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Spare Tire Compatibility Calculator | Diameter Difference Check

Compare spare tire diameter with primary tires. Crucial for AWD/4WD safety and drivetrain health. Check for significant differences.

Enter specs for your primary and spare tires to check diameter compatibility.

Primary Tire (Normal Use)

Spare Tire

About This Calculator

Using a spare tire that has a significantly different overall diameter from your vehicle's primary tires can lead to serious issues, especially for All-Wheel Drive (AWD) and Four-Wheel Drive (4WD) vehicles. Such a mismatch can strain or damage the drivetrain components like differentials and transfer cases. It can also interfere with Anti-lock Braking Systems (ABS), traction control, and stability control systems, compromising vehicle safety.

Most vehicle manufacturers recommend that the overall diameter of all tires, including a temporary spare if used on a driven axle, be within a very small tolerance (often 1-3%) of each other. This calculator helps you compare the overall diameters of your primary tires and your spare tire, clearly showing the percentage difference. This allows you to understand the potential risks and make informed decisions about using your spare. Always remember to adhere to any speed and distance limitations specified for your spare tire, especially if it's a compact or 'donut' spare.

How to Use This Calculator
  1. Enter the P-Metric specifications (Width, Aspect Ratio, Rim Diameter) for your vehicle's Primary Tires (the ones normally used).
  2. Enter the P-Metric specifications for your Spare Tire. If it's a compact spare, its size will still be on its sidewall.
  3. Click the "Compare Diameters" button.
  4. The results will display the overall diameters for both tires, the absolute difference in millimeters and inches, and the percentage difference.
  5. Pay close attention to the percentage difference and any warnings, especially if your vehicle is AWD or 4WD.
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Disclaimer

All tools and information provided on TireCalculatorHub are for informational purposes only. Always consult your vehicle manufacturer's owner's manual for specific guidelines on spare tire usage, including speed and distance limitations. Incorrect spare tire use can be dangerous and may damage your vehicle.

TireCalculatorHub is not liable for any damages or issues arising from the use of information or tools on this website.