Does the speed rating of a tire effect its performance?
 

lets say you have two identical tires. same size, manufacturer, and model, but one of them is Z rated and the other W rated for example. will the Z rated tire perform better? and whats the difference in the compound of the tire to withstand a higher speed?

TIA

A tire with a Z rating does not mean it will perform better than a W rated tire. The compound has nothing to do with the rating as far as I know, its the radials, and internals of the tire that gives a tire its rating. I am not positive of this though.

i think it's usually just more testing for the higher speed rating. i believe the testing to get the z rating is less precise, so many tires are tested for z (which is a semi-generic rating) instead of the higher ratings - W & Y.
my guess for your specific question is that the tires are actually IDENTICAL besides the speed rating. the z rated tire is probably older (an initial release from the manufacturer that hadn't been through all the tests yet), and the W rated tire is newer.

http://www.tirerack.com/tires/tirete...eral/speed.htm

after reading that, it could also be that the tires were first released here in the states where speed ratings aren't as important, and the Y rated tire reflects new international marketing for the tire, since international markets prefer more precise measurements than Z.

Z-rated tires are open-ended speed ratings...good to speeds greater than 149 mph. W rated tires are-closed ended speed ratings...good UP TO 168 mph; Y rated tires are good UP TO 186 mph. Higher speed rated tires tend to have much stiffer internal construction and stickier rubber, while lower speed rated tires have softer internal construction and harder rubber...IMO a Y-rated tire will outperform a W-rated (or Z-rate) tire at very high speeds (with regard to high-speed stability). Obviously if you don't plan to go 186 mph, or if your car isn't capable of 186 mph, then there's no point in having a Y-rated tire, is there?

The answer is "Not necessarily, what qualities are you looking for?"

To get a higher speed rating, the tire must create less heat and dissipate it better. Usually this means much stiffer sidewalls. Whether that is good or bad depends on what you are looking for. There are other subtle difference not directly related to the speed rating - typically a manufacturer will use a softer, stickier rubber on the higher speed-rated tires because they figure that, if the driver wants higher speed ratings, they're gonna be driving hard. (Plus there's the obvious thought of not wanting to drive 200mph on tires with poor grip)

So, per se, it doesn't necessarily mean better. But, it usually does.

If I remember correctly... my Kuhmo Ecsta z rated tires had a different tread rating than my buddies. I'm not sure if his was V-rated or Y-rated. But I do remember his tread where rating was 320 and I believe mine are 280. I could be wrong. But if I'm right... then yes, speed rating would make a difference in perfomance.

For our racing car, we use a varation of a pilot sport (mmmx). We run at top speed (229 , not an rx7) for up to 1/2 hour at a time in Nevada. If you contact Michelin, the will tell you that these tires are good for speeds in the range we are running. No W or Y rated tire would last at this speed. The cords would seperate.

El Paalo, a z rated tire is not an older tire. It is still the highest performance rated tire out there.

Now, if you are not running at the extreme end, you would not notice a difference between a W\Y\Z tire.

Hope this helps (or confuses you more).

earl

Yeah, Y-rated is only good for 186 mph, NOT 229 mph!

sleepr1...sounds like a sacaristic reply....I have a video of us blowing a tire at 190 (we blew the tire Sept last year). Running the incorrect tires for your application is not a joke. I have the video on digital format. If someone can tell me how to post the video, I will do so.

No not a sarcastic reply...at all...I'm just stating that a Y-rated tire would NOT hold up past 186 mph...at least that's how I understand the Y-rating to be...So if you went up to 229 mph with a set of Pilot Comp Sports, then Michelin must be low-balling their Y-rating:)

ok.....sorry...

I don't think Michelin is low-balling the y rating. As you posted earlier, every rating other than a z rating is closed end. I think bridgestone makes a very good tire and I would run it except for the fact that they will not give an 'open ended rating'. They will tell you it is good for the 149+ z rating but when you talk to them they will tell you it is not a racing tire. I asked them why give a y or z rating to a non-racing tire..ie, why would I be doing 186 and not be racing! The tech guy just snickered and said nothing. I am sure there are liability issues at stake for them as it wouldn't look good for someone to race on their 'street tires' and have a tire related failure.

thanks guys. the decision was between a Z-rated Pirelli P-Zero and a W-Rated Potenza S-03 PP.

the S-03 is the tire of choice. :)

JoeD...I haven't tried the S-03s, but I have had a set of Pirelli P-Zero Asimmetricos in 225/50-16s. The Pirellis were outstanding tires for the money, and have been one of the best combination road/track/wet tires I've had. At full tread depth, they did not chunk very badly at all, and they were quite fast in the dry. I even managed to get 12,000 miles out of them:)