Noted for its aerodynamic body shape with a drag coefficient of 0.318, [4] fully independent hydro-pneumatic brakes and self-levelling suspension, and air-cooled flat-four engine, the GS was styled by Robert Opron, with a low nose, a two-box silhouette, semi-enclosed rear wheels and a sharply vertical Kamm-tail.

When the GS was named the European Car of the Year for 1971, the design was noted as technologically advanced,[5][6] with class leading comfort, safety and aerodynamics.

The GS filled the gap in Citroën's range, between the 2CV and Ami economy cars and the luxurious DS executive sedan.

A US export model was nearly finished when Citroën withdrew from the US market, with a few dozen cars brought over in 1971 for testing purposes and to be displayed in showrooms.

[citation needed] On its launch, its main competitors in Europe included the Fiat 128, Ford Escort, Renault 6 and Vauxhall Viva.

Both the early GS (until 1976) and the GSA were fitted with a rotating drum speedometer (similar in construction to bathroom scales), rather than the dials found in a conventional instrument panel.

On the later GSA, controls were organized in flanking satellites and a diagram of the car provided information on indicator lights or mechanical problems.

[19] It also had a revised dashboard with the auxiliary controls on column-shaped pods so they could be reached without moving the hands from the single-spoked steering wheel; similar to the CX layout.

Contemporary journalists noted the smooth ride quality – the hydropneumatic suspension is designed to absorb bumps and ripples that would be uncomfortable in a conventionally sprung car with just a slight body movement.

Mated to a four speed gearbox, these were able to pull this car up to steady 151 km/h (94 mph) at 6,250 rpm (with a 1,222 cc engine), due to the very aerodynamic body shape.

Both axles comprised rigid sub frames that gave the car unmatched ride quality and road holding for the time, even on its narrow tires (factory-mounted Michelin ZX 145SR15).

Its central hydraulic system, powering the four disc brakes (inboard in front to help lower unsprung weight) and the advanced hydro-pneumatic self-levelling suspension, was derived from the Citroën DS.

The hydraulic suspension allowed the car to be raised for rough terrain at low speeds (a feature taking account of the country lanes of its native France) and to full height for easy access to the partially enclosed rear wheels.

Discs all around (ventilated in front), different wheels with a five-bolt pattern rather than three, and a three-speed semi-automatic transmission were combined with a more luxurious interior and flared fenders to set the Birotor apart from its lesser siblings.

[25] Since it was not economical for its size, and was launched in October 1973, the exact start of the 1973 oil crisis, the Birotor version achieved poor sales and was quickly pulled from the market, after 847 units were sold.

385,000 units were built in Vigo, Spain[26] Besides Portugal, production or assembly took place in countries as varied as South Africa, Chile, and Rhodesia (now Zimbabwe).

This model received the uprated 1,222 cc engine producing 48 kW (65 PS) achieved by using high compression pistons, round, rather than oval inlet manifolds, a Weber carburetor, and larger diameter driveshafts.

[27] All three body-styles, GS and GSA versions and a mix thereof were built in Cakung in East Jakarta, Indonesia by PT Alun Indah.

These modified and reinforced models were fitted with various improvements to deal with warm climates, dust, unpaved roads, and other conditions which would be encountered in French overseas departments and other markets in the developing world.