Tire Conversion Calculator

Tire Conversion Calculator

Use this calculator to compare two tire sizes and understand how changes in width, aspect ratio, and rim diameter affect overall tire dimensions, speedometer accuracy, and vehicle performance.

Tire 1 (Original/Current)

Tire 2 (New/Target)

function calculateTireConversion() { var tire1Width = parseFloat(document.getElementById('tire1Width').value); var tire1Aspect = parseFloat(document.getElementById('tire1Aspect').value); var tire1Rim = parseFloat(document.getElementById('tire1Rim').value); var tire2Width = parseFloat(document.getElementById('tire2Width').value); var tire2Aspect = parseFloat(document.getElementById('tire2Aspect').value); var tire2Rim = parseFloat(document.getElementById('tire2Rim').value); if (isNaN(tire1Width) || isNaN(tire1Aspect) || isNaN(tire1Rim) || isNaN(tire2Width) || isNaN(tire2Aspect) || isNaN(tire2Rim) || tire1Width <= 0 || tire1Aspect <= 0 || tire1Rim <= 0 || tire2Width <= 0 || tire2Aspect <= 0 || tire2Rim <= 0) { document.getElementById('tire1Details').innerHTML = 'Please enter valid positive numbers for all tire dimensions.'; document.getElementById('tire2Details').innerHTML = ''; document.getElementById('comparisonResults').innerHTML = ''; return; } var tire1 = calculateTireDimensions(tire1Width, tire1Aspect, tire1Rim); var tire2 = calculateTireDimensions(tire2Width, tire2Aspect, tire2Rim); displayTireDetails('tire1Details', tire1, 'Tire 1'); displayTireDetails('tire2Details', tire2, 'Tire 2'); displayComparisonResults('comparisonResults', tire1, tire2); } function calculateTireDimensions(width, aspect, rim) { var sidewall_mm = width * (aspect / 100); var sidewall_in = sidewall_mm / 25.4; var overall_diameter_in = rim + (2 * sidewall_in); var overall_diameter_mm = overall_diameter_in * 25.4; var circumference_in = overall_diameter_in * Math.PI; var circumference_mm = overall_diameter_mm * Math.PI; var revs_per_mile = (5280 * 12) / circumference_in; // 5280 feet/mile * 12 inches/foot var revs_per_km = (1000 * 1000) / circumference_mm; // 1000 meters/km * 1000 mm/meter return { width_mm: width, width_in: width / 25.4, aspect: aspect, rim_in: rim, sidewall_mm: sidewall_mm, sidewall_in: sidewall_in, overall_diameter_mm: overall_diameter_mm, overall_diameter_in: overall_diameter_in, circumference_mm: circumference_mm, circumference_in: circumference_in, revs_per_mile: revs_per_mile, revs_per_km: revs_per_km }; } function displayTireDetails(elementId, tire, label) { var output = '

' + label + ' (' + tire.width_mm + '/' + tire.aspect + 'R' + tire.rim_in + ')

'; output += 'Section Width: ' + tire.width_mm.toFixed(1) + ' mm (' + tire.width_in.toFixed(2) + ' inches)'; output += 'Sidewall Height: ' + tire.sidewall_mm.toFixed(1) + ' mm (' + tire.sidewall_in.toFixed(2) + ' inches)'; output += 'Overall Diameter: ' + tire.overall_diameter_mm.toFixed(1) + ' mm (' + tire.overall_diameter_in.toFixed(2) + ' inches)'; output += 'Overall Circumference: ' + tire.circumference_mm.toFixed(1) + ' mm (' + tire.circumference_in.toFixed(2) + ' inches)'; output += 'Revolutions per Mile: ' + tire.revs_per_mile.toFixed(0) + "; output += 'Revolutions per Kilometer: ' + tire.revs_per_km.toFixed(0) + "; document.getElementById(elementId).innerHTML = output; } function displayComparisonResults(elementId, tire1, tire2) { var diameter_diff_mm = tire2.overall_diameter_mm – tire1.overall_diameter_mm; var diameter_diff_in = tire2.overall_diameter_in – tire1.overall_diameter_in; var diameter_diff_percent = (diameter_diff_in / tire1.overall_diameter_in) * 100; var sidewall_diff_mm = tire2.sidewall_mm – tire1.sidewall_mm; var sidewall_diff_in = tire2.sidewall_in – tire1.sidewall_in; var sidewall_diff_percent = (sidewall_diff_in / tire1.sidewall_in) * 100; var width_diff_mm = tire2.width_mm – tire1.width_mm; var width_diff_in = tire2.width_in – tire1.width_in; var width_diff_percent = (width_diff_mm / tire1.width_mm) * 100; var speedometer_error_percent = diameter_diff_percent; var actual_speed_at_60mph = 60 * (tire2.overall_diameter_in / tire1.overall_diameter_in); var actual_speed_at_100kmh = 100 * (tire2.overall_diameter_mm / tire1.overall_diameter_mm); var output = "; output += 'Overall Diameter Difference: ' + formatDifference(diameter_diff_mm, 'mm') + ' (' + formatDifference(diameter_diff_in, 'inches') + ') 0 ? 'green' : (diameter_diff_percent (' + diameter_diff_percent.toFixed(2) + '%)'; output += 'Sidewall Height Difference: ' + formatDifference(sidewall_diff_mm, 'mm') + ' (' + formatDifference(sidewall_diff_in, 'inches') + ') 0 ? 'green' : (sidewall_diff_percent (' + sidewall_diff_percent.toFixed(2) + '%)'; output += 'Section Width Difference: ' + formatDifference(width_diff_mm, 'mm') + ' (' + formatDifference(width_diff_in, 'inches') + ') 0 ? 'green' : (width_diff_percent (' + width_diff_percent.toFixed(2) + '%)'; output += '

Speedometer Error:

'; if (speedometer_error_percent > 0) { output += 'Your speedometer will read slower than your actual speed by approximately ' + Math.abs(speedometer_error_percent).toFixed(2) + '%.'; output += ' If your speedometer reads 60 MPH, your actual speed will be approximately ' + actual_speed_at_60mph.toFixed(1) + ' MPH.'; output += 'If your speedometer reads 100 KM/H, your actual speed will be approximately ' + actual_speed_at_100kmh.toFixed(1) + ' KM/H.'; } else if (speedometer_error_percent < 0) { output += 'Your speedometer will read faster than your actual speed by approximately ' + Math.abs(speedometer_error_percent).toFixed(2) + '%.'; output += ' If your speedometer reads 60 MPH, your actual speed will be approximately ' + actual_speed_at_60mph.toFixed(1) + ' MPH.'; output += 'If your speedometer reads 100 KM/H, your actual speed will be approximately ' + actual_speed_at_100kmh.toFixed(1) + ' KM/H.'; } else { output += 'There will be no significant speedometer error.'; } document.getElementById(elementId).innerHTML = output; } function formatDifference(value, unit) { var sign = value >= 0 ? '+' : "; return sign + value.toFixed(2) + ' ' + unit; } // Run calculation on page load with default values window.onload = calculateTireConversion; .tire-conversion-calculator-container { font-family: Arial, sans-serif; max-width: 800px; margin: 20px auto; padding: 20px; border: 1px solid #ccc; border-radius: 8px; background-color: #f9f9f9; } .calculator-inputs { display: flex; justify-content: space-around; margin-bottom: 20px; flex-wrap: wrap; } .tire-input-group { flex: 1; min-width: 280px; margin: 10px; padding: 15px; border: 1px solid #eee; border-radius: 5px; background-color: #fff; } .tire-input-group label { display: block; margin-bottom: 5px; font-weight: bold; } .tire-input-group input[type="number"] { width: calc(100% – 10px); padding: 8px; margin-bottom: 10px; border: 1px solid #ddd; border-radius: 4px; } button { display: block; width: 100%; padding: 12px 20px; background-color: #007bff; color: white; border: none; border-radius: 5px; font-size: 18px; cursor: pointer; transition: background-color 0.3s ease; margin-bottom: 20px; } button:hover { background-color: #0056b3; } .calculator-results h3 { margin-top: 25px; border-bottom: 1px solid #eee; padding-bottom: 5px; } .tire-details-output, .comparison-output { background-color: #fff; border: 1px solid #eee; border-radius: 5px; padding: 15px; margin-bottom: 15px; } .tire-details-output h4, .comparison-output h4 { margin-top: 0; color: #333; } .tire-details-output p, .comparison-output p { margin: 5px 0; line-height: 1.5; }

Understanding Your Tires: A Guide to Tire Conversion

Tires are a critical component of your vehicle, directly impacting safety, performance, and fuel efficiency. Understanding tire sizing and how to convert between different sizes is essential for anyone considering a tire change, whether for aesthetic reasons, performance upgrades, or simply replacing worn-out tires.

What Do Tire Numbers Mean?

A typical tire size, like 225/55R17, contains a wealth of information:

• 225: Section Width (mm) – This is the width of the tire in millimeters from sidewall to sidewall.
• 55: Aspect Ratio (%) – This number represents the height of the tire's sidewall as a percentage of its section width. In this case, the sidewall height is 55% of 225mm.
• R: Construction Type – 'R' stands for Radial, the most common type of tire construction.
• 17: Rim Diameter (inches) – This indicates the diameter of the wheel (rim) that the tire is designed to fit, measured in inches.

Why Use a Tire Conversion Calculator?

A tire conversion calculator is an invaluable tool for several reasons:

1. Speedometer Accuracy: Changing your tire's overall diameter can significantly affect your speedometer reading. If the new tire is larger, your speedometer will read slower than your actual speed, and vice-versa. This can lead to speeding tickets or inaccurate navigation.
2. Vehicle Clearance: Larger tires might rub against wheel wells, suspension components, or fender liners, especially during turns or over bumps. The calculator helps you predict potential clearance issues.
3. Performance and Handling: Changes in tire width and sidewall height can alter your vehicle's handling characteristics. A wider tire generally offers more grip, while a lower aspect ratio (shorter sidewall) can improve steering response but might result in a harsher ride.
4. Aesthetics: Many car enthusiasts change tire and wheel sizes to achieve a specific look. The calculator helps visualize how different sizes will appear.
5. ABS/Traction Control Systems: Modern vehicles rely on precise wheel speed sensor readings for Anti-lock Braking Systems (ABS) and Traction Control Systems (TCS). Significant changes in tire diameter can confuse these systems, potentially leading to malfunctions or reduced effectiveness.
6. Fuel Economy: Larger or wider tires can increase rolling resistance and vehicle weight, potentially leading to a slight decrease in fuel efficiency.

How to Interpret the Results

Our calculator provides detailed information for both your original and new tire sizes, along with a direct comparison:

• Section Width: Shows how much wider or narrower your new tire will be.
• Sidewall Height: Indicates how much taller or shorter the tire's sidewall will be. A shorter sidewall often means a sportier look and feel.
• Overall Diameter: This is the most crucial measurement for speedometer accuracy and clearance. A difference of more than 3% is generally not recommended without professional advice.
• Overall Circumference: Directly related to the overall diameter, this affects how many revolutions the tire makes per mile or kilometer.
• Revolutions per Mile/Kilometer: Useful for understanding the tire's rotational speed at a given vehicle speed.
• Speedometer Error: This percentage indicates how much your speedometer will be off. For example, if it says +3%, your speedometer will read 60 MPH when you are actually going 61.8 MPH.

Important Considerations Before Changing Tire Sizes

• Consult Your Vehicle Manufacturer: Always check your vehicle's owner's manual or a reputable tire guide for recommended tire sizes.
• Professional Installation: Tire mounting and balancing should always be done by qualified professionals.
• Test Fit: If you're making a significant change, especially to a larger diameter or wider tire, a test fit is highly recommended to ensure proper clearance under all driving conditions.
• Local Laws: Be aware of any local regulations regarding tire protrusion or overall vehicle height.

By using this tire conversion calculator and understanding its results, you can make informed decisions about your vehicle's tires, ensuring both safety and optimal performance.