Moss became a successful London dentist, and from his mid-twenties he was also an enthusiastic competition driver, beginning his racing career at the Essex Motor Club's Winter Trial in 1921 driving a 1000 cc AV cyclecar. He was disqualified for seeking help after his rear tyres had burst twice. His AV later caught fire in Park Lane, and Moss then acquired a GN cyclecar, with which he enjoyed success in trials and hillclimbs, and which he raced at Brooklands. In 1922, he bought and began to race a Crouch Le Mans sports car which had no front brakes. In the 1924 Indianapolis 500, he placed 14th or 16th (sources differ) in a Fronty Ford.