Tire Converter Calculator

Tire Size Converter Calculator

Use this calculator to compare two different tire sizes and understand how changing your vehicle's tires can affect its speedometer reading, overall diameter, and revolutions per mile.

function calculateTireConversion() { // Get original tire inputs var originalWidth = parseFloat(document.getElementById('originalWidth').value); var originalAspect = parseFloat(document.getElementById('originalAspect').value); var originalWheelDiameter = parseFloat(document.getElementById('originalWheelDiameter').value); // Get new tire inputs var newWidth = parseFloat(document.getElementById('newWidth').value); var newAspect = parseFloat(document.getElementById('newAspect').value); var newWheelDiameter = parseFloat(document.getElementById('newWheelDiameter').value); var resultDiv = document.getElementById('tireConversionResult'); resultDiv.innerHTML = "; // Clear previous results // Input validation if (isNaN(originalWidth) || isNaN(originalAspect) || isNaN(originalWheelDiameter) || isNaN(newWidth) || isNaN(newAspect) || isNaN(newWheelDiameter) || originalWidth <= 0 || originalAspect <= 0 || originalWheelDiameter <= 0 || newWidth <= 0 || newAspect <= 0 || newWheelDiameter <= 0) { resultDiv.innerHTML = 'Please enter valid positive numbers for all tire specifications.'; return; } // — Calculations for Original Tire — var originalSidewallHeightMM = (originalWidth * (originalAspect / 100)); var originalOverallDiameterMM = (originalWheelDiameter * 25.4) + (2 * originalSidewallHeightMM); var originalOverallDiameterInches = originalOverallDiameterMM / 25.4; var originalCircumferenceInches = originalOverallDiameterInches * Math.PI; var originalRevsPerMile = 63360 / originalCircumferenceInches; // 63360 inches in a mile // — Calculations for New Tire — var newSidewallHeightMM = (newWidth * (newAspect / 100)); var newOverallDiameterMM = (newWheelDiameter * 25.4) + (2 * newSidewallHeightMM); var newOverallDiameterInches = newOverallDiameterMM / 25.4; var newCircumferenceInches = newOverallDiameterInches * Math.PI; var newRevsPerMile = 63360 / newCircumferenceInches; // — Comparison Calculations — var diameterDifferencePercent = ((newOverallDiameterInches – originalOverallDiameterInches) / originalOverallDiameterInches) * 100; var circumferenceDifferencePercent = ((newCircumferenceInches – originalCircumferenceInches) / originalCircumferenceInches) * 100; var revsPerMileDifferencePercent = ((newRevsPerMile – originalRevsPerMile) / originalRevsPerMile) * 100; // Speedometer reading adjustment: If speedometer reads 60 MPH (calibrated for original tire), what is actual speed? var actualSpeedAt60MPH = (newOverallDiameterInches / originalOverallDiameterInches) * 60; var speedometerErrorAt60MPH = actualSpeedAt60MPH – 60; // Display Results var resultsHTML = '

Comparison Results

'; resultsHTML += ''; resultsHTML += '

Speedometer Impact

'; resultsHTML += 'If your speedometer (calibrated for the original tire) reads 60 MPH:'; resultsHTML += 'Your actual speed will be: ' + actualSpeedAt60MPH.toFixed(2) + ' MPH'; resultsHTML += 'Speedometer error: ' + speedometerErrorAt60MPH.toFixed(2) + ' MPH'; if (Math.abs(diameterDifferencePercent) > 3) { resultsHTML += 'Warning: A diameter difference greater than 3% can significantly affect speedometer accuracy, ABS, traction control, and potentially cause transmission issues. Consult a professional.'; } else { resultsHTML += 'The diameter difference is within a generally acceptable range (less than 3%). However, always verify with a professional.'; } resultDiv.innerHTML = resultsHTML; } .tire-converter-calculator { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; background-color: #f9f9f9; padding: 25px; border-radius: 10px; box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1); max-width: 800px; margin: 30px auto; color: #333; border: 1px solid #e0e0e0; } .tire-converter-calculator h2 { text-align: center; color: #2c3e50; margin-bottom: 20px; font-size: 1.8em; } .tire-converter-calculator h3 { color: #34495e; margin-top: 25px; margin-bottom: 15px; font-size: 1.3em; border-bottom: 1px solid #eee; padding-bottom: 5px; } .tire-converter-calculator p { line-height: 1.6; margin-bottom: 15px; } .calculator-container { display: flex; flex-wrap: wrap; gap: 20px; justify-content: center; margin-bottom: 20px; } .input-group { background-color: #ffffff; padding: 20px; border-radius: 8px; box-shadow: 0 2px 5px rgba(0, 0, 0, 0.05); flex: 1; min-width: 280px; border: 1px solid #e8e8e8; } .input-group label { display: block; margin-bottom: 8px; font-weight: bold; color: #555; font-size: 0.95em; } .input-group input[type="number"] { width: calc(100% – 20px); padding: 10px; margin-bottom: 15px; border: 1px solid #ccc; border-radius: 5px; font-size: 1em; box-sizing: border-box; } .tire-converter-calculator button { display: block; width: 100%; padding: 12px 20px; background-color: #28a745; color: white; border: none; border-radius: 5px; font-size: 1.1em; cursor: pointer; transition: background-color 0.3s ease; margin-top: 20px; } .tire-converter-calculator button:hover { background-color: #218838; } .result-section { background-color: #eaf7ed; padding: 20px; border-radius: 8px; margin-top: 25px; border: 1px solid #d4edda; color: #155724; } .result-section h3 { color: #155724; margin-top: 0; border-bottom: 1px solid #c3e6cb; padding-bottom: 8px; } .result-section p { margin-bottom: 10px; font-size: 1.05em; } .result-section .error { color: #dc3545; font-weight: bold; background-color: #f8d7da; border: 1px solid #f5c6cb; padding: 10px; border-radius: 5px; } .result-section .warning { color: #856404; background-color: #fff3cd; border: 1px solid #ffeeba; padding: 10px; border-radius: 5px; font-weight: bold; } .result-section .info { color: #004085; background-color: #cce5ff; border: 1px solid #b8daff; padding: 10px; border-radius: 5px; } .results-table { overflow-x: auto; margin-top: 20px; } .results-table table { width: 100%; border-collapse: collapse; margin-bottom: 15px; } .results-table th, .results-table td { border: 1px solid #ddd; padding: 10px; text-align: left; font-size: 0.95em; } .results-table th { background-color: #e9ecef; font-weight: bold; color: #495057; } .results-table tr:nth-child(even) { background-color: #f2f2f2; } @media (max-width: 600px) { .calculator-container { flex-direction: column; } .input-group { min-width: unset; width: 100%; } }

Understanding Your Tire Size Converter

A tire size converter calculator is an essential tool for anyone considering changing their vehicle's tires. Whether you're upgrading for aesthetics, performance, or simply replacing worn-out tires with a different size, understanding the implications of these changes is crucial for safety, vehicle performance, and legal compliance.

How to Read Tire Sizes

Tire sizes are typically displayed in a standardized format, for example, 205/55R16:

• 205: This is the tire's width in millimeters (mm) from sidewall to sidewall.
• 55: This is the aspect ratio, representing the sidewall height as a percentage of the tire's width. In this case, the sidewall height is 55% of 205mm.
• R: Indicates a radial construction tire, which is the most common type today.
• 16: This is the diameter of the wheel (rim) in inches that the tire is designed to fit.

Why Use a Tire Converter?

Changing tire dimensions can have several significant effects on your vehicle:

1. Speedometer Accuracy: The most common reason to use a converter. Your vehicle's speedometer is calibrated based on the original tire's diameter. If you install tires with a different overall diameter, your speedometer will no longer read accurately. A larger tire will make your speedometer read slower than your actual speed, while a smaller tire will make it read faster.
2. Odometer Accuracy: Similar to the speedometer, your odometer will also become inaccurate, affecting mileage tracking and potentially resale value.
3. Gear Ratios: The effective gear ratio of your vehicle changes with tire diameter. Larger tires effectively "raise" your gear ratio, potentially reducing acceleration and increasing fuel economy (though this can be offset by increased rolling resistance). Smaller tires do the opposite.
4. ABS and Traction Control: 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, leading to erratic behavior or malfunction.
5. Clearance Issues: Larger tires might rub against fender wells, suspension components, or other parts of the vehicle, especially during turns or when the suspension compresses.
6. Aesthetics and Ride Quality: Different tire sizes can drastically alter the look of your vehicle and impact ride comfort and handling characteristics.

How the Calculator Works

Our calculator takes the width, aspect ratio, and wheel diameter for both your original and new tires. It then performs the following calculations:

• Sidewall Height: Calculates the height of the tire's sidewall based on width and aspect ratio.
• Overall Diameter: Determines the total height of the tire from the ground to the top.
• Circumference: Calculates the distance the tire travels in one full rotation.
• Revolutions Per Mile: Estimates how many times the tire rotates to cover one mile.
• Speedometer Impact: Shows you your actual speed when your speedometer, calibrated for the original tires, reads 60 MPH. This is a critical metric for safety and avoiding speeding tickets.

Important Considerations

• Stay Within 3% Diameter Difference: Most experts recommend keeping the overall tire diameter difference within +/- 3% of the original size to minimize issues with speedometer accuracy, ABS, and transmission.
• Test Fit: Always test fit new tires, especially if they are significantly different, to ensure proper clearance.
• Professional Advice: For major changes or if you have concerns, always consult with a professional tire technician or your vehicle manufacturer.
• Load Index and Speed Rating: Ensure your new tires have appropriate load index and speed ratings for your vehicle's requirements.

Example Usage:

Let's say your original tires are 205/55R16 and you're considering upgrading to 225/45R17.

• Original Tire: Width = 205mm, Aspect Ratio = 55%, Wheel Diameter = 16 inches
• New Tire: Width = 225mm, Aspect Ratio = 45%, Wheel Diameter = 17 inches

Input these values into the calculator. You'll see that the new tire has a slightly larger overall diameter, which means if your speedometer reads 60 MPH, you'll actually be going a bit faster. This difference is usually within acceptable limits for this specific change, but the calculator will give you the precise figures.