Tire Size Calculator
Original Tire Size
225/55R17
New Tire Size
235/50R18
Tire Size Format
Example: 225/55R17
Related Calculators
Understanding Tire Sizes
Reading Tire Size Notation
P225/55R17 97H
P = Passenger vehicle tire
225 = Section width in mm
55 = Aspect ratio (sidewall height = 55% of width)
R = Radial construction
17 = Rim diameter in inches
97H = Load index and speed rating
Why Tire Size Matters
Speedometer Accuracy
Changing tire size affects speedometer readings. A larger tire will make your speedometer read slower than actual speed.
Clearance & Rubbing
Larger tires may rub against fenders or suspension components. Check fitment before changing sizes significantly.
Fuel Economy
Larger, heavier tires can reduce fuel economy. Rolling resistance also varies by tire design.
Handling
Wider tires provide more grip but may affect ride comfort. Lower aspect ratios improve handling but reduce cushioning.
Safety Warning
Tire size changes beyond 3% difference from original can affect ABS, traction control, and vehicle stability systems. Always consult a tire professional before making significant changes and check local regulations.
Frequently Asked Questions
What does 225/55R17 mean on a tire?
225 = section width in mm, 55 = aspect ratio (sidewall height is 55% of width), R = radial construction, 17 = rim diameter in inches. So a 225/55R17 tire is 225mm wide with sidewalls 123.75mm tall, fitting a 17-inch wheel.
How much will my speedometer be off with different tire sizes?
Speedometer error equals the percentage change in tire diameter. A 3% larger tire makes your speedometer read 3% slow (shows 60mph when actually going 62mph). Most vehicles tolerate up to 3% difference safely.
What is the Plus Zero/Plus One/Plus Two sizing system?
Plus sizing increases wheel diameter while decreasing sidewall height to maintain similar overall diameter. Plus One: 1" larger wheel, lower profile tire. This improves handling but may reduce ride comfort. Stay within 3% of original diameter.
Can I put different size tires on my car?
Yes, within limits. Stay within 3% of original diameter to avoid speedometer/odometer errors and clearance issues. Larger tires may rub fenders or affect ABS/traction control. Always check vehicle manual and local regulations.