.tire-speed-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;
box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}
.tire-speed-calculator-container h2 {
color: #333;
text-align: center;
margin-bottom: 20px;
}
.tire-speed-calculator-container .input-group {
display: flex;
flex-wrap: wrap;
gap: 15px;
margin-bottom: 20px;
justify-content: space-between;
}
.tire-speed-calculator-container .input-field {
flex: 1 1 calc(33% – 15px); /* Adjust for 3 columns */
min-width: 150px;
display: flex;
flex-direction: column;
}
.tire-speed-calculator-container label {
margin-bottom: 5px;
font-weight: bold;
color: #555;
font-size: 0.9em;
}
.tire-speed-calculator-container input[type="number"] {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1em;
width: 100%;
box-sizing: border-box;
}
.tire-speed-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;
transition: background-color 0.3s ease;
margin-top: 10px;
}
.tire-speed-calculator-container button:hover {
background-color: #0056b3;
}
.tire-speed-calculator-container .results {
margin-top: 25px;
padding: 15px;
border: 1px solid #e0e0e0;
border-radius: 6px;
background-color: #eef;
}
.tire-speed-calculator-container .results h3 {
color: #333;
margin-top: 0;
margin-bottom: 15px;
text-align: center;
}
.tire-speed-calculator-container .results p {
margin: 8px 0;
font-size: 1em;
color: #444;
display: flex;
justify-content: space-between;
align-items: center;
}
.tire-speed-calculator-container .results p strong {
color: #000;
flex-basis: 60%;
}
.tire-speed-calculator-container .results p span {
flex-basis: 40%;
text-align: right;
font-weight: normal;
}
.tire-speed-calculator-container .results .warning {
color: #d9534f;
font-weight: bold;
text-align: center;
margin-top: 15px;
}
.tire-speed-calculator-container .section-title {
background-color: #e0e0e0;
padding: 8px 15px;
border-radius: 4px;
margin-bottom: 15px;
font-weight: bold;
color: #333;
text-align: center;
width: 100%;
box-sizing: border-box;
}
@media (max-width: 600px) {
.tire-speed-calculator-container .input-field {
flex: 1 1 100%; /* Stack inputs on small screens */
}
}
function calculateTireDiameter(sectionWidth, aspectRatio, wheelDiameter) {
// Sidewall height in mm = Section Width * (Aspect Ratio / 100)
// Sidewall height in inches = (Section Width * (Aspect Ratio / 100)) / 25.4
// Total diameter in inches = (Sidewall height in inches * 2) + Wheel Diameter
var sidewallHeightInches = (sectionWidth * (aspectRatio / 100)) / 25.4;
var totalDiameter = (sidewallHeightInches * 2) + wheelDiameter;
return totalDiameter;
}
function calculateTireSpeedDifference() {
// Get original tire inputs
var originalSectionWidth = parseFloat(document.getElementById("originalSectionWidth").value);
var originalAspectRatio = parseFloat(document.getElementById("originalAspectRatio").value);
var originalWheelDiameter = parseFloat(document.getElementById("originalWheelDiameter").value);
// Get new tire inputs
var newSectionWidth = parseFloat(document.getElementById("newSectionWidth").value);
var newAspectRatio = parseFloat(document.getElementById("newAspectRatio").value);
var newWheelDiameter = parseFloat(document.getElementById("newWheelDiameter").value);
// Get speedometer reading
var speedometerReading = parseFloat(document.getElementById("speedometerReading").value);
// Validate inputs
if (isNaN(originalSectionWidth) || isNaN(originalAspectRatio) || isNaN(originalWheelDiameter) ||
isNaN(newSectionWidth) || isNaN(newAspectRatio) || isNaN(newWheelDiameter) || isNaN(speedometerReading) ||
originalSectionWidth <= 0 || originalAspectRatio <= 0 || originalWheelDiameter <= 0 ||
newSectionWidth <= 0 || newAspectRatio <= 0 || newWheelDiameter <= 0 || speedometerReading speedometer reading. Error is positive.
// If new tire is smaller, actual speed 0 ? "mph/km/h" : "");
var diameterWarning = document.getElementById("diameterWarning");
if (Math.abs(diameterDifference) > 3) {
diameterWarning.innerText = "Warning: A diameter difference of " + diameterDifference.toFixed(2) + "% is generally not recommended and can cause issues with speedometer, odometer, ABS, and traction control systems.";
diameterWarning.style.display = "block";
} else {
diameterWarning.style.display = "none";
}
document.getElementById("tireSpeedResult").style.display = "block";
}
Understanding Tire Size and Its Impact on Speed
Changing your vehicle's tire size might seem like a simple modification for aesthetics or performance, but it can have significant implications for your vehicle's speedometer accuracy, odometer readings, and even safety systems like ABS and traction control. This calculator helps you understand these impacts by comparing your original tire specifications to new ones.
How Tire Size Affects Speedometer Readings
Your vehicle's speedometer is calibrated from the factory based on the original tire size. It measures how many times your wheels rotate to determine your speed. When you change the tire's overall diameter, the number of rotations required to cover a certain distance changes:
- Larger Diameter Tires: A larger tire covers more ground with each rotation. If your speedometer is still calibrated for smaller tires, it will read a speed lower than your actual speed. For example, if your speedometer shows 60 mph, you might actually be traveling at 63 mph.
- Smaller Diameter Tires: A smaller tire covers less ground with each rotation. Your speedometer will read a speed higher than your actual speed. If your speedometer shows 60 mph, you might actually be traveling at 57 mph.
This discrepancy is known as "speedometer error." A small error might be negligible, but a significant one can lead to speeding tickets, inaccurate fuel economy calculations, and incorrect mileage readings on your odometer.
Key Tire Specifications Explained
Tire sizes are typically expressed in a format like "205/55R16". Let's break down what these numbers mean:
- Section Width (e.g., 205): This is the width of the tire in millimeters, measured from sidewall to sidewall.
- Aspect Ratio (e.g., 55): This is the height of the tire's sidewall as a percentage of its section width. So, for a 205/55 tire, the sidewall height is 55% of 205mm.
- Wheel Diameter (e.g., 16): This is the diameter of the wheel (rim) in inches that the tire is designed to fit.
The combination of these three numbers determines the overall diameter and circumference of the tire, which directly impacts how many revolutions it makes per mile.
Beyond Speedometer Error: Other Impacts
While speedometer accuracy is a primary concern, changing tire size can also affect:
- Odometer Accuracy: Your odometer will also be inaccurate, leading to incorrect mileage readings, which can affect resale value and maintenance schedules.
- ABS and Traction Control Systems: These systems rely on accurate wheel speed sensor readings. Significant tire size differences can confuse these systems, potentially leading to malfunction or reduced effectiveness.
- Gear Ratios: Changing tire diameter effectively changes your final drive ratio. Larger tires can make your vehicle feel sluggish (like having taller gears) and potentially reduce acceleration, while smaller tires can improve acceleration but might increase engine RPM at highway speeds, affecting fuel economy.
- Fender Clearance: Larger tires might rub against your vehicle's fenders or suspension components, especially during turns or over bumps.
- Ride Comfort and Handling: Changes in sidewall height can alter ride comfort and handling characteristics.
Using the Calculator
To use this calculator, simply input the specifications for your current (original) tires and the new tires you are considering. Then, enter your current speedometer reading. The calculator will provide:
- The overall diameter of both tire setups.
- The percentage difference in diameter, circumference, and revolutions per mile.
- The calculated speedometer error.
- Your actual speed when your speedometer shows the entered reading.
It's generally recommended to keep the overall tire diameter difference within +/- 3% to avoid significant issues. Always consult with a professional tire specialist before making significant changes to your vehicle's tire size.