Speedometer Calibration Calculator
Use this calculator to find the differences in speedometer reading and actual speed when changing to a tire size other than stock.
Original Tire Size
New Tire Size
The relationship between tire size and vehicle performance extends beyond speedometer accuracy. Different tire dimensions can affect handling, ground clearance, gear ratios, and overall driving dynamics. To fully understand these impacts and compare various tire options side by side, our tire size comparison calculator provides comprehensive analysis tools.
Need to explore more speed comparisons or tire specifications?
Use our Tire Size Comparison Calculator for in-depth analysisWhy Speedometer Calibration Matters
When you modify your vehicle with non-standard tire sizes, your speedometer's accuracy is affected. This happens because your vehicle's speedometer calculates speed based on the number of wheel rotations over time, assuming the factory tire dimensions.
Larger tires cover more ground with each rotation, causing your actual speed to be faster than what your speedometer displays. Conversely, smaller tires result in your true speed being lower than indicated. This discrepancy can lead to unintentional speeding tickets, affect your fuel economy calculations, and impact navigation system accuracy.
Our speedometer calibration calculator provides a precise way to determine your true speed with aftermarket tires. Simply enter your original equipment tire size and your new tire dimensions to see the difference between what your speedometer shows and how fast you're actually traveling. This information is invaluable for safe driving and avoiding unexpected traffic citations.
Frequently Asked Questions
Why does changing tire size affect my speedometer?
Your vehicle's speedometer calculates speed based on wheel rotations, assuming factory tire dimensions. Larger tires cover more ground per rotation, making your actual speed faster than displayed. Smaller tires result in slower actual speeds than indicated. The difference is proportional to the change in tire circumference.
How much will my speedometer be off with new tires?
The speedometer error depends on the difference in circumference between your original and new tires. For example, increasing your tire diameter by 3% will cause your actual speed to be 3% faster than what your speedometer shows. A 60 mph reading would actually be 61.8 mph.
Can I recalibrate my speedometer for new tire sizes?
Yes, many vehicles can have their speedometers recalibrated to account for new tire sizes. Options include:
- Dealer/mechanic recalibration using specialized equipment
- Aftermarket calibration devices that connect to your vehicle's computer
- Speed calibrators that sit between the speed sensor and speedometer
The best method depends on your vehicle make, model, and year.
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