On August 21, 2018, Biffle tested a Stadium Super Truck that was driven by fellow ex-NASCAR driver Casey Mears. A day later, he announced he would make his series debut at Road America.[16] He finished seventh and second in the weekend's two races,[17] though he did not receive points in the standings as he drove the No. 57 truck in place of Bill Hynes, who received the points earned by Biffle under series rules.[18]