P was injured while driving a tractor manufactured by D. The design of the steering mechanism made the tractor unusually difficult to maneuver. Unrelated to any steering difficulty P struck a guardrail adjoining the shoulder with the right front tire of the tractor. This collision caused the steering wheel to spin rapidly in the direction opposite to the turn. The spokes of the spinning steering wheel struck P's right arm, fracturing his wrist and forearm. Evidence adduced at trial indicated that the force and speed of the steering wheel's counter rotation were directly related to the design of the steering mechanism. D was held liable under Section 402A of Restatement (Second) of Torts (1965) for the injuries sustained by P. The Superior Court affirmed and this court granted allocatur limited to the issue of the availability of contributory negligence as a defense to a 402A action.