How to Read a Tire Sidewall

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Tires are one of the most essential components of a vehicle that directly affecting performance, safety, and efficiency. However, many vehicle owners overlook the detailed information printed on the sidewall of their tires. It might seem random, but every mark has a purpose. Knowing how to read it helps you pick the right tires, check for wear, and even understand speed ratings.

If you’re replacing tires, checking air pressure, or making sure you have the right fit for your car, the sidewall tells you everything. It’s not as complicated as it looks once you break it down. Let’s go step by step and make sense of those markings so you can read your tire sidewall like a pro.

What’s on a Tire Sidewall?

The sidewall is the outermost part of the tire, between the tread and the inner rim. It has several key information such as tire size, load index, speed rating, manufacturing details, treadwear ratings, and safety markings. Each of these plays a role in performance and safety. Below are details of key informations in a tire sidewall and how to read them with examples.

To read a tire sidewall, first locate the sidewalls markings which are usually series of numbers and letters. The first part is usually a combination of letters and numbers (e.g. 225/60R17), this represents the tire size.

The number that follows such as 91H or M+S, indicate the tire’s load index, speed raing, and traction type. Further down, you’ll find the tire’s maximum inflation pressure, usually marked as “inflation pressure” or “maximum inflation pressure”.

Finally, the sidewall will also display the tire’s DOT number, which includes the manufacturing date (the last four digits represent the week and year of production). Below are more details of each of the numbers and letters on a tire side wall.

Tire Size

One of the most noticeable markings is the tire size, usually written as something like P215/65R16. Here’s what it means:

P – Passenger vehicle tire (LT for light truck, ST for special trailer).
215 – Width of the tire in millimeters.
65 – Aspect ratio (height compared to width, expressed as a percentage).
R – Radial construction (most common type of tire).
16 – Diameter of the wheel in inches.

Knowing this helps you choose a tire that fits your vehicle’s requirements for stability, comfort, and handling.

Tire Type

The first letter in the tire code indicates the tire’s intended use:

P – Passenger vehicle tire (for cars, SUVs, and light trucks).
LT – Light truck tire (for trucks and SUVs that carry heavy loads).
T – Temporary tire (a spare tire meant for short-term use).
ST – Special trailer tire (designed for trailers, not passenger vehicles).

If there is no letter, it generally means it is a European metric tire, designed to follow European standards.

Load Index and Speed Rating

Next to the tire size, you’ll find a number and a letter, like 98H. This represents the load index and speed rating. It shows how much your tire can handle

Load Index (98 in this case) – How much weight each tire can support. Higher numbers mean more weight capacity.

Speed Rating (H here) – The maximum speed the tire is designed for. Ratings range from L (75 mph) to Y (186 mph).

L: 75 mph
M: 81 mph
N: 87 mph
P: 93 mph
Q: 99 mph
R: 106 mph
S: 112 mph
T: 118 mph
U: 124 mph
H: 130 mph
V: 149 mph
W: 168 mph
Y: 186 mph
(Y): more than 186 mph
Z: more than 149 mph

Choosing the right load index and speed rating ensures your tires perform well under normal driving conditions and don’t wear out too quickly.

Treadwear, Traction, and Temperature Ratings

These tell you how durable and safe your tire is:

Treadwear (e.g., 400) – Higher numbers mean longer-lasting tires. A tire rated 400 lasts twice as long as one rated 200.
Traction (AA, A, B, or C) – AA provides the best wet-road grip, helping prevent skidding in rainy conditions.
Temperature (A, B, or C) – A means the best heat resistance, reducing the risk of blowouts in hot climates.

DOT Code

The Department of Transportation (DOT) code tells you where and when your tire was made. The last four digits reveal the week and year of production. If it says 4421, the tire was made in the 44th week of 2021. Tires older than six years should be checked for wear, as rubber deteriorates over time, even if tread depth looks fine.

M+S and Snowflake Symbols

If you see M+S, it means the tire is rated for mud and snow (all-season). A three-peak mountain snowflake symbol means it meets winter tire standards for icy roads and provides better traction in freezing conditions.

Maximum PSI and Load Capacity

Your sidewall also shows the maximum air pressure (PSI) and load capacity. Always follow your vehicle’s manual for proper inflation rather than going by the max PSI. Overinflating can cause poor traction and a rough ride, while underinflating leads to increased tire wear and reduced fuel efficiency.

M+S or 3PMSF Markings

M+S (Mud and Snow) – Suitable for light snow and muddy conditions.
3PMSF (Three-Peak Mountain Snowflake) – Meets severe winter condition standards.

Run-Flat and Reinforced Tires

Some sidewalls have markings like RFT (Run-Flat Tire) or XL (Extra Load). Run-flat tires let you drive for a short distance even after losing air, while extra load tires handle heavier weights without compromising performance.

Example Breakdown:

For a tire labeled P205/55R16 91V:

“P” = Passenger tire
“205” = 205mm width
“55” = 55% aspect ratio
“R” = Radial construction
“16” = 16-inch rim diameter
“91” = Load index (91 = 1356 lbs)
“V” = Speed rating (149 mph max speed)

How to Use a Tire Sidewall Information When Buying New Tires

When purchasing new tires, match the specifications of your current tires or refer to the manufacturer’s recommendations found in your vehicle’s manual. Consider the following:

If you need a smooth, comfortable ride, look for a higher aspect ratio.
If you need better handling, opt for a lower profile (smaller aspect ratio).
Ensure the speed rating meets or exceeds your driving needs.
Check the DOT code for recent manufacturing dates to avoid old tires.

Conclusion

Being able to read a tire sidewall gives you valuable knowledge about your vehicle’s tires. From understanding the width, aspect ratio, and construction type to deciphering load index and speed ratings; Reading your tire sidewall helps you:

Know when your tires need replacing.
Buy the right replacement tires.
Check for safety standards.
Avoid overloading your vehicle.
Ensure proper speed and handling.

Next time you check your tires, take a closer look at the sidewall, you’ll know exactly what all those numbers and letters mean and exactly what’s keeping your car safe on the road! Now that you have this knowledge, you can confidently choose the best tires for your vehicle and drive with peace of mind.

What’s on a Tire Sidewall?