Motorcycle Tire Size Calculator | Dimensions & Specs
Calculate motorcycle tire dimensions: overall diameter, sidewall height, circumference & revs per mile. Works for sport bikes, cruisers, and touring bikes. Free tool.
Understanding your motorcycle tire dimensions is crucial for fitment, handling, and safety. This calculator takes the standard metric inputs for motorcycle tires (width in mm, aspect ratio as a percentage, and rim diameter in inches) and calculates the overall diameter, sidewall height, section width (converted to inches), circumference, and revolutions per mile/km. Essential for comparing sizes or planning upgrades for various motorcycle types like sport bikes, cruisers, and touring bikes. Always confirm calculated dimensions with manufacturer specifications.
- Enter the Tire Width in millimeters (e.g., 120 for a 120/70R17 tire).
- Input the Aspect Ratio as a percentage (e.g., 70 for a 120/70R17 tire).
- Enter the Rim Diameter in inches (e.g., 17 for a 120/70R17 tire).
- Click 'Calculate Dimensions'.
- The results will show key tire dimensions in both metric and imperial units.
What does a motorcycle tire size like 120/70R17 mean?
The three numbers decode as: 120 = section width in millimetres, 70 = aspect ratio (sidewall height is 70% of 120mm = 84mm), R = radial construction, 17 = rim diameter in inches. This is the universal metric sizing system used on modern motorcycles. The same formula applies to car tires.
Can I fit a wider rear tire on my motorcycle?
Often yes, but within limits. You need to check swingarm clearance, chain line (on chain-drive bikes), belt or shaft clearance, and fender/hugger clearance. Going one size wider (e.g., 180 to 190) is usually fine on most naked bikes and cruisers. Going two or more sizes wider typically requires aftermarket swingarm modifications. Always verify against your specific model.
How does a tire size change affect my speedometer?
Like cars, a larger overall diameter means the wheel travels further per revolution, so the speedometer reads lower than actual speed. A 2% taller tire makes your speedo under-read by 2%. Use the overall diameter output from this calculator and compare it to your OEM spec to quantify the difference.
What is the standard front tire size for sport bikes?
120/70R17 is the near-universal front tire size for 600cc–1000cc sport bikes. The rear varies by class: 180/55R17 for 600cc supersports, 190/50R17 or 190/55R17 for litre-class bikes. Cruisers and touring bikes use wider, lower-speed-rated sizes with higher aspect ratios (e.g., 130/90B16, MH90-21).
How do I convert an old alphanumeric motorcycle tire size to modern metric?
Older alphanumeric sizes (e.g., MT90B16, MH90-21) used a letter for width and a number for aspect ratio. MT90B16 ≈ 130/90B16 in modern metric (MT ≈ 130mm wide, 90 = 90% aspect ratio, B = bias belted, 16 = rim diameter). For precise conversions, look up the ISO equivalents in a tire brand fitment guide.
All tools and information provided on TireCalculatorHub are for informational purposes only. Calculated dimensions are theoretical. Always verify actual tire dimensions with the manufacturer and ensure compatibility with your motorcycle.
TireCalculatorHub is not liable for any damages or issues arising from the use of information or tools on this website.