A motorcycle frame assembly arranged to have a desirable amount of rigidity in both transverse and vertical directions. The frame assembly desirably includes a head pipe configured to support a front wheel and associated suspension assembly. A main tube and down tube extend in a rearward direction from the head pipe. Desirably, the main tube is elliptical in cross-section, with the longer dimension being arranged generally horizontally and the shorter dimension being arranged generally vertically. Preferably, the main tube is arcuate along its length and defines a convex outer surface portion opposing a concave outer surface portion. Preferably, the main tube is arranged such that the convex outer surface portion faces the down tube. Desirably, the main tube also extends from the head pipe such that the main tube is lower than perpendicular with respect to the head pipe.