Wheel Rim Size Calculator
body {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
background-color: #f4f7f6;
color: #333;
line-height: 1.6;
margin: 0;
padding: 20px;
}
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max-width: 900px;
margin: 30px auto;
background-color: #ffffff;
border-radius: 8px;
box-shadow: 0 4px 15px rgba(0, 74, 153, 0.1);
padding: 30px;
display: flex;
flex-wrap: wrap;
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.input-group select {
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box-sizing: border-box; /* Ensures padding doesn't affect width */
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transition: background-color 0.3s ease;
width: 100%;
margin-top: 10px;
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button:hover {
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#result {
margin-top: 25px;
padding: 20px;
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color: #004a99;
margin-top: 25px;
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.article-section p, .article-section ul {
margin-bottom: 15px;
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.article-section ul {
padding-left: 25px;
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.article-section li {
margin-bottom: 8px;
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@media (max-width: 768px) {
.calculator-container {
flex-direction: column;
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.input-section, .output-section, .article-section {
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}
New Tire Size Recommendation
Please enter your current rim diameter, tire profile, and desired new rim diameter.
Understanding Wheel Rim Size and Tire Fitment
Changing your vehicle's wheel rim size is a popular modification for aesthetic appeal, performance enhancement, or accommodating larger brakes. However, it's crucial to do this correctly to ensure your speedometer remains accurate, your car handles safely, and there are no mechanical issues.
The Math Behind Tire Size Changes
The key to maintaining proper fitment when changing rim size is to keep the overall tire diameter (rim + two tire sidewalls) as close as possible to the original. This ensures that the rolling circumference of the tire doesn't significantly change, which would throw off your speedometer, odometer, and potentially affect your car's transmission and ABS systems.
The calculation works by adjusting the tire's sidewall height (profile) proportionally to the change in rim diameter.
Formula Breakdown:
- Original Overall Tire Diameter: (Current Rim Diameter) + 2 * (Current Rim Diameter * (Tire Profile / 100))
- Target New Tire Diameter: Same as Original Overall Tire Diameter
- New Tire Sidewall Height: (Target New Tire Diameter – New Rim Diameter) / 2
- New Tire Profile (%): (New Tire Sidewall Height / New Rim Diameter) * 100
This calculator estimates the ideal tire profile percentage to maintain a similar overall tire diameter when you change your rim size. Always consult with a professional tire fitter or refer to your vehicle manufacturer's specifications for precise recommendations and to confirm clearance.
Important Considerations:
- Speedometer Accuracy: A significant change in overall tire diameter will make your speedometer read incorrectly (e.g., if the tires are larger, your speed will be lower than indicated).
- Clearance: Ensure the new wheel and tire combination fits within your wheel wells without rubbing against the fenders, suspension components, or brake calipers.
- Load Rating: The new tires must have a load index sufficient to carry the weight of your vehicle.
- Speed Rating: Ensure the new tires are rated for the speeds your vehicle is capable of reaching.
- Ride Comfort: Lower profile tires (larger rims, shorter sidewalls) generally result in a firmer ride and can be more susceptible to damage from potholes.
This calculator provides a starting point for your tire size selection. Always verify fitment and consult professionals.
function calculateRimSize() {
var currentRimDiameter = parseFloat(document.getElementById("currentRimDiameter").value);
var tireProfile = parseFloat(document.getElementById("tireProfile").value);
var newRimDiameter = parseFloat(document.getElementById("newRimDiameter").value);
var resultDiv = document.getElementById("result");
if (isNaN(currentRimDiameter) || isNaN(tireProfile) || isNaN(newRimDiameter) ||
currentRimDiameter <= 0 || tireProfile <= 0 || newRimDiameter <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Calculate original overall tire diameter
var originalTireSidewallHeight = currentRimDiameter * (tireProfile / 100);
var originalOverallTireDiameter = currentRimDiameter + 2 * originalTireSidewallHeight;
// Calculate new tire profile percentage
var newTireSidewallHeight = (originalOverallTireDiameter – newRimDiameter) / 2;
var newTireProfile = (newTireSidewallHeight / newRimDiameter) * 100;
if (newTireProfile < 0) {
resultDiv.innerHTML = "The desired new rim diameter is too large for the original tire profile. Please choose a smaller rim or larger tire profile.";
return;
}
// Display results
var roundedNewTireProfile = newTireProfile.toFixed(1);
var roundedOriginalOverallDiameter = originalOverallTireDiameter.toFixed(2);
var roundedNewOverallDiameter = (newRimDiameter + 2 * newTireSidewallHeight).toFixed(2);
resultDiv.innerHTML = "Original Overall Diameter:
" + roundedOriginalOverallDiameter + " inches" +
"Recommended New Tire Profile:
" + roundedNewTireProfile + "%" +
"Approximate New Overall Diameter:
" + roundedNewOverallDiameter + " inches";
}