Every Number on Your Tire Sidewall, Decoded

The Size Code: What P225/65R17 Actually Means

The largest text on your sidewall is the size code. Here is how to read it, using P225/65R17 as an example:

P = Passenger vehicle tire (LT means Light Truck, which uses a different load calculation). If there is no letter prefix, the tire follows European metric standards -- functionally identical for most buyers.

225 = Section width in millimeters. This is the tire's width from sidewall to sidewall when mounted on the recommended rim width. A wider tire (255, 275) provides more contact area and grip but increases rolling resistance and road noise. A narrower tire (195, 205) offers better fuel economy and performs better in snow.

65 = Aspect ratio. The sidewall height is 65% of the section width. Lower numbers (45, 50) mean a shorter, stiffer sidewall -- sharper handling and sportier appearance, but a harsher ride and more vulnerability to pothole damage. Higher numbers (70, 75) mean a taller, more cushioned sidewall -- smoother ride and better pothole absorption, but less precise handling.

R = Radial construction. Virtually all modern passenger tires are radial. If you see a B (bias-ply) or D (diagonal), it is a specialty tire for trailers or vintage vehicles.

17 = Rim diameter in inches. This must match your wheel exactly. You cannot put a 17-inch tire on a 16-inch wheel.

What this means for buying

Your owner's manual lists the original tire size. You should stay within one size increment of the original (for example, going from 225/65R17 to 235/60R17) if you want to change the width. Going wider by more than one increment can cause clearance issues and throw off your speedometer calibration. When in doubt, match your original size exactly.

Load Index and Speed Rating: The Numbers After the Size

After the size code, you will see something like 102H. These two pieces of information are critical and frequently misunderstood.

102 = Load index. This means each tire can support up to 1,874 pounds. The number is not the weight itself -- it references a standardized chart. Common values: 91 = 1,356 lbs, 95 = 1,521 lbs, 100 = 1,764 lbs, 105 = 2,039 lbs. Your replacement tires should meet or exceed the load index specified in your owner's manual. Going below it is a safety risk, especially if you carry passengers or cargo regularly.

H = Speed rating. This indicates the maximum sustained speed the tire is designed to handle safely. Common ratings: S = 112 mph, T = 118 mph, H = 130 mph, V = 149 mph, W = 168 mph, Y = 186 mph. For most daily drivers, an H or T rating is more than sufficient. A V or W rating on a family sedan is paying extra for a capability you will never use.

What this means for buying

Match or exceed your vehicle's specified load index. For speed rating, match the original or go one step down if you are prioritizing ride comfort and treadwear over top-speed performance you will never reach. Going from an H-rated to a T-rated tire on a commuter car is perfectly safe and often gives you a softer-riding, longer-lasting tire at a lower price.

UTQG Grades: The Government Ratings That Actually Help You Compare

UTQG stands for Uniform Tire Quality Grading. The U.S. Department of Transportation requires these three grades on every passenger tire sold in America. They are the closest thing to an apples-to-apples comparison tool that exists in the tire world.

Treadwear (the number, e.g., 700)

A relative longevity rating tested on a government course. A tire rated 400 should last twice as long as one rated 200 under the same conditions. Important caveats: the test conditions are standardized but do not perfectly represent real-world driving, and manufacturers self-report their results. Use treadwear as a rough comparison tool, not an exact mileage predictor. Most all-season tires fall between 400-800. Performance tires often rate 200-400. Budget tires can rate 500+ but achieve it through harder rubber that sacrifices wet grip.

Traction (A, B, or C)

Measures the tire's ability to stop on wet pavement. The grades are AA (best), A, B, and C (worst). Any tire rated A or AA is acceptable for normal driving. Avoid C-rated tires entirely -- their wet braking distance is significantly longer. Nearly all name-brand tires achieve A or AA, so this grade is most useful for filtering out low-quality budget options.

Temperature (A, B, or C)

Measures the tire's ability to dissipate heat at sustained speeds. Grade A handles heat best, C worst. For normal highway driving, A or B is appropriate. This grade matters most for drivers who regularly sustain high speeds or carry heavy loads in hot climates.

What this means for buying

When comparing two tires at similar price points, the UTQG treadwear number is the fastest way to estimate relative longevity. Combine it with the mileage warranty: a tire with a 700 treadwear rating and a 70,000-mile warranty is the manufacturer putting money behind its durability claim. A high treadwear rating with no warranty is a marketing number with no commitment behind it.

The DOT Code: How to Check Your Tire's Age

On one sidewall, you will find a code starting with DOT followed by a string of characters. The last four digits are the ones that matter: they indicate the week and year the tire was manufactured. For example, 2523 means the tire was made in the 25th week of 2023.

Tire rubber degrades over time regardless of tread depth. Most manufacturers and safety organizations recommend replacing tires that are six years old or older, even if the tread looks fine. UV exposure, ozone, and temperature cycles cause the rubber compounds to harden and lose flexibility, reducing grip in wet conditions and increasing the risk of a blowout.

What this means for buying

Always check the DOT date code when buying tires -- especially if you are purchasing from a discount retailer, online marketplace, or buying a set that has been sitting in a warehouse. A tire manufactured two years ago and sold as new is two years closer to its replacement date. Ask for the most recently manufactured stock, and never buy a tire that is more than two years old at the time of purchase.

Markings You Can Safely Ignore

Not every sidewall marking requires your attention. These are informational but rarely affect a buying decision:

M+S (Mud and Snow): Nearly every all-season tire carries this marking. It indicates a basic tread pattern standard, not actual winter capability. For real winter performance, look for the Three-Peak Mountain Snowflake (3PMSF) symbol instead.

Max pressure (e.g., Max Press 51 PSI): This is the maximum cold inflation pressure the tire can handle -- not the recommended pressure for your vehicle. Your correct inflation pressure is on the sticker inside the driver's door jamb or in your owner's manual. Inflating to the tire's maximum will give you a harsh ride and uneven wear.

Ply ratings and material composition: These describe the internal construction. Unless you are comparing commercial or off-road tires, the ply information is not actionable for buying decisions.

Putting It All Together: A Sidewall Reading Checklist

When comparing tires, pull these five data points from the sidewall and put them side by side:

1. Size -- must match your vehicle specification
2. Load index -- must meet or exceed your vehicle's requirement
3. Speed rating -- match the original or adjust intentionally
4. UTQG treadwear -- higher is longer-lasting (compare tires at similar price points)
5. UTQG traction -- A or AA only; avoid B and C

Then check the DOT date code to make sure you are buying fresh stock. With these five numbers, you can compare any two tires objectively -- regardless of brand, marketing, or salesperson pitch. If you are ready to decide between tire types, our tire type comparison guide covers when each category makes sense. For budget comparisons, see our tier-by-tier tire breakdown.