A three-wheel vehicle has two forward steered wheels, one rear powered wheel, and a straddle-type seat disposed between the forward and rear wheels. The vehicle's frame has interconnected tubular members that create a strong, light, rigid frame that can accommodate a high performance engine. The frame's components include upper spars, lower spars, rear suspension plates, a front suspension sub-frame, rear suspension braces, a pyramid-shaped upper support assembly, various cross braces, and a rear sub-frame, among other components. Two or more of the frame components may be integrally formed and removably connected to the other frame components to simplify assembly, maintenance, and replacement. The frame is designed to lower the center of gravity of the vehicle and rider so as to stabilize the vehicle. The front suspension sub-frame includes a longitudinal air passage that directs air into the engine compartment and around an oil cooler.