Speed rating differences in the same tire model ?

[Cressida]

I have noted that several tires that I have looked at come in different speed ratings. For example, the brand and model of tire may have a "T", "H" and "V" speed rating. I am focusing on an "H" speed rating since when you get into the "H" rating most tires will have the nylon belt overlay; and that is what one of our tire experts here recommends.

For a family sedan where one prefers ride comfort over crisp handling I assumed that an "H" rated tire would be a bit softer than the same tire in the higher speed rating ("V"). However, I was in one of the large warehouse clubs this weekend and their tire person told me that is was just the opposite. She said that the "V" would offer a softer side wall (more flex) vs. the "H" and that an "S" would be harder still. In fact, she pulled down two premium brand tires, the same model and size, except one "H" and one was "V" rated to demonstrate. Sure enough the "V" tire was easier to flex the sidewall when pushing on the upright tire vs. their "H" rated model. I sure was surprised.

Is this indeed the case across most tire models?

If so can anyone explain why the higher speed ratings have more flex (softer) sidewalls and wouldn't that tend to support better ride comfort overall?

I normally just ran "S" and "T" rated tires but am moving up to "H" for better internal construction. Since I have never considered a "V" speed rating before I wouldn't mind learning more about the construction differences when you get into that high level. I still can't wrap my mind around this concept - softer/better ride = higher speed rating?

 

[Wolf359]

The flip side to consider on a higher speed rated tire is that they don't last as long. That's why I got a T rated tire instead of an H rated one, the T had an extra 10k worth of tread wear. I had a set of H rated tires once, great for cornering and really quiet, but they had a 40k warranty and by 30k they were worn out. Stopped getting H rated tires for that car.

 

[stephen9666]

What T-rated tires have you considered? Any quality T-rated tire I've considered in recent years also had a cap ply.

Hankook H727
Cooper CS5
General RT43

Not trying to take this off track, just pointing out that there are T-rated tires with cap plies.

 

[GaleHawkins]

I just went with the T rated version of Mastercraft (Cooper) Avenger LSR's since I do not plan to run over 118 MPH for more than one hour at a time.

As noted the T's are rated for 80K where the H's are 60K rated. If I get 40-60K miles I will be OK.

 

[CapriRacer]

Allow me to clear up a few things before I address the question:

* Speed capability is pretty much controlled by the presence (or absence) of cap plies. Generally, S and T rated tires do not have a cap ply, H rated tires need a single cap ply, and anything V or higher need 2.

Yes, there are plenty of exceptions to the above.

* Treadwear, grip, and fuel economy are more or less controlled by the tread rubber compound. Those 3 properties are in conflict so you can't get great properties for one without sacrificing one or more of the others.

HOWEVER, it is possible to slightly modify a tread compound so that - say - fuel economy is slightly improved, while the other 2 properties are unchanged - BUT - these are small changes compared to the range possible. In general, tires with very high treadwear ratings or very high grip levels have poor fuel economy - and vice versa.

* Ride and handling are basically controlled by the lower sidewall - both the height of of the turnup and the height of the filler. Those 2 things affect the stiffness of the sidewall and change how quickly the tire reacts to steering input (the definition of "handling"), and the ride harshness.

As you can see, these 3 properties are controlled by different things and aren't tied together. HOWEVER, high performance tires TEND to be used on high performance cars, so good grip, high speed ratings, and good handling TEND to be found together (as well as the opposite) - but that isn't always the case. Low aspect ratios, too!

So here's the answer to the question:

Tire manufacturers tend to have aftermarket tire lines that meet the car manufacturers speed rating specs, but have a common design goal, such as long wear life. But even the ubiquitous 4 door sedan sometimes comes with V speed rated tires, so a line of tires might have S, T, H and V rated tires - all geared towards usage on 4 door sedans.

You can tell those types of tire lines by the sheer number of tire sizes available (somewhere over 30 different sizes) and usually a given tire size has a single speed rating - the highest one needed to meet all the OEM specs.

But the entire line will have similar ride, handling, wear, grip, and fuel economy characteristics REGARDLESS of the speed rating.

But there are tire lines that are designated for OE usage (where the tire is designed to meet each vehicle manufacturer's specs and is, therefore, different for each tire), and those will come with whatever speed rating the vehicle manufacturer specifies. NONE of those tires is anything alike the other - each is unique. You can tell those tire lines by the small number of sizes.

But there are situations where a tire line might be PRIMARILY for aftermarket usage, but there are a few OE sizes in the mix - and that situation might be hard to detect. One clue is if a tire comes in different speed ratings for the same size. Tire Rack will sometimes call out the OE vehicle in those situations (but not always!)

And interesting situation was when the tire manufacturer I used to work for produced the same size tire and model in 5 different configurations for different vehicle manufacturers. On paper, you couldn't tell which was which and each one was different. There were codes on the sidewalls so anyone with a decoder could tell, but that didn't help anyone without the decoder. Internally, we could tell because there was an inventory identifying number (SKU) that was different for each.

 

[Traction]

In addition, the same make, model of tire can have different characteristics based on diameter, width, sidewall height, and the vehicle it is used on. Which is why it is hard to pick a tire based on tire tests done by TR, or CR, because they are not using the same vehicle, or size you are trying to choose, unless it is the same car the tire was tested on. The same tire tested on a BMW, is going to act different on a Camry.