Frequently Asked Questions
The tire size 255/55R18 means that the tire has a tread width of 255 millimeters, a sidewall height equal to 55% of the tread width, and a rim diameter of 18 inches. It can be generally seen on midsize and large SUVs, crossovers, and light trucks that offer a compromise between on-road comfort and off-road performance.
The appropriate air pressure for the 255/55R18 tire can vary. The pressure can depend on such factors as a particular vehicle, load conditions, and the recommendations of the tire manufacturer. In general, the tires should have about 30–35 PSI, when cold.
Although the tire sizes may look similar, they are not meant to be replaced with each other. As a main difference, 235/55R18 is 235 millimeters in tread width, which is around 9.3 inches, while 225/55R18 is only 225 millimeters or 8.9 inches. Tread width can influence several factors, such as handling, traction, and load-carrying capacity.
It is the tire size information. The number 225 means the tire’s tread width in millimeters, which, in this case, is 225 mm or approximately 8.9 inches. The number 55 is the aspect ratio, i.e., the height of the sidewall as a percent of the tread width. Specifically, in a 225/55 tire size, the side walls are 55 percent of the 225 mm wide tread. The letter R is for radial construction, and the number 18 is the rim diameter in inches.
