Performance Calculator

Tire Size Calculator

Compare two tire sizes and see the impact on speedometer accuracy, diameter, and ride height. Enter sizes in standard format (e.g., 205/55R16).

What does plus-sizing mean?

Plus-sizing means going to a larger rim diameter while reducing the aspect ratio to maintain the same overall tire diameter. E.g., 205/55R16 → 205/50R17. The speedometer stays accurate, handling improves, but ride comfort decreases.

How much speedometer error is acceptable?

Generally ±3% is considered acceptable. Most states and countries allow up to 4% error. Note that factory speedometers often already read 1–2% high for safety reasons.

Will different tire size affect my car's ABS or traction control?

Significant diameter differences (>3%) can confuse ABS, traction control, and AWD systems that compare wheel speeds. Always check your vehicle's specification sheet for allowed tire size ranges.

Can I put bigger tires on my car?

Usually yes, within limits. Keep the overall diameter within about 3% of stock to avoid speedometer error and rubbing against the fender or suspension at full lock. Plus-sizing — a larger rim with a lower-profile tire — keeps the diameter the same while changing the look and handling. The calculator above shows the exact diameter change for any pairing.

Do bigger tires affect fuel economy and performance?

They can. Larger, heavier tires add rolling resistance and rotating mass, which slightly reduces acceleration and fuel economy. A taller overall diameter also effectively lowers your gearing, dropping cruising RPM but blunting off-the-line response. Wider tires improve grip at the cost of a little efficiency.