Singer Nine Model 4AB Roadster, introduced in October 1950, is an improved version of the Model 4A (launched in Sept. 1949). Modifications include a shorter radiator with a small valance at its base, longer and sweeping front wings, fixed bonnet sides and centrally hinged bonnet top, plain bumpers, full disc type wheels, improved seats, larger brakes and independent front suspension with coil springs. The Model AB, which sold at £666, was
discontinued in October 1951.
Engine size of the saloon is reduced to place the car in lower tax class. The same engine is used in the new SM Roadster initially built for export only..