Abstract: An undercarriage spoiler system for a race motor vehicle utilizes a first spoiler plate disposed parallel and adjacent to the horizontal slotted rear bumper of the vehicle and secondary spoiler plates disposed in the vehicle rear quarter panels and perpendicularly to the first spoiler plate. During high speed vehicle spin-out and rearward movement, the spoiler plates pivotally move from a spring-retained position, parallel with the vehicle undercarriage, to an angular relationship therewith to spoil the reverse high speed air flow over the vehicle undercarriage and assist in effecting stabilization of the vehicle. Tension or torsion springs return the spoiler plates to their static un-deployed position once the vehicle recovers from the spin-out.