[Toyobaru]

Hi,

I am very new to Subaru and I am wondering if two different tire patterns on a forester, will this kill the diff? What I mean is, front of the car is using one set of tire and the rear has a different pair. I have heard that if tires sizes are different, this will kill the diff. But what about just the tire pattern?? All four tires are the same size. I am wondering if I should replace the tires immediately.

I guess previous owner has a bad tires and they just replaced one pair in the front.

Thank you

 

[frogstar7055]

Your fine,tire O.D. must be the same but the tread is all but irrelevant.

 

[bbottomley]

The measurement that counts is rolling circumference. It's possible that two different tires of the same "size" could indeed have different rolling circumferences, depending on how they squish down when loaded, or even on things more fundamental than that. All that "size" really means is the type of rim they will fit.

Mixing tires is something I've always tended to avoid due to differing handling characteristics.

 

[adc]

Make sure the circumference is within 1/2 inch I believe.

 

[bbottomley]

1/4" is what Subaru used to specify, and it's rolling circumference, not 2*PI*R circumference. With the advent of donut spares they have backed off this exact specification, but the principle is still there.

 

[frogstar7055]

1/4" is what Subaru used to specify, and it's rolling circumference, not 2*PI*R circumference. With the advent of donut spares they have backed off this exact specification, but the principle is still there.

I agree,a 1/4 inch is the max.
Mixing tires is not a good idea but if it's what he's got and their the same size he should be OK until he puts a new set on.(money being tight for a lot of people)

 

[frogstar7055]

Hey I got a Robin powered generator too.:rock:

 

[SuperRu]

The measurement that counts is rolling circumference. It's possible that two different tires of the same "size" could indeed have different rolling circumferences, depending on how they squish down when loaded, or even on things more fundamental than that. All that "size" really means is the type of rim they will fit.

Mixing tires is something I've always tended to avoid due to differing handling characteristics.

I could not agree more. You can seldom find rolling circumference data. But that is the measurement that really counts.

 

[bbottomley]

... that is the measurement that really counts.

because that's what the differential sees.