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Speedometer Calibration

Calculate speedometer error and actual speed when upgrading or changing tire and rim sizes on your vehicle. Fast, free, and 100% private browser tool.

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About Speedometer Calibration

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1

Current Size

Enter your stock tire width, aspect ratio, and rim size.

2

New Size

Enter the dimensions of the new tires or wheels you plan to install.

3

Check Speed

Input a target speed to see the variance in real-time.

Changing your vehicle's tire or wheel size directly impacts your speedometer's accuracy. This professional tool compares your original tire dimensions to your new setup, calculating the diameter difference and the resulting speedometer variance. Know exactly how fast you are really going to avoid speeding tickets and ensure your car's safety systems remain calibrated.

Key Features

Diameter Comparison

Calculates the exact rolling circumference difference between two setups.

Actual Speed Check

Tells you your true velocity when your speedometer shows a specific speed.

Safety Warnings

Alerts you if the percentage difference exceeds safe manufacturer tolerances (3%).

Frequently Asked Questions

Most experts recommend staying within a 3% diameter difference of the original tire to ensure ABS and traction control systems function properly.

Speedometers measure wheel RPM. A larger tire travels further per rotation, meaning you are going faster than the gauge indicates.

It is the height of the tire sidewall expressed as a percentage of its width.

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