Tire speed rating and car behaviour

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My Mazda3 comes with V-rated tires. I think it's strange that my car doesn't have cheaper insurance than the base model, which has S-rated tires, since those drivers must be constantly getting killed in accidents from the dangerous situation of having lower speed ratings.
rolleyes.gif


If I were a lawyer, I think it would be easy to argue that a lot of V-rated tires that are called "all-season" would constitute negligence on the part of the tire manufacturers since someone might actually use them in the winter. If I had to use one tire year-round, I'd take Q-rated Winter Slaloms over V-rated RS-A's any day.
 
I have to say I'm surprised. I had the 60 series 512s on a 91 grand am (not a performance car by any stretch) and they seemed OK for an all season tire, but labeling them UHP is just stupid; they're not as sticky or stiff as the "high performance all season" Yokohama H4S my car has on it now. It's gotta be a marketing thing to get the "import" crowd to buy them. Whoever sold you those tires (assuming you didn't get them from a place like the tire rack) should have known they aren't really UHP and told you that.
 
Discount Tire Direct dot com and Consumer Reports, so no 30 day/500 mile test drive. Honestly, the biggest tire mistake I ever made and I've owned cars since 1979.
 
Nick the 512s are UHP per Falken. From the horse's mouth, check out the link below to the 512's specs. At the very bottom you can see that "UHP" (55 and lower series) are rated 360 treadwear, traction A and temp A. They are all so squirmy that they should be classified as just touring.

http://www.falkentire.com/tires_512_sizes.htm
 
Performance tires cost, but I look at it this way... Will you wish that you had the extra performance at some point during the life of the tire? My experience says yes, at least once in those 20-40 thousand miles, I will need to make a stop or evasive manuver that is "close."

One failed stop or other manuver will cost me much more in terms of deductible, aggravation, raised insurance premium, or pain and suffering than I spend on the better tires. So, for me it's a no-brainer - use the best rubber I reasonably can. That means at least good H or preferably V rubber for the sedans in the summer, dedicated snow tires when conditions require, and similarly appropriate tires for the 4x4s (at least a good S tire for the summer months).

Yes, I have a lot of money tied up in tires (including a set of cheap S rated Bridgestones that came with my last sedan - they were downright scary when the road got wet and were replaced by a set of V rated Bridgstone LSVs - what a wonderful difference), but I like to enjoy my driving, and my philosophy has saved my bacon on more occasions than I can count over the last 500,000 miles.

Put a cheap set of tires on a Porsche and it will drive like a car that came with cheap tires (an old Datsun I owned comes to mind), except with way too much power. Put an expensive set of tires on an old Datsun, and it won't be a Porsche, but at least it won't scare the **** out of you. You get what you pay for (mostly).

[ April 11, 2006, 12:59 AM: Message edited by: mzugg ]
 
quote:
Originally posted by jmacmaster:
SNIP

The tire speed rating is the maximum SUSTAINED speed that the tire (not the vehicle that the tire is on) is capable of so long as the load rating of the tire is not exceeded. Sustained speed does not include such things as passing someone or driving for another reason for a short period of time.
SNIP
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Incidentally, it seems that the powers that be think SUSTAINED equals 30 minutes. No test past that point that I know of.
 
The OEM tires on my GS-R were V-rated tires. After they wore out, I replaced them with H-rated tires to get better all-season traction. I didn't really notice any difference in the handling of the car.

After they wore out, I went to an S-rated tire, which I still have to this day. I definitely notice that the car doesn't handle as crisply as before thanks to the softer sidewalls. On the plus side, they have much better snow traction and cost much less.

Once these wear out, I'll probably go back to an H-rated tire.
 
quote:
Originally posted by Goodyear:
Speed ratings do not indicate how well a tire handles or corners. They certify the tire’s ability to withstand high speed.
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I would agree with this statement in a sense that there is no empirical way to show how certain speed rating translates into handling/cornering. However, when staying with the same tire model but going up to a higher speed rating, one may expect the steering response (which is one of the factors of handling to me) to improve.

Making the tire withstand higher speeds involves reinforcing the sidewall. Reinforced sidewall is stiffer and thus provides quicker steering response.
 
I have four of the tires in the link below enroute to my house from tirerack.com. as I write this. It's Kumho's standard touring all-season tire. I'm putting them on my wife's 03 Subaru Forester. This tire comes in numerous sizes, all of which have the 112 mph "S" speed rating. If you click on "Reviews" near the top of the page in the link below you'll get 391 reviews sent in by purchasers of this tire. It has been put on a very wide range of vehicles. The reviews do not indicate any safety problems arising from the speed rating or from driving the vehicle at whatever top speeds the reviewers drive at.

http://www.tirerack.com/tires/tires.jsp?tireMake=Kumho&tireModel=Touring+A/S+795

Here's what Goodyear's home page has to say about speed ratings -- note especially the second paragraph and the last paragraph:

"Many Goodyear tires are available in speed-rated versions to match the speed capabilities of the world’s fastest cars. Generally, it is recommended that a speed-rated tire be replaced with a tire having an equivalent or greater speed rating.

However, if you never drive at speeds near the limits of your speed rated tires, you may choose to replace them with tires having a lesser top speed rating.

In situations where tires having different top speed ratings are mixed on a vehicle, the maximum speed certification is limited to the top speed certification of the tire with the lowest speed rating.

Speed ratings do not indicate how well a tire handles or corners. They certify the tire’s ability to withstand high speed."

In the 4 years that we've had the Forester we've never driven it at even 100 mph, much less at 100 mph for a sustained period of time or at the 112 mph that the "S" speed rated tire is good for. It would be a waste of money for us to spend more money to install "H" speed rated 130 mph tires, which is what the Forester came stock from the factory with (presumably because the Forester's top speed is, or is near, 130 mph).
 
quote:
Originally posted by Primus:
And how about braking distance ?
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The UTQG "traction" rating is based on the tire's traction during braking in wet conditions.

I can definitely say that the AA rated Michelins I put on my car have more traction on dry and wet pavement than any of the A rated tires I've used!
 
quote:
And how about braking distance ?
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I'd say, beyond "stickiness" of the tire, a stable tread block design that maximizes the contact patch will ensure good breaking (and maneuvering). The demands on tires with a higher speed ratings are higher, so they may well offer an advantage at lower speeds also.
 
I can appreciate that it is difficult for the average guy to make sense of the vehicle manufacturer's speed rating specification for the original tires . The easiest way to think of this is that it is a just test result. Even though it does a pretty good job of indicating the actual speed capability of a tire, a lot more research has taken place since the test was implemented and some of the research indicates that the speed ratings as delineated aren't enough. If some of us tire engineers had our way, we'd redefine the test and eliminate the confusion. Unfortunately, once it is defined it can't be changed.

This leads me to the issue of "reserve capacity". A good example of this is the load carrying capacity of tire. Typically, the load carrying capacity of a tire is much more than the theoretical maximum loading. Long ago it was discovered than utilizing larger tires improved the durability.

The basic principle is that increasing the "reserve" reduces the failure rate. Put another way, more capability = more safety!

In an earlier posting, jmacmaster point out that out of 391 enries there were no speed rated failures reported and that justified the use of an S rated tire. One failure out of 400 would be 0.25%, which is higher than the failure rate for the infamous Firestone Wilderness AT!

Another interesting tidbit is that in order to get a tire to pass an H rating, the tire generally must have a belt over the steel belts - usually nylon. This simple change has an enormous affect on real world failure rates - way out of proportion to what is registered by the speed rating alone.

This is one of the reasons car manufacturers are specifying higher speed ratings.

In essence, using lower speed rated tires is increasing the risk that something tragic will happen.

I want to thank jmacmaster for bringing to my attention that the Goodyear web site seems to permit the use of lower speed ratings. This is a different position than what other Goodyear spokesmen are taking in other arenas. This will certainly be a future discussion point with them and I wouldn't be surprised if the web site gets changed in the next few months.

So to sum up:

I just want folks to realize that when they decide to use lower speed rated tires, they are increasing their risk and this is especially true when it comes to using tires lower than H.
 
increasing the risk of what? i have run q speed rates tyres before and had no problems.

most people dont use their car to its fullest extent. most people dont need 149mph rates tyres man. its OVERKILL. its also a marketing ply used by car makers to make a car appear more racey. they take some normal car and fit 16's or 17's on it with h or v rated tyres and try and get people to believe the car is sporty.

why does a corolla or a kia rio need tyres rated to go 118mph, or 124+. these cars dont even have suspensions or brakes capable of utlising the higher speed rated tyres "possible" better handling capability.

its just a marketing ploy. totally overkill.
 
As Capriracer mentions, the higher speed rating does provide a greater margin of safety, just like designing a lifting device with a safety factor of 15 is provides a better safety margin than a safety factor of 10. Under normal use, a safety factor of ten will never fail. But when used in an abusive manner, the safety factor of 15 may be preferred. Same thing for tires. Under normal use, a Q-rated tire isn't going to have any problems. But when run underinflated at high speeds in hot weather, like those Firestones on the Explorers, an H-rated tire is definitely preferred.

I just don't like the idea of someone telling me I can't use Q-rated winter tires on a car when they're far safer than any V-rated "winter" or "all-season" tire in winter driving. And many S-rated tires have a tread pattern that is more suitable for all-season use than higher speed-rated tires, and more forgiving on poor/dirty road conditions. If the driver is not driving really fast and keeps his tires properly inflated, I think he's safer with a more forgiving and multi-season tread. Of course, it's even better if he can find a tread like that with a higher speed rating.

I just put Y-rated Michelin Pilot Sport A/S tires on my car, which are a best of both worlds tire, but they're definitely overkill and that was reflected in the cost. There's not too many economy-level 205/50R17s!
 
We all know well it's a must to use tires with at least not lower speed rating than a maximum speed specified by the manufacturer for its car. And, for safety reasons it's better to be 1 step up.

However, how often do we drive over 160, 190 and 210 km/h ? If to take my experience in long distance journeys, 25 % of time comes for the speed 160-180, 2 % for 180-200 km/h (may be 2-3 % more when I'm travelling in Germany) and less then 1 % for 200-210 km/h. I drove at 210-225 km/h (speedo) 2-3 times only and even during a very limited time, may be 1 hour in total.

I don't speak about "S" rated tires, but do I really need "W" or "Y", or even "V" ? The only real argument to use them would be their better behaviour (handling and braking) at speeds 100-200 km/h then "H" rated tires. To my regret I could not find a direct comparison of "H" and "V", or "V and "W"/"Y" tires in usual test disciplines.
 
A few more thoughts:

The speed rating of a tire does not mean the rating holds 100% of the time for 100% of the life of the tire for 100% of the conditions a tire encounters.

Tires get damaged (curbs, debris, potholes, etc) and a higher speed rated tire fails less often due to these situations.

Failure rates in tires is measured in fractions of a percent, so I would caution anyone using their own experience that their sample size isn't large enough.

Most folks don't pay attention to their tires, especially inflation pressure. I don't think that includes any BITOGer's, so the discussion here is less appropriate than for the general public.

Hope this helps.
 
CapriRacer says:

"In essence, using lower speed rated tires is increasing the risk that something tragic will happen.

I just want folks to realize that when they decide to use lower speed rated tires, they are increasing their risk and this is especially true when it comes to using tires lower than H."

Well, if that's the case, then it applies across the whole range of speed ratings. For a tire of any given speed rating, its always safer to move up to the next highest speed rating, no matter how fast one is actually going to drive. The logical conclusion is that no matter how fast a vehicle will go or how fast you'll actually drive it, everyone should put on tires with one of the two or three highest speed ratings. This seems to me to be patently unreasonable. At what point is the incremental safety gained by buying and paying more for a tire with the next highest speed rating overkill?

It seems to me that CapriRacer, who's a tire engineer, doesn't think that his industry's speed ratings are trustworthy, or at the least, have not built enough safety into the speed ratings. If I can't trust a 112 mph "S" rated tire even though I never even go 100 mph, how high a rating tire CAN I trust?

And what are we to do about snow tires, and I'm talking about TRUE snow tires. The vast majority of them are "Q" (99 mph) or "S" (112 mph) rated. Are we to stop using snow tires for that reason? (I'm familiar with the relatively new, so-called "performance", snow tires with higher ratings, but the fact is that almost all snow tires are, and always have been, "Q" or "S" rated.) Under CapriRacer's analysis, we thus should not run them. Yet, millions of us do, particularly in the northern states, Canada, and northern Scandinavia. I've lived in Minnesota, Vermont, and Montana for 62 years. I've always given a lot of thought to the tires I run and have done a lot of research on the subject. I've always run snow tires, studded ones, in the winter. I have yet to see anyone argue that they are not safe because of their low speed rating. Nor have I seen any reports, statistics, or studies arguing against their use on the basis that at a speed rating of "Q" or "S" they are not safe enough.
 
quote:
Originally posted by jmacmaster:
.....Well, if that's the case, then it applies across the whole range of speed ratings. For a tire of any given speed rating, it’s always safer to move up to the next highest speed rating, no matter how fast one is actually going to drive...
Click to expand...
From an engineering perspective, this is true.

quote:
....The logical conclusion is that no matter how fast a vehicle will go or how fast you'll actually drive it, everyone should put on tires with one of the two or three highest speed ratings...
Click to expand...
Only if everyone wants to be as safe as humanly possible and is willing to pay the price for that.

quote:
.....This seems to me to be patently unreasonable. At what point is the incremental safety gained by buying and paying more for a tire with the next highest speed rating overkill?.....
Click to expand...
Good question! My purpose in this discussion is to help folks answer that question.


quote:
....It seems to me that CapriRacer, who's a tire engineer, doesn't think that his industry's speed ratings are trustworthy, or at the least, have not built enough safety into the speed ratings. If I can't trust a 112 mph "S" rated tire even though I never even go 100 mph, how high a rating tire CAN I trust?....
Click to expand...
It isn’t a matter of trusting the ratings. The ratings are the ratings. But to assume that they apply 100% across the board is a bit naive.

What I am pointing out is that there is an elevated risk associated with using a lower speed rated tire, even if you don’t exceed that speed.


quote:
....And what are we to do about snow tires, and I'm talking about TRUE snow tires. The vast majority of them are "Q" (99 mph) or "S" (112 mph) rated. Are we to stop using snow tires for that reason? (I'm familiar with the relatively new, so-called "performance", snow tires with higher ratings, but the fact is that almost all snow tires are, and always have been, "Q" or "S" rated.) Under CapriRacer's analysis, we thus should not run them. Yet, millions of us do, particularly in the northern states, Canada, and northern Scandinavia. I've lived in Minnesota, Vermont, and Montana for 62 years. I've always given a lot of thought to the tires I run and have done a lot of research on the subject. I've always run snow tires, studded ones, in the winter. I have yet to see anyone argue that they are not safe because of their low speed rating. Nor have I seen any reports, statistics, or studies arguing against their use on the basis that at a speed rating of "Q" or "S" they are not safe enough....
Click to expand...
And that is a really good discussion point:

The test used for speed rating is run at 77 degrees F. Clearly snow tires operate in a much cooler environment, plus the operating conditions for snow tires is quite different than an all season tire – folks generally drive slower in winter. Therefore, a Q rated winter tire could be quite adequate.

If I can bottomline this: If you chose to use something different than what the vehicle manufacturer recommends, please do so with as much knowledge as you can.
 
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