Tire Circumference

Simple arithmetic says that this translates into a difference in radius (i.e. tire wear) of about 4/100 of an inch. Are manufacturing tolerances even that tight?

As much as I like my Subaru, I think it is a ridiculous spec as well. Does anyone out there actually measure their tires on a regular basis? Is it in the maintenance schedule?

If there is a danger of destroying the viscous coupler from like type tires that are slightly different in dimensions, I'd think that the reasonably thing to do would be to provide an overtemp light for the coupler. Then at least, you could stop and let it cool down then get the situation fixed.

That's why you're supposed to go with 4 tires of the same size/brand/model. I've seen BIG differences in true size in tires of different brands labeled in the same size.

We did *just* get home with a new Legacy (it now has 36 miles on the odo!) and that would at least be interesting to note. I think it's time to roll the car on the drive with some chalk on the tread!

little brouhaha on this over here:

Subaru is always overstating the sensitivity of the drive train components. To read my Loyale's manual, you'd think the transfer case would be toast every time you put the car in 4WD and had one low tire, or were driving along icy roads with the 4WD on and had to go over a dry patch stretching about a hundred feet before you got back to the slippery stuff.

It's like someone else said, it's just so they can insulate themselves against paying for major drivetrain work if they feel like it.

--Decimal Cat