  The tire rack as well as some tire chains do offer a lesser known service called tire shaving this is where you can buy one new tire and have it “shaved” to match the rest of the tires on your car.  If you are not in a hurry this may be an option for you.

The tread depth of the tires on your car now should be measured, than compared to the tread depth measurement of the new tire.  Once you know the difference the decision can be made on whether you need one, two or four.

Measuring the tread depth on a tire