Mix Z and W ratings on same tires?

[A Quiet Boom]

I know you're not supposed to mix tires on 911s but I've got a problem. I've got Yoko AVS Sports on my car and the fronts are about 60 percent or better. The rears are badly worn on the inside and need replaced ASAP. All I can find are the AVS Sports in the W rating while my originals are Z rated. Sizes are 215/45/17 Front and 234/45/17 Rear. Is it OK to put W rated tires in the rear? I'd rather not replace all four tires right now, especially when the fronts are in decent shape.

[lateapex911]

I assume you have 7s and 8s as rims, as the 245 is really too large for a 7" rim width, according to Yokohama. My opinion, is that the Z rating of your original meant that you were good for a max speed above 149MPH. The W rating is good up to 168MPH.

Both are probably in excess of what the car will see, I imagine.

I think there are bigger concerns with the mismatch of compounds and treadwear due to aging, but even that is rather slight...a few pounds of underinflation would be a more significant issue, and most tires aren't inflated properly.

Personally, I wouldn't sweat it. If in doubt, call the Tire Rack, or read this section:

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

[widgeon13]

I did it some time ago and the car was really squirelly, unsafe at speed. I immediately took it back to where I got the tires and corrected the problem by putting the same speed ratings on front and rear (stickers had not even completely worn off tires). The sidewall construction is different in order to disipate heat and consequently they behave differently. Personally, I would not do it again but you are asking and I am giving results from real experience. Perhaps it was unique to the particular tire manufacturer, I believe I had BFG's on at the time. The car was fine once I corrected my error.

Let us know how you make out.

[Shaun @ Tru6]

I tried to buy SO3's from Tirerack that were mixed Z and W and they wouldn't sell them to me. Said it was dangerous to mix ratings, especially if the car goes on the track where temperature plays a big role in concert with the rubber/speed rating.

[A Quiet Boom]

That is what I was afraid of. I'm going to call some local stores an see if they have any older stock. I've had these Yokos for only three years and don't know when the Z's where discontinued and the W's started. I wonder if it isn't the same tire that just passed the W testing protocol?

[A Quiet Boom]

Ok, I learned something new. My tires say 235/45/ZR17 93W on the side which means they are W rated. I figured it out after re-reading the link provided by lateapex911. Boy do I feel dumb LOL. So I guess it's just a pair for the rear right now. Thanks all.