[4] USAC, the governing body of the Indy 500, had implemented new rules aimed at handicapping turbine powered racing cars by drastically reducing the air intake size.

The Lotus 56 made up for reduced power with a sophisticated suspension design, retaining the four-wheel drive concept of the Silent Sam, but with lighter weight, and advanced aerodynamics.

For the second year in a row STP turbine cars had brought innovation to the Indy 500 and had failed to win while leading within a few laps of the end of the race.

Colin Chapman had developed the 56 as a potential F1 contender, part of his plan to have a single design to compete at both the Indy 500 and in Formula 1.

Dave Walker then ran the car in the Dutch Grand Prix, and had progressed from 22nd to 10th in five laps of the very wet track, before sliding off the road and into retirement.