DBrian

I did a forum search so hopefully this hasn't been covered in excruciating detail. I know a lot of owners here love the Michelin PSS, but my topic is looking more for general opinions on W-rated versus Y-rated tires.
I believe our cars came with Y and we know the IS-F is capable of 170+. The tire companies say:
"The speed rating of a tire is based on U.S. Government standards for reaching and sustaining a specified speed", and:
W - Up to 168 mph
Y - Up to 186 mph

Seems like the word "sustaining" could be a key word in that sentence. I don't really plan to do much track time but I may have been known to dabble in a high speed run once in a while.... But I suspect if you ever get up to 170, you're not likely to stay there very long...

One reason I ask is depending on the tire manufacturer, there can be a cost benefit in going with W-rated, and/or there is sometimes more availability of a certain tire...

mindcrime

iTrader: (2)

disregard with what I said lol.

SpeedFreaksUSA

iTrader: (1)

I believe all of the tires available in the sizes this car uses or could use will hold one of three speed ratings:

W - Up to 168 mph
Y - Up to 186 mph
(Y) - 186+ mph

I personally feel comfortable using any of those speed ratings on any of my vehicles. I track my cars often and will occasionally, allow my cars to find their natural top speed if the time and place will allow to do so relatively safely. Most of the EHP street tires I use are W rated. Admittedly I have exceeded 168mph on W rated tires (for short bursts) and although I acknowledge the chances of something failing are higher at those speeds than with a Y or (Y) rated tire, I really don't think it's an issue unless you're going to be sitting at those speeds for a while or you're really pushing far beyond the speed rating (beyond 20-30% of what the tire is rated for). The lawyers at these tire companies make sure there is a big margin in the speed, pressure, load ratings to keep from getting sued as much as possible- I've heard as much as 30%.

There is no need to worry about it as long as it's at least a W rated tire. For a car that can't get too far above 170mph I would never buy one tire over another just because it has the higher Y or (Y) speed rating. If we were talking about cars that can and will exceed 200mph then I would only buy (Y) rated

-Matt M.

DBrian

Thanks Matt, just a point of clarification: when you make reference to "(Y)" is that the same as what Discount Tire refers to as "Z" rating? I see a Y but not a (Y).....

digger08

iTrader: (1)

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

When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities.

Digger08

flowrider

iTrader: (9)

No, "Z" is an outdated speed rating - Good for over 149MPH. Tire Rack does include the (Y) designation, scroll down to the bottom:

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

When the "Z" rating is used today, it is used in conjunction ties the "W", "Y" or "(Y)" ratings.

Lou

DBrian

Thanks for the feedback! I'm getting close to needing a new set, I plan to go with a minimum of a W rating.