The 1921 S.T.D. 'Works' Grand Prix chassis was built to the three-litre and minimum weight of 800 kilogrammes formula for that year's Indianapolis 500 and French Grand Prix de l’A.C.F. These team cars were modified by the Sunbeam Experimental department in Wolverhampton for the 1922 Isle of Man Tourist Trophy, which was won by one of the cars. A few months later, and with 1916 4.9-litre engines, two of the T.T. cars competed in the Coppa Florio, Sicily and gained second and fourth position.

The 9th International 500-Mile Sweepstakes Race was held at the Indianapolis Motor Speedway on Monday, May 30, 1921.