Now, with the string still carefully positioned, see how it looks against the front tire. Have a helper nudge the front tire left or right to get it parallel to both sides of the string (6). That done, compare the distance of the string from one side of the wheel to the other. Properly aligned, the string will be both parallel to the front wheel and equidistant on both sides (7). If the string is closer to the right side of the front tire -- as you are viewing it, looking back -- then the rear wheel is cocked leading-edge right (8). Obviously, if the string is closer to the left side (looking back), the rear tire is leading-edge left.