Although the base car is an open two-seater, an occasional rear seat and bolt-on steel hard top were available as extras. The TR3 is powered by a
Standard wet liner engine. This
OHV straight-four initially produced , an increase of 5 hp over the TR2 thanks to larger
SU H6 carburettors. 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 electrically engaged overdrive, controlled by a switch on the dashboard. In 1956, the front brakes were changed from drums to
discs, a first for a British series production car. Front suspension is by
double wishbones,
manganese bronze
trunnions, coil springs and telescopic dampers, with an optional anti-roll bar. Steering is a worm and peg system. Unlike
MGs of the same period, the steering mechanism and linkage have considerable play and friction, which increase with wear. The rear suspension comprises
leaf springs, a
beam axle, and lever arm dampers. The (box) frame rails are slung under the axle. 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 matte chrome and bright chrome were also available. Under most conditions the car is responsive and forgiving, but it has some
handling issues. The chassis, which is shared by the TR2, TR3, TR3A, TR3B, and TR4, has limited wheel travel. As a result, on very hard cornering, the inside rear wheel can lift, causing sudden
oversteer due to the increased load on the outside rear tyre. This is particularly true with radial tyres; the original TR2/3/3A suspension was built for crossply tyres. The wheel lifting is more sudden than that of other cars, because it is caused by coming to the end of the suspension travel while there is still load on the tyre, so the load on the other (outside) rear wheel is a discontinuous function of cornering load, rather than just changing slope. The TR3 is designed for sunny weather, but with removable rain protection. It has a convertible
hood that snaps on and off and removable side curtains, allowing very low doors with padding for the driver's arm to rest on. There are holes in the floor, with rubber plugs, so that the originally supplied jack might be used from inside the car, as in the
Jaguar XK120. The optional heater is poor, and the shut-off valve is under the
bonnet. Some 13,377 examples of the original "pre-facelift" TR3 were produced, of which 1,286 were sold within the UK; the rest were exported, mainly to the United States. As of Q1 2011 there were approximately 826 licensed and 115
SORN TR3/3As registered with the
DVLA.
Specifications • Production period – October 1955 to Summer 1957 • Original price (basic model) – £950 • Suspension – Front: independent by unequal-length double wishbones, coil springs and telescopic dampers. Rear: live axle, half-elliptic springs, lever arm dampers. • Brakes – First 4408 models (1955–56): drums all around. Remaining 9000 (1956–57): front discs; rear drums. • Factory options – Triumph offered a wide range of options and accessories for both the competition-minded owner and those simply wishing to personalise their vehicle. While many of these items were factory fitments, local dealers supplied some as well. Among these were: overdrive, 48-spoke wire wheels, steel hardtop kit (part No. 900711), occasional rear seat (No. 801264), push-button radio, interior heater, leather upholstery, windscreen washer (No. 553729), cast aluminium sump (No. 502126), aluminium ‘Al-fin’ brake drums (No. 202267 or No. 301590 (9- and 10-inch respectively)), spot and fog lamps (Nos. 501703, 501702), and a continental touring kit (No. 502022, spares for travels in remote regions).
Performance British auto magazine
The Motor tested a hardtop TR3 with overdrive in 1956. The car returned a top speed of and could accelerate from 0– in 10.8 seconds. A fuel consumption of was recorded. The test car cost £1,103 including taxes. Other figures recorded included: } ==TR3A (1957–1962)==