Understanding Tire Speed Ratings: Your Guide to Tire Safety & Performance

What are Tire Speed Ratings? at Germain Cars

While tires are a relatively simple component of your vehicle, there are still a wide range of terms and keywords used to describe the tires themselves and the specific rubber compounds that they use. You’re probably familiar with different categories of tires such as all-season, off-road, winter, or summer tires. However, one of the most common questions that our service experts are often asked is – what is the speed rating of my tires?

Speed ratings serve an important purpose in helping you determine the right type of tire based on your vehicle’s recommended specifications and your individual driving habits. Even if you don’t consider yourself a “driving enthusiast”, knowing the speed rating of your tires is a great way to maximize your safety and get the most out of your vehicle. The Germain Motor Company has created this helpful tire speed rating guide that covers this topic in greater detail. You’ll have all the knowledge you need to shop like a pro the next time you need tires for your vehicle!

Tire Speed Ratings Explained

Mercedes-AMG SL Tire Speed Ratings

Before we dive into the specifics of tire speed ratings, let’s start with the basics. You’ve probably seen a long combination of letters and numbers stamped into the sidewall of your vehicle’s tires. While this might seem like a jumbled mess of characters, these numbers provide a wealth of information about your tires. It’s as simple as understanding what each portion of the code means. Let’s start with an example that we can decode piece-by-piece.

Tire Code Example: P185/50R15 87S

P = Tire Class

In this example, “P” indicates passenger vehicle. You might also see other classes like LT for light truck, ST for special trailer tire, T for temporary spare, etc.

185 = Section Width

Measured in millimeters, this is the width of the tire tread. This measurement is taken from the inner to the outer sidewalls. Wider tires have a higher number while skinnier tires have a smaller number.

50 = Aspect Ratio

Aspect radio refers to the height-to-width ratio of the tire, expressed as a percentage. In this example, a 50 aspect ratio indicates that these tires are 50% as tall as they are wide.

R = Tire Construction

For this example, “R” refers to radial tire construction. This is the most common type used for modern tires, indicating that the plies of the tires are used radially relative to the circumference. Tires of the past used bias-ply construction, indicated with a “B”.

15 = Tire Diameter

You guessed it! 15 stands for 15 inches of tire diameter in this example.

87 = Load Index

This figure is a numerical representation of the maximum load that a properly inflated tire can withstand. These numbers are referenced against a load index chart that typically ranges between 70 to 126.

S = Speed Rating

Finally, we’ve come to the speed rating of the tire. In this example, the “S” means that these particular tires are rated for maximum speeds of up to 112 MPH. We’ll cover all the various speed ratings in greater detail below.

Common Tire Speed Ratings & Vehicle Recommendations

Audi Q5 Tires

Remember, tire speed ratings only apply to tires that are in proper operating condition and have not been driven while under-inflated, driven while overloaded, altered, or damaged in any way.

Speed Rating

Max Speed

Common Tire Type

L 75 MPH Off-Road / Light Duty Truck
M 81 MPH Temporary Spare
N 87 MPH
P 93 MPH
Q 99 MPH Studdable / Studless Winter
R 106 MPH Heavy-Duty Light Truck
S 112 MPH Family Sedan / Van
T 118 MPH Family Sedan / Van
U 124 MPH
H 130 MPH Sports Sedans / Coupes
V 149 MPH Sports Cars
W 168 MPH Exotic Sports Cars
Y 186 MPH Exotic Sports Cars