A tire speed rating chart turns the letter after the size into a speed. On a 275/65R20 116T, the T is 118 mph. That is a sustained-speed service limit, not a suggestion and not a performance upgrade. This calculator ignores the letter on purpose. This page does not.
Passenger and light-truck letters
These are the ISO / UTQG letters you will see on a passenger car, crossover or half-ton. Q through H cover most trucks and family cars. V, W and Y show up on sports sedans and the occasional Type R.
| Rating | Max sustained speed | Typical use |
|---|---|---|
| Q | 99 mph / 160 km/h | Winter, some LT |
| R | 106 mph / 170 km/h | LT, some winter |
| S | 112 mph / 180 km/h | Passenger, older cars |
| T | 118 mph / 190 km/h | Most family cars and trucks |
| U | 124 mph / 200 km/h | Uncommon |
| H | 130 mph / 210 km/h | Sport sedans, many crossovers |
| V | 149 mph / 240 km/h | Performance all-season |
| W | 168 mph / 270 km/h | High-performance summer |
| Y | 186 mph / 300 km/h | Ultra-high performance |
| (Y) | over 186 mph | Above Y, listed in parentheses |
How to read it on the sidewall
The letter sits after the load index. 116T is load 116, speed T. A ZR in the size (265/30ZR19) is an older way to mark a high-speed tire. The service description after it (93Y) is the one that counts. The how to read tire size page puts the tokens in order.
Z by itself (no Y after it) is an older mark that only promised 149 mph and up. Treat a bare Z as "at least V" and look for a modern service description. Do not buy on Z alone.
What you are allowed to change
- Same or higher is fine. A T-rated truck can take an H. The door-jamb T is a minimum.
- Lower is not fine. Putting an S on a car that left with an H is how you miss the service description the vehicle was certified with.
- Winter tires are the usual exception. Q and T winter tires on an H-rated car are common, and you drive them slower. That is a seasonal, not a permanent, swap.
A V-rated all-season is not a summer tire. The letter is a lab speed. Tread, temperature grade and construction decide whether the tire is any good in a corner. Do not buy a V to make a Camry a sports car.
Speed rating vs load index
They travel as a pair and they answer different questions. Load index is pounds per tire. Speed rating is sustained speed. A 116T and a 116H share a capacity and do not share a speed letter. The load index page is the pounds table. Match both to the placard.
Neither one changes overall diameter. A T-rated 275/65R20 and an H-rated 275/65R20 are the same height in this calculator. Construction can add a few tenths on the truck. That is build, not the letter.