.wheel-fitment-calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 10px;
background-color: #f9f9f9;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
color: #333;
}
.wheel-fitment-calculator-container h2 {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 1.8em;
border-bottom: 2px solid #3498db;
padding-bottom: 10px;
}
.wheel-fitment-calculator-container .input-group {
margin-bottom: 18px;
display: flex;
flex-wrap: wrap;
align-items: center;
gap: 10px;
}
.wheel-fitment-calculator-container .input-group label {
flex: 1 1 180px;
font-weight: bold;
color: #555;
font-size: 0.95em;
}
.wheel-fitment-calculator-container .input-group input[type="number"] {
flex: 2 1 250px;
padding: 10px 12px;
border: 1px solid #ccc;
border-radius: 5px;
font-size: 1em;
box-sizing: border-box;
transition: border-color 0.3s ease;
}
.wheel-fitment-calculator-container .input-group input[type="number"]:focus {
border-color: #3498db;
outline: none;
box-shadow: 0 0 5px rgba(52, 152, 219, 0.4);
}
.wheel-fitment-calculator-container button {
display: block;
width: 100%;
padding: 12px 20px;
background-color: #3498db;
color: white;
border: none;
border-radius: 5px;
font-size: 1.1em;
font-weight: bold;
cursor: pointer;
transition: background-color 0.3s ease, transform 0.2s ease;
margin-top: 25px;
}
.wheel-fitment-calculator-container button:hover {
background-color: #2980b9;
transform: translateY(-2px);
}
.wheel-fitment-calculator-container .result-section {
margin-top: 30px;
padding-top: 25px;
border-top: 1px solid #eee;
}
.wheel-fitment-calculator-container .result-section h3 {
color: #2c3e50;
margin-bottom: 15px;
font-size: 1.5em;
text-align: center;
}
.wheel-fitment-calculator-container .result-item {
background-color: #eaf6ff;
border: 1px solid #cce7ff;
border-radius: 8px;
padding: 12px 18px;
margin-bottom: 10px;
display: flex;
justify-content: space-between;
align-items: center;
font-size: 1.05em;
color: #2c3e50;
}
.wheel-fitment-calculator-container .result-item strong {
color: #34495e;
}
.wheel-fitment-calculator-container .result-item span {
font-weight: normal;
color: #0056b3;
}
.wheel-fitment-calculator-container .section-title {
background-color: #ecf0f1;
padding: 8px 15px;
border-radius: 5px;
margin-top: 20px;
margin-bottom: 15px;
font-weight: bold;
color: #34495e;
font-size: 1.1em;
text-align: center;
}
.wheel-fitment-calculator-container .error-message {
color: #e74c3c;
background-color: #fdeded;
border: 1px solid #fbc4c4;
padding: 10px;
border-radius: 5px;
margin-top: 15px;
text-align: center;
font-weight: bold;
}
@media (max-width: 600px) {
.wheel-fitment-calculator-container .input-group label,
.wheel-fitment-calculator-container .input-group input[type="number"] {
flex: 1 1 100%;
}
}
function calculateWheelFitment() {
var currentWheelWidth = parseFloat(document.getElementById('currentWheelWidth').value);
var currentWheelOffset = parseFloat(document.getElementById('currentWheelOffset').value);
var currentTireWidth = parseFloat(document.getElementById('currentTireWidth').value);
var currentTireAspect = parseFloat(document.getElementById('currentTireAspect').value);
var currentWheelDiameter = parseFloat(document.getElementById('currentWheelDiameter').value);
var newWheelWidth = parseFloat(document.getElementById('newWheelWidth').value);
var newWheelOffset = parseFloat(document.getElementById('newWheelOffset').value);
var newTireWidth = parseFloat(document.getElementById('newTireWidth').value);
var newTireAspect = parseFloat(document.getElementById('newTireAspect').value);
var newWheelDiameter = parseFloat(document.getElementById('newWheelDiameter').value);
var errorMessage = document.getElementById('errorMessage');
var resultContent = document.getElementById('resultContent');
// Input validation
if (isNaN(currentWheelWidth) || isNaN(currentWheelOffset) || isNaN(currentTireWidth) || isNaN(currentTireAspect) || isNaN(currentWheelDiameter) ||
isNaN(newWheelWidth) || isNaN(newWheelOffset) || isNaN(newTireWidth) || isNaN(newTireAspect) || isNaN(newWheelDiameter) ||
currentWheelWidth <= 0 || currentTireWidth <= 0 || currentTireAspect <= 0 || currentWheelDiameter <= 0 ||
newWheelWidth <= 0 || newTireWidth <= 0 || newTireAspect <= 0 || newWheelDiameter 0) {
speedometerError = ((newOverallTireDiameter – currentOverallTireDiameter) / currentOverallTireDiameter) * 100;
}
// — Combined Tire & Wheel Clearance —
// Assuming tire width change impacts inner/outer clearance equally relative to the wheel's center line
var tireWidthDifference = newTireWidth – currentTireWidth;
var innerTireClearanceChange = innerWheelClearanceChange + (tireWidthDifference / 2);
var outerTireClearanceChange = outerWheelPositionChange + (tireWidthDifference / 2);
// Display results
document.getElementById('innerWheelClearanceChange').textContent = innerWheelClearanceChange.toFixed(2) + ' mm';
document.getElementById('outerWheelPositionChange').textContent = outerWheelPositionChange.toFixed(2) + ' mm';
document.getElementById('tireDiameterChange').textContent = tireDiameterChange.toFixed(2) + ' mm';
document.getElementById('sidewallHeightChange').textContent = sidewallHeightChange.toFixed(2) + ' mm';
document.getElementById('speedometerError').textContent = speedometerError.toFixed(2) + ' %';
document.getElementById('innerTireClearanceChange').textContent = innerTireClearanceChange.toFixed(2) + ' mm';
document.getElementById('outerTireClearanceChange').textContent = outerTireClearanceChange.toFixed(2) + ' mm';
}
// Calculate on page load with default values
window.onload = calculateWheelFitment;
Wheel & Tire Fitment Calculator
Current Setup
New Setup
Fitment Analysis
Inner Wheel Clearance Change: 0.00 mm
Outer Wheel Position Change: 0.00 mm
Overall Tire Diameter Change: 0.00 mm
Tire Sidewall Height Change: 0.00 mm
Speedometer Error: 0.00 %
Inner Tire Clearance Change: 0.00 mm
Outer Tire Clearance Change: 0.00 mm
Understanding Wheel Fitment: A Comprehensive Guide
Choosing the right wheels and tires for your vehicle is crucial not just for aesthetics, but also for performance, safety, and avoiding costly modifications. The term "wheel fitment" refers to how a wheel and tire combination sits within your vehicle's fender wells and interacts with suspension components. Getting it right ensures proper clearance, optimal handling, and a correct speedometer reading.
Key Wheel & Tire Parameters Explained:
- Wheel Width (inches): This is the measurement from bead seat to bead seat on the wheel. A wider wheel can accommodate a wider tire, but too wide might cause rubbing.
- Wheel Offset (mm): Offset is the distance from the wheel's mounting surface to the centerline of the wheel.
- Positive Offset: The mounting surface is towards the front (outboard) of the wheel's centerline. This pulls the wheel further into the fender.
- Negative Offset: The mounting surface is towards the back (inboard) of the wheel's centerline. This pushes the wheel further out from the fender, creating a "deeper dish" look.
- Zero Offset: The mounting surface is exactly at the wheel's centerline.
- Tire Width (mm): The first number in a tire size (e.g., 225 in 225/40R18) indicates the tire's section width in millimeters. This is the width of the tire from sidewall to sidewall.
- Tire Aspect Ratio (%): The second number (e.g., 40 in 225/40R18) is the sidewall height as a percentage of the tire's width. A 40% aspect ratio for a 225mm wide tire means the sidewall height is 40% of 225mm.
- Wheel Diameter (inches): The third number (e.g., 18 in 225/40R18) is the diameter of the wheel in inches. This determines the overall size of the wheel and affects tire sidewall height.
Why Use a Wheel Fitment Calculator?
Our Wheel Fitment Calculator helps you understand the precise changes when you switch from your current wheel and tire setup to a new one. It provides critical measurements:
- Inner Wheel Clearance Change: How much closer or further the inner edge of your new wheel will be to your suspension components (struts, control arms, etc.). A positive value means it moves further in, potentially causing rubbing.
- Outer Wheel Position Change: How much further out or in the outer edge of your new wheel will sit relative to your fender. A positive value means it moves further out, potentially causing fender rubbing or requiring fender rolling.
- Overall Tire Diameter Change: The difference in the total height of your new tire compared to your old one. Significant changes can affect ride height, gearing, and speedometer accuracy.
- Tire Sidewall Height Change: The difference in the height of the tire's sidewall. This impacts ride comfort and the visual "meatiness" of the tire.
- Speedometer Error: A crucial calculation that tells you how much your speedometer reading will be off due to a change in overall tire diameter. If your new tires are larger, your speedometer will read lower than your actual speed, and vice-versa.
- Inner/Outer Tire Clearance Change: These combine the wheel position changes with the change in tire width to give you a more complete picture of how the tire itself will sit relative to your vehicle's inner and outer clearances.
Practical Examples:
Let's consider a common scenario:
Scenario 1: Going Wider and More Aggressive
- Current: 18×8.0″ wheel, +35mm offset, 225/40R18 tire
- New: 18×9.0″ wheel, +30mm offset, 245/35R18 tire
Using the calculator, you might find:
- Inner Wheel Clearance Change: -1.35 mm (moves slightly away from suspension)
- Outer Wheel Position Change: +11.35 mm (moves significantly further out, potentially requiring fender work)
- Overall Tire Diameter Change: -10.5 mm (slightly smaller tire)
- Speedometer Error: +1.5% (when your speedometer reads 60 mph, you're actually going 59.1 mph)
This example shows that while the inner clearance might be fine, the outer position change is substantial, and the speedometer will be slightly off.
Scenario 2: Maintaining Diameter, Changing Aesthetics
- Current: 17×7.5″ wheel, +45mm offset, 215/45R17 tire
- New: 18×8.0″ wheel, +40mm offset, 225/40R18 tire
The calculator would reveal:
- Inner Wheel Clearance Change: -1.35 mm (moves slightly away)
- Outer Wheel Position Change: +8.65 mm (moves further out)
- Overall Tire Diameter Change: +0.1 mm (virtually identical diameter, good for speedometer)
- Speedometer Error: -0.01% (negligible error)
In this case, the overall tire diameter is maintained, which is excellent for speedometer accuracy, but the new wheel will still sit further out, requiring a check for fender clearance.
Important Considerations:
- Fender Clearance: Always check for potential rubbing against the fender lip, especially when turning or under suspension compression.
- Suspension Clearance: Ensure the inner edge of the wheel and tire clears struts, control arms, and brake lines.
- Brake Clearance: Larger wheels might clear big brake kits, but the wheel's spoke design and offset can still cause issues.
- Steering Lock: Test full lock-to-lock steering to ensure no rubbing occurs.
- Load Rating: Ensure new tires have an adequate load rating for your vehicle.
- Local Laws: Some regions have laws regarding how far wheels can protrude from fenders.
Always double-check measurements on your specific vehicle, as manufacturing tolerances and aftermarket suspension components can influence actual fitment. This calculator provides a powerful starting point for making informed decisions about your wheel and tire upgrades.