Tire Calculator Compare

Tire Size Comparison Calculator

Understanding Your Tire Size Comparison

Changing tire sizes can have a significant impact on your vehicle's performance, appearance, and even its speedometer accuracy. Our Tire Size Comparison Calculator helps you understand these changes by comparing two different tire specifications side-by-side.

How to Read Tire Sizes

Tire sizes are typically displayed in a format like 205/55R16:

• 205: This is the tire's width in millimeters (mm) from sidewall to sidewall.
• 55: This is the aspect ratio, representing the sidewall height as a percentage of the tire's width. In this case, the sidewall height is 55% of 205mm.
• R: Indicates a radial construction tire.
• 16: This is the wheel (rim) diameter in inches.

What the Calculator Shows You

The calculator provides detailed specifications for both your original and new tire sizes, along with crucial comparison metrics:

• Sidewall Height: The vertical distance from the wheel rim to the outer tread. This affects ride comfort and the tire's visual profile.
• Overall Diameter: The total height of the tire when mounted and inflated. This is critical for speedometer accuracy and fender clearance.
• Overall Circumference: The distance covered by one full rotation of the tire. This directly relates to revolutions per mile.
• Revolutions Per Mile: How many times the tire rotates to travel one mile. A higher number means the engine works harder for the same distance, potentially affecting fuel economy and gearing.
• Diameter Difference (%): The percentage difference in overall diameter between the two tires. A difference of more than 3% is generally not recommended as it can significantly impact speedometer accuracy and potentially cause issues with ABS or traction control systems.
• Speedometer Difference (%): This tells you how much your speedometer reading will be off if you switch to the new tire size without recalibration. For example, if it shows +3%, when your speedometer reads 60 mph, you're actually going 61.8 mph.
• Actual Speed: Provides a direct example of your true speed when your speedometer reads 60 mph, based on the new tire size.

Why Tire Comparison Matters

• Speedometer Accuracy: A change in overall tire diameter directly impacts your speedometer and odometer readings. An inaccurate speedometer can lead to speeding tickets or incorrect mileage tracking.
• Vehicle Clearance: Larger tires might rub against fender wells or suspension components, especially during turns or over bumps.
• Ride Comfort: A taller sidewall generally provides a more comfortable ride, while a shorter sidewall can offer better handling and a sportier feel.
• Gearing and Performance: A larger overall diameter effectively "raises" your vehicle's gearing, potentially reducing acceleration but improving fuel economy at highway speeds. Conversely, a smaller diameter "lowers" gearing, improving acceleration but increasing engine RPMs at speed.
• ABS/Traction Control: Modern vehicles rely on precise wheel speed sensor data. Significant changes in tire diameter can confuse these systems, leading to malfunction.

Example Scenario:

Let's say your original tires are 205/55R16 and you're considering new tires that are 225/50R17.

• Tire 1 (205/55R16):
  • Sidewall Height: 112.75 mm
  • Overall Diameter: 24.88 inches
  • Revolutions Per Mile: 839
• Tire 2 (225/50R17):
  • Sidewall Height: 112.5 mm
  • Overall Diameter: 25.86 inches
  • Revolutions Per Mile: 807
• Comparison:
  • Diameter Difference: +3.94% (Tire 2 is larger)
  • Speedometer Difference: -3.79% (When your speedometer reads 60 mph, you are actually going 62.27 mph)

In this example, the new tires are significantly larger, causing a noticeable speedometer error. This highlights the importance of using a tire calculator before making a purchase.