In 1963 Lederle broke a leg in practice for the Rand 9 Hours sports car race and missed a large part of the 1964 season whilst recovering. He returned with his Lotus 21 for the end-of-season 1964 Rand Grand Prix where he finished 10th, but he narrowly failed to qualify for January's 1965 South African Grand Prix. After this disappointment, Lederle effectively retired from racing to concentrate on business interests, which included a Volkswagen dealership.