How to Read a Tire Sidewall: Every Number Explained

Decode every marking on your tire sidewall — size, load index, speed rating, DOT date code, UTQG grades, and the max pressure number most drivers misread.

Everything you need to know about a tire is molded into its sidewall. Size, how much weight it can carry, how fast it is rated to run, the week it was built, and whether it is built for snow. Most drivers never read any of it. Then they buy the wrong tire, keep a tire that is eight years old, or set their pressure to the wrong number because they read the one figure on the sidewall that was never meant to be a target.

The size string: P225/65R17 102H

That block of letters and numbers looks like a serial number. It is actually six separate pieces of information stacked together.

The letter in front

A P means P-metric — a passenger tire, standard on cars, crossovers, and most half-ton pickups. LT means Light Truck: more plies, a stiffer casing, higher pressures, real load capacity. No letter at all means Euro-metric. If your truck came with LT tires from the factory, do not let anyone talk you into P-metrics to save money. You are throwing away capacity you actually use.

Section width and aspect ratio

The first number — 225 — is the width of the tire in millimeters, sidewall to sidewall, mounted and inflated. Not the tread width. The whole carcass.

The 65 after the slash is a percentage, not a measurement: sidewall height is 65 percent of section width. A 225/65 has a taller sidewall than a 225/45. Lower aspect ratio means a shorter, stiffer sidewall — sharper steering, harsher ride, and much less rubber between your wheel and the pothole. That matters on Lubbock streets that crack and get patched every spring.

Construction and rim diameter

The R stands for radial, which is virtually every tire on the road today. The number after it — 17 — is the wheel diameter in inches. That one is not negotiable. A 17-inch tire goes on a 17-inch wheel, full stop.

Load index and speed rating

The trailing 102H is two ratings jammed together. 102 is the load index, a coded number tied to a maximum weight the tire can carry at its rated pressure. Higher number, more capacity. H is the speed rating — the sustained speed the tire is engineered to handle. Never replace a tire with one carrying a lower load index than the original. That number was chosen by the people who engineered your vehicle's weight distribution, and dropping below it is how sidewalls fail under load on a hot day.

The DOT code: your tire's birthday

Somewhere on the sidewall you will find DOT followed by a string of characters. The part that matters is the last four digits — a date code. First two digits are the week of the year, last two are the year. A tire stamped 2225 was built in the 22nd week of 2025. A tire stamped 0819 was built in early 2019, and if that is on your vehicle right now you are driving on rubber well past its useful life no matter how much tread is left.

UTQG: treadwear, traction, temperature

Passenger tires carry three grades under the Uniform Tire Quality Grading system, usually molded together in a row.

• Treadwear — a comparative number like 400 or 600. Higher generally means longer expected life, but each manufacturer grades against its own control tire. Compare within a brand, not across brands.
• Traction — AA, A, B, or C. It measures straight-line wet braking grip on specified test surfaces. It says nothing about cornering, dry grip, or snow.
• Temperature — A, B, or C. The tire's resistance to heat buildup at speed. In a place that runs triple digits and where people cruise Loop 289 at 70 in July, this grade is not decoration.

Max load and max pressure — the number people get wrong

Near the rim edge you will see something like MAX LOAD 1874 LBS AT 44 PSI MAX PRESS. Read it carefully. That is the pressure at which the tire can carry its absolute maximum rated weight. It is a structural ceiling. It is not a recommendation, and it is not your target.

Your target lives on the placard in the driver's door jamb — front and rear cold pressures chosen by the people who built the vehicle for its weight, suspension, and handling balance. That number is usually well below the sidewall max. Inflate to the sidewall figure instead and you get a rock-hard ride, a shrunken contact patch, and tread that wears out from the middle.

Winter and severe-weather markings

M+S (or M/S, M&S) means mud and snow. It is a tread-pattern designation, largely self-declared, and it appears on most all-season tires. Low bar.

3PMSF — the three-peak mountain snowflake — is the real one. A tire only earns it by passing a snow traction test. Most drivers here do fine on all-seasons, but if you are running US-84 at 5am in January when a front comes off the Caprock and the roads glaze, that symbol is worth having.

XL, Reinforced, and load range letters

XL or Reinforced on a passenger tire means it carries a higher maximum load at a higher maximum pressure than a standard-load tire of the same size. Heavier crossovers and loaded family haulers often specify XL. Swap in a standard-load tire and you quietly delete carrying capacity.

Light truck tires use letters instead — progressively stiffer construction and higher pressure ceilings:

• Load Range C — light duty, commonly 50 PSI max. Fine for a half-ton that rarely carries weight.
• Load Range D — mid duty, more plies, higher pressure ceiling.
• Load Range E — heavy duty, typically 80 PSI max. What belongs under a work truck hauling a loaded trailer out on caliche county roads. It also rides like a brick empty, which is the trade every contractor makes.

Direction, position, and wear bars

Some tires are directional and carry an arrow showing which way they must roll — mount one backward and you lose the water evacuation the tread was designed for. Asymmetric tires are marked OUTSIDE and INSIDE, and those faces are not interchangeable. You will also see small triangles or the letters TWI on the shoulder, pointing to the tread wear indicator bars sunk in the grooves. When the tread wears flush with those bars, the tire is done.

Read the sidewall once and you never buy a tire blind again. If you are standing in your driveway squinting at a wall of numbers and want a straight answer on whether the tire on your vehicle is the right one — or too old to keep — call Elite Mobile Tire & Brake at (806) 281-0513. We will read it with you over the phone, or roll a fully equipped mobile truck to your driveway, your office lot, or a parking garage at Texas Tech. We run 24/7 mobile service across Lubbock, Wolfforth, Shallowater, Slaton, Idalou and Levelland, and the shop is on Frankford Ave when you would rather bring it to us.