What does R18 cross-section mean?
2 Answers
R18 tire cross-section refers to the sample obtained by radially cutting the tire from bead to bead during a tire dissection test, which is called the cross-section, representing the radial cross-sectional profile of the tire. Tire composition: A tire typically consists of three parts: the outer tire, inner tube, and flap. Tire marking meanings: Tire markings refer to the internationally standardized tire codes, usually located on the sidewall of the tire, indicating the section width and aspect ratio as a percentage, with the unit being mm. Taking 225/55R18 as an example, the meanings of these numbers are as follows: 225 represents the tire section width in mm, generally ranging between 145-285mm in increments of 10mm; 55 is the aspect ratio, which is the ratio of the tire sidewall height to the tire section width, with 55 representing 55%. Typically, tire aspect ratios range between 30%-80%. Under normal circumstances, ordinary passenger cars should not use tires with an aspect ratio greater than 75%, while luxury cars and high-performance sports cars are recommended to use tires with an aspect ratio <60%; R is the abbreviation for Radial, indicating the tire has a radial structure, and 15 is the rim diameter in inches.
Oh, this is actually a very common question that I often encounter when repairing cars myself. R18 refers to the rim diameter in car tires, which is the size of the wheel itself, 18 inches. As for the cross-section, in tire sizing, it usually refers to the width value, such as 205 in 205/55R18, indicating the width of the part of the tire that contacts the ground, measured in millimeters. This width directly affects the vehicle's stability, steering performance, and fuel consumption—a wider cross-section provides better grip but slightly higher fuel consumption, while a narrower one saves fuel but may feel a bit floaty when cornering. If you're changing tires, check your car's manual or consult a professional shop for compatibility. Don't get it wrong; the R also stands for radial construction, which is the standard for modern tires.
