Understanding Tire Specs: The Complete Guide
Everything on your sidewall decoded — size, load index, speed rating, DOT date, and UTQG ratings.
Your Tire Sidewall Is a Data Label
Every tire sold in the United States has a standardized set of markings on the sidewall. Once you know how to read them, you can instantly verify that any tire you buy is the right fit, the right age, and built to the right performance standard.
The Tire Size (e.g., 225/65R17)
- 225 — Section width in millimeters
- 65 — Aspect ratio (sidewall height as % of width)
- R — Radial construction (virtually all modern tires)
- 17 — Wheel diameter in inches
Full guide: How to read tire size numbers →
Load Index & Speed Rating (e.g., 102H)
These two characters follow the tire size and define the tire's weight capacity and maximum speed capability.
Full guide: Load index and speed rating explained →
DOT Date Code
A code starting with "DOT" ends in 4 digits: week + year of manufacture. A tire ending in 4922 was made in the 49th week of 2022.
Full guide: How to check tire age with the DOT code →
UTQG Treadwear, Traction, Temperature
Three grades molded into the sidewall by law:
- Treadwear — relative mileage (higher = longer lasting)
- Traction — wet stopping ability (AA > A > B > C)
- Temperature — heat resistance (A > B > C)
Full guide: What UTQG treadwear ratings mean →
Other Sidewall Markings
| Marking | Meaning |
|---|---|
| M+S | Mud & Snow rated (basic all-season) |
| 3PMSF (snowflake symbol) | Severe snow service — true winter/all-weather tire |
| XL / Extra Load | Reinforced sidewall, higher load capacity |
| P | Passenger car (P-metric sizing) |
| LT | Light truck (higher load rating) |
| Max Inflate | Maximum safe inflation pressure (not your target PSI) |
Frequently Asked Questions
What is the most important number on a tire sidewall?
The tire size (e.g., 225/65R17) is most important for fitment. The load index and speed rating are most important for safety. The DOT date tells you how old the tire is.
What does P mean before a tire size?
P stands for Passenger. It indicates the tire is built to P-metric standards used for passenger cars. LT before a size means Light Truck, which has different load ratings.
Is the max pressure on the sidewall what I should inflate to?
No. The max pressure is the tire's structural limit, not your target. Inflate to the pressure listed on your driver door jamb sticker — usually 32–36 PSI for most passenger cars.