An anti-tip system is adapted for use in a powered wheelchair for purposes of curb-climbing and ride stability. The anti-tip system includes at least one anti-tip wheel, a suspension arm for mounting the anti-tip wheel and a pair of links coupling the suspension arm to the main structural frame of the wheelchair. Each of the links is pivotally mounted to the main structural frame of the wheelchair about a first pivot point and is pivotally mounted to the suspension arm about a second pivot point. In a first embodiment of the anti-tip system, the links include an upper and lower link, wherein the upper link is extensible to facilitate angular displacement of the suspension arm to permit rearward displacement of the anti-tip wheel in response to an externally applied load.