I've got 315/30ZR18 tires on the rear wheels. I got a screw in one of them so I just went to TireRack to order a new tire. However they have the tire listed as a 315/30 *YR* tire. Did Michelin change the tire at some point? More importantly, is it OK to mix this with my 3 other ZR tires??

 

i think the Y rating is the new rating system for Z rating tires.

here is good info u might want to check it out:

http://www.tirerack.com/tires/tirete....jsp?techid=35

 

Are your other tires pretty new (70% tread remaining at least)? If not, you may consider replacing both on the same axle.

 

Your tire now is a Y rated tire. Check out the sidewall on it further down from the size. See where it's marked "93Y"? That's the actual speed rating. It may be lister as ZR18 because a Z rating is non-specific to 150 OR MORE miles per hour. Y is rated all the way to 186. So, a Y rated tire is ALSO a Z rated tire and some makers mark the tires with both letters.

I know, it's confusing.......

 

Yup, it all makes sense now. Thanks. I just ordered one from ya. These are actually 98Y BTW, not 93 ...