Find the letter, then check what your car requires
- The speed rating is a letter showing the tire's maximum sustained speed under specified load conditions.
- Look beside the load number on the sidewall. In 91V, V is the speed rating.
- Proper inflation and loading are part of the rating, too.
- Before buying replacements, compare the vehicle's required size, load rating and speed rating with the proposed tire.
A sidewall gives you plenty to read when all you want is one letter. We'd start with the service description, the number-and-letter pair that puts the load and speed ratings together. Find that pair first, then check the rating your vehicle requires before choosing a replacement.
The key word is sustained. A speed rating describes a speed the tire can maintain over time under specified conditions. Tire manufacturers test their tires and assign the ratings, so the letter represents a defined capability.
What to look for in the tire-size marking
Look for a marking like 205 / 55 R 17 91 V on the tire's sidewall. At the end of this example, 91 is the load rating and V is the speed rating. You may also see the pair written together as 91V.
The full marking combines dimensions, aspect ratio, construction and the service description. In this example, R means radial construction and V is the speed letter. Use V beside the load number to identify it.
If you also need to work out your tire size, keep the complete marking handy. For the speed-rating lookup, pull out the load number or numbers and speed letter after the rim size and label them in your notes, such as “91V, load rating 91, speed rating V.”
The number is about weight
The load rating tells you about the weight a tire can carry. The speed rating tells you the maximum speed at which it can carry its maximum load under specified conditions. They're separate ratings, but you need both to understand the tire's operating limits.
This matters when you're shopping, too. Tires with the same size dimensions can have different load or speed ratings. Matching the size is one check; comparing the ratings is another.
If the sidewall has other codes or no speed letter
Your sidewall also identifies the tire's manufacturer and other characteristics. Many vehicle manufacturers require symbols or codes that identify their original-equipment tires. Those markings help owners find exact replacements when the original tires wear out.
Chevrolet example: On most original-equipment tires designed to GM's specific tire performance criteria, you'll find a TPC specification code molded into the sidewall. That's an original-equipment identifier. To find the speed rating, keep looking for the letter beside the load number.
When comparing a replacement with your original tire, keep those details separate in your notes. Record the full size and service description, then any original-equipment identification.
A light-truck marking can look different. For example, LT245/75R16 120/116Q Load Range E has two load numbers before its speed letter, Q. Copy the complete marking so a tire shop can compare it with your vehicle's requirement.
If there's no service description or speed symbol on the tire, contact the tire's manufacturer (its name is on the sidewall) to confirm its speed capability. Have the full sidewall marking ready.
What H, V and other speed letters mean
Once you've found the letter, match it to its maximum speed. Here are some of the letters in miles per hour. They're rating categories, not the rating your particular car requires. Proper inflation and loading remain conditions of the rating.
| Speed-rating letter | Maximum speed in mph |
|---|---|
| M | 81 |
| N | 87 |
| P | 94 |
| Q | 99 |
| R | 106 |
| S | 112 |
| T | 118 |
| U | 124 |
| H | 130 |
| V | 149 |
| W | 168 |
| Y | 186 |
That number is the most the tire is built to sustain, not a speed to drive at. It no longer applies if the tire is underinflated, overloaded, worn or damaged, and bad weather and the law still set your limit.
In the 91V example above, a properly inflated and loaded V-rated tire is designed to handle speeds up to 149 mph.
For an H-versus-V comparison, H means 130 mph and V means 149 mph. V is the higher maximum-speed category of those two. To choose between them for your car, compare the rating with your vehicle's requirements.
Keep “mph” beside any value you copy from the table. The number you've just looked up is a speed, while the number printed beside the letter on the tire is its load rating.
Why the rating matters at normal road speeds
You might look at 130 or 149 mph and wonder why the rating matters for your driving. Speed ratings also reflect a tire's structural integrity and heat resistance. A properly rated tire is engineered to the tolerances the vehicle manufacturer specified and performs more predictably at normal highway speeds.
Keep within both the load and speed limits. Exceeding either can cause excessive heat buildup, which may reduce durability and increase the risk of tire damage or failure.
A lower-rated tire isn't designed to manage the heat from sustained high speeds in the same way as the specified tire. That's why the replacement decision starts with the vehicle's required rating, even when the maximum speeds in the table seem far removed from your everyday driving.
The maximum speed assumes the right pressure, so find the right pressure for your car if you're not sure yours is set correctly.
Compare the replacement with your vehicle's requirement
Start with your owner's manual or the Tire and Loading Information Label on the driver's door edge or post. Check where to find the label (opens in a new tab) if the printed manual isn't handy. Use the vehicle's requirement as your reference when you compare tires.
- Write down the required tire size, load rating and speed rating from the vehicle information.
- Compare all three with the proposed tire. A replacement should have the recommended size, load index and speed rating designation. Bring your vehicle details and the complete tire marking to the shop.
- If the proposed rating is lower or another part of the marking differs, stop there and ask the tire shop to verify fitment against your vehicle's requirement before you buy, and ask for the installed price.
For speed rating, match or exceed what the vehicle specifies. A higher speed rating may be installed, but keep the size and load rating in the comparison. If you're choosing winter-capable tires with a lower rating, ask the shop to confirm the fitment.
Questions that come up while shopping
Keep the vehicle requirement and the complete tire marking in front of you as you narrow the choices.
Can I choose a higher speed rating?
Yes. A higher speed rating may be installed. Compare the size and load index with the vehicle's requirement as well.
Can two tires of the same size have different ratings?
Yes. Tires with the same dimensions can have different load or speed ratings, so compare the complete service description.
What if the tires already on the car differ from its label?
Use the vehicle's tire label or owner's manual as your reference. Take both the vehicle requirement and the fitted tire's marking to the shop for a fitment check.
Winter tires need a separate check
A lower speed rating may be an option for winter-capable tires, including winter or all-season tires marked with the 3-Peak Mountain Snowflake symbol, also called 3PMSF. Under that exception, keep the vehicle at or below the tire's maximum rated speed.
If the winter tire has a lower rating than your vehicle specifies, ask the tire shop to confirm the fitment and the tire's maximum speed before buying. The lower rating changes the speed limit you must observe for that tire.
Winter tires are designed for increased traction on snow and ice. They may also bring decreased dry-road traction, increased road noise and shorter tread life. After changing to winter tires, watch for changes in handling and braking.
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