function calculateTireComparison() {
var originalSectionWidth = parseFloat(document.getElementById('originalSectionWidth').value);
var originalAspectRatio = parseFloat(document.getElementById('originalAspectRatio').value);
var originalRimDiameter = parseFloat(document.getElementById('originalRimDiameter').value);
var newSectionWidth = parseFloat(document.getElementById('newSectionWidth').value);
var newAspectRatio = parseFloat(document.getElementById('newAspectRatio').value);
var newRimDiameter = parseFloat(document.getElementById('newRimDiameter').value);
var resultMessage = document.getElementById('resultMessage');
if (isNaN(originalSectionWidth) || isNaN(originalAspectRatio) || isNaN(originalRimDiameter) ||
isNaN(newSectionWidth) || isNaN(newAspectRatio) || isNaN(newRimDiameter) ||
originalSectionWidth <= 0 || originalAspectRatio <= 0 || originalRimDiameter <= 0 ||
newSectionWidth <= 0 || newAspectRatio <= 0 || newRimDiameter <= 0) {
resultMessage.innerHTML = "Please enter valid positive numbers for all tire dimensions.";
resultMessage.style.color = "red";
document.getElementById('originalTireOD').innerHTML = '0.00';
document.getElementById('newTireOD').innerHTML = '0.00';
document.getElementById('diameterDifference').innerHTML = '0.00';
document.getElementById('percentageDifference').innerHTML = '0.00';
document.getElementById('speedometerError').innerHTML = '0.00';
return;
}
// Calculate Original Tire Overall Diameter
var originalSidewallHeightMM = originalSectionWidth * (originalAspectRatio / 100);
var originalOverallDiameterMM = (2 * originalSidewallHeightMM) + (originalRimDiameter * 25.4);
var originalOverallDiameterInches = originalOverallDiameterMM / 25.4;
// Calculate New Tire Overall Diameter
var newSidewallHeightMM = newSectionWidth * (newAspectRatio / 100);
var newOverallDiameterMM = (2 * newSidewallHeightMM) + (newRimDiameter * 25.4);
var newOverallDiameterInches = newOverallDiameterMM / 25.4;
// Calculate Differences
var diameterDifference = newOverallDiameterInches – originalOverallDiameterInches;
var percentageDifference = (diameterDifference / originalOverallDiameterInches) * 100;
// Calculate Speedometer Error (assuming original tire is accurate)
var speedoFactor = newOverallDiameterInches / originalOverallDiameterInches;
var originalSpeed = 60; // Example speed
var newSpeedReading = originalSpeed * speedoFactor;
var actualSpeedWhenSpeedoReads60 = originalSpeed / speedoFactor; // If new tire is on, and speedo reads 60, what is actual speed?
var speedoErrorAt60 = newSpeedReading – originalSpeed; // How much faster/slower the speedo will read compared to actual speed if original was accurate
document.getElementById('originalTireOD').innerHTML = originalOverallDiameterInches.toFixed(2);
document.getElementById('newTireOD').innerHTML = newOverallDiameterInches.toFixed(2);
document.getElementById('diameterDifference').innerHTML = diameterDifference.toFixed(2);
document.getElementById('percentageDifference').innerHTML = percentageDifference.toFixed(2);
document.getElementById('speedometerError').innerHTML = speedoErrorAt60.toFixed(2);
if (Math.abs(percentageDifference) <= 1) {
resultMessage.innerHTML = "Excellent match! The diameter difference is minimal, and speedometer error will be negligible.";
resultMessage.style.color = "green";
} else if (Math.abs(percentageDifference) <= 3) {
resultMessage.innerHTML = "Good match. The diameter difference is acceptable, but speedometer error might be noticeable.";
resultMessage.style.color = "orange";
} else if (Math.abs(percentageDifference) <= 5) {
resultMessage.innerHTML = "Moderate difference. Consider potential issues with speedometer accuracy, ABS/traction control, and fender clearance.";
resultMessage.style.color = "#e6b800"; // Darker yellow/orange
} else {
resultMessage.innerHTML = "Significant difference! This tire size change is not recommended due to potential speedometer errors, ABS/traction control issues, and fitment problems.";
resultMessage.style.color = "red";
}
}
.calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
background-color: #f9f9f9;
border: 1px solid #ddd;
border-radius: 8px;
padding: 25px;
max-width: 700px;
margin: 30px auto;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
color: #333;
}
.calculator-container h2 {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 1.8em;
}
.calculator-content {
display: flex;
flex-wrap: wrap;
gap: 20px;
justify-content: center;
}
.input-group {
background-color: #ffffff;
border: 1px solid #e0e0e0;
border-radius: 6px;
padding: 20px;
flex: 1;
min-width: 280px;
box-shadow: 0 2px 5px rgba(0, 0, 0, 0.05);
}
.input-group h3 {
color: #34495e;
margin-top: 0;
margin-bottom: 15px;
font-size: 1.3em;
text-align: center;
}
.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: 4px;
font-size: 1em;
box-sizing: border-box;
}
button {
display: block;
width: calc(100% – 40px);
padding: 12px 20px;
margin: 25px auto;
background-color: #007bff;
color: white;
border: none;
border-radius: 5px;
font-size: 1.1em;
cursor: pointer;
transition: background-color 0.3s ease, transform 0.2s ease;
box-shadow: 0 4px 8px rgba(0, 123, 255, 0.2);
}
button:hover {
background-color: #0056b3;
transform: translateY(-2px);
}
button:active {
transform: translateY(0);
box-shadow: 0 2px 4px rgba(0, 123, 255, 0.3);
}
.result-group {
background-color: #eaf4ff;
border: 1px solid #cce0ff;
border-radius: 6px;
padding: 20px;
margin-top: 20px;
width: 100%;
box-sizing: border-box;
box-shadow: 0 2px 5px rgba(0, 0, 0, 0.05);
}
.result-group h3 {
color: #0056b3;
margin-top: 0;
margin-bottom: 15px;
font-size: 1.4em;
text-align: center;
}
.result-group p {
margin-bottom: 10px;
font-size: 1.05em;
line-height: 1.6;
color: #333;
}
.result-group p span {
font-weight: bold;
color: #007bff;
}
.result-group .message {
margin-top: 20px;
padding: 10px;
border-radius: 4px;
font-weight: bold;
text-align: center;
background-color: #fff3cd; /* Default for warnings */
color: #856404;
border: 1px solid #ffeeba;
}
/* Specific message colors */
.result-group .message[style*="green"] {
background-color: #d4edda;
color: #155724;
border-color: #c3e6cb;
}
.result-group .message[style*="orange"] {
background-color: #fff3cd;
color: #856404;
border-color: #ffeeba;
}
.result-group .message[style*="#e6b800″] { /* For moderate difference */
background-color: #fff8e1;
color: #a07a00;
border-color: #ffecb3;
}
.result-group .message[style*="red"] {
background-color: #f8d7da;
color: #721c24;
border-color: #f5c6cb;
}
@media (max-width: 600px) {
.calculator-content {
flex-direction: column;
}
.input-group {
min-width: unset;
width: 100%;
}
button {
width: calc(100% – 20px);
}
}
Understanding the 1010 Tire Size Comparison Calculator
When considering a change in your vehicle's tire size, it's crucial to understand how the new tires will affect your vehicle's performance, aesthetics, and most importantly, its speedometer accuracy. The "1010 Tire Calculator" is a tool designed to help you compare your original tire size with a potential new size, providing critical data like overall diameter difference and speedometer error.
Why is Tire Diameter Important?
The overall diameter of your tires directly impacts several aspects of your vehicle:
Speedometer Accuracy: Your vehicle's speedometer is calibrated based on the original tire diameter. Changing the diameter will cause your speedometer to read either faster or slower than your actual speed.
Odometer Accuracy: Similar to the speedometer, your odometer will also be affected, leading to inaccurate mileage readings.
ABS and Traction Control Systems: Modern vehicles rely on wheel speed sensors for their Anti-lock Braking System (ABS) and Traction Control System (TCS). Significant changes in tire diameter can confuse these systems, potentially leading to malfunction or reduced effectiveness.
Fender Clearance: Larger tires might rub against your vehicle's fenders or suspension components, especially during turns or over bumps.
Gear Ratios: A larger tire diameter effectively "raises" your gear ratio, which can impact acceleration and fuel economy. Smaller tires will have the opposite effect.
How to Read Tire Sizes (e.g., 205/55R16)
A tire size designation provides three key pieces of information:
Section Width (205): This is the width of the tire in millimeters, measured from sidewall to sidewall. In our example, it's 205mm.
Aspect Ratio (55): This number represents the sidewall height as a percentage of the section width. So, a 55 aspect ratio means the sidewall height is 55% of the 205mm section width.
Rim Diameter (16): This is the diameter of the wheel (rim) in inches that the tire is designed to fit. In our example, it's a 16-inch rim.
How the Calculator Works
Our 1010 Tire Calculator takes these three values for both your original and new tire sizes and performs the following calculations:
Sidewall Height: It first calculates the sidewall height for each tire by multiplying the section width by the aspect ratio percentage.
Overall Diameter (mm): It then adds twice the sidewall height to the rim diameter (converted to millimeters) to get the total diameter of the tire in millimeters.
Overall Diameter (inches): This millimeter diameter is then converted to inches for easier comparison.
Diameter Difference: The difference in overall diameter between the new and original tires is calculated.
Percentage Difference: This is the most critical metric. It shows the percentage change in diameter. Generally, a difference of within 1% to 3% is considered acceptable to minimize speedometer error and avoid other issues. Differences greater than 3% can lead to noticeable speedometer inaccuracies and potential problems with vehicle systems.
Speedometer Error: The calculator estimates how much your speedometer will be off at a given speed (e.g., 60 mph) if you switch to the new tires.
Example Scenario:
Let's say your original tires are 205/55R16, and you're considering new tires that are 225/45R17.
Original Tire (205/55R16):
Section Width: 205 mm
Aspect Ratio: 55%
Rim Diameter: 16 inches
Calculated Overall Diameter: Approximately 24.88 inches
New Tire (225/45R17):
Section Width: 225 mm
Aspect Ratio: 45%
Rim Diameter: 17 inches
Calculated Overall Diameter: Approximately 25.00 inches
Using the calculator, you would find:
Diameter Difference: +0.12 inches
Percentage Difference: +0.48%
Speedometer Error (at 60 mph): Your speedometer would read approximately 0.29 mph slower than your actual speed (i.e., when your speedo reads 60 mph, you're actually going ~60.29 mph).
In this example, a 0.48% difference is well within the acceptable 1-3% range, indicating a good match for a tire size upgrade.
Always consult with a professional tire installer to confirm fitment and any potential issues before making a tire size change.