What Do Tire Speed Rating Codes Mean?

Confused by the numbers on your tires? You’re not alone. Here’s a quick guide to what those tire speed rating codes mean.

Introduction

Do you know what the numbers and letters on your tires mean? If not, you’re not alone. In fact, many people don’t know what tire speed rating codes mean, let alone how important they are.

A tire speed rating is simply the maximum speed a tire can safely maintain over a long period of time. The ratings are usually represented by a letter or letters, and they range from A (the lowest) to Z (the highest).

While most people will never drive fast enough to reach the top end of the tire speed rating scale, it’s still important to know what the ratings mean. That’s because the ratings are also an indicator of a tire’s overall quality. In other words, tires with higher speed ratings are usually made with higher-quality materials and construction methods, which means they will last longer and perform better than tires with lower ratings.

Here is a breakdown of the most common tire speed rating codes:

-A: Up to 15 mph

-B: Up to 20 mph

-C: Up to 25 mph

-D: Up to 30 mph

-E: Up to 35 mph

-F: Up to 40 mph

-G: Up to 45 mph

-H: Up to 50 mph

-J: Up to 55 mph 

K: Up 57 mph 

L: 60 mph Up to 62 mph M: 65 mph Up tp 68mph N 87mph P 108mph Q 124mph R 133mph S 112mph T 118mph U 124mph V 154mph W 168mph Y 186mph Z Over 149

What do the numbers on tires mean?

Speed ratings are based on laboratory tests under controlled conditions. The test uses a standard size tire mounted on a wheel and inflated to the manufacturer’s recommended pressure. The heavily instrumented vehicle is then placed on a dyno, or roller test rig, and runs at increasing speeds. Tests are conducted in both directions so any directional effects can be detected and accounted for. 

There are currently eight speed rating symbols, each with a defined maximum speed capability:

-symbol: `J` – maximum speed: `62 mph (100 km/h)`

-symbol: `K` – maximum speed: `68 mph (110 km/h)`

-symbol: `L` – maximum speed: `75 mph (120 km/h)`

-symbol: `M` – maximum speed: `81 mph (130 km/h)`

-symbol: `N` – maximum speed: `87 mph (140 km/h)` 

-symbol: `P` – maximum speed: `93 mph (150 km/h)` 

-symbol:: `Q : 99 mph160 km/h) 

symbol:: R106 mph(170 km/h) 

symbol:: S 112mph(180km/h))

Speed Rating Codes

The speed rating of a tire is represented by a letter of the alphabet and indicates the maximum speed a tire can safely maintain over a long period of time. Speed ratings range from A (the lowest) to Y (the highest).

Below is a list of common speed ratings and their corresponding maximum speeds.

Speed Rating|Maximum Speed

A|6 mph

B|12 mph

C|18 mph

D|25 mph

E|30 mph

F|37 mph 

G|44 mph

J|62 mph

K|68 mph 

L|75 mph 

M|81 mph 

N|87 mph 

P|93mph 

Q|99mph

R | 106mph 

S | 112mph 

T | 118mph 

U | 124mph  

V | 149mph 

W | 168mph  

Y | 186+mph

Load Index

The load index is a numerical code listed on a tire sidewall that corresponds to the maximum load (mass, or weight) the tire can safely carry at its industry-specified pressure. 

For example, A tire with a load index of “92” can safely carry 1,389 pounds at its industry-specified pressure, but carrying more weight than recommended will result in premature tire failure. In order to determine your vehicle’s specific load-carrying capacity, please consult your owner’s manual or contact the vehicle manufacturer.

Tire Ratings

Tire ratings are based on speed and load capacity and provide guidance for drivers when selecting tires. Speed ratings are represented by a letter code, with “S” denoting the fastest single-digit speed rating and “Y” denoting the slowest. Speed ratings range from 5 mph (8 km/h) to over 186 mph (300 km/h). The speed symbol is moulded into the sidewall of every tire, following the load index number. A load index is a whole number ranging from 0 to 279 that corresponds with the maximum weight that the tire can support when properly inflated.

Conclusion

The speed rating of a tire is represented by a letter of the alphabet at the end of the tire size code and specifies the maximum speed capacity of the tire. The Speed Rating System features 14 unique speed symbols, each symbol representing a different maximum speed limit. The speed rating chart below lists each symbol along with its corresponding maximum speed limit.

Speed ratings are categorized into three groups: Standard Load (SL), Extra Load (XL), and Light Load (LL). Standard Load tires feature a service Description following the tire size that includes the load index, while Extra Load and LightLoad tires feature a load index that is 10-points higher than their Standard Load counterparts. 

You can find your vehicle’s recommended tire load index range in your Owner’s Manual or on the placard located on your driver’s door or door jamb.