How crtical is tire rotation direction?

[skid542]

Well I'm slowly getting my car tuned out. It's taking a bit but I'm getting there - I'm way rich right now but I'd rather replace plugs and oil than pistions...

Anywho, I'm ready to put on my new rims that already have tires mounted. The tires are not new - have some wear but I cannot effectively determine which side is left and which is right.

The tires are Perrelli P-zero nero's. I can figure out which are the fronts and which are the backs due to similar tread depth (there's a small difference, but not large). When I have all the rims stacked with the outside facing up all the tread patterns are identical. The pattern is not symmetric about the centerline but I cannot discern any difference in the siping to indicate two are mounted different than the other two.

So, my question is - I've already heard that once you run a tire in a particular direction you should keep the rotation due to belts and such shifting and 'settling'. How critical is this? If this is critical, any suggestions on know which goes on which side?

Thank you in advance.

[Deride]

I ran those same tires in the past, there should be an arrow showing the rotation direction on the sidewall of the tire.

[beanis05]

There is an arrow on the side you have to have two rights and two lefts unless they are mounted wrong but those are nice tires

[Aerotech]

I have personally experienced tread separation on a used tire set, but it was lite truck tires, non-directional tread... it's not a myth, if that's what you're asking

[Apex3]

Yup, those are directional tires, just find the arrow. Almost all modern tires are directional

[93Leg-c]

So, my question is - I've already heard that once you run a tire in a particular direction you should keep the rotation due to belts and such shifting and 'settling'. How critical is this? If this is critical, any suggestions on know which goes on which side?

I've asked this question to a few tire guys and those who seem to be knowledgeable have given similar answers: with the newer tires made (in the last decade or two), it doesn't matter if the tire rotates in the same direction as it formerly used to be rotating. (I personally would try to mount them to rotate in the same direction as formerly, but that's just me.)

As regards directional tires mounted the "wrong" way, the tire guys said there would not be much performance difference in dry weather, only in wet weather (about 10-20% less performance if compared to the proper way the tire should be mounted) because the tread pattern is designed to cut through the water for better resistance against hydroplaning.