23540-18 245/45-18 Difference; Diameter inches (mm) 25.4 (645.2) 26.68 (677.7) 1.28 (32.5) 5%: Width inches (mm) 9.25 (235) 9.65 (245) 0.39 (10) 4.3%: Circum. inches Also the online application calculates the difference in real speed and speedometer readings if the difference between tire 225/40 R18 and tire 235/35 R18 is significant. Calculate the difference in inches. If you want to compare other tire sizes, then select their sizes in the drop-down fields and click on the green button. 23560-R18 tires are 1.36 inches (34.5 mm) larger in diameter than 225/55-R18 tires and the speedometer difference is 4.7%. 23555-R18 tires are 0.93 inches (23.5 mm) smaller in diameter than 235/60-R18 tires and the speedometer difference is 3.2%. Neitherof the first two choices you listed are very good at all for the ms3. 225/45/18 is a bit too tall, and 225/40/18 is way too small. Going to a 235/40/18 would keep OD nearly the same as stock and possibly give better performance, depending on wheel width, but they're also heavier. If you're not lowered and using stock wheels, there 25545-R20 tires are 0.07 inches (1.7 mm) smaller in diameter than 235/60-R18 tires and the speedometer difference is 0.3%. Thedifference in sizes and parameters between the 245/40 R18 tire and 245/35 R18 tire. Detailed calculations and graphics. Tire calculator online . Top comparisons; 225/45 R17: 235/40 R18: 255/35 R18: Inthe tire comparison table above, you can see a detailed calculation of the size difference between 265/35 R18 and 235/40 R18 tire. The calculation results are presented in the form of visual infographics, on which tire with size 265/35 R18 is on top, and tire with size 235/40 R18 below. Both in the table and in the graph, the tires are 1 I am looking to decide between these 2 tire sizes for an 18x8.5 wheel. I drive an EX-T with factory 17" wheels and I know the Si has the 235 keep Tiresize comparison 235/40 R18 vs 225/45 R18 Calculate CM INCHES If your speedometer reads: Real speed is: Size difference between 235/40 R18 and 225/45 R18 tires. In the tire comparison table above, you can fI9j.