Riley, under long serving chief engineer Harry Rush, had begun developing their post-war range of cars in late 1943. Two “foreign” cars that had been at the Coventry factory during 1938/39 had a considerable influence on Rush and his small team responsible for the company’s post-war cars-the BMW 327 coupe and the Citroen Light 15. The BMW was admired for its sleek styling, the Citroen for its torsion bar independent front suspension, rack and pinion steering and general proportions.
Resources were not available to develop a new family of engines and so Rush had to be content with further development of the existing 1½-litre and 2½-litre units. Although having origins dating back to the 1920’s they were still superior in performance to virtually every other British four-cylinder engine in 1945.
For the 2½-litre model the engine was a development of the pre-war “Big Four” that was rated at 16 hp under the English system. With a cylinder bore of 80.5mm and a crankshaft stroke of 120mm it had a capacity of 2443cc. Its post-war redevelopment included driving the twin camshafts by a duplex chain instead of gears and the adoption of twin SU carburettors to raise output from 82 bhp to 90 bhp at 4,000 rpm. By the time the Roadster became available in the summer of 1948 the power had risen to 100 at 4,500 rpm using larger intake valves. Intriguingly, the 2½-litre engine retained white metal bearings.
The Riley 1½-litre saloon appeared first, in August 1945, with the 2½-litre saloon derivative following in July 1946 with availability from November of that year.

Why a Roadster?
With the need to export high on the agenda it was imperative that new markets be found. As part of the huge Nuffield Organization, Riley was aware of the export potential of convertibles because of the success of the MG TC, particularly in America. The reasoning of Riley management could have been if MG could succeed beyond all expectations with their small, cramped and uncomfortable, underpowered TC sports car then if they offered a larger and more powerful convertible they, too, should enjoy considerable success. It was also noted from observations that the several American automobile manufacturers did not offer buyers convertibles so the Riley people within the Nuffield Export Organisation believed that they could successfully sell to this untapped niche market with something a little larger and far more comfortable than the MG TC.
According to British motoring historian Jon Pressnell in Classic and Sportscar, August 1987:
Indeed, the story goes that the Roadster had its origins in a sketch on the back of an envelope brought back from the States by a member of the sales force, the man claiming that this was the sort of car for which the Americans were clamouring. It apparently transpired that the enthusiastic salesman had only talked to around a third of the American dealers…
So the 2½-litre Roadster began limited volume production. Interestingly it was not called Roadster but rather a “Three Seater Tourer.”
The basis for the Roadster was the 2½-litre’s sedan 119-inch wheelbase chassis. The chassis had additional outriggers to suit the different Roadster body mountings and the front suspension cradle was from the Riley 1½-litre that had a lower ride height.
It was the only Riley then with a bench front seat, allowing the driver to sprawl out to allow for implausibly large testicles (They were nearly all male owners) and grip the large steering wheel to avoid toppling out when cornering because of the cut down doors. Speaking of doors, the story goes that the front and rear sections of the body were first mounted onto the chassis, then a craftsman would come and make a door to fill the hole between these sections. This probably explains why these doors vary in length from car to car.
The front dampers were different from the saloon’s; the rear semi-elliptic leaf springs had only nine leaves instead of eleven in the saloon; a one-inch shorter radiator was used; the fuel tank held 20 Imperial gallons (up from 12.5 Imp gallons) and was mounted differently to the chassis; and the bumper brackets were made of heavier metal to support the bumpers that were set at 18-inches from the ground to meet American market requirements.
The steering wheel diameter was reduced from 18″ to 17″ and the steering column was offset to the driver’s side to provide more room for three people. This necessitated an additional steering box connected to the original rack mechanism and altered the steering ratio so that three turns were needed lock-to-lock instead of 21/2 turns. And for the first time on a Riley there was a column gearshift to support the perceived American taste for a bench front seat and three-abreast seating.
That Riley was losing money on each Roadster produced is not surprising given the unique nature of the car, especially the body. For reasons never divulged the company chose to not use any panels from the 2½-litre saloon in an effort to contain production costs. Every single body panel was different and unique to the Roadster. If the body panels were unique so, too, was the ash framework. The engine hood line was lower and the traditional chromed radiator grille was cut down by two-inches from that of the saloon. Additionally, the dashboard and firewall assembly was mounted further back on the chassis necessitating a special pedal assembly, longer cables for the hand controls, a different wiring harness with longer cables and a longer pipe to the engine oil pressure gauge. As well, the dashboard itself was wider and because the fuel tank was so large the Roadster had a different fuel gauge with a switch to allow different readings from the two sender units in the tank. In Riley litreature this feature was called a “reserve level switch” but in fact there was no reserve fuel capacity.
As an aside, the boot lid and doors of the Roadsters were individually “fitted” to their particular body and marked with the last three digits of the body No. in wax crayon on the inside face before being removed for separate spraying.
All these changes probably resulted from a lack of planning time. Drawings and the first hand-built body are believed to have been completed in less than a month, in December 1947. The first running prototype was not completed until March 1948, in time for General Manager Jack Tatlow to drive it to the Geneva Motor Show where it was Riley’s centre of attraction.
Actual production of the three-seater tourer began after the Geneva Show in March 1948. For that year only 121 were built, and all were exported. Riley advertising of the time showed a sketch of the Roadster driving past an English mansion, the driver being on the left-hand side of the car. A notation on their literature informed prospective buyers that the Roadster was “for Export only” and no price was quoted.
The Roadster was not a sales success in America. Perhaps it was the advent of the new Jaguar XK120, or the high pricing, but the Americans never warmed to the Roadster and with its major market rejecting it out of hand the decision was taken to withdraw it from production. On January 27, 1950, the last Roadster rolled off the Abingdon line.