225/50-R17 tires are 0.39 inches (10 mm) smaller in diameter than 235/50-R17 tires and the speedometer difference is 1.5%. Tire Size and Comparison Calculator calculate tire diameter from code and compare speedometer differences for tire sizes. The first number 235 is the tire width in millimeters. The 2nd number 55 is used to calculate the sidewall height or "aspect ratio", by percentage. So, the sidewall height of a 235/55 R 17 tire is 60% of 235 = 192. 235/60-R17 tires are 2.24 inches (57 mm) larger in diameter than 225/50-R17 tires and the speedometer difference is 8.0%. 235/70-R16 tires are 0.44 inches (11.1 mm) larger in diameter than 225/65-R17 tires and the speedometer difference is 1.5%. 225/70-R17 tires are 0.89 inches (22.5 mm) larger in diameter than 225/65-R17 tires and the speedometer difference is 3.0%. 205/50-R17 tires are 0.26 inches (6.5 mm) smaller in diameter than 235/45-R17 tires and the speedometer difference is 1.0%. .

235 65 r17 vs 225 65 r17