What do the numbers and letters on tires mean?
Understanding tire service description, load rating, and speed rating
If you look at the sidewall of a tire, you’ll see a whole slew of characters and numbers. This is basically a code that includes information about size, construction, and guidelines for use of the tire -- and we’re here to help you decipher it. In this article, we’ll look at just one small part of the code: the service description.
As an example, we’ll be using a 2012 Audi A3 TDI. This car’s “tire code” is 225/45R17 94H. You can usually find this information on a sticker on the driver’s side door jamb.
Tire load index chart and understanding your tire's code
The service description is simply the speed rating and the load rating together. In our example, the service description is the last three characters: 225/45R17 94H 94 is the load rating and H is the speed rating. But what exactly does that mean…?
Tire load rating or load index
The load rating tells you how many pounds a tire can safely carry. In our example, the number 94 has been assigned to a load carrying capacity of 1477 pounds (per tire). So if your car was fully loaded up with, let’s say, bags and bags of dog food, you’d want to be sure the weight of the car plus the weight of the cargo didn’t exceed 5908 pounds (1477 x 4).
The GVWR (gross vehicle weight rating) for the Audi A3 is 4597 pounds. This includes the car, driver, passengers, dog, and dog food. Since the combined load rating (5908 pounds) for the four tires is greater than the 4597-pound GVWR, you’re good to go.
If you know the tire load rating for your vehicle, you can use our handy load index chart to check out the load carrying capacity of your tires.
|Load Index||Pounds (lbs)||Kilograms||Load Index||Pounds (lbs)||Kilograms|
When you shop for tires and give us your vehicle’s make/model/style information, we show you only the tires that have the proper load rating for that vehicle. If you choose a tire with a different load rating for some reason, that tire must meet or exceed the load rating for your vehicle.
How are tires rated for speed?
Tire speed ratings are set by the tire manufacturers and based on testing. Note that a speed rating is an indication of the tire's maximum speed capability in ideal conditions.
Just like with load rating, when you shop by vehicle we only show you tires with the correct speed rating for your car. If necessary, you can use a tire with a speed rating that is greater than the speed rating recommended for your car (for example, instead of using an H-rated tire on the Audi A3, you could use a V-rated tire (149 mph). If you must mix tires with different speed ratings, be sure to observe the lowest speed rating when driving.
What do the speed ratings mean?
Speed rating ensures a vehicle’s tires match its top speed capability. Going back to our Audi, the H speed rating is equal to 130 miles per hour, meaning that under optimal conditions, the tire can perform at speeds up to 130 mph. Now just a second, leadfoot … that doesn’t mean you should drive 130 mph. It means the Audi A3 is capable of a top speed of 130 – but here in the U.S., it’s generally a good idea to observe the posted speed limits.
H speed rating
An H speed rating indicates the tire is approved for speeds up to 130 mph (210 km/h) under optimal conditions.
An H speed rating is at the low end, or start of the performance tire speed ratings. H speed rated tires are ideal for sport and luxury coupes and sedans, but not typically considered full-fledged performance vehicles.
H speed ratings are common in the grand touring all season tire category.
T speed rating
A T speed rating indicates the tire is approved for speeds up to 118 mph (190 km/h) under optimal conditions.
T ratings are most associated with standard touring tires, and everyday passenger vehicles. You’ll find T speed rated tires commonly fitted to family sedans and minivans.
W speed rating
A W speed rating means the tire is approved for speeds up to 168 mph (270 km/h) under optimal conditions.
W speed rated tires land firmly at the performance end of the tire speed rating spectrum. Ws are suitable for performance coupes and sedans, and even street driven exotic sports cars.
W tires are common in the ultra-high performance all season tire category.
W speed rated tires generally offer plenty of performance for the street, including “spirited” (but responsible) drivers. At the same time, W tires don't necessarily sacrifice everyday driving factors like comfort (ride quality, road noise), and treadlife warranty.
V speed rating
A V speed rating indicates the tire is approved for speeds up to 149 mph (240 km/h) under optimal conditions.
H and V speed rated tires often go hand in hand. While the V speed rating technically allows for a higher maximum speed, practically speaking, this a distinction without much of a difference (in light of U.S. speed limits). Like H speed rated tires, V speed rated tires can deliver a taste of the performance attributes associated with high speed rated and high performance tires (W, Y, and Z).
Y speed rating
Y speed rated tires have been tested at speeds up to, and in excess of, 186 mph (300 km/h) under optimal conditions.
If Y speed rating is indicated without parentheses (as normal), this means the tire is rated up to 186 mph. If the Y speed rating is indicated inside of parentheses, this means that particular tire size and specification has been tested at speeds in excess of 186 mph.
A Y speed rating denotes maximum tire performance. Top level ultra-high performance tires like the Michelin Pilot Sport 4 S and Continental ExtremeContact Sport are Y speed rated tires. The Pilot Sport 4 S has been tested at speeds in excess of 186 mph is rated (Y). The Continental at speeds up to 186 mph is rated Y. (Select sizes of the ExtremeContact Sport are W speed rated.)
Q speed rating
Q speed rated tires are approved for speeds up to 99 mph (160 km/h) under optimal conditions.
Tires toward the low end of the speed rating range often prioritize a particular function or unique performance over maximum speed rating. Some studdable and studless winter tires, for example, are Q speed rated.
R speed rating
Speed rating R allows for speeds up to 106 mph (170 km/h) under optimal conditions.
Like Q speed rated tires, R rated tires generally prioritize a particular function or unique performance over maximum speed capability. R speed tires are rare, but can be found on some heavy duty light truck (LT) tires, as well as studdable and studless winter tires.
S speed rating
An S speed rating indicates the tire has been approved for speeds up to 112 mph (180 km/h) under optimal conditions.
Everyday passenger vehicle tires can be S speed rated, but S tires often prioritize specific performance or function.
Many all-terrain LT tires are becoming available in an S rating as that’s the OE spec for many of these vehicles like the Ford Raptor. M & N speed ratings
An M speed rating indicates the tire has been approved for speeds up to 87 mph (140 km/h) and an N is approved for speeds up to just 81 mph (130 km/h) under optimal conditions.
You’ll find M and N ratings on tires for temporary use like spare tires.
P speed rating
A P speed rating indicates the tire has been approved for speeds up to 93 mph (150 km/h) under optimal conditions.
P speed rated tires are uncommon these days. Even tires with specialty function and performance such as winter tires and off-road tires typically achieve at least a Q speed rating.
Z speed rating
A Z speed rating indicates the tire has been approved for speeds of 149+ mph (240+ km/h) under optimal conditions. This rating is associated with maximum tire performance and is a match for performance coupes and sedans, sports cars, and supercars.
While speed rating is typically adjacent to the load index, and outside of (after) the tire size expression, the Z speed rating can be found within the structure of the tire size:
To understand the speed restriction of a Z speed rated tire, refer to the additional speed rating adjacent to the load index. In the case of a Z tire, the speed rating will either be W, Y, or (Y).
Is there a tire speed symbol or code?
The tire speed rating is expressed as a letter adjacent to the tire's load index. Refer to the speed rating chart above for what each letter signifies.
|M||81 mph||130 km/h|
|N||87 mph||140 km/h||Temporary spare tires|
|P||93 mph||150 km/h|
|Q||99 mph||160 km/h||Studless and studded winter tires|
|R||106 mph||170 km/h||Heavy duty light truck tires|
|S||112 mph||180 km/h||Family sedans and vans|
|T||118 mph||190 km/h||Family sedans and vans|
|U||124 mph||200 km/h|
|H||130 mph||210 km/h||Sport sedans and coupes|
|V||149 mph||240 km/h||Sport sedans, coupes and sports cars|
|W||168 mph||270 km/h||Exotic sports cars|
|Y||186 mph||300 km/h||Exotic sports cars|
|Z||149+ mph||240+ km/h||Sports cars|
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