Biffle returned to SST for the 2019 season, sharing a Continental AG-sponsored truck with Sheldon Creed and Ryan Beat. He ran his first races of the year in late July at Mid-Ohio Sports Car Course. In the weekend's first round, he battled with Gavin Harlien for the lead until Harlien began suffering mechanical trouble; on the final restart, Cole Potts passed Biffle to take the race win. The second round saw Biffle pit under caution for damage, but was able to finish fourth. In October, he ran his first SST race in Australia at Surfers Paradise Street Circuit. In practice, he was the fastest in the ten-driver field but did not set a qualifying time after flipping his truck when he hit a tire barrier. He ran in second for much of the first race before falling to fourth after an erratic landing; the second race saw a late spin drop him to eighth.