As to the tires. The width is the first number ie. 255 in milimeters, divide by 25.4 to have side wall width. the next number ie 55 is the mutliplier to determine tire height. Multiply the tire width by the multiplier to get tire height. Double height and add to wheel diameter to get over all tire wheel diameter ie.
255/25.4=10.04 inches wide at side wall.
10.04*.55= 5.52 inches tall tire.
5.52*2+ wheel diameter 17 = over all wheel height. All of this information is available in an easy to understand on the Tire Rack Web site
www.tirerack.com.