How To Read Tire Ratings | Decode The Sidewall Marks

Tire ratings show a tire’s size, load limit, speed class, grip grade, heat grade, and age in one sidewall code.

A tire sidewall looks dense at first glance, but it follows a clean pattern. Once you know what each letter and number stands for, you can tell whether a tire fits your wheel, how much weight it can carry, how fast it is rated to run, and what kind of traction and heat score it earned.

That pays off when you’re buying replacements, checking a used car, or trying to spot a mismatch before it drains your wallet. Start with the main code, read left to right, then scan the smaller marks around it.

How To Read Tire Ratings On The Sidewall

Take a common sidewall code: P225/65R17 102H. That one line gives you most of the story.

• P = passenger vehicle tire
• 225 = tire width in millimeters
• 65 = aspect ratio, or sidewall height as a share of width
• R = radial construction
• 17 = wheel diameter in inches
• 102 = load index
• H = speed rating

You may also see marks like XL, M+S, 3PMSF, UTQG grades, and a DOT serial. Those add detail, but the size, load index, and speed symbol do most of the work when you’re checking fit.

What The Opening Letters Mean

The first letter tells you the tire class. P means passenger. LT means light truck. ST is for trailer tires. Some tires start with no letter at all. In that case, you’re often looking at a Euro-metric passenger tire. That can matter when you compare load capacity across tires that seem close in size.

What The Number String Means

The first number is width. In 225, the tire is about 225 mm wide at its widest point. The next number is the aspect ratio. A 65 series tire has a sidewall height that is 65% of the width. Lower ratios usually mean a shorter sidewall, a firmer feel, and less cushion over rough pavement.

The R tells you the tire is radial, which is what most passenger vehicles use. Then the rim diameter appears. A 17 means the tire fits a 17-inch wheel. If the tire says 17 and your wheel is 18, that tire is out. No wiggle room there.

Then comes the pair many drivers skip: the load index and speed symbol. That’s where a lot of buying mistakes start. A tire can match your wheel size and still be the wrong choice if the load or speed class drops below what your vehicle calls for.

Sidewall Mark	What It Means	What To Check
P	Passenger tire class	Make sure it matches the type of vehicle use
225	Section width in millimeters	Width affects fit, grip, and ride feel
65	Aspect ratio	Lower numbers mean a shorter sidewall
R	Radial construction	Common on modern passenger vehicles
17	Wheel diameter in inches	Must match your wheel exactly
102	Load index	Shows how much weight one tire can carry
H	Speed rating	Shows the tire’s rated speed class
XL	Extra load construction	Often used on heavier cars and crossovers

What Each Part Of The Code Tells You When You Shop

Wheel size gets attention, but the load index and speed symbol deserve the same care. Michelin’s load and speed rating explainer lays out the basics: those marks set the tire’s approved carrying ability and speed class under set test conditions.

That means a tire marked 102H is not equal to one marked 95T, even if both are the same size. A lower load index can leave less carrying margin. A lower speed symbol can change the tire’s behavior under heat and sustained pace. When you buy replacements, match the vehicle placard and owner’s manual unless a tire professional has approved a different fitment.

Also watch for extra-load marks such as XL or Reinforced. Those tires can carry more weight at a given size when inflated to their rated pressure. You’ll see them often on SUVs, EVs, and sedans with heavier curb weight.

UTQG Grades Tell You How A Tire Was Scored

Many passenger tires sold in the United States also carry three grades under the Uniform Tire Quality Grading system: treadwear, traction, and temperature. NHTSA’s UTQG overview explains what those grades compare and which tire types fall outside the system.

• Treadwear: A comparative score based on a government test program. A 600 grade is meant to last longer in that test than a 300 grade, though real road life still shifts with alignment, inflation, load, road surface, and driving habits.
• Traction: Usually shown as AA, A, B, or C. This grade measures straight-line wet braking, not dry grip and not cornering grip.
• Temperature: Usually A, B, or C. This grade reflects the tire’s ability to handle and shed heat at speed.

These grades are useful, but they are not a full personality profile for a tire. A quiet grand touring tire and a sporty summer tire can both post decent grades and still feel nothing alike on the road. Read UTQG as one piece of the puzzle, not the whole story.

Mark	Meaning	Why It Matters
UTQG 600 A A	Treadwear 600, traction A, temperature A	Gives a quick read on test-based wear, wet braking, and heat resistance
M+S	Mud and snow mark	Common on all-season tires, but not the same as a severe snow stamp
3PMSF	Three-Peak Mountain Snowflake	Shows the tire met a snow-service test
DOT	Department of Transportation serial code	Lets you find plant, spec, and build date
4424	Built in week 44 of 2024	Useful when tread looks fine but age may be a factor
Max Load / Max Pressure	Tire limit markings	These are not your day-to-day inflation target

Marks People Miss On The First Read

The DOT serial is easy to skip, yet it can save you from buying old stock. The last four digits show the build week and year. A tire ending in 4424 was made in the 44th week of 2024. That matters on vehicles that sit a lot, on spare sets, and on trailers. Deep tread does not erase age.

The seasonal marks also trip people up. M+S means the tread meets a mud-and-snow labeling standard. It does not mean the tire passed a severe snow traction test. The 3PMSF stamp does carry that snow-test meaning, so it tells you more when winter grip is part of the brief.

Then there’s the pressure issue. The sidewall’s max pressure and max load tell you the tire’s limit, not the pressure you should run every day. Your normal fill target is on the driver’s door placard or in the owner’s manual. Mixing those up can leave you with a harsh ride, uneven wear, or poor grip.

Mistakes That Throw Off The Read

• Reading only the size: A tire can fit the wheel and still miss the proper load index or speed rating.
• Treating treadwear like a mileage contract: It is a comparative test grade, not a promise stamped in stone.
• Ignoring age: A clean-looking used tire may still be older than you’d expect.
• Mixing tire types without a plan: Swapping in one odd tire with a different class or rating can upset the feel of the car.
• Using sidewall max pressure as your fill target: That number is a limit, not the placard setting.

A 30-Second Reading Order That Works

1. Read the full size code from left to right.
2. Match the wheel diameter first.
3. Check load index and speed symbol next.
4. Scan UTQG grades for wear, wet braking, and heat score.
5. Look for M+S, 3PMSF, XL, and the DOT date code.
6. Compare the tire with your door placard before you buy.

Once you know the pattern, tire ratings stop looking like a jumble of letters and numbers. They read like a label. That makes it easier to buy the right replacement tire, spot a bad match, and know what you’re paying for before the tire ever leaves the rack.