“A roadster (also spider, spyder) is an open two-seat car with emphasis on sporting appearance or character. Initially an American term for a two-seat car with no weather protection, usage has spread internationally and has evolved to include two-seat convertibles.
The roadster was also a style of racing car driven in United States Auto Club (USAC) Championship Racing, including the Indianapolis 500, in the 1950s and 1960s. This type of racing car was superseded by rear-mid-engine cars.” wikipedia
“The term roadster was used to describe a style of racing cars competing in the AAA/USAC Championship Cars series (the IndyCar equivalents of the time) from 1952 to 1969. The roadster engine and drive shaft are offset from the centerline of the car. This allows the driver to sit lower in the chassis and facilitates a weight offset which is beneficial on oval tracks.
One story of why this type of racing car is referred to as a “roadster” is that a team was preparing a new car for the Indianapolis 500. They had it covered in a corner of their shop. If they were asked about their car they would try and obscure its importance by saying that it was just their (hot rod) “roadster”. After the Indianapolis racer was made public, the “roadster” name was still attached to it.
Frank Kurtis built the first roadster to race and entered it in the 1952 Indianapolis 500. It was driven by Bill Vukovich who led for most of the race until a steering failure eliminated him. The Howard Keck owned team with Vukovich driving went on to win the 1953 and 1954 contests with the same car. Bob Sweikert won the 1955 500 in a Kurtis after Vukovich was killed while leading. A. J. Watson, George Salih and Quinn Epperly were other notable roadster constructors. Watson-built roadsters won in 1956, 1959 – 1964 though the 1961 and 1963 winners were actually close copies built from Watson designs. The 1957 and 1958 winner was the same car built by Salih with help by Epperly built with a unique placement of the engine in a ‘lay down’ mounting so the cylinders were nearly horizontal instead of vertical as traditional design dictated. This gave a slightly lower center of mass and a lower profile.
Roadsters continued to race until the late 1960s, although they became increasingly uncompetitive against the new rear-engined racing cars. The last roadster to complete the full race distance was in 1965, when Gordon Johncock finished fifth in the Wienberger Homes Watson car. The last roadster to make the race was built and driven by Jim Hurtubise in the 1968 race and dropped out early.
Some pavement midgets roadsters were built and raced into the early 1970s but never were dominant” wikipedia
“Early roadster competing for the Vanderbilt Cup
The term “roadster” originates in the United States, where it was used in the nineteenth century to describe a horse suitable for travelling. By the end of the century the definition had expanded to include bicycles and tricycles. In 1916, the United States Society of Automobile Engineers defined a roadster as: “an open car seating two or three. It may have additional seats on running boards or in rear deck.” Due to it having a single row of seats, the main seat for the driver and passenger was usually further back in the chassis than it would have been in a touring car.(p258) Roadsters usually had a hooded dashboard.(p257)
In the United Kingdom, historically the preferred terms were “open two-seater” and “two-seat tourer”. Since the 1950s, the term “roadster” has also been increasingly used in the United Kingdom. It is noted that the optional 4-seat variant of the Morgan Roadster would not be technically considered a roadster.” wikipedia