Wheel and Tire Size Calculator
Use this calculator to compare your current tire and wheel setup with a potential new setup. Understand how changes in tire width, aspect ratio, and wheel diameter affect overall tire diameter, sidewall height, and speedometer accuracy.
Original Tire & Wheel Specs
e.g., 205 (from 205/55R16)
e.g., 55 (from 205/55R16)
e.g., 16 (from 205/55R16)
New Tire & Wheel Specs
e.g., 225 (from 225/45R17)
e.g., 45 (from 225/45R17)
e.g., 17 (from 225/45R17)
Calculation Results
'; resultsHTML += '| Metric | Original Setup | New Setup | Difference |
|---|---|---|---|
| Tire Size | ' + originalTireWidth + '/' + originalAspectRatio + 'R' + originalWheelDiameter + ' | ' + newTireWidth + '/' + newAspectRatio + 'R' + newWheelDiameter + ' | |
| Sidewall Height | ' + originalSidewallHeight.toFixed(2) + ' mm | ' + newSidewallHeight.toFixed(2) + ' mm | ' + sidewallDifference.toFixed(2) + ' mm |
| Overall Diameter | ' + originalOverallDiameter.toFixed(2) + ' mm (' + originalOverallDiameterInches.toFixed(2) + ' in) | ' + newOverallDiameter.toFixed(2) + ' mm (' + newOverallDiameterInches.toFixed(2) + ' in) | ' + diameterDifference.toFixed(2) + ' mm |
| Circumference | ' + originalCircumference.toFixed(2) + ' mm | ' + newCircumference.toFixed(2) + ' mm | ' + circumferenceDifference.toFixed(2) + ' mm |
| Ground Clearance Change | ' + groundClearanceChange.toFixed(2) + ' mm | ||
';
resultsHTML += 'Speedometer Difference: ' + speedometerDifferencePercent.toFixed(2) + '%';
if (Math.abs(speedometerDifferencePercent) > 3) {
resultsHTML += 'Warning: A difference greater than ±3% can significantly affect speedometer accuracy and potentially cause issues with ABS/Traction Control systems. Consider recalibration or choosing a closer size.';
} else if (Math.abs(speedometerDifferencePercent) > 0.5) {
resultsHTML += 'If your speedometer reads 100 km/h (or mph) with the original tires, it will read ' + speedometerReadingNew.toFixed(2) + ' km/h (or mph) with the new tires.';
} else {
resultsHTML += 'The speedometer difference is minimal and generally acceptable.';
}
resultsHTML += '
';
resultDiv.innerHTML = resultsHTML;
}
Understanding Your Tire and Wheel Sizes
Changing your vehicle's wheel and tire size is a common modification, whether for aesthetics, performance, or simply replacing worn-out tires. However, it's crucial to understand the implications of these changes. Our Wheel and Tire Size Calculator helps you compare your current setup with a new one, providing vital information about how different dimensions affect your vehicle.
How to Read a Tire Size Code (e.g., 205/55R16)
- 205: Tire Width (mm) – This is the width of the tire in millimeters, measured from sidewall to sidewall.
- 55: Aspect Ratio (%) – This number represents the sidewall height as a percentage of the tire's width. In this example, the sidewall height is 55% of 205mm. A lower aspect ratio means a shorter sidewall.
- R: Construction Type – 'R' stands for Radial, the most common type of tire construction.
- 16: Wheel Diameter (inches) – This is the diameter of the wheel (rim) in inches that the tire is designed to fit.
Key Metrics Explained
- Sidewall Height: The vertical distance from the wheel rim to the top of the tread. A shorter sidewall often means better handling but a harsher ride.
- Overall Diameter: The total height of the tire from the ground to the top. This is critical for speedometer accuracy, gear ratios, and fender clearance.
- Circumference: The distance covered by one full rotation of the tire. Directly related to overall diameter and speedometer readings.
- Ground Clearance Change: How much higher or lower your vehicle will sit off the ground due to the new tire size.
- Speedometer Difference: This is perhaps the most important output. If your new tires have a different overall diameter than your original ones, your speedometer will read inaccurately. A positive percentage means your speedometer will read lower than your actual speed (e.g., if it reads 100 km/h, you're actually going 103 km/h). A negative percentage means it will read higher (e.g., if it reads 100 km/h, you're actually going 97 km/h).
Why is Speedometer Accuracy Important?
A significant speedometer error (generally anything over ±3%) can lead to:
- Traffic Fines: Unknowingly speeding.
- Safety Issues: Misjudging speed relative to other traffic.
- Odometer Inaccuracy: Affecting resale value and service intervals.
- Vehicle System Malfunctions: Modern vehicles rely on accurate wheel speed data for systems like Anti-lock Braking System (ABS), Electronic Stability Control (ESC), and Traction Control. A large discrepancy can confuse these systems, potentially leading to warning lights or impaired performance.
Considerations When Changing Wheel and Tire Sizes
- Fender Clearance: Ensure the new, larger tire doesn't rub against the fender wells or suspension components, especially during turns or when the suspension compresses.
- Brake Clearance: Larger wheels might interfere with brake calipers, especially if upgrading to bigger brakes.
- Ride Quality: Shorter sidewalls (lower aspect ratio) typically result in a firmer ride but improved handling. Taller sidewalls offer more comfort.
- Performance: Larger diameter tires can affect acceleration (making it slower) and fuel economy. Wider tires can improve grip but may increase rolling resistance.
- Aesthetics: The visual impact of different wheel and tire combinations is a major factor for many.
- Cost: Larger wheels and lower profile tires are often more expensive.
Always consult your vehicle's manufacturer recommendations or a professional tire specialist before making significant changes to your wheel and tire setup.