.tire-size-calculator-container {
font-family: 'Arial', sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ddd;
border-radius: 8px;
background-color: #f9f9f9;
}
.tire-size-calculator-container h2, .tire-size-calculator-container h3 {
color: #333;
text-align: center;
margin-bottom: 20px;
}
.tire-size-calculator-container .input-group {
margin-bottom: 15px;
display: flex;
flex-wrap: wrap;
align-items: center;
}
.tire-size-calculator-container .input-group label {
flex: 1 1 180px;
margin-right: 10px;
font-weight: bold;
color: #555;
}
.tire-size-calculator-container .input-group input[type="number"] {
flex: 2 1 200px;
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
font-size: 1em;
}
.tire-size-calculator-container button {
display: block;
width: 100%;
padding: 12px 20px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 1.1em;
cursor: pointer;
margin-top: 20px;
transition: background-color 0.3s ease;
}
.tire-size-calculator-container button:hover {
background-color: #0056b3;
}
.tire-size-calculator-container .results-section {
margin-top: 30px;
padding-top: 20px;
border-top: 1px solid #eee;
}
.tire-size-calculator-container .results-section h3 {
color: #333;
margin-bottom: 15px;
}
.tire-size-calculator-container .results-table {
width: 100%;
border-collapse: collapse;
margin-bottom: 20px;
}
.tire-size-calculator-container .results-table th,
.tire-size-calculator-container .results-table td {
border: 1px solid #ddd;
padding: 10px;
text-align: left;
}
.tire-size-calculator-container .results-table th {
background-color: #e9e9e9;
font-weight: bold;
color: #333;
}
.tire-size-calculator-container .results-table td {
background-color: #fff;
}
.tire-size-calculator-container .difference-summary {
background-color: #e6f7ff;
border: 1px solid #b3e0ff;
padding: 15px;
border-radius: 5px;
margin-top: 20px;
}
.tire-size-calculator-container .difference-summary p {
margin: 5px 0;
color: #0056b3;
font-weight: bold;
}
.tire-size-calculator-container .error-message {
color: #dc3545;
font-weight: bold;
margin-top: 10px;
text-align: center;
}
.tire-size-calculator-container .calculator-section {
display: flex;
justify-content: space-between;
gap: 20px;
flex-wrap: wrap;
}
.tire-size-calculator-container .calculator-section > div {
flex: 1 1 350px;
padding: 15px;
border: 1px solid #eee;
border-radius: 5px;
background-color: #fff;
}
.tire-size-calculator-container .calculator-section h4 {
text-align: center;
margin-top: 0;
color: #007bff;
}
@media (max-width: 600px) {
.tire-size-calculator-container .input-group {
flex-direction: column;
align-items: flex-start;
}
.tire-size-calculator-container .input-group label {
margin-bottom: 5px;
}
.tire-size-calculator-container .calculator-section {
flex-direction: column;
}
}
function calculateTireSize() {
var originalSectionWidth = parseFloat(document.getElementById('originalSectionWidth').value);
var originalAspectRatio = parseFloat(document.getElementById('originalAspectRatio').value);
var originalWheelDiameter = parseFloat(document.getElementById('originalWheelDiameter').value);
var newSectionWidth = parseFloat(document.getElementById('newSectionWidth').value);
var newAspectRatio = parseFloat(document.getElementById('newAspectRatio').value);
var newWheelDiameter = parseFloat(document.getElementById('newWheelDiameter').value);
var errorMessageDiv = document.getElementById('errorMessage');
errorMessageDiv.style.display = 'none';
errorMessageDiv.innerHTML = ";
if (isNaN(originalSectionWidth) || isNaN(originalAspectRatio) || isNaN(originalWheelDiameter) ||
isNaN(newSectionWidth) || isNaN(newAspectRatio) || isNaN(newWheelDiameter) ||
originalSectionWidth <= 0 || originalAspectRatio <= 0 || originalWheelDiameter <= 0 ||
newSectionWidth <= 0 || newAspectRatio <= 0 || newWheelDiameter <= 0) {
errorMessageDiv.innerHTML = 'Please enter valid positive numbers for all tire specifications.';
errorMessageDiv.style.display = 'block';
document.getElementById('tireSizeResults').style.display = 'none';
return;
}
var originalTire = calculateTireMetrics(originalSectionWidth, originalAspectRatio, originalWheelDiameter);
var newTire = calculateTireMetrics(newSectionWidth, newAspectRatio, newWheelDiameter);
displayResults(originalTire, newTire, originalSectionWidth, originalAspectRatio, originalWheelDiameter, newSectionWidth, newAspectRatio, newWheelDiameter);
document.getElementById('tireSizeResults').style.display = 'block';
}
function calculateTireMetrics(sectionWidth, aspectRatio, wheelDiameter) {
var sectionWidthInches = sectionWidth / 25.4;
var sidewallHeightInches = sectionWidthInches * (aspectRatio / 100);
var overallDiameterInches = wheelDiameter + (2 * sidewallHeightInches);
var circumferenceInches = overallDiameterInches * Math.PI;
var revolutionsPerMile = 63360 / circumferenceInches; // 1 mile = 63360 inches
return {
sidewallHeight: sidewallHeightInches,
overallDiameter: overallDiameterInches,
circumference: circumferenceInches,
revolutionsPerMile: revolutionsPerMile
};
}
function displayResults(originalTire, newTire, originalSW, originalAR, originalWD, newSW, newAR, newWD) {
// Tire Size Notation
document.getElementById('originalNotation').innerText = originalSW + '/' + originalAR + 'R' + originalWD;
document.getElementById('newNotation').innerText = newSW + '/' + newAR + 'R' + newWD;
// Input values
document.getElementById('originalSectionWidthResult').innerText = originalSW.toFixed(0) + ' mm';
document.getElementById('originalAspectRatioResult').innerText = originalAR.toFixed(0) + '%';
document.getElementById('originalWheelDiameterResult').innerText = originalWD.toFixed(0) + ' inches';
document.getElementById('newSectionWidthResult').innerText = newSW.toFixed(0) + ' mm';
document.getElementById('newAspectRatioResult').innerText = newAR.toFixed(0) + '%';
document.getElementById('newWheelDiameterResult').innerText = newWD.toFixed(0) + ' inches';
// Calculated metrics
document.getElementById('originalSidewallHeight').innerText = originalTire.sidewallHeight.toFixed(2) + ' inches';
document.getElementById('originalOverallDiameter').innerText = originalTire.overallDiameter.toFixed(2) + ' inches';
document.getElementById('originalCircumference').innerText = originalTire.circumference.toFixed(2) + ' inches';
document.getElementById('originalRevsPerMile').innerText = originalTire.revolutionsPerMile.toFixed(2);
document.getElementById('newSidewallHeight').innerText = newTire.sidewallHeight.toFixed(2) + ' inches';
document.getElementById('newOverallDiameter').innerText = newTire.overallDiameter.toFixed(2) + ' inches';
document.getElementById('newCircumference').innerText = newTire.circumference.toFixed(2) + ' inches';
document.getElementById('newRevsPerMile').innerText = newTire.revolutionsPerMile.toFixed(2);
// Differences
var diameterDiff = ((newTire.overallDiameter – originalTire.overallDiameter) / originalTire.overallDiameter) * 100;
var sidewallDiff = ((newTire.sidewallHeight – originalTire.sidewallHeight) / originalTire.sidewallHeight) * 100;
var circumferenceDiff = ((newTire.circumference – originalTire.circumference) / originalTire.circumference) * 100;
document.getElementById('diameterDifference').innerText = diameterDiff.toFixed(2) + '%';
document.getElementById('sidewallDifference').innerText = sidewallDiff.toFixed(2) + '%';
document.getElementById('circumferenceDifference').innerText = circumferenceDiff.toFixed(2) + '%';
// Speedometer Error
var speedometerError = ((originalTire.overallDiameter / newTire.overallDiameter) – 1) * 100;
document.getElementById('speedometerError').innerText = speedometerError.toFixed(2) + '%';
var speedometerExplanation = '';
if (Math.abs(speedometerError) 0) {
speedometerExplanation = 'Your speedometer will read ' + (100 + speedometerError).toFixed(2) + '% higher than your actual speed. For example, if your speedometer reads 60 MPH, your actual speed will be approximately ' + (60 / (1 + (speedometerError / 100))).toFixed(1) + ' MPH.';
} else {
speedometerExplanation = 'Your speedometer will read ' + (100 + speedometerError).toFixed(2) + '% lower than your actual speed. For example, if your speedometer reads 60 MPH, your actual speed will be approximately ' + (60 / (1 + (speedometerError / 100))).toFixed(1) + ' MPH.';
}
document.getElementById('speedometerExplanation').innerText = speedometerExplanation;
}
// Initial calculation on page load for default values
window.onload = function() {
calculateTireSize();
};
Tire Size Calculator
Use this calculator to compare two tire sizes and understand their impact on your vehicle's performance, speedometer accuracy, and overall fitment.
Original Tire Specifications
New Tire Specifications
Comparison Results
| Metric | Original Tire | New Tire |
|---|---|---|
| Tire Size Notation | ||
| Section Width (mm) | ||
| Aspect Ratio (%) | ||
| Wheel Diameter (inches) | ||
| Sidewall Height (inches) | ||
| Overall Diameter (inches) | ||
| Circumference (inches) | ||
| Revolutions per Mile |
Differences & Speedometer Impact
Overall Diameter Difference:
Sidewall Height Difference:
Circumference Difference:
Speedometer Error:
Understanding Your Tire Size
Tires are a critical component of your vehicle, affecting everything from safety and handling to fuel efficiency and speedometer accuracy. Understanding the numbers and letters on your tire's sidewall is essential for proper maintenance and when considering a change in tire size.
Decoding Tire Size Notation (e.g., P205/55R16)
Most passenger vehicle tires use a standardized P-metric or European metric system. Let's break down the common notation:
- P (or LT): This prefix indicates the tire type. 'P' stands for Passenger car, while 'LT' stands for Light Truck. If there's no letter, it's typically a European metric tire.
- 205 (Section Width in mm): This is the width of the tire in millimeters from sidewall to sidewall. A larger number means a wider tire.
- 55 (Aspect Ratio %): This number represents the height of the tire's sidewall as a percentage of its section width. In this example, the sidewall height is 55% of 205mm. A lower aspect ratio means a shorter sidewall, often found on performance tires.
- R (Construction Type): 'R' stands for Radial, which is the most common type of tire construction today. Other less common types include 'D' for Diagonal (bias ply) or 'B' for Bias belted.
- 16 (Wheel Diameter in inches): This number indicates the diameter of the wheel (rim) that the tire is designed to fit, measured in inches.
Why Use a Tire Size Calculator?
Our Tire Size Calculator helps you compare your current tires with a potential new size, providing crucial information:
- Overall Diameter: Changing the overall diameter of your tires can affect your vehicle's gearing, acceleration, and ground clearance.
- Sidewall Height: A shorter sidewall (lower aspect ratio) can improve handling and steering response but may result in a harsher ride. A taller sidewall offers more cushioning.
- Speedometer Accuracy: This is one of the most critical factors. If your new tires have a different overall diameter than your original ones, your speedometer will read incorrectly. The calculator shows you the percentage difference and how it impacts your actual speed.
- Fitment: Knowing the overall diameter and width helps determine if a new tire size will physically fit within your vehicle's wheel wells without rubbing.
- Revolutions Per Mile: This metric indicates how many times the tire rotates to cover one mile. It's directly related to the tire's circumference and overall diameter.
When to Use This Calculator:
- Upgrading Wheels: If you're changing your wheel size (e.g., from 16-inch to 17-inch wheels), you'll need to adjust the tire's aspect ratio and/or width to maintain a similar overall diameter.
- Performance Tuning: Enthusiasts might change tire sizes for better handling, grip, or a specific aesthetic.
- Replacing Worn Tires: While usually you'd replace with the same size, sometimes a slightly different size might be available or preferred.
- Off-Roading: Off-roaders often opt for larger diameter tires for increased ground clearance.
Important Considerations:
- Manufacturer Recommendations: Always consult your vehicle's owner's manual or the tire placard (usually on the driver's side door jamb) for recommended tire sizes.
- Rubbing Issues: Even small changes in diameter or width can cause tires to rub against fenders or suspension components, especially during turns or over bumps.
- Load Capacity: Ensure any new tire size meets or exceeds the load capacity requirements for your vehicle.
- TPMS (Tire Pressure Monitoring System): Significant changes in tire size can sometimes affect TPMS calibration.
- Aesthetic Preference: While not performance-related, the visual impact of different tire sizes is a common reason for changes.
Example Calculation:
Let's say your original tire is 205/55R16 and you're considering a new tire size of 225/45R17.
Original Tire (205/55R16):
- Section Width: 205 mm
- Aspect Ratio: 55%
- Wheel Diameter: 16 inches
- Calculated Sidewall Height: (205mm / 25.4) * 0.55 = 4.45 inches
- Calculated Overall Diameter: 16 + (2 * 4.45) = 24.90 inches
- Calculated Circumference: 24.90 * π = 78.23 inches
- Revolutions per Mile: 63360 / 78.23 = 809.92
New Tire (225/45R17):
- Section Width: 225 mm
- Aspect Ratio: 45%
- Wheel Diameter: 17 inches
- Calculated Sidewall Height: (225mm / 25.4) * 0.45 = 3.99 inches
- Calculated Overall Diameter: 17 + (2 * 3.99) = 24.98 inches
- Calculated Circumference: 24.98 * π = 78.59 inches
- Revolutions per Mile: 63360 / 78.59 = 806.18
Comparison:
- Overall Diameter Difference: (24.98 – 24.90) / 24.90 * 100 = 0.32% larger
- Sidewall Height Difference: (3.99 – 4.45) / 4.45 * 100 = -10.34% shorter
- Speedometer Error: If your speedometer reads 60 MPH with the new tires, your actual speed would be approximately 60.19 MPH (a very minor difference due to the similar overall diameter).
This example shows that while the wheel diameter increased, the aspect ratio decreased, resulting in a very similar overall tire diameter, which is ideal for minimizing speedometer error.