Comparison of tire sizes 225/45 R17 and 225/40 R18. Old size. 225 / 45. R. 17. New size . 225 / 40. R. 18. Compare. 2 2 5 / 4 5 R 1 7. 225 Tire width . 45 Profile 245/75 R17 vs 225/70 R19; 225/40 R18 vs 225/45 R17; 225/60 R17 vs 215/65 R16; 225/55 R17 vs 215/55 R17; 265/70 R18 vs 265/75 R17; 165/65 R17 vs 165/55 R20; 225/50-R17 tires are 0.17 inches (4.4 mm) smaller in diameter than 255/40-R18 tires and the speedometer difference is 0.6%. The Barum Bravuris 5HM is an ultra-high performance tire that delivers responsive handling, strong grip and unbeatable value—available exclusively at Discount Tire. Barum is known for its ability to manufacture dynamic performance tires using methods that cut unnecessary costs, which it uses to pass savings on to enthusiasts. 225/45-R17 tires are 1.71 inches (43.4 mm) smaller in diameter than 245/45-R18 tires and the speedometer difference is 6.4% Compare 225/50 R17 vs 245/40 R18. Tire Size and Comparison Calculator calculate tire diameter from code and compare speedometer differences for tire sizes. The first number 225 is the tire width in millimeters. The 2nd number 50 is used to calculate the sidewall height or "aspect ratio", by percentage. 225 vs 235 tires: So when someone mentioned their tire size is 225/45 R17, what does this actually mean? 225 actually denotes the width of the tires in mm. For example a 225/45R17 tire size, it means that the width of the tire is 225mm (~ 8.9 inch) wide. The picture below shows an illustration of the 225mm length tire width. 225/50-R17 tires are 0.46 inches (11.6 mm) larger in diameter than 235/40-R18 tires and the speedometer difference is 1.8%. 1st: 2012 Sport Auto Winter Sports Tyre Test (225/40 R18) 3rd: 2012 Auto Bild Performance Winter Tyre Test (225/45 R17) 2011 Tyre Tests; 1st: 2011 EVO Winter Tyre Test (225/45 R17) 1st: 2011 Auto Express Winter Tyre Test (225/45 R17) 4th: 2011 Winter Tyre Buying Guide (205/55 r16) 4th: 2011 Auto Bild Performance Winter Tyre Test (225/40 R18) In the tire comparison table above, you can see a detailed calculation of the size difference between 225/55 R18 and 225/50 R18 tire. The calculation results are presented in the form of visual infographics, on which tire with size 225/55 R18 is on top, and tire with size 225/50 R18 below. Both in the table and in the graph, the tires are VrKS5.