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Thread: Tire speed ratings?!

  1. #1
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    Tire speed ratings?!

    I took my Subaru Outback for an oil change yesterday. They called to say that the tires were about worn out. He has always seemed honest in the past, so I told him to go ahead.

    He put V speed rated tires on; Subaru recommends H. From what I have read, V is good for 130mph and H is good to 149mph. H has stiffer sidewalls and will give better handling, while V will be more comfortable. My wife is unlikely to drive much over 75.

    Does it matter?
    I called Subaru and they told me to talk to a dealer. The dealer will obviously tell me I should have gotten my tires from him and I absolutely need H.

    Anyone actually know about these things?

  2. #2
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    The main thing about speed rating is to not exceed the speed rating of the tire with the vehicle for extended periods. Some overkill is fine, but there is no need to spend money for a higher speed rating unless you take a lot of long freeway road trips. Once the tire can go faster than the car is going to be driven, weather and tread pattern are next to consider. I have a cousin in San Diego where it is dry 360 days of the year, but the five days it rains, it generally comes down in buckets. He has a lot of flexibility, but wants a tire that isn't hopeless on wet roads. Up here it makes sense to have two sets of rims, one set with summer tires mounted and the other set with winter tires mounted. Another improtant axis is treadlife v- traction. A really soft sticky tire will have terrific dry grip, but not last very long. An extrememly hard compound might offer long long tread life, but never offer a lot of grip. Load rating is another, probably not an issue with most Subaru's, but does matter in fullsize working pickup trucks and trailers. Temperature rating can make a difference, dedicated summer tires can get flat spots when parked overnight at low temperatures.

    I wouldn't sweat H/V as the price difference for otherwise identical tires should be fairly minimal.

    After you have the perfect tire, you next need to maintain the correct tire pressure range for the tire to function as designed, probably another thread.

  3. #3
    Speed ratings are determined by more than just straight line speed.
    Vehicle weight, suspension cargo capacity, and so on and so on. The tire is the first (or last depending on your point of view) component in your suspension system. If you alter one of the variables in the tire's equation, something else has to compensate, ball joint, torsion bar, etc.
    In the OP's case, a thicker sidewall may be necessary for the car/truck to handle properly. Using a different rated tire may not have any immediate effects but could down the line.
    JMO

  4. #4
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    My experience has been that for a given speed rating the sidewall stiffness can vary between brands and models.

    To some degree a different tire weight also comes into play as to how the suspension responds. That said, the tire weight also changes as the tire wears.

    I guess I'm in the don't sweat it group as long as you're happy with the ride, handling, etc..
    Maryland

  5. #5
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    I was so upset that I got it all wrong. My tires are "T", good for 118mph. Subaru recommends "H" good for 130mph. But it is the same issue.

    As Edward says, Subaru designed the other suspension components to go with an H. However, my wife doesn't really push the car all that hard so maybe the softer tire is okay. I don't want to be a jerk about it, but also don't want her to die because I just let it go.

    I don't know where I came up with "V".

  6. #6
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    Check what your insurance says about fitting lower rated tyres.

  7. #7
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    I'm more inclined to accept a higher speed rating, a lower one not so much.

    On tire sites I've seen higher rated tires offered for a given vehicle, can't say i ever recall seeing a lower suggested
    Maryland

  8. #8
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    I uderstand in Europe many countries require the tire be rated for the max speed of the car. This means fast cars must use pricier, faster rated,tires.
    Bill D

  9. #9
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    Quote Originally Posted by Bill Dufour View Post
    I uderstand in Europe many countries require the tire be rated for the max speed of the car. This means fast cars must use pricier, faster rated,tires.
    Bill D
    The last few cars I've owned have all come with tires whose speed rating was pretty much equal to or slightly higher than the maximum speed of the car. Two of those cars were Japanese, one was German, and my current car has a Japanese make's name on it, but it's built in Austria using a German make's parts. I can't remember what the tire speed ratings were on the cars I had before that. They were all sporty in nature, or simply classified as sports cars, so it could be a "sports-style" thing to have tires rated like that and not just a European thing. Although I could definitely see cars in Europe requiring that regardless of their type.
    And there was trouble, taking place...

  10. #10
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    The tire speed rating is supposed to match the top speed governed on the vehicle as Bill mentions. In reality, however, the small difference isn't going to pose an issue given almost nobody drives at these high speeds. If you bought a quality tire, I honestly wouldn't worry about it. Truth be told, I "think" that the (excellent) tires I have on my Ascent currently were one rating removed from the (not so excellent) OEM tires, but I'm working on feeble memory here.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  11. #11
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    Companies pick tires that are rated for the maximum speed the car can go at simply because putting lower speed rated tires would open them up to being sued. It wouldn't bother me one bit to go with a lower speed rated tire as long as it's not so low that I might exceed the rating. Speed ratings came from Europe where it's possible to drive on a road without speed limits. In reality in the US I seriously doubt you can find a road where you can safety travel at more than 118 mph for the amount of time needed to damage the tires.

  12. #12
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    So how much time do you spend driving at 120 mph? If you are like most of us, not much, and the lower speed rating won't hurt a bit. Even if you drive 80 regularly that's still a substantial safety margin.

    If you take it to the track you probably want a whole different class of tires anyway.

  13. #13
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    We are keeping the T tires. I couldn't bring myself to make the shop eat them. However I probably won't be using that shop again. They either don't know what they are doing, or should have told me about the substitution before doing it.

    Interestingly, before we knew the difference my wife told me she the new tires gave a much better ride. Yeah, softer sidewalls will do that. But she is unlikely to drive the car hard enough for the difference in handling to matter.
    I don't know if it is true or not, but I have read that T gives better traction in snow than H. That would be nice.

  14. #14
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    From the perspective of that actual tire, I would think you'd be fine. And I agree with not forcing the tire shop to replace a tire that's likely perfectly good. But I tend to think about legal issues, and for just a bit of leverage I'd send the tire place a note mentioning that they installed lower rated tires, and "do you think this is an issue since they aren't the factory-recommended tire?". Email, so that you have their response in writing and can save that email for the hugely unlikely situation where it might come in handy. Then they get to decide whether to replace the tires or to take on the (teeny) liability.

  15. #15
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    Quote Originally Posted by Dave Mills View Post
    From the perspective of that actual tire, I would think you'd be fine. And I agree with not forcing the tire shop to replace a tire that's likely perfectly good. But I tend to think about legal issues, and for just a bit of leverage I'd send the tire place a note mentioning that they installed lower rated tires, and "do you think this is an issue since they aren't the factory-recommended tire?". Email, so that you have their response in writing and can save that email for the hugely unlikely situation where it might come in handy. Then they get to decide whether to replace the tires or to take on the (teeny) liability.
    I called them as soon as I found out. He assured me the tires were perfectly fine and I would be happy with them. They would last longer than the recommended tires, ride better, and have better winter traction. As long as she didn't take off ramps at 60mph, the handling would be fine. And... what did I want, the tires replaced?! I told him I would think about it; I didn't think he was actually offering to replace them, but expressing bewilderment over my complaint.
    I sent him an email saying that was all true, but I was uncomfortable ignoring manufacturers recommendations. They have never responded to my emails in the past, so maybe they don't read them.
    I called him the next day and agreed to let it go. So he is on notice that I know they they don't offer the same handing as the H tires.

    If I hadn't googled the tires to see what they were going for elsewhere and Walmart said they were incompatible with my Outback, I never would have know the difference. T? H? I didn't know there was such a thing as speed ratings before this week.

    As far as legal liability; he would have to claim that I requested the T tires and insisted on them even though he warned me against them. He had to refuse or get a liability waiver in writing. The onus is on him as the expert. Yeah, something in writing from him would be nice, but that boat has sailed.

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