Understanding Tire Sizes
The numbers on the side of your tire, like 225/45R17, aren't just for show. They represent a standardized code that tells you the exact dimensions of the tire. Understanding this code is crucial when you're considering new wheels or tires for your vehicle.
Decoding the Numbers
Let's break down a common tire size, 225/45R17:
- 225 (Tire Width): This is the width of the tire in millimeters, measured from sidewall to sidewall. So, this tire is 225mm wide.
- 45 (Aspect Ratio): This is the height of the tire's sidewall, expressed as a percentage of the width. In this case, the sidewall height is 45% of 225mm, which is 101.25mm.
- R (Construction): This indicates the tire's construction. 'R' stands for Radial, which is the most common type of car tire today.
- 17 (Rim Diameter): This is the diameter of the wheel (or rim) that the tire is designed to fit on, measured in inches. This tire fits a 17-inch wheel.
Why Does Changing Size Matter?
Changing your tire size affects more than just the look of your car. The overall diameter of the wheel and tire combination is what your car's speedometer and odometer are calibrated for. If you install tires with a larger or smaller overall diameter, your speedometer will be inaccurate. A larger tire will cause your speedometer to read slower than your actual speed, while a smaller tire will make it read faster. This calculator helps you see that difference before you make a change.
General Rule: It's generally recommended to keep the new tire's overall diameter within 3% of the original tire's diameter to avoid significant issues with speedometer accuracy, ABS, and traction control systems.