Tyre Size Calculator helps you determine tyre size when you place larger wheels.

Enter the original tyre size and the new wheel size into the form below.

The calculator will make a list of optional tyre sizes for the new wheel.

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original tyre size

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new wheel size

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Note: The optional tyres have a diameter in the range of -3% to +4% of the difference between the outer tyre diameter and the wheel diameter (D-W). This formula is used by leading tyre manufacturers Tyre interchangeability is not always possible, so be sure to consult your car manufacturer’s manual before changing your tyres. This is for informative purposes only.

What is Plus Sizing?

Plus sizing or up-stepping is the practice of replacing the wheel with a larger one and mounting a lower profile tyre while maintaining the same (or approximately the same) diameter and circumference as the original tyre. These dimensions must be maintained in order to prevent considerable changes in speedometer accuracy, torque and traction control. Our tyre plus sizing calculator can help you to find optimal tyre dimensions for plus sizing. Plus x sizing means increasing the wheel diameter by x inches, so plus one sizing means increasing the wheel by one inch. A special case of the tyre plus sizing is the Plus Zero sizing which means switching to a wider tyre without changing the existing rim diameter. But beware, take into account that a wider tyre may require a wider rim/wheel. Changing to a wider tyre requires reducing the aspect ratio (which is the second number in the sequence of numbers that describes the tyre’s size e.g. 195/65 R15). Since the aspect ratio is the ratio of a tyre’s width to its height, it follows that if the width is increased, the aspect ratio should be decreased if the final result is to remain the same—which is the objective of plus sizing.

Why Plus Sizing?

Plus sizing is usually done to improve aesthetics but also performance since original tyres are fitted with respect to, beside performance, noise, abrasion resistance, and comfort. Therefore, they may not be good enough for performance enthusiasts.

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