Sims is frequently credited with inventing the first modern snowboard. He built his "Skiboard" prototype in wood shop class in seventh grade in 1963, and followed with several skateboard and snowboard industry firsts, including the first snowboard with metal edges, the first pro-model and women's-specific snowboard. He was also the first to incorporate some of the earliest high-back binding systems.
Sims ran a skateshop and founded Sims Skateboards in Santa Barbara in 1976 and won the Skateboard World Championships that same year. He was featured, alongside Stacy Peralta, in the 1976 skate film "Freewheelin.'" Christian Hosoi and the late Jeff Phillips both turned pro for Sims shortly thereafter.