The Triumph TR3A was the first production car to include standard disk brakes. The car was known for its superior braking ability, making it an autocross favorite.
The Triumph TR3"B" was produced in 1962 and was offered concurrent with the TR4, which started production in 1961. In fact, the TR3"B" was a special short production run produced in response to dealer concerns that the buying public might not welcome the TR4. The TR3"B" is not actually labeled as such, but the model name is common usage. It had the body of the TR3A, but the 2,138 cc. engine and all synchromesh transmission of the TR4. The gearbox has an excellent feel. The engine is a straight 4, push rod, 3 bearing, with wet liners. It had 9:1 compression, was very rigid and had wonderful slow running and clutch feel. It was fitted with two H6 SU carburettors. It had 105 hp (78 kW) at 4,650 rpm and 172 N·m (127 ft·lbf) of torque at 3,350 rpm. It got around 20 mpgU.S. (11.76 L/100 km / 24 mpgimp) to 30 mpgU.S. (7.84 L/100 km / 36 mpgimp). The top speed was limited to about 110 mph (177 km/h) by the gear ratio, unless it had overdrive. Electrically triggered overdrive (Laycock-de-Normanville Type A) was available as an option and operated on 2nd, 3rd, and 4th gears.
It weighed 2,137 lb (969 kg) which was significantly more than the Morgan +4 and the "Bath Tub" (pre-911) Porsches, but not much more than the MGA and MGB. All except the Morgan, which shared the same engine, were substantially less powerful. Though, under most conditions it was very responsive and forgiving, it had some handling vices. The chassis, which it shared with the TR2, TR3, TR3A and TR4 had limited wheel travel, and the car was somewhat tall and narrow for a high performance sports car. As a result, on very hard cornering, the inside rear wheel would lift, causing sudden over-steer due to the increased load on the outside rear tire. This was particularly true with increasingly common radial tires. The original TR2/3/3A suspension was built with older, bias ply tire designs in mind.
The TR3"B" is a true roadster, designed for sunny weather with removable rain protection. It has a convertible top (hood) that snaps on and off and removable side curtains, allowing very low doors with padding to rest one's arm on. There are holes in the floor, with rubber plugs, so that the originally supplied jack might be used from inside the car, as did the Jaguar XK 120. The optional heater was poor and the shut-off valve was under the hood (bonnet). A third person could get behind the seats, if absolutely necessary.Source: Wikipedia.