225 45 R17 is a common notation used to describe the size of a car tire. Each part of this notation represents a different aspect of the tire:
225: This number represents the tire's width in millimeters. In this case, the width is 225 millimeters.
45: This number represents the aspect ratio of the tire. It is the ratio of the tire's sidewall height to its width. In this case, the sidewall height is 45% of the tire's width.
R: This letter indicates that the tire has a radial construction. Almost all modern tires are radial, so "R" is quite common.
17: This number represents the diameter of the wheel in inches. In this case, the tire is designed to fit a 17-inch diameter wheel.
So, "225 45 R17" tells you that the tire is 225 millimeters wide, has a sidewall height that is 45% of its width, and is designed to fit a 17-inch diameter wheel with radial construction. This information is important when selecting the right tires for a vehicle.