Plus Sizing Guide: Upgrading to Larger Wheels and Tires
How to upgrade your wheels without affecting speedometer accuracy
Plus sizing is the practice of increasing your wheel diameter while decreasing the tire's aspect ratio to maintain the same overall tire diameter. Done correctly, plus sizing improves handling and appearance without affecting your speedometer, odometer, or ABS calibration. This guide explains the plus sizing system, how to calculate compatible tire sizes, and the real-world benefits and drawbacks of going to larger wheels.
What Is Plus Sizing?
Plus sizing refers to increasing the wheel (rim) diameter by one or more inches while fitting a lower-profile tire to maintain the same overall diameter. Plus 1 means going up one inch in rim diameter (e.g., 16 to 17 inches). Plus 2 means going up two inches. The key is that the overall tire diameter must remain within 3% of the original to avoid speedometer error and maintain proper ABS calibration. For example, if your original tire is 205/55R16 with a diameter of 632mm, a Plus 1 upgrade might use 215/45R17 with a diameter of 634mm — nearly identical.
How to Calculate Compatible Plus Sizes
Start with your original tire's overall diameter. For each inch increase in rim diameter, you need to reduce the aspect ratio to compensate. The formula: New aspect ratio ≈ (Original diameter - New rim diameter × 25.4) / (2 × New section width) × 100. In practice, use our tire circumference calculator to find the diameter of any tire size and compare it to your original. Aim for a diameter within 1-2% of your original for the best results.
Benefits of Plus Sizing
Larger wheels with lower-profile tires offer several advantages. Handling improves because shorter sidewalls flex less during cornering, providing more precise steering response. Braking can improve because larger wheels allow for larger brake rotors. Appearance is enhanced — larger wheels fill the wheel well more completely and give a sportier look. Heat dissipation improves because larger wheels allow more airflow to the brakes. These benefits are most noticeable when going from Plus 1 to Plus 2.
Drawbacks of Plus Sizing
Lower-profile tires have shorter sidewalls, which means less cushioning from road imperfections. Ride quality typically decreases with each plus size increment. Tires with lower aspect ratios are more susceptible to damage from potholes and curbs. Larger wheels are heavier, which increases unsprung weight and can slightly reduce fuel economy and acceleration. Replacement costs are higher — lower-profile tires in larger sizes cost more than standard tires.
Checking Fitment Before Purchasing
Before purchasing plus-sized wheels and tires, verify several fitment parameters. Wheel offset must be compatible with your vehicle's suspension geometry. Wheel width must accommodate the new tire width. Clearance must be sufficient — check that the tire doesn't rub the fender or suspension components at full lock and full compression. Bolt pattern must match your vehicle's hub. Use our tire circumference calculator to verify the overall diameter of your proposed plus-sized tire before purchasing.
FAQ
Will plus sizing affect my speedometer?
If done correctly, plus sizing maintains the same overall tire diameter, so your speedometer accuracy is unchanged. The key is to choose a tire with an aspect ratio that compensates for the larger rim diameter. Use our calculator to verify the diameter before purchasing.
How much does plus sizing improve handling?
The improvement depends on how much you increase the rim size and how much the aspect ratio decreases. Going from 55-series to 45-series tires typically provides noticeable improvement in steering precision and cornering stability. The improvement is most significant on sporty vehicles where handling is already a priority.
Is Plus 2 or Plus 3 too extreme?
Plus 2 is common and generally works well. Plus 3 and beyond can result in very low-profile tires (30-series or lower) that are extremely sensitive to road damage and provide a harsh ride. For daily driving, Plus 1 or Plus 2 is the sweet spot between appearance, handling, and comfort.