How important is OEM speed rating

[Quattro Pete]

quote:

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there is no guarintee that a "z" "s" "h" etc tyre would stop quicker or have better handling than a "Q" rated tyre.

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Theoretically, the higher the speed rating, the better the handling, and by handling I mean quicker steering response. This is because as a result of having to withstand higher speeds, the sidewalls had to be made stiffer. And stiffer sidewalls translates into quicker steering response.

 

[ChrisW]

Umm, as a tire goes faster, as does the heat; it will go up depending on how fast the tire is going. The speed rating also has to do with how well a tire can take heat at speed capacity. You most certainly can take a lower rated (and its just that, a lower rating) tire past its speed rating. Is it safe for the tire? No; when a tire is tested for a certain speed rating, I'm sure that they test it beyond its given speed because at speeds any higher, the tire's integrity begins to degrade hence the rating given.

 

[Master ACiD]

i dont put too much stock in oem speed ratings. higher speed rated tyres are touted as supposedly having better traction for stopping and better construction etc, but the speed rating of a tyre has only a bearing on the speed. the stopping distance isnt factored into the speed rating, nor is construction.

for example, there is no guarintee that a "z" "s" "h" etc tyre would stop quicker or have better handling than a "Q" rated tyre. the only guarintee is that the Q rated tyre cant go as fast as the rest of em. 99 mph if i remember correctly.

what i look for when selecting a tyre, is not so much the speed rating, but i want AA's on traction and a single A on tempature. i let the speed rating of a tyre be ****ed. im more concerned about stopping traction than going 149+ mph.

 

[CapriRacer]

Just to correct a couple of imsconceptions:

The speed capability of a tire is more a function of the centrifugal force on the tread/belt package than heat buildup. That's why you'll find high speed rated tires with a nylon cap ply, and tires on the upper end of the ratings generally have 2 cap plies.

Also, because tires with high speed ratings are generally fitted to high performance cars, the tread compound generally has better grip and the sidewalls are made stiffer for better steering response. Yes, the speed rating doesn't have anything to do with grip or steering response, but the vehicle fitment generally dictates these things go hand in hand.

 

[ccs2k1]

I no longer have the mag with the article, but if anyone has time, look up the news story about the guy and his wife who entered a Testarossa in a Nevada race on closed roads (Open Road Classic?) back in the late 80s. IIRC, the guy shrugged off the potential of tire failure (his tires did not meet the 183 mph max speed the car was capable of but organizers still let him race with the promise not to exceed the tires' speed rating). Somewhere above 170 mph a rear tire let go and his wife paid the ultimate price.

 

[labman]

posted December 30, 2005 11:32 PM
I no longer have the mag with the article, but if anyone has time, look up the news story about the guy and his wife who entered a Testarossa in a Nevada race on closed roads (Open Road Classic?) back in the late 80s. IIRC, the guy shrugged off the potential of tire failure (his tires did not meet the 183 mph max speed the car was capable of but organizers still let him race with the promise not to exceed the tires' speed rating). Somewhere above 170 mph a rear tire let go and his wife paid the ultimate price.

And what does that have to do with the real world?

 

[ccs2k1]

Lawyers, bean counters, engineers and safety factors.

 

[Master ACiD]

capriracer and others, we are not talking about performance machines here. no corvette or ferrari. the original poster has a fwd toyota camry!