Wheel Size Calculator (Plus Sizing)

When swapping to larger wheels and lower-profile tires, keeping the overall diameter close to stock is critical — otherwise your speedometer reads incorrectly and your car's calibration is thrown off. Enter your original setup (tire width, profile, wheel diameter, width, and offset) and your new setup into the Wheel Size Calculator to see the speedometer error, overall diameter difference, ride height change, and offset difference between the two configurations.

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Results

Speedometer Error

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Original Overall Diameter

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New Overall Diameter

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Diameter Difference

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Ride Height Change

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Offset Difference

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Results Table

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Frequently Asked Questions

What is plus sizing for wheels and tires?

Plus sizing involves increasing wheel diameter while decreasing tire sidewall height to maintain similar overall diameter. This provides better handling and appearance while keeping speedometer accuracy.

How does changing tire size affect my speedometer?

When the overall tire diameter changes, your speedometer will read incorrectly. A larger diameter makes the speedometer read slower than actual speed, while smaller diameter makes it read faster.

What is wheel offset and why does it matter?

Wheel offset (ET) is the distance from the wheel's mounting surface to its centerline. Changing offset affects how far the wheel sits in or out from the vehicle, impacting clearance and handling.

Can I use any wheel and tire combination on my car?

No, you must consider load ratings, speed ratings, clearance issues, and manufacturer recommendations. Always consult your vehicle manual or a tire professional before making changes.

How do I calculate the overall diameter of a tire?

Multiply tire width by aspect ratio to get sidewall height, then add twice the sidewall height to the wheel diameter. For example: 225/60R16 = 225 × 0.60 × 2 + 16 inches.

Will larger wheels improve my car's performance?

Larger wheels with lower profile tires can improve handling and braking due to less sidewall flex, but may reduce ride comfort and increase susceptibility to pothole damage.

Do I need to recalibrate my TPMS after changing wheel size?

Yes, when changing wheel and tire sizes significantly, your TPMS sensors may need recalibration or replacement to ensure accurate pressure monitoring in the new setup.

What happens if my new tires are too big for my car?

Oversized tires can rub against wheel wells, suspension components, or body panels, especially during turning or suspension compression. This can cause damage and safety issues.