Tire Size Calculator
Compare two tire sizes instantly. Check diameter differences and speedometer error.
1 Current Tire
2 New Tire
Comparison Results
Target calculated| Metric | Tire 1 | Tire 2 | Difference |
|---|---|---|---|
| Diameter | - | - | - |
| Width | - | - | - |
| Sidewall | - | - | - |
| Circumference | - | - | - |
| Revs/Mile | - | - | - |
Speedometer reading is accurate.
Tire Sizes Explained: Reading the Sidewall
Ever wondered what all those numbers on your tire mean? Understanding tire sizes is crucial when buying replacements or upgrading your wheels.
Let's break down a typical size like 205/55 R16:
205 (Width)
The first number is the width of the tire in millimeters, measured from sidewall to sidewall. A wider tire generally offers better grip but may increase fuel consumption.
55 (Aspect Ratio)
This is the height of the sidewall as a percentage of the width. In this case, the sidewall height is 55% of 205mm. Lower numbers mean a shorter / "low profile" sidewall.
16 (Diameter)
The last number is the diameter of the wheel rim in inches. You can only mount a 16-inch tire on a 16-inch rim. This is critical for fitment.
Why Speedometer Error Matters
When you change tire sizes, you alter the overall diameter of the wheel. Since your car's speedometer calculates speed based on wheel rotations, changing the diameter affects the reading.
- Larger Diameter: Your speedometer will read slower than your actual speed. You might be speeding without knowing it.
- Smaller Diameter: Your speedometer will read faster than your actual speed. You'll pile up odometer miles faster than actual.
Frequently Asked Questions
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