02 Subaru Outback sp


I was told that having two different tire brands on AWD vehicles (or Subarus specifically) is bad news. It’s an automatic with about 65k.


The main problem is different sizes, like a new spare and the worn tires and also two new ones and two old ones because the wear makes so much difference. Measure the circumference of your tires and if the sizes are different, you can worry.


What you were told is correct.

If you read your Owner’s Manual, it will verify the importance of having tires that are very closely matched in circumference. Failure to have closely matched tires will result in failure of the center differential, which is a fairly expensive repair, and it is not covered by the warranty as the tire problem constitutes owner negligence.


It can be.

However if the rolling circumference is the same between the two different brands(they differ mostly) you are fine. The rule with Subaru is rolling circumference(part that touches road) must be within 1/4" of each other.

Tread depth is absolutely meaningless unless you are comparing the same make, model and size of a tire.


Ok. I had never realized this was an issue until I was recently told by someone at firestone a couple of weeks ago. But I’ve had these two seperate tire brands on the car since 6/06. The front set put on 1/06 and the rear 6/06. Would the center differential thing come up already if this had been a problem?


Yes, it is very possible, perhaps even likely. I really wish that people would read the Owner’s Manual when they buy a car, in order to avoid potentially expensive problems like this.

What type of symptoms are you experiencing?


Not necessarily. The only way is to measure with a steel tape measure circumference around the middle of each tire and compare the results, lowest vs highest. Months doesn’t matter as much as miles driven and tread wear in that time frame, as a determining factor if you are out of spec on the tires.


None really. Recently replaced the knock sensor. It was mostly just something mentioned by the mechanic. I’ll measure the treads.


The issue that comes up is your clutch pack. It costs about $500-$1000 to replace and you’ll know when it is gone but getting a binding feeling when turning sharply.

Basically if the tire size front set to back set is different enough you are constantly slipping this clutch pack which eventually burns it out. Like others posters state and I did too, take a piece of string and pull around tire(in same spot) and then measure after with a tape measure for each tire.