Tyre Size Comparison Calculator
Use this calculator to compare two different tyre sizes and understand how changing your vehicle's tyres can affect its dimensions, speedometer reading, and ground clearance.
Original Tyre Size
New Tyre Size
Comparison Results
'; htmlOutput += '';
htmlOutput += '
';
htmlOutput += 'Original Tyre (' + originalWidth + '/' + originalAspect + 'R' + originalRim + ')
'; htmlOutput += 'Sidewall Height: ' + originalSidewallHeight.toFixed(2) + ' mm'; htmlOutput += 'Overall Diameter: ' + originalOverallDiameter.toFixed(2) + ' mm'; htmlOutput += 'Circumference: ' + originalCircumference.toFixed(2) + ' mm'; htmlOutput += 'Revolutions per km: ' + originalRevsPerKm.toFixed(2) + ''; htmlOutput += '';
htmlOutput += '
';
htmlOutput += 'New Tyre (' + newWidth + '/' + newAspect + 'R' + newRim + ')
'; htmlOutput += 'Sidewall Height: ' + newSidewallHeight.toFixed(2) + ' mm'; htmlOutput += 'Overall Diameter: ' + newOverallDiameter.toFixed(2) + ' mm'; htmlOutput += 'Circumference: ' + newCircumference.toFixed(2) + ' mm'; htmlOutput += 'Revolutions per km: ' + newRevsPerKm.toFixed(2) + ''; htmlOutput += '';
htmlOutput += '
';
resultDiv.innerHTML = htmlOutput;
}
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min-width: 280px;
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.input-group label {
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font-weight: bold;
color: #555;
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.input-group input[type="number"] {
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margin-bottom: 20px;
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@media (max-width: 600px) {
.calculator-form {
flex-direction: column;
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}
Summary of Differences
'; htmlOutput += 'Diameter Difference: ' + diameterDifference.toFixed(2) + ' mm (' + diameterDifferencePercent.toFixed(2) + '%)'; htmlOutput += 'Circumference Difference: ' + circumferenceDifference.toFixed(2) + ' mm (' + circumferenceDifferencePercent.toFixed(2) + '%)'; htmlOutput += 'Ground Clearance Change: ' + groundClearanceChange.toFixed(2) + ' mm'; htmlOutput += 'When your speedometer reads 100 km/h:'; htmlOutput += 'Your actual speed will be: ' + actualSpeedAt100.toFixed(2) + ' km/h'; if (speedometerError > 0) { htmlOutput += 'Your speedometer will read ' + Math.abs(speedometerError).toFixed(2) + ' km/h SLOWER than your actual speed.'; } else if (speedometerError < 0) { htmlOutput += 'Your speedometer will read ' + Math.abs(speedometerError).toFixed(2) + ' km/h FASTER than your actual speed.'; } else { htmlOutput += 'Your speedometer reading will be accurate.'; } htmlOutput += 'Understanding Tyre Size Comparison
Changing your vehicle's tyre size is a common modification, whether for aesthetic reasons, performance upgrades, or simply replacing worn-out tyres with a different specification. However, it's crucial to understand the implications of such changes. A tyre size comparison calculator helps you visualize the differences between your original tyres and a potential new set.
What Do Tyre Size Numbers Mean?
A typical tyre size, like 205/55R16, breaks down as follows:
- 205: Section Width (mm) – This is the width of the tyre from sidewall to sidewall in millimeters. A wider tyre generally offers more grip but can affect fuel economy and steering feel.
- 55: Aspect Ratio (%) – This number represents the sidewall height as a percentage of the section width. In this example, the sidewall height is 55% of 205mm. A lower aspect ratio means a shorter sidewall, often found on performance tyres, offering better handling but a harsher ride.
- R: Construction Type – 'R' stands for Radial, which is the most common type of tyre construction today.
- 16: Rim Diameter (inches) – This is the diameter of the wheel rim in inches that the tyre is designed to fit.
Why Compare Tyre Sizes?
Comparing tyre sizes is essential for several reasons:
- Speedometer Accuracy: The most critical factor. Your vehicle's speedometer is calibrated based on the original tyre's overall diameter and circumference. Changing these dimensions will cause your speedometer to read inaccurately. If the new tyre has a larger diameter, your speedometer will read slower than your actual speed, potentially leading to speeding tickets. If it's smaller, your speedometer will read faster.
- Ground Clearance: A larger overall diameter will increase your vehicle's ground clearance, while a smaller diameter will reduce it. This can affect off-road capability or the risk of scraping the undercarriage.
- Fender Clearance: Tyres that are too wide or have too large an overall diameter might rub against the fender wells or suspension components, especially during turns or when the suspension compresses.
- Handling and Ride Comfort: Changes in sidewall height and tyre width can significantly alter your vehicle's handling characteristics and ride comfort. Lower aspect ratio tyres (shorter sidewalls) generally offer sharper handling but a firmer ride.
- Fuel Economy: Larger or wider tyres can increase rolling resistance and weight, potentially leading to a slight decrease in fuel efficiency.
- Braking Performance: While wider tyres can offer more grip, significant changes in overall diameter can affect braking dynamics and ABS calibration.
- Aesthetics: Many people change tyre sizes for a specific look, such as larger rims or a more aggressive stance.
- Legal Compliance: Some regions have regulations regarding how much you can change your tyre size from the original specification.
Using the Calculator
Simply input the section width, aspect ratio, and rim diameter for both your original tyres and the new tyres you are considering. The calculator will then provide detailed information on:
- Sidewall Height: The actual height of the tyre's sidewall.
- Overall Diameter: The total height of the tyre when inflated.
- Circumference: The distance the tyre travels in one full rotation.
- Revolutions per km: How many times the tyre rotates to cover one kilometer.
- Diameter and Circumference Difference: The absolute and percentage difference between the two tyre sizes.
- Ground Clearance Change: How much your vehicle's ground clearance will increase or decrease.
- Speedometer Difference: A crucial metric showing your actual speed when your speedometer reads a certain value (e.g., 100 km/h).
Important Considerations
While this calculator provides valuable data, it's always recommended to consult with a professional tyre specialist or your vehicle manufacturer before making significant changes to your tyre size. They can advise on compatibility, safety, and any potential impact on your vehicle's warranty or performance systems (like ABS, traction control, and stability control).