tire time again

[Astro14]

Can't explain it Skater...different year car, different spec...who knows?

At least you're checking.

The point is tires are more than just round and black...they have to meet specs...just like oil (or transmission fluid) is more than simply SAE viscosity, there are many different specs...and the folks who have trashed a turbo, blown the trans or had the engine fill up with sludge have found that out...

Honestly, though, I am getting tired of repeating myself on this set of subjects...I am ready to tell everyone to just put whatever crap 5W30 you want in it...and whatever rubber fits on the rim is fine...and use any transmission fluid you want...they're all the same...then, when the engine dies, the trans dies, or the tires blowout a la Ford Explorer, they can blame Volvo for making such a lousy car...and pat themselves on the back for all the money they have saved by being "too smart" to be fooled by that stupid owner's manual and the greedy car companies who specify particular service items, just to make a profit...

[wgriswold]

I'm interested in speed ratings and am trying to educate myself. I went to Google and found this:

http://answers.yahoo.com/question/in...8171217AA81Uyg

It has a description of a guy that had the opportunity to drive identical cars on a track with different speed rated tires. He found substantial differences in handling with changes in speed ratings. Interesting.

[Ars Gladius]

Excellent answer that really sums up part of what Astro has been trying to get across.

As one who drives a boring 4 door sedan (non luxury, non sports) primarily to get to place A to B reliably and safely, I found that my car had a tire rating of "V" for speed (up to 149 mph). The auto store salesperson was adamant that for safety reasons, I should only buy a V, or at worst, one level down, a H at up to 130 mph at about a $30 premium over an S rated tire (up to 112 mph) with similar mileage warranty.

Given that I never go over 75mph, and most of my drive is at actually 60 at best, how significant are these "race-car" or "immortal teenager" speed rated tires? Is it a slick way to pocket an extra 30-35 bucks from an easy mark such as me or is his statement true. If so, what exactly do these speed ratings mean?

In the last decade especially most cars and even some light trucks and SUV's have switched to "performance" tires with speed ratings of H (130mph) or very often V (149mph) or even higher. Such performance tires now make up about 70% of the tires fitted on new cars and trucks at the factory. Why? Your "boring family sedan" I would bet probably has 250hp or more - in other words the kind of power a Ford Mustang GT couldn't even touch just 20 years ago. So what used to be the private reserve of Porsche's and Ferrari's is now found on Accords and Camry's. Does that mean you can or should drive that fast? No. But does that mean the car will drive differently at "normal" speeds?

A few months ago Bridgestone Tire sent me to a clinic where we got to thrash 4 identical BMW 328i sedans around a small test track. Each vehicle was equipped with Bridgestone tires, the primary difference being the Speed Rating of each tire. Car #1 had T (118mph) speed rated tires, Car #2 had H (130mph) speed rated tires, matching the OEM tires on that model BMW, Car #3 and V (149mph) and Car #4 had W (168mph). All of the tires were various models of Bridgestones - no cheap junk.

On the T speed rated tires the car felt like driving an old Buick. It was spongy and imprecise with noticeably more under-steer and required longer braking distances - it was easy to overshoot the corner. The H speed rated tires felt much better. Now it felt like I was driving a BMW instead of a sloppy old Buick and the speed rating difference is only 12mph. As we progressed up to the next two cars steering responsiveness, overall grip and braking performance improved noticeably. The difference in lap times was stunning yet. And guess what? Top speeds in this test probably never exceeded 50-55mph.

Tire construction changes the higher the speed rating. Different components and different tread compounds are used in order to ensure that the tire can hold together at high speeds. This can and does have an impact in how your vehicle will drive at legal road speeds. If you want to chance it, take those V-rated tires off, put on some S or T rated tires then take that cloverleaf on the way to work the same way you used to. I guarantee you won't like the result. Unsafe? Probably not, but you will definitely be reducing the capabilities engineered into your car.

No single item has a greater impact on how a vehicle drives than the tires. I presume the reason you bought the car is because you liked how it drove. The reason the car drives like it does is because it was engineered around a V rated tire.

[sjonnie]

Excellent answer that really sums up part of what Astro has been trying to get across.

While technically correct I still don't believe it is relevant to the every day driver. If 'V' rated tires were so important how come almost everybody on this board has 'H'-rated tires installed? If H rated are okay why aren't T? Or S? The answer is there is a trade off between tire performance and the way you drive the car. His point that modern cars have 200+ horses is irrelevant if you never use the 200 horses. Horse power has nothing to do with steering or braking where tires really matter.

It was spongy and imprecise with noticably more understeer and required longer braking distances - it was easy to overshoot the corner.

Now I know what "overshoot the corner" means, it means you were driving too fast. So what he's saying is that higher speed rated tires allow you to go around corners dangerously fast. Awesome. Slow down!

Braking distance is important for sure, which is why the best thing you can do is increase the distance between you and the vehicle in front rather than expect your V rated tires to stop you in the 3 yards you have in between you and the vehicle infront. Or maybe instead of charging through neighborhoods at 40mph perhaps the 25mph speed limit would be a better call. Or how about driving on the Interstate like you're not in the Daytona 500?

But it is this line that really bugs me:

No single item has a greater impact on how a vehicle drives than the tires

Errrr, nope. That'll be left to the driver.

[Astro14]

Sigh...then you really didn't get what I was saying.

V-rated doesn't mean that you're going to drive 149 MPH. It means that under certain conditions, you can, but the car's weight, load, and specified inflation pressure have to be taken into account. A V-rated tire, operated under those conditions, may fail at a speed well below 149 MPH. The T-rated may fail at far lower than its rated speed...depends on how it's used...
V-rated (149 MPH) may only be good up to 100 MPH, or even less, if the car specifies a heavy load, different inflation pressure, or is operated in high heat...

You haven't engineered this car, you don't know what the compromises or decisions were, so you can't say it will be safe unless you've done the testing...

In choosing to go less than specified, you've become a test pilot...only without the test design or instrumentation on what you're measuring, like heat, deformation, load, etc...and I don't want my wife or kids doing that testing in the family Volvo.

I simply can't believe the logic of buying a $40,000 car, known for its safety, and then compromising its safety with inadequate tires to save $100....why? Why cheap out on tires on a car like this? It's penny-wise and pound-foolish...

Do whatever you like...and on your next flush, just throw some Dex II in the tranny...don't let those silly people who engineered it to run on T-IV fool you, you know what the car needs more than the folks who designed or tested it...fluid is fluid, after all...you don't need anything fancy...you're not driving it hard...think of the $20 you'll save in buying that fluid that's "good enough"...

[Xilikon]

In short, if I understand well, the rating will determine the sidewall strength. I drove Michelin Hydroedge during the summer with a 89T rating and it felt satisfactory. Then I put Toyo Observe GO-2 winter tires which were speced to match the rating of a S70, 88T. I felt immediately a big difference in sidewall stiffness in the sense that if I want to do lane change on the highway, the winter tire cause a wobbly rear.

After this, I researched for the proper rating and it seems Volvo recommend a 92H at a minimum so I was not following this... I now understand why it's hard to find proper tires for the Volvo.

[GI Joe]

Cool! The Geolandar AT/S is a 98H tire!!!!!

I think I'll price them at the local TireBarn!! They use Nitrogen!!!

Some interesting reads on this forum for sure! Thanks for the input y'all!

[billr99]

In short, if I understand well, the rating will determine the sidewall strength. I drove Michelin Hydroedge during the summer with a 89T rating and it felt satisfactory. Then I put Toyo Observe GO-2 winter tires which were speced to match the rating of a S70, 88T. I felt immediately a big difference in sidewall stiffness in the sense that if I want to do lane change on the highway, the winter tire cause a wobbly rear.

After this, I researched for the proper rating and it seems Volvo recommend a 92H at a minimum so I was not following this... I now understand why it's hard to find proper tires for the Volvo.

Probably not a great example in that winter tires typically have softer sidewalls as well as a more flexible tread as part of the basic design versus a summer tire. Additionally, tire manufacturers take other design steps if they are interested in making a compromise to achieve better road feel or a softer, or comfortable ride.

Michelin, IMHO, have always had a stiff sidewall and I think that it is part of their design to get good wear characteristics. I also think that Pirellis and Bridgestones have always had softer sidewalls and treads than Michelins. The many Japanese brands seem to fall somewhere in the middle but trending more to the soft side. The Chinese makes (or manufactured in the case of some Uniroyals that were recommended to me recently) tires I've experience so far seem to be going toward a firmer sidewall. Nothing scientific, of course, and my experience of particular brands spans a lot of years and encompasses a lot of design changes over those years.

In any case, my point is that your weight spec along with the temperature and wear ratings are probably a better indicator than speed ratings which I am starting to think are more of a marketing ploy these days since most speed ratings will never be "tested" by the average consumer anyway. Hell, as it is, no matter what I buy or how much I spend, I never can get anything that wears like iron and sticks like glue in all conditions.

Cheers,

Bill

[billr99]

They use Nitrogen!!!

So does most everyone else. Well, at least to 78.08%

Cheers,

Bill

[wgriswold]

I have to confess that I put Toyo 98T tires on the Volvo with the recommendation of a well known local tire dealer. The mileage more than doubled compared to the OEM Scorpions but I do believe that the performance was degraded. I only notice it when driving curvy mountain roads. Of course, that is not a very good comparison because I am depending on my years old memory of the OEM tires.

In a related note, I cannot find and speed rating recommendation in my owners manual or on the sticker on the fuel door. The car did come with 98V but there is no recommendation for a speed rating I can find in my documents. In this thread some people have reported that their XC's have a recommendation for H tires. Does Volvo publish a required speed rating for the various models?