Triumph's TR range of cars were the result
of the evolution rather than instant design inspiration. The
4A variant featuring the majority of the previous TR4
car's running gear and body but with a new chassis offering
greater stiffness and allowing the fitment of an independent
rear suspension (IRS) setup.
This suspension was a close relative
of the system that had appeared on the Triumph
2000 saloon in 1963. For some markets IRS was an option,
so the chassis could also accomodate a solid axle and leaf springs.
The front suspension had a new upper wishbone design and revised
geometry, but most other parts were the same.
suspension changed the character of the TR range, the 4A being
a softer car with a more natural inherent understeer,
rather than the oversteer nature that the earlier cars' solid
axle gave. Wheels were 15 inch diameter, 4.5 inch wide in either
pressed steel or wire, with cross-ply tyres originally. The engine got a few more horsepower
through a redesigned manifold and camshaft, it featured either
twin SU or Stromberg carburettors depending on the production
year. It was still the old Standard Vanguard unit (incidentally
also shared with Ferguson
tractors of the time, both petrol & diesel) and, at 2.2 litres,
not exactly the smoothest sportscar motor. There was also a
servo assisted brake option and the handbrake lever was moved
to a "conventional" central position instead of its earlier
floor mounting. This unfortunately meant a shorter lever and
substantially less braking ability, corrected in the later 250/5/6
cars by the addition of extra-long levers at the rear wheels.
Inside the cockpit there were
small changes to the instruments and a wooden dash panel became
standard. Outside the grille went from a steel pressing to a
welded alloy design, and the sidelights and indicator repeaters
were combined into a wing-mounted unit to meet californian regulations
(such a requirement didnt enter UK law until 1983...). Overall the car was heavier and a little
slower, but still offered better performance and fuel economy
compared to the likes of the MGB, which was its major competitor
in the UK sportscar market.