Visually similar to the TR4, the TR5 roadster sported Triumph's much more powerful 2.5 -litre straight-6, fitted with Lucas mechanical fuel-injection standard equipment included front disc brakes, independent rear suspension, rack and pinion steering and a four speed gearbox. Optional extras included overdrive and wire wheels.
A curious feature of the TR5/Lucas petrol injection system was the very frequent occurrence of an intermittent power failure when the fuel tank was no more than a quarter full. In order to provide fresh fuel at the distributor, free from overheating/soak, unused fuel was returned to the tank where it entered very close to the high-pressure fuel pump. When the fuel level fell below critical (about 3 gallons), sloshing would cause the pump to pick up a slightly aerated mixture which was sent to the fuel distributor. Unused fuel (still aerated) then passed back to the tank and was discharged close to the pump, a proportion of it being picked up and recycled to the distributor. As this cycle was repeated, gradually the volume of air in the pumped fuel reached a level where it began to affect the running of the engine. Adding as little as one gallon to the tank seemed to cure the problem. The similarly engineered contemporary saloon overcame this problem with a petrol tank specially designed for the fuel injected model. This incorporated an anti-slosh cup to ensure that the fuel outlet remained covered with fuel when the tank level was low.
The "Surrey Top" hard top, a weather protection system with rigid rear section including the rear window and removable fabric section over the driver and passenger's heads.
The Triumph TR250 was built during the same period for the North American market. Tighter emission regulations resulted in twin Zenith-Stromberg carburettors being fitted instead of the TR5's Lucas fuel injection system. Otherwise it is nearly identical. The TR250 was also available with the Surrey Top system.