How do you read this tire size: 225/55R17?
1. Width (225)
- The first number (225) is the width of the tire in millimeters, measured from sidewall to sidewall.
- So this tire is 225 mm wide (about 8.9 inches).
2. Aspect Ratio (55)
- The second number (55) is the aspect ratio, or the height of the sidewall as a percentage of the tire’s width.
- Here, the sidewall height = 55% of 225 mm ≈ 124 mm (about 4.9 inches).
- A lower number (like 40) = shorter sidewall, sportier feel, stiffer ride.
- A higher number (like 70) = taller sidewall, smoother ride, less sporty handling.
3. Construction (R)
- The letter R means Radial, which is the most common tire construction today (plies run radially across the tire).
- You might also see D (Diagonal or Bias ply) or B (Belted Bias), but those are rare outside specialty tires.
4. Wheel Diameter (17)
- The last number (17) is the diameter of the wheel (rim) in inches.
- This tire fits a 17-inch wheel.
5. Extra Markings (after size)
You might also see extra info on the tire:
- Load Index (e.g., 94): How much weight each tire can carry.
- Speed Rating (e.g., H, V, W): The max safe speed (H = 130 mph, V = 149 mph, W = 168 mph, etc.).
So if you see 225/55R17 94V, it means:
- Width: 225 mm
- Sidewall: 55% of 225 mm
- Radial construction
- Fits 17-inch rims
- Load index: 94 (1,477 lbs per tire)
- Speed rating: V (149 mph max speed)
