The Triumph TR4 is a sports car produced by Triumph Motor Company from 1961 to 1965. Code called "Zest" during development was the successor of the TR3A. The car was based on the chassis and powertrain of previous TR sports cars, but with a modern body design by Michelotti. As 40,253 cars were built during its production years, it proved to be very successful.
The TR4's new body style has eliminated the cutting-edge design of previous TRs to allow roll-up windows in place of less convenient side curtains. The angled rear end allowed a boot (trunk) of considerable capacity for a sports car.

1964 TR4 Backlit "Surrey Top"
Advanced features included the use of adjustable fascia ventilation and the option of a unique hardtop consisting of a fixed glass rear window (called a backlight) with an integrated scroll bar and a detachable steel central panel (aluminum for the first 500 units). This was the first roof system of its kind in a production car and preceded by five years the Porsche 911/912 Targa, which has since become a generic name for this top style.

On the TR4, the rigid ceiling panel was replaceable with a neatly folding vinyl insert and a support frame called the "Surrey top". The entire hardtop assembly is often mistakenly called the Surrey hood. In the original factory parts catalogs, the top rigid and backlight assembly is listed as the Hard Top kit. The insert and vinyl frame are offered separately as a Surrey top.

Features such as drop-down windows have been seen as a necessary step to face competition and make good sales in the major US market, where the vast majority of TR4s have finally been sold. Resellers were concerned that buyers did not fully appreciate the new amenities, so a special short period of TR3As (commonly called TR3Bs) was produced in 1961 and 62.

As of the first quarter of 2011, there were approximately 739 licensees and 138 SORN TR4s registered with DVLA.

Engineering
The standard pushrod four-engine is designed for use by the Ferguson TE20 tractor. The TR4 engine was continued from previous TR2 / 3 models, but displacement was increased from 1991cc to 2138 cc on TR4, increasing the hole size. Gradual improvements in manifolds and cylinder heads have allowed some improvements that culminated in the TR4A model. The 1991 cc engine became a free option for racing cars in the under-two-liter classes of the day. Some cars were equipped with vane superchargers, as the three main bearing engine was prone to crankshaft failure if it accelerated beyond 6,500 rpm; Superchargers allowed a TR4 to produce much more power and torque in relatively modest revolutions. The standard engine produced 105 hp (78 kW) SAE, but, supercharged and tuned to performance, a 2.2 liter I4 version could produce over 200 hp (150 kW) on the steering wheel. The TR4, in common with its predecessors, was equipped with a wet-sleeved engine so that, for competition use, the engine's cubic capacity could be changed by changing cylinder liners and pistons, allowing a competitor to race. under different capacity rules (ie below or above 2 liters, for example).

Late TR4 engine layout showing two Zenith Stromberg carburetors and short neck radiator
Other key enhancements over the TR3 included a wider front and rear lane, slightly larger standard engine displacement, full synchronization at all forward gears, and rack and pinion steering. In addition, the optional electrically operated Normanville Laycock overdrive can now be selected for second and third gears and the fourth, effectively providing the TR4 with a seven-speed manual gearbox with close ratio.

The TR4 was originally fitted with 15x4.5 "disc wheels. Optional 48 lace wire wheels can be ordered painted the same color as the car's (rare), kiln-glazed bodywork (matt silver with chrome spinners plus matte or polished chrome finish (originally rare, but now more commonly assembled) The most common originally assembled tires were 590-15 bias or optional radial tires. In the US at one point, Racing American alloy wheels were offered ( magnesium and aluminum) as an option, in the size of 15x5.5 "or 15x6". Tires were a problem for original owners who opted for 60-spoke wire wheels as the right-sized radial canvas tire 155-155 At the moment, only available from Michelin at a considerable cost, TR4 midsize tires reported that the original radial size was 165-15. The much more common 185-15 radials were too wide to fit.be mounted securely. they had new and wider rims mounted and their wheels replaced.

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