The overall diameter directly affects your speedometer and odometer accuracy.
Differences greater than 3% (up or down) are generally not recommended without recalibration.
`;
}/**
* Main calculation handler function.
*/
function handleCalculate() {
resultsContainer.innerHTML = ''; // Clear previous results
const originalSize = originalInput.value.trim().toUpperCase();
const newSize = newInput.value.trim().toUpperCase();if (!originalSize || !newSize) {
renderError("Please enter both the Original and New tire sizes in the format W/ARXX (e.g., 205/55R16).");
return;
}const parsedOriginal = parseTireSize(originalSize);
const parsedNew = parseTireSize(newSize);if (!parsedOriginal.valid) {
renderError(`Original size "${originalSize}" is invalid. Use the format 205/55R16.`);
return;
}
if (!parsedNew.valid) {
renderError(`New size "${newSize}" is invalid. Use the format 205/55R16.`);
return;
}try {
const originalDims = calculateDimensions(parsedOriginal);
const newDims = calculateDimensions(parsedNew);renderResults(originalDims, newDims);
} catch (e) {
console.error("Calculation Error:", e);
renderError(`An unexpected error occurred during calculation. Ensure all inputs are numerical.`);
}
}// Attach event listeners
calculateButton.addEventListener('click', handleCalculate);
originalInput.addEventListener('keydown', (event) => {
if (event.key === 'Enter') handleCalculate();
});
newInput.addEventListener('keydown', (event) => {
if (event.key === 'Enter') handleCalculate();
});// Optional: Pre-fill with common sizes on load
document.addEventListener('DOMContentLoaded', () => {
originalInput.value = '205/55R16';
newInput.value = '225/45R17';
});
Tire Size Calculator: Compare Dimensions and Check Speedometer Error
The Tire Size Calculator is an indispensable tool for comparing two different tire sizes—your current factory-installed size and a potential replacement or upgrade size. This is crucial for maintaining safety, accuracy, and vehicle integrity when purchasing new tires or custom wheels.
Our calculator analyzes the technical specifications of both tires and provides a clear breakdown of the difference in height, circumference, and, most importantly, the resulting speedometer error.
Decoding the Tire Label
Every tire size is represented by a sequence of numbers and letters (e.g., P225/50R17). Understanding these three core dimensions is key to using the calculator:
Component
Example Value
Definition
Unit
Tire Width (A)
225
The width of the tire sidewall, measured in millimeters.
Millimeters ($\text{mm}$)
Aspect Ratio (B)
50
The height of the sidewall as a percentage of the width (A).
Percentage ($\%$)
Rim Diameter (C)
17
The diameter of the wheel (rim) the tire fits on.
Inches ($\text{in}$)
The Impact of Changing Tire Size
Changing your tire size, even slightly, affects your vehicle’s performance and onboard computer systems:
Speedometer Error: This is the most critical factor. If the new tire’s circumference is larger than the original, your speedometer will read slower than your actual speed, leading to unintended speeding. If the circumference is smaller, the speedometer will read faster.
Gear Ratio and Acceleration: A larger tire circumference increases the effective final drive ratio, leading to slower acceleration but potentially better fuel economy (though the speedometer inaccuracy must be accounted for).
Physical Fit (Clearance): The difference in overall diameter and width determines if the new tire will rub against the wheel wells or suspension components, posing a major safety hazard.
The calculator provides the Overall Diameter Difference (%) to show you the severity of the change. A difference greater than $3\%$ is generally discouraged by experts.