Every tire carries a compact code stamped into its rubber. Those raised letters and numbers on the sidewall tell you the size, load capacity, speed rating, age, and construction of the tire you are driving on. Reading them correctly means you can replace a tire with the right match, avoid dangerous mismatches, and confirm your wheels and tires actually fit your vehicle.
At Santa Ana Wheel we have handled OEM wheels and factory fitments since 1958, and the questions we hear most often start right here: what do the numbers on the side of my tire mean? This guide walks through every marking, section by section, so you can decode any passenger tire in a few minutes.
The main tire size code explained
The most important string on the sidewall looks something like P225/60R16 98H. It packs six separate pieces of information into one code. Here is what each part means:
- P — Service type. “P” stands for P-metric, a passenger vehicle tire built to U.S. standards. “LT” means Light Truck, and no letter at all usually means a Euro-metric passenger tire. A “T” prefix marks a temporary spare.
- 225 — Section width in millimeters, measured from sidewall to sidewall. A 225 tire is 225 mm wide at its widest point.
- 60 — Aspect ratio. This is the sidewall height expressed as a percentage of the width. A 60 means the sidewall height equals 60% of 225 mm, or 135 mm. Lower numbers mean shorter, sportier sidewalls; higher numbers mean taller, more cushioned sidewalls.
- R — Construction type. “R” means radial, the standard for nearly every modern passenger tire. “D” means bias-ply (diagonal), and “B” means belted bias.
- 16 — Wheel diameter in inches. This tire fits a 16-inch wheel. This number must match your rim diameter exactly.
- 98 — Load index. A coded number that corresponds to the maximum weight the tire can carry. 98 equals 1,653 lbs per tire.
- H — Speed rating. A letter that indicates the maximum safe speed for the tire. H is rated to 130 mph.
Read that single line and you already know the width, profile, rim size, weight rating, and speed capability of the tire. Everything else on the sidewall adds detail.
Load index and speed rating in detail
The load index and speed rating sit right after the size code, and drivers overlook them more than any other marking. They matter because replacing a tire with a lower rating than the factory spec can compromise safety and even void coverage.
The load index is a two- or three-digit number. It is not the weight in pounds; it is a code that maps to a weight table. Common passenger values include:
- 91 = 1,356 lbs
- 95 = 1,521 lbs
- 98 = 1,653 lbs
- 100 = 1,764 lbs
- 105 = 2,039 lbs
The speed rating is a letter that follows the load index. Each letter caps the tire at a maximum sustained speed:
- S = 112 mph
- T = 118 mph
- H = 130 mph
- V = 149 mph
- W = 168 mph
- Y = 186 mph
Always match or exceed your factory load index and speed rating. Your original spec is printed on the driver’s door jamb placard, and it accounts for the full loaded weight and performance envelope of your specific vehicle.
The DOT code and how to read your tire’s age
Every tire sold in the United States carries a DOT code, showing it meets Department of Transportation safety standards. The full code identifies the manufacturing plant, tire size, manufacturer specs, and, most usefully, the week and year the tire was built.
Look for the letters “DOT” followed by a string of characters. The final four digits are the date code. For example, a code ending in 2224 means the tire was manufactured in the 22nd week of 2024. The first two digits are the week (01 to 52), and the last two are the year.
Tire age matters even on tires with plenty of tread left. Rubber degrades over time regardless of mileage. Most manufacturers and safety organizations recommend replacing tires that are six to ten years old, and inspecting anything older than five years annually. A quick check of the DOT date code tells you exactly how old a used or spare tire really is, which is why it is worth knowing when you buy used wheels and tires.
Traction, temperature, and treadwear: the UTQG grades
The Uniform Tire Quality Grading (UTQG) system prints three ratings on the sidewall to help you compare tires:
- Treadwear — A comparative number such as 400 or 600. Higher numbers indicate a tire that should last longer under standardized testing. A 600 tire is theoretically rated to last roughly twice as long as a 300 tire, though real-world results vary with driving habits and conditions.
- Traction — Graded AA, A, B, or C, from best to worst. This measures straight-line wet braking on standardized surfaces. AA is the top grade.
- Temperature — Graded A, B, or C. This measures the tire’s resistance to heat at speed. A is the highest, C is the minimum legal grade.
These grades are self-certified by manufacturers within the government framework, so use them to compare tires within a single brand’s lineup rather than as absolute cross-brand truth.
Other markings you will find on the sidewall
Beyond the essentials, the sidewall carries several more stamps worth recognizing:
- M+S — Mud and Snow. Indicates an all-season tread pattern with some capability in light snow and mud.
- Three-Peak Mountain Snowflake — A pictogram of a mountain with a snowflake. This certifies the tire meets a defined severe-snow performance standard, a stronger claim than M+S alone.
- Max Load and Max Pressure — The maximum load the tire can carry and the maximum cold inflation pressure the tire structure can hold. Note this is the tire’s limit, not your recommended pressure, which lives on the door jamb placard.
- Treadwear Indicators (TWI) — Small arrows or triangles on the sidewall point to wear bars molded into the tread grooves. When tread wears down level with these bars, the tire has reached 2/32″ and is due for replacement.
- Rotation arrow — On directional tires, an arrow shows the correct rolling direction. Mount these tires so the arrow points forward.
- Brand, model, and country of manufacture — The tire maker’s name, the specific tread model, and where it was built.
How sidewall markings connect to your wheels
Reading the tire is only half the fitment picture. The wheel diameter in the size code (the “16” in P225/60R16) has to match your rim, but tire width and aspect ratio also need to sit within the wheel’s approved range. A tire that is too wide or too narrow for a given rim width will not seat or perform correctly.
This is where OEM specifications earn their keep. Factory wheels are engineered around a specific tire size, load rating, and offset. When you keep the tire size within the range your vehicle’s manufacturer designed for, you preserve the handling, speedometer accuracy, and clearance the car was built to deliver. If you are replacing a damaged factory wheel, matching the original size and load characteristics is the safest path.
A quick step-by-step for reading any tire
- Find the largest alphanumeric code on the sidewall and break it into service type, width, aspect ratio, construction, and rim diameter.
- Read the load index and speed rating immediately after it, and compare against your door jamb placard.
- Locate the DOT code and read the last four digits to confirm the tire’s age.
- Check the UTQG treadwear, traction, and temperature grades if you are comparing tires.
- Scan for M+S, the snowflake symbol, rotation arrows, and max load and pressure figures.
- Confirm the rim diameter matches your wheel and the size falls within your vehicle’s factory range.
Once you have done this a few times, decoding a sidewall becomes second nature. It is the fastest way to confirm you are buying the right tire and that it belongs on your wheel.
Frequently asked questions
What do the numbers on the side of a tire mean?
They describe the tire’s size and ratings. In a code like P225/60R16 98H, the letters and numbers indicate service type, section width in millimeters, aspect ratio, radial construction, wheel diameter in inches, load index, and speed rating.
How do I read the age of my tire?
Find the DOT code on the sidewall and read the final four digits. The first two are the week and the last two are the year of manufacture. A code ending in 2224 means the 22nd week of 2024.
What does the R in a tire size mean?
The R stands for radial construction, which is standard on nearly all modern passenger tires. It sits between the aspect ratio and the wheel diameter, as in the “R16” of P225/60R16.
Should I match the speed rating on a replacement tire?
Yes. Match or exceed the factory speed rating and load index printed on your driver’s door jamb. These ratings account for your vehicle’s full loaded weight and intended performance, and dropping below spec can compromise safety.
What does M+S mean on a tire?
M+S means Mud and Snow, indicating an all-season tread with some capability in light mud and snow. For certified severe-snow performance, look instead for the three-peak mountain snowflake symbol.
