How Tire Size Comparison Works
When considering a tire size change, the most critical factor is the overall tire diameter. Even small changes in diameter can affect your speedometer accuracy, gear ratios, ground clearance, and whether the tire will rub against suspension components or fenders.
Our comparison calculator breaks down every dimension so you can make an informed decision before buying. All calculations use industry-standard formulas matching TireSize.com and major tire retailers.
Key Measurements Explained
- Overall Diameter: The total height of the tire. Changes affect speedometer accuracy and ground clearance. Keep within ±3% of stock.
- Sidewall Height: The distance from the rim to the tread. Lower aspect ratios = stiffer ride, better handling. Higher = softer ride, more protection.
- Circumference: The distance around the tire. Directly affects speedometer, odometer, and ABS calibration.
- Revolutions per Mile: How many times the tire rotates per mile. Used by your vehicle's computer to calculate speed and distance.
- Speedometer Error: How much faster or slower your speedometer will read at 60 mph with the new size.
Plus Sizing: What You Need to Know
Plus sizing is popular for improving a vehicle's appearance and handling. Here's how it works:
- Plus 0: Same wheel size, wider tire or different aspect ratio. Minimal impact.
- Plus 1: Wheel diameter increases by 1 inch, aspect ratio decreases to maintain similar overall diameter. Improves cornering response.
- Plus 2: Wheel diameter increases by 2 inches. Very sporty look, but ride quality may suffer due to thinner sidewalls.
Important: When plus-sizing, the overall diameter should stay within ±3% of the original size. Beyond that, you may experience rubbing, speedometer errors, and drivetrain stress (especially on AWD vehicles). Use our comparison tool to verify before buying.