Editing Triumph TR4 (section)

==Features==
===Body and chassis===
The TR4's new body, produced in Triumph's Speke factory, does away with the cutaway door design and sloping boot lid of the previous TRs.<ref name="trdc-tr4"/> The taller doors allow room for wind-down windows in place of the previous side-curtains, making the TR4 a true convertible. The taller, more squared-off rear body line encloses a capacious boot for a sports car.

The car's bonnet has a power bulge or "bubble" offset to one side to clear the engine's two carburettors. Early cars have a short bubble, while cars after CT 6429 have a longer bubble.<ref name="bcf-nov2004"/><ref name="te-mar2001"/>

[[File:TR4 with surrey top.jpg|thumb|left|Hardtop with centre panel removed]]
The TR4 offered an optional hard top consisting of a fixed glass backlight with integral rollbar and a detachable centre panel made of aluminium on the first 500 units, and steel on subsequent cars. Featured on one of the ''Zoom'' prototypes, this was the first such roof system on a production car, predating the [[Porsche 911]]/[[Porsche 912|912]] [[Targa top|Targa]] by five years.<ref name="revington-zoom"/>

On the TR4 the rigid roof panel could be replaced with a vinyl insert and supporting frame. While the rigid panel could not be stowed in the car, the vinyl insert and frame could be. The factory offered the rigid top and backlight assembly as the "Hard Top kit", and the vinyl insert and frame separately as the "Surrey top".

[[File:Nottuln, Oldtimermuseum, Triumph TR4 -- 2021 -- 4516.jpg|thumb|Fascia]]
The revised interior introduced adjustable [[fascia (car)|fascia]] ventilation and a collapsible steering column.<ref name="msm-sep1961"/> Features such as these were seen as necessary to keep pace with the competition, particularly in the important US market where the majority of TR4s were sold.

The TR4 uses essentially the same ladder chassis with central cruciform bracing as the TR3. At {{cvt|88.1|in|mm|0}}, the TR4 has the same wheelbase as the earlier car, but its track widths are {{cvt|4|in|mm|0}} wider in front and {{cvt|2.5|in|mm}} wider in back than the earlier model.<ref name="trdc-tr4"/><ref name="rbros-catalogue1"/>

===Powertrain===
[[File:Triumph TR4 (1963) - 14253179157.jpg|thumb|TR4 engine with SU carburettors]]
The TR4 uses the same [[Standard wet liner inline-four engine]] that powered the TR2 and TR3 models, but with displacement increased from 1991&nbsp;cc to 2138&nbsp;cc by enlarging the bore from {{cvt|83| to |86|mm|in|3}}. The cast iron block carries the crankshaft in three main bearings, and the cast iron head has two valves per cylinder driven from a camshaft in the block via pushrods and rocker arms. The 1991&nbsp;cc engine was a no-cost option for cars whose owners planned to race in the under-two-litre classes of the day. At different times the factory installed either a pair of SU H6 carburettors, or a pair of Zenith-Stromberg CD175s.

The car's four speed plus reverse [[manual transmission]] has [[synchromesh]] on all forward gears, an upgrade from the transmission in the TR3 which did not synchronize first gear. Additionally, the optional [[Overdrive (mechanics)#In Europe|Laycock de Normanville]] electrically operated overdrive could be selected for second, third, and fourth gears, effectively providing the TR4 with a seven-speed close ratio gearbox.

===Running gear===
The TR4's front suspension consists of upper and lower wishbones, and telescopic dampers. Running changes to the car included a revised front suspension geometry, indicated by a smooth upper wishbone, and a revised front brake caliper and pad size.<ref name="trdc-tr4"/>

The rear suspension includes a [[Beam axle|live axle]] with semi-elliptical springs, and lever-arm dampers.

The TR4 is fitted with [[rack and pinion steering]], replacing the cam and lever system used on the earlier TR models.<ref name="trdc-tr4"/>

The TR4 was originally fitted with 15x4.5" disc wheels. Optional 48-lace wire wheels could be ordered with one of three finishes: painted the same colour as the car's bodywork (rare), stove-enamelled (matte silver with chrome spinners, most common) or in matte or polished chrome finishes (originally rare, but now more common). Originally, the tyres most commonly fitted were 590-15 [[Bias-ply tire|bias ply]] or optional radial tyres. At one point, American Racing alloy (magnesium and aluminium) wheels were offered in the US as an option, in 15x5.5" or 15x6" size.