An active anti-tip system is provided for a wheelchair having a main structural frame and a drive assembly. The anti-tip system includes at least one anti-tip wheel, a suspension arm assembly pivotally mounting the anti-tip wheel to the main structural frame, a pendulum mount for coupling the drive assembly to the main structural frame and intermeshing gears for conveying the motion of the drive assembly to the suspension arm assembly. The pendulum mount causes the drive assembly to traverse in a substantially horizontal path in response to torque input from the drive assembly. The motion of the drive train assembly is converted to pivot motion of the suspension arm by the intermeshing gears. The pivot motion of the suspension arm assembly causes the anti-tip wheel to be raised for curb/obstacle climbing and effectively lowered for pitch stability.