How to Decode Tire Size and Other Data
On February 25, 2026 By newsroom Topic: Automotive
Tire sidewalls hold crucial information for selecting and maintaining the right tires for your vehicle. Here’s how to read the codes and what they mean:
1. Tire Size
- Example: P235/65R17
- P: Passenger car tire (or LT for light trucks).
- 235: Width of the tire in millimeters.
- 65: Aspect ratio (sidewall height is 65% of the width).
- R: Radial-ply construction.
- 17: Diameter of the wheel (in inches).
2. Load Index
- Number after tire size (e.g., 103 in P235/65R17 103T).
- Indicates the maximum weight the tire can carry.
- 103 = 1,929 lbs.
- Match or exceed the load index specified on your vehicle placard.
3. Speed Rating
- Letter following the load index (e.g., T in 103T).
- Indicates maximum sustainable speed:
- S: 112 mph
- T: 118 mph
- H: 130 mph
- V: 149 mph
- W: 168 mph
- Y: 186 mph
- ZR: Over 149 mph
- Higher speed ratings often improve handling, even at legal speeds.
4. Treadwear Rating
- A numerical value (e.g., 500–800).
- Theoretically, a tire with a 400 treadwear rating lasts twice as long as one rated 200.
- For a more accurate measure, refer to tread life predictions.
5. Traction and Temperature Scores
- Traction: Wet-stopping ability.
- AA (best) to C (worst).
- Temperature: Heat resistance.
- A (best) to C (lowest).
6. Maximum Pressure
- Listed in PSI (pounds per square inch).
- Do not inflate to this number!
- Follow the manufacturer’s recommended pressure on your car’s placard.
7. Manufacturing Date
- Found in the DOT code (last 4 digits).
- Example: 0424 = 4th week of 2024.
- Avoid tires over 2 years old when purchasing. Replace tires after 6–10 years, even if treadwear is minimal.
Tips for Tire Selection
- Match recommended size, speed, and load ratings from your car’s placard or owner’s manual.
- Check front and rear tire specs, especially on sports cars (they may differ).
- Inspect manufacturing dates to ensure tires are fresh.
Keep your tires in top shape for better safety, performance, and efficiency!
