🇮🇳 Performance Calculator

Tyre Size Calculator

Compare two tyre sizes and see the impact on speedometer accuracy, diameter, and ride height. Enter sizes in standard format (e.g., 185/65R15).

What does plus-sizing mean?

Plus-sizing means going to a larger rim diameter while reducing the aspect ratio to maintain the same overall tyre diameter. E.g., 185/65R15 → 195/55R16. The speedometer stays accurate, handling improves, but ride comfort decreases.

How much speedometer error is acceptable?

Generally ±3% is considered acceptable, and Indian regulations (like most countries) allow a small positive error by design. Note that factory speedometers often already read 1–2% high for safety reasons.

Will a different tyre 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 handbook or RC-approved specification sheet for allowed tyre size ranges.

Can I fit bigger tyres on my car in India?

Usually yes, within limits, though changes beyond the manufacturer-approved size may need to be noted for RTO/insurance purposes in some states. 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 tyre - keeps the diameter the same while changing the look and handling. The calculator above shows the exact diameter change for any pairing.

Do bigger tyres affect mileage and performance?

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