|The speed rating is the maximum service speed
of a passenger car tire. Light truck (LT type) tires may not be speed rated.
Here is a list of rating indicators & their mile-per-hour equivalents.
This rating system applies to all tire makers.
||Above 130 mph (without service
||149 mph (with service
||Above 149 mph
When "ZR" appears in the size designation with the service description, the
maximum speed is as indicated by the service description.
||270 km/h (168 mph)
||300 km/h (186 mph)
For tires having a maximum speed capability above 240 km/h (149 mph), a "ZR"
may appear in the size designation. For tires having a maximum speed
capability above 300 km/h (186 mph), a "ZR" must appear in the size
designation. Consult the tire manufacturer for maximum speed when there is
no service description.
* For unlimited V Tires without
Service Description, the speed category is over 210 km/h (130 mph)
** For unlimited Z Tires without Service Description, the speed category is
over 240 km/h (149 mph)
Do speed-rated tires cost more than other radials?
Tires are highly engineered products designed to support the weight (load)
of the vehicle, its passengers, & its contents. In addition the tires have
the responsibility to make the car accelerate, decelerate (or stop), &
corner under a wide variety of weather & road conditions. They must do
this under normal conditions & in evasive maneuvers. We as drivers &
passengers also ask the tires to carry us in quiet comfort & security &
provide a reasonable tread life.
As we increase the tire's performance capability, moving up through the
speed ratings from non-rated passenger tires to the highest of the Z-Rated
tires, the prices of tires usually follow suit. However, one of the best
values today is a tire designed, engineered, & produced for your vehicle
& the way you drive. While the price for the most of life's necessities
have increased over the years, tire prices have continued to be quite
My car came equipped with V-rated tires. Can I switch to a lower rating?
We do not recommend downgrading the speed ratings of tires for your vehicle.
Speed Ratings are a durability standard defining a tire's ability to
withstand, or control, heat & growth. The components engineered to do this
add performance characteristics & benefits to the tire commiserate with
each speed rating level. This is not to say that all tires of equal speed
rating are equal in all respects. However, within a tire manufacturer's line
of products an H-Rated tire usually handles, or "performs" better than an
S-Rated tire, & a Z-Rated tire usually handles better (has crisper
steering response & overall greater cornering grip) than an H-Rated tire.
Each tire line (or model) within a speed rating can be designed &
engineered to provide specific performance characteristics depending upon
the typical user's wants, needs, & desires.
You should try to match the tire's handling personality to that of your car.
Your car is probably one of the most expensive purchases you have made.
Ensure that you maintain the performance characteristics you like about the
vehicle by selecting a tire with equal or greater performance capabilities.
|Load Index & Load in lbs.
One pound is equal to 0.4536 kg.
The load index is an assigned number that corresponds with the load-carrying
capacity of a tire. Most passenger car tire load indexes range from 75 to
100 but a few carry more.
How is the tire's speed capability achieved?
As the speed of a tire increases, its components tend to grow or deform.
This deformation leads to heat generation. This is a normal effect of the
deformation of the tire's components due to centrifugal force. The faster
the tire spins, the greater its tendency to deform. And the more it deforms,
the more heat is generated.
But for tires driven at high speeds, controlling heat levels is critical.
Engineers must find ways to control tire growth so that heat levels are
confined to acceptable tolerances.
To overcome this problem, speed-rated tires are designed with advanced belt
configurations engineered to resist & control deformation. This allows the
tire to be driven at higher speeds without excessive heat buildup.
How does the speed rating relate to handling?
There is no requirement or standard that stipulates that the handling of a
tire improves as the speed ratings move up the scale. However, as stipulated
earlier, the components used to control the growth or deformation of the
tire tend to also contribute to more control of the tire's footprint. As we
control the tire for durability moving up the scale, we have the components
readily available to control the handling & performance expected of the
higher speed ratings.
Sumitomo Tire does not advocate or recommend the use of any of its products
in excess of the legal speed limit.