The Triumph TR3 is a British sports car produced between 1955 and 1962 by the Standard-Triumph Motor Company of Coventry, England. A traditional roadster, the TR3 is an evolution of the company's earlier TR2 model, with greater power and improved braking. Updated variants, popularly but unofficially known as the "TR3A" and "TR3B", entered production in 1957 and 1962 respectively. The TR3 was succeeded by the Michelotti-styled, mechanically similar Triumph TR4.
The rugged "sidescreen" TR, so named for its employment of removable plexiglass side curtains, was a sales and motorsport success. Although the car was usually supplied as an open two-seater, an occasional rear seat and bolt-on steel hard top were available as extras.
The car is powered by the Standard wet liner inline four, a 1,991 cc (121.5 cu in) straight-four OHV engine initially producing 95 bhp (71 kW; 96 PS), an increase of 5 hp over the TR2 thanks to the larger SU-H6 carburettors fitted. This was later increased to 100 bhp at 5000 rpm by the addition of a "high port" cylinder head and enlarged manifold. The four-speed manual gearbox could be supplemented by an overdrive unit on the top three ratios, electrically operated and controlled by a switch on the dashboard. In 1956, the front brakes were changed from drums to discs, the TR3 thus becoming the first British series production car to be so fitted.
The suspension is by double A-arms, manganese bronze trunnion, coil springs and tube shocks at the front, optional anti-roll bar, and with worm and peg steering. Unlike MGs of the same period, the steering mechanism and linkage have considerable play and friction, which increase with wear.
The rear is conventional leaf springs, with solid axle and lever arm dampers, except that the (box) frame rails are slung under the axle. The wheels are 15 inches in diameter and 4.5 inches wide (increased from 4 inches after the first few TR2s), with 48-spoke wire wheels optional. Wire wheels were usually painted, either body colour or argent (silver), but matt chrome and bright chrome were also available. The front disc or drum brakes and rear drums have no servo assistance.
In 1957 the TR3 was updated with various changes including a full width radiator grille and this facelifted model was commonly referred to as the Triumph "TR3A". However, the cars were not badged as such and the "TR3A" name was not used officially, as is evident from contemporary sales brochures. The "TR3A" was built between 1957 and 1962.
The "TR3A" was a minor update from the TR3. The updates included the new wide front grill, exterior door handles, lockable boot handle and came with a full tool kit as standard (this was an option on the TR3). The total production run of the "TR3A" was 58,236. This makes it the third best-selling TR after the TR6 and TR7. The TR3A was so successful that the original panel moulds eventually wore out and had to be replaced. In 1959 a slightly modified version came out that had raised stampings under the bonnet and boot hinges and under the door handles, as well as a redesigned rear floor section. In addition, the windscreen was attached with bolts rather than the Dzus connectors used on the early "A" models.
The Triumph TR3 was the first production car to include standard disc brakes, which were continued on the "TR3A" facelift. The car was known for its superior braking ability, making it an autocross favourite.
The "Triumph TR3B" is an unofficial name given to the final version of the TR3, which was produced in 1962. It was offered concurrent with the TR4, which started production in 1961. The "TR3B" was a special short-production run in response to dealer concerns that the buying public might not welcome the TR4. Appearance is identical to the late US-version of the "TR3A", with the same wider head light rims, for the rest very similar to the TR3, except for a wider grille and door handles.
In 1959, three extensively modified TR3s, referred to as "TR3S" models, were run at the 24H du Mans. Resembling the production TR3, the Le Mans cars employed glass fibre body shells, were six inches longer than the production vehicle, and powered by the prototype 1,985 cc (121.1 cu in) twin-cam "Sabrina" engine.