Calculate the essential parameters for your 1010 tires.
Results
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Section Width:— mm
Sidewall Height:— mm
Overall Diameter:— inches
Circumference:— mm
Revolutions per Mile:—
Speedometer Error (if larger):— %
Understanding Your 1010 Tire Data
The numbers on your tire's sidewall, often presented in a format like "205/55R16", contain crucial information about the tire's dimensions and performance characteristics. This calculator helps you decipher these numbers and understand how they relate to your vehicle's speedometer and overall tire dynamics.
What Each Input Means:
Tire Width (mm): This is the first number in the tire code (e.g., 205 in 205/55R16). It represents the width of the tire from sidewall to sidewall in millimeters.
Aspect Ratio (%): This is the second number (e.g., 55 in 205/55R16). It indicates the ratio of the tire's sidewall height to its width, expressed as a percentage. A 55 aspect ratio means the sidewall height is 55% of the tire's width.
Wheel Diameter (inches): This is the last number in the tire code (e.g., 16 in 205/55R16). It's the diameter of the wheel rim that the tire is designed to fit, measured in inches.
Tire Pressure (PSI): This is the recommended air pressure for your tire, measured in pounds per square inch. While not directly used in dimension calculations, it's critical for optimal tire performance, safety, and longevity.
How the Calculations Work:
The calculator uses standard tire sizing formulas to derive key metrics:
Section Width: This is essentially the same as the 'Tire Width (mm)' input.
Sidewall Height (mm): Calculated as (Tire Width (mm) * Aspect Ratio (%)) / 100.
Overall Diameter (inches): Calculated as Wheel Diameter (inches) + (2 * Sidewall Height (mm) / 25.4). We convert the sidewall height from mm to inches by dividing by 25.4 (since 1 inch = 25.4 mm).
Circumference (mm): Calculated using the formula for the circumference of a circle: Overall Diameter (inches) * 25.4 * π.
Revolutions per Mile: This is calculated by dividing the total distance of a mile (in mm) by the tire's circumference. 1 mile = 63,360 inches = 1,609,344 mm. So, 1,609,344 mm / Circumference (mm).
Speedometer Error: This calculation compares the actual speed your car is traveling (based on tire revolutions) to the speed indicated by your speedometer. If you've installed tires with a significantly different overall diameter than the original equipment, your speedometer might be inaccurate. This calculator estimates the percentage error if the newly calculated diameter is larger than a hypothetical standard. A positive percentage indicates the speedometer will read higher than actual speed (e.g., speedometer shows 65 mph, but you're only going 60 mph).
Why Use This Calculator?
This calculator is invaluable for:
Understanding Tire Upgrades: If you're considering larger wheels or tires with different aspect ratios, this tool helps you predict the impact on your car's speedometer accuracy and overall tire size.
Performance Tuning: Knowledge of tire dimensions can influence handling, gearing ratios, and odometer readings.
Ensuring Correct Fitment: While this calculator focuses on dimensions, it helps you grasp the physical size implications of different tire choices.
Always consult with a professional tire specialist or your vehicle's manual for specific fitment recommendations and safety guidelines.
function calculateTireMetrics() {
var tireWidth = parseFloat(document.getElementById("tireWidth").value);
var aspectRatio = parseFloat(document.getElementById("aspectRatio").value);
var wheelDiameter = parseFloat(document.getElementById("wheelDiameter").value);
var tirePressurePSI = parseFloat(document.getElementById("tirePressurePSI").value);
var resultValueElement = document.getElementById("result-value");
var sectionWidthValueElement = document.getElementById("sectionWidthValue");
var sidewallHeightValueElement = document.getElementById("sidewallHeightValue");
var overallDiameterValueElement = document.getElementById("overallDiameterValue");
var circumferenceValueElement = document.getElementById("circumferenceValue");
var revolutionsPerMileValueElement = document.getElementById("revolutionsPerMileValue");
var speedometerErrorValueElement = document.getElementById("speedometerErrorValue");
// Clear previous results
resultValueElement.innerText = "–";
sectionWidthValueElement.innerText = "–";
sidewallHeightValueElement.innerText = "–";
overallDiameterValueElement.innerText = "–";
circumferenceValueElement.innerText = "–";
revolutionsPerMileValueElement.innerText = "–";
speedometerErrorValueElement.innerText = "–";
// Input validation
if (isNaN(tireWidth) || isNaN(aspectRatio) || isNaN(wheelDiameter) || isNaN(tirePressurePSI) ||
tireWidth <= 0 || aspectRatio <= 0 || wheelDiameter <= 0 || tirePressurePSI referenceDiameter_205_55_16_inches) {
// If the new tire is larger, the car travels further per revolution than the speedometer thinks.
// Speedometer will read higher than actual speed.
speedometerErrorPercent = ((overallDiameterInches – referenceDiameter_205_55_16_inches) / referenceDiameter_205_55_16_inches) * 100;
} else if (overallDiameterInches 0) {
speedometerErrorValueElement.innerText = "+" + speedometerErrorPercent.toFixed(2) + "% (Speedo reads high)";
} else if (speedometerErrorPercent < 0) {
speedometerErrorValueElement.innerText = speedometerErrorPercent.toFixed(2) + "% (Speedo reads low)";
} else {
speedometerErrorValueElement.innerText = "0.00% (No error relative to reference)";
}
}