[Zeke]

Originally Posted by 1990C4S

Thanks for the suggestions. I had not thought of it until now, but I did replace a snow tire a month ago. The one new tire is exactly the same as the other three, with only about 2,000 miles less, so I doubt that is the issue, but it is something to look at. Tire pressure may be a contributor also.

Snow tire rims and lug nuts fit correctly.

Even new tires can have a slightly different circumference.

Subarus: Subarus have, to our knowledge, the tightest tolerance of any AWD system. Since we see so many, we can tell you what the tolerance is. It can be stated in two ways: The first is 2/32nds tread depth across all four tires. The problem with this is that actual tire dimensions can vary from brand to brand and even from model to model. Therefore the 2/32nds rule is only good if you have the exact same size, brand, and model tire. The other way to check is to measure the tire around the circumference and then the tolerance is 1/4". That was circumference, not diameter, so you have to have a flexible tape ruler and measure around the tread of the tire. Also, having air in the tire affects the circumference. Though the change due to having air in it is only about 1/8", it's pretty critical since the tolerance is only 1/4". Therefore, to get an accurate measurement, it's necessary to let the air out before you measure (since the prospective replacement probably won't be aired up). This second method allows you to check compatibility with any make or model of tire. When we were almost finished with this article, a Subaru came in that needed only one tire, so the picture shows us measuring the prospective replacement tire with our "Subaru Tool".


You may ask what the big deal is? Well, on the Subarus, if all four tires aren't matched within 1/4" around the circumference, you will break the transmission, not maybe or sometimes - it definitely happens. Granted it won't happen overnight, and the AWD on many Subarus can be disabled, but the transmissions can definitely get ruined and then they have to be repaired or replaced. Then the cost will be a lot more than the cost of tires!

Source.