How to Read a Tire Code (e.g., P205/55R16 91H)

• **205 (Width)**: Width of the tire in millimeters.
• **55 (Aspect Ratio)**: The height of the sidewall as a percentage of the width.
• **16 (Rim Diameter)**: Diameter of the wheel in inches.
• **91 (Load Index)**: Numerical code for the maximum weight capacity (e.g., 91 = 1356 lbs).
• **H (Speed Rating)**: Maximum safe speed (e.g., H = 130 mph).

Key Tire Terms

Total Diameter

The measurement from the top of the tire to the bottom, essential for ground clearance and gear ratio.

Load Index

Indicates the maximum weight the tire can support when properly inflated.

Speedometer Error

The percentage difference in circumference between the new and original tire size. Over 3% is generally considered unsafe.

Best Practices

Always match or exceed the vehicle's original Load Index and Speed Rating. Changes in diameter should be kept below ±3% to maintain safety and speedometer accuracy.