Late to this question, but its possible to switch from 225/45R17 to 225/50R17. The 45-50 number is the aspect ratio of the tire, bigger the number the larger the sidewall. Though in this case, the difference is small, around an inch, but still affects final drive ratio as other have mentioned. At low speeds probably off by 1mph and difference In the tire comparison table above, you can see a detailed calculation of the size difference between 225/45 R17 and 225/40 R18 tire. The calculation results are presented in the form of visual infographics, on which tire with size 225/45 R17 is on top, and tire with size 225/40 R18 below. Both in the table and in the graph, the tires are 245/45-R18 tires are 1 inch (25.4 mm) larger in diameter than 245/45-R17 tires and the speedometer difference is 3.8% 245/40-R17 tires are 0.1 inches (2.5 mm) larger in diameter than 215/45-R17 tires and the speedometer difference is 0.4%. 225/45-R17 tires are 1.28 inches (32.5 mm) smaller in diameter than 235/50-R17 tires and the speedometer difference is 4.8%. This chart has been designed to enable you to look up your Mercedes' model number and identify the range of wheel sizes and dimensions that are compatible with your vehicle. It is usually used when browsing our product range manually and can also be useful to identify which tyre sizes you need to order for your Mercedes. .

225 50 r17 vs 245 45r17