REVISED AND UPDATED — Mac’s Motor City Garage takes a fond look back at maybe the greatest Indy cars ever, the fabulous roadsters. Here’s a brief history and giant photo gallery.
There’s an entire generation of American gearheads for whom, when you say the words “race car,” one image appears in their minds: the classic Indianapolis roadster. Icon is surely one of the most overused words in motor writing, but the roadster truly qualifies. The look, the sound, the yards-long exhaust header, the acres of chrome: The roadsters have it all.
California builder Frank Kurtis is generally credited as both the creator of the design and the originator of the term “roadster” to describe it. (Others insist driver Bill Vukovich launched the name.) To better manage the size and mass of the gigantic 401 CID inline diesel six used in the 1952 Cummins Diesel Special, Kurtis laid the engine on its side, offsetting the driveline to the left and the driver’s seat to the right in the chassis.
1952 Cummins Diesel Special—Frank Kurtis at left, Don Cummins center, and Freddie Agabashian in driver’s seat
To Kurtis, the low, wide stance that resulted said “roadster,” and while the Cummins Special was far too heavy to be competitive, shredding its tires at a prohibitive rate, the superiority of the basic layout was immediately obvious up and down Gasoline Alley. Along with the car commissioned by the Cummins Diesel Company, Kurtis-Kraft offered a chassis for more conventional engines, the KK500. In a few short years the entire Indy 500 field was made up of roadsters, rendering the old upright cars obsolete.
The two most prolific roadster builders were Kurtis-Kraft and A.J. Watson, but there were others, including Trevis, Salih, Epperly, Lesovsky, and Kuzma, to name a few. Their chassis could be copies, official or otherwise, of Watson or Kurtis designs, adaptations, or original creations.
A.J. Watson with roadster chassis, 1960
The engine—usually the classic Offy four, with some interesting exceptions—was installed upright or inclined at any angle up to a full 90 degrees, and driveline/driver offsets were swapped left/right to suit the theory of the moment. Almost invariably, the suspension consisted of beam axles and torsion bars front and rear—a simple, rugged setup. A typical roadster chassis was competitive at Indy for years.
We all know the eventual fate of the roadsters: done in by the rear-engine revolution. The Cooper of Jack Brabham in 1961, Mickey Thompson’s Buick specials in 1962, and Colin Chapman’s Lotus in 1963 obsoleted the roadsters, just as the roadsters had put the old uprights to pasture a decade earlier. In 1964, A.J. Foyt was the last driver to wheel a roadster into victory lane at Indy.
There were two swan songs in the roadster story. In 1966, crafty Herb Porter grafted an outboard turbo setup to a Watson-Offy for driver Bobby Grim, who qualified 31st and finished in the same position. In 1968, Jim Hurtubise was the last driver to qualify (30th) a front-engine car in the Indy 500 with the Mallard-Offy, an updated, lightweight version of the classic roadster he designed himself. You’ll find all these cars and more in the gallery below.