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 found 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 255/55R18 tires can vary depending on the vehicle and manufacturer's specifications, as well as the load conditions. In general, the tires should have between 30–35 PSI when cold.
Although the tire sizes may look similar, they can’t be replaced with each other. As a key difference, 235/55R18 is 235 millimeters in tread width (around 9.3 inches), while 225/55R18 is only 225 millimeters (8.9 inches). Tread width can influence several factors, such as handling, traction, and load-carrying capacity.
The number 225 is the tire’s tread width in millimeters. 55 is the aspect ratio, i.e., the height of the sidewall as a percent of the tread width, 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.
