What Is Tire Upsizing?
Tire upsizing (or "plus sizing") involves fitting larger diameter wheels while using lower-profile tires to keep the overall outer diameter close to the original. The result is a sportier appearance and improved cornering grip, but it comes with tradeoffs: potential speedometer error, higher costs, and a firmer ride.
Outer Diameter Formula
Outer Diameter (mm) = Rim Size (inches) × 25.4 + Tire Width (mm) × Aspect Ratio × 2
Speedometer Error (%) = (New OD − Original OD) ÷ Original OD × 100
A positive error means your actual speed is higher than what the speedometer shows. Keep errors within ±3% for accurate speed readings.
Frequently Asked Questions
Most experts recommend staying within ±3% of the original diameter. This keeps speedometer error within a safe and legal range and avoids compatibility issues with ABS and traction control systems.
In the US, dealers cannot void your warranty solely for using different wheels unless they can prove the modification caused a specific component failure. However, check your specific lease or warranty terms to be safe.
Beyond tire costs, budget for new rims ($200–$1,000 per set depending on style), mounting and balancing ($50–$100), and a wheel alignment ($80–$150). Total out-of-pocket is often $500–$2,000 above the tire price.