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Citroën

Citroën ID

1955-1976

Citroën Traction Avant

Citroën CX

Mid-size luxury car / Executive car

4-door sedan 5-door Safari station wagon 2-door convertible

MF layout

3124 mm (123 in) [1]

4826 mm (190 in) (saloon) 4991 mm (196.5 in) (estate)

1791 mm (70.5 in)

1464 mm (57.6 in) (saloon) 1537 mm (60.5 in) (estate)

1270 kg (2800 lb)(saloon) 1384 kg (3051 lb)(estate)

64 L (17 US gal/14 imp gal)

Citroën SM

Flaminio Bertoni

1974 Citroën DS23 Pallas

Directional headlight detail of a Citroën DS21

Swedish-spec Citroën DS with headlight wipers

Citroën DS Break - also known as the Safari, Familiale, or Wagon

Citroën DS Convertible

Turn indicators were mounted in the upper corners of the rear window

The Citroën DS (also known as Déesse, or Goddess, after the punning initials in French) is an executive car that was produced by the French manufacturer Citroën between 1955 and 1975. Citroën sold nearly 1.5 million D-series during its 20 years of production. The DS is well-known for its futuristic, aerodynamic body design, styled by the Italian sculptor and industrial designer Flaminio Bertoni, and for its innovative technology, including its hydropneumatic self-leveling suspension system.

The DS advanced the achievable standards in terms of ride quality, roadholding, handling and braking in an automobile.^[2] The DS came in third in the 1999 Car of the Century competition, recognizing the world's most influential auto designs. Winner and second place went to the Ford Model T and the Mini.

[edit] Model history

After 18 years of development in secret as the successor to the venerable Traction Avant, the DS 19 was introduced on October 5, 1955 at the Paris Motor Show. The car's appearance and innovative engineering captured the imagination of the public and the automobile industry almost overnight. In the first 15 minutes of the show 743 orders were taken, and orders for the first day totalled 12,000.^[3]

Far from being just a fascinating technology in search of a purpose, contemporary journalists were effusive in noting how the DS dramatically pushed the envelope in the ride vs. handling compromise possible in a motor vehicle.^[4]

To a France still deep in reconstruction after the devastation of World War II, and also building its identity in the post-colonial world, the DS motor car was a symbol of French ingenuity.^{[citation needed]} It defied virtually every automotive design convention of that era.^{[original research?]}

It also posited the nation's relevance in the Space Age, during the global race for technology of the Cold War.^{[original research?]} Structuralist philosopher Roland Barthes, in an essay about the car, said that it looked as if it had "fallen from the sky".^[5]

The high price tag, however, hurt general sales in a country still recovering from World War II 10 years earlier, and a cheaper submodel, the ID (another pun: in French, Idée, or Idea), was introduced in 1957. The ID shared the same body with the DS, but had more traditional features under the hood. It had no power steering (though this was added as an option later), and instead of the hydraulically controlled manual transmission and clutch, it had a conventional clutch and transmission. Interestingly, the first model series was called 11D, a clear reminder of the last model of the Traction Avant, the 11C. A station wagon variant, the ID Break, was introduced in 1958.

Outside of France, the car's radical and cosmopolitan design appealed to non-conformists. A United States advertisement summarised this selling point: "It takes a special person to drive a special car".^{[citation needed]}

Throughout its model lifetime, the DS managed to remain ahead of its time.^{[original research?]} It featured power disc brakes, a hydropneumatic suspension including an automatic levelling system and variable ground clearance, power steering and a semi-automatic transmission, and a fiberglass roof which reduced weight transfer.^{[citation needed]} Inboard front brakes (as well as an independent suspension) reduced unsprung weight. Different front and rear track widths and tire sizes reduced the understeer typical of front-engined and front-wheel drive cars.^{[citation needed]}

As with all French cars, the DS design was affected by the tax horsepower system, which effectively mandated very small engines. Unlike the Traction Avant predecessor, there was no top-of-range model with a powerful six cylinder engine.

Despite the rather leisurely acceleration afforded by its small four-cylinder engine, the DS was successful in motorsports like rallying, where sustained speeds on poor surfaces are paramount, and won the Monte Carlo Rally in 1959 and 1966.

The DS placed fifth on Automobile Magazine "100 Coolest Cars" listing in 2005.^{[citation needed]}

The DS was historically significant for many reasons, one being that it was the first production car with front disc brakes.^[6]

[edit] Technical Innovation - Hydraulic System

In conventional cars, hydraulics are only used in brakes and power steering. In the DS they were also used for the suspension, clutch and transmission, although the later ID19 did have manual steering and a simplified power braking system.

At a time when few passenger vehicles had independent suspension on all wheels, the application of the hydraulic system to the car's suspension system to provide a self-levelling system was an innovative move. This suspension allowed the car to achieve sharp handling combined with very comfortable ride quality, frequently compared to a 'magic carpet'. The system used - 'hydropneumatic suspension' - was pioneered the year before, on the rear of another car from Citroën, the top of range Traction Avant 15CV-H.

[edit] Impact on Citroën brand development

The 1955 DS in one stroke cemented the Citroën brand name as an automotive innovator. In fact, the DS caused such a huge sensation that Citroën was fearful future models would not be bold enough. Other than variations on the very basic 2 cylinder economy car Citroën 2CV, like the Citroën Ami, no new models were introduced from 1955 to 1970.

The DS was a large, expensive executive car and a downward brand extension was attempted, but without result. Throughout the late 1950s and 1960s Citroën developed many new vehicles for the very large market segments between the 2CV and the DS, occupied by vehicles like the Peugeot 403, Renault 16 and Ford Cortina. None made it to production. Either they had uneconomic build costs, or were ordinary "me too" cars, not up to the company's high standard of innovation. Because Citroën was owned by Michelin as a sort of research laboratory, such experimentation was possible. Citroën finally did introduce the clever Citroën GS in 1970, which sold a spectacular 2.5 million units.

[edit] Replacing the DS

The DS remained popular and competitive throughout its production run. Its peak production year was 1970. Certain design elements like the somewhat narrow cabin, column mounted gear shifter, and separate fenders began to seem a little old fashioned in the 1970s.

Citroën invested enormous resources to design and launch an entirely new vehicle in 1970, the Citroën SM, which was a thoroughly modernized, slightly larger, version of the DS.

Few parts are directly interchangeable between the two cars (many SM parts are modified DS parts - such as the rear swingarms, the front suspension housings, front suspension lateral arms, hydraulic pump, suspension cylinders, spheres (accumulators), wheel bearing housings, front brake calipers, transaxle, suspension height correctors, etc.), but the DS and SM were both assembled on the same production lines in Paris. The SM construction was conceptually similar to that of the DS: a platform frame with many pieces spotwelded together, with detachable front fenders, and trailing arm rear suspension. On the SM, the roof and rear quarter panels were welded on. Unlike the DS, the factory never authorized a convertible model, since Citroën felt the roof was integral to the structure of the SM. [The DS convertibles used the break (station wagon) frame, which was reinforced on the sidemembers and rear suspension swingarm bearing box.]

The SM had to fulfill another purpose beyond just upgrading the DS however - it also had to launch Citroën into a new Grand Touring market segment. This meant that unlike the DS, the SM was not designed to be a practical 4-door sedan suitable as a large family car, the key market for vehicles of this type in Europe. Typically, manufacturers would introduce low volume coupés based on parts shared with an existing sedan, not as unique models - a contemporary example being the Mercedes-Benz SLC-Class. The SM's high price, driven by the Maserati engine and limited utility of the 2+2 configuration, meant the SM as actually produced could not seize the mantle from the DS. Perhaps, if the Peugeot-Renault-Volvo Douvrin V6 had been used in the SM instead of the Maserati, the SM's price could have been significantly lower.^{[citation needed]} The Douvrin V6 was about the same size and could be tuned to the same power range. Nevertheless, when the DS was phased out, the SM had to go too.

The DS was finally phased out in 1975 after 1,455,746 cars were produced. The DS was replaced in the model range by the more compact CX. The SM, based as it was on the DS, went at the same time.

[edit] Nations assembling the DS

The majority of DS cars were built in Paris, France. They were also made in the United Kingdom, South Africa, the former Yugoslavia (mostly Break Ambulances), and Australia.

Australia constructed their own D variant in the 1960s at Heidelberg, Victoria. These are identified as the ID 19 "Parisiene." Australian market cars were all fitted with options as standard equipment like the "DSpecial DeLuxe" that were never available on domestic European models.

British built cars are distinguished by their leather seats, wooden dashboards, and Lucas made electrics.

Within some parts of the former Yugoslavia, DS sedans are still in normal use as taxis.

[edit] DS in the US

US-spec 1969 Citroën DS with exposed headlights

While the DS was a hit in Europe, it seemed rather odd in the United States. Ostensibly a luxurious car, it did not have the basic features that buyers of that era expected to find on such a vehicle - fully automatic transmission, air conditioning, power windows and a reasonably powerful V8 engine instead of a relatively modest 4-cylinder inline engine. The DS price point was similar to the contemporary Cadillac luxury car. Also, people at the time wanted only the newest models, which changed every year, like fashions, while the DS appeared vaguely derivative of the 1950 Hudson Hornet step-down design.

Outdated US legislation also banned one of the car's more advanced features, aerodynamic headlamps, now common in US automobiles. The first year of aerodynamic glass enclosing the DS's headlights, along with driving lights turned by the steering, was also the first year those features were outlawed in the US. The VW Beetle and Jaguar XKE had aerodynamic faired glass over their (fixed) headlights until the same time.

The DS was sold in the United States from 1956 to 1972. Ultimately, 38,000 units were sold.

[edit] Design variations

The DS always maintained its size and shape, with easily removable, unstressed body panels, but certain design changes did occur.

A station wagon version was introduced in 1958. It was known by various names in different markets (Break in France, Safari and Familiale in the UK, Wagon in the US, and Citroën Australia used the terms Safari and Station-Wagon). It had a steel roof to support the standard roof rack.

In September 1962, the DS was restyled with a more aerodynamically efficient nose, better ventilation and other improvements. It retained the open two headlamp appearance, but was available with an optional set of driving lights mounted on the front fenders. In 1965 a luxury upgrade kit, the DS Pallas (after Greek goddess Pallas), was introduced. This included comfort features such as better noise insulation, leather upholstery and external trim embellishments.

In 1967, the DS and ID was again restyled. This version had a more streamlined headlamp design, giving the car a notably shark-like appearance. This design had four headlights under a smooth glass canopy, and the inner set swivelled with the steering wheel. This allowed the driver to see 'around' turns, especially valuable on twisting roads driven at high speed at night.

However, this feature was not allowed in the US at the time (see World Forum for Harmonization of Vehicle Regulations), so a version with four exposed headlights that did not swivel was made for the US market.

The station wagon edition, the Break (called the ID Safari on the UK market) and "Familiale", was also upgraded. The hydraulic fluid changed in all markets (except the US) to the technically superior LHM (Liquide Hydraulique Minérale).

Rarest and most collectible of all DS variants, a convertible was offered from 1958 until 1973. The convertibles were built in small series by French carrossier Henri Chapron, for the Citroën factory. In addition, Chapron also produced a few coupés, non-works convertibles and special sedans (DS Lorraine for instance).

[edit] Technical Details

[edit] Suspension

In a hydropneumatic suspension system, each wheel is connected, not to a spring, but to a hydraulic suspension unit consisting of a sphere of about 12 cm in diameter containing pressurised nitrogen, a cylinder containing hydraulic fluid screwed to the suspension sphere, a piston inside the cylinder connected by levers to the suspension itself, and a damper valve between the piston and the sphere. A membrane in the sphere prevented the nitrogen from escaping. The motion of the wheels translated to a motion of the piston, which acted on the oil in the nitrogen cushion and provided the spring effect. The damper valve took place of the shock absorber in conventional suspensions. The hydraulic cylinder was fed with hydraulic fluid from the main pressure reservoir via a height corrector, a valve controlled by the mid-position of the anti-roll bar connected to the axle. If the suspension was too low, the height corrector introduced high-pressure fluid; if it was too high, it released fluid back to the fluid reservoir. In this manner a constant ride height was maintained. A control in the cabin allowed the driver to select one of five heights: normal riding height, two slightly higher riding heights for poor terrain, and two extreme positions for changing wheels. [The correct term oleopneumatic (oil-air) has never gained widespread use. Hydropneumatic (water-air) continues to be preferred overwhelmingly.]

The DS did not have a jack for lifting the car off the ground. Instead, the hydraulic system enabled wheel changes with the aid of a simple adjustable stand. To change a flat tyre, one would adjust the suspension to its topmost setting, insert the stand into a special peg near the flat tyre, then readjust the suspension to its lowermost setting. The flat tyre would then retract upwards and hover above ground, ready to be changed. This system, used on the SM also, was superseded on the CX by a screw jack that, after the suspension was raised to the high position, lifted the tire a fraction of an inch off the ground. The DS system, while impressive to use, sometimes dropped the car quite suddenly, especially if the stand was not placed precisely or the ground was soft or unlevel.

[edit] Source and reserve of pressure

The central part of the hydraulic system was the high pressure pump, which maintained a pressure of between 130 and 150 bar in two accumulators. These accumulators were very similar in construction to the suspension spheres. One was dedicated to the front brakes, and the other ran the other hydraulic systems. (On the simpler ID models, the front brakes operated from the main accumulator.) Thus in case of a hydraulic failure (a surprisingly infrequent occurrence), the first indication would be that the steering became heavy, followed by the gearbox not working; only later would the brakes fail.

[edit] Hydraulic fluid

The original hydropneumatic system used a vegetable oil liquide hydraulique végétal (LHV), similar to that used in other cars at the time. Later, Citroën changed to using a synthetic fluid liquide hydraulique synthétique (LHS). Both of these had the disadvantage that they are hygroscopic, as is the case with most brake fluids. Disuse allows water to enter the hydraulic components causing deterioration and expensive maintenance work. The difficulty with hygroscopic hydraulic fluid was exacerbated in the DS/ID due to the extreme rise and fall in the fluid level in the reservoir, which went from nearly full to nearly empty when the suspension "got up" and the 6 accumulators in the system filled with fluid. With every "inhalation" of fresh moisture- (and dust-) laden air, the fluid absorbed more water. In August 1967, Citroën introduced a new mineral oil-based fluid liquide hydraulique minéral (LHM). This fluid was much less harsh on the system, and remains in use to the present day.

Briefly illegal in the United States (US federal law required motor vehicle brake systems to use DoT approved brake fluid - an exception had to be granted to Citroën), LHM has since been adopted by manufacturers like Rolls-Royce, Jaguar, BMW, and Audi under various labels, like "Total," "Pentosin," and others.

LHM required completely different materials for the seals. Using either fluid in the incorrect system would completely destroy the hydraulic seals very quickly. To help avoid this problem, Citroën added a bright green dye to the LHM fluid and also painted all hydraulic elements bright green. The former LHS parts were painted black.

Several different hydraulic pumps were used. The DS used a seven-cylinder axial piston pump driven off two belts and delivering 175 bar of pressure. The ID19, with its simpler hydraulic system, had a single cylinder pump driven off an eccentric on the cam.

[edit] Gearbox and clutch

Late 1960's Pallas interior with Hydraulic gear selector - mounted top right of steering collumn

The mechanical aspects of the gearbox and clutch were completely conventional and the same elements were used in the ID 19. The gear change control though, consisted of: a hydraulic gear selector, and clutch control. The speed of engagement of the clutch was controlled by: a centrifugal regulator sensing engine rpm and driven off the camshaft by a belt, the position of the butterfly valve in the carburettor (i.e. the position of the accelerator), and the brake circuit. When the brake was pressed, the engine idle speed dropped to a rpm below the clutch engagement speed, thus preventing friction while stopped in gear at traffic lights. When the brake was released, the idle speed increased to the clutch dragging speed. The car would then "creep" much like automatic transmission cars. This drop in idle throttle position also caused the car to have more engine drag when the brakes were applied even before the car slowed to the idle speed in gear, preventing the engine from "pulling" against the brakes.

[edit] Engines

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