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Citroën SM
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The Citroën SM was a high performance coupé produced by the French manufacturer Citroën between 1970 and 1975. The SM placed third in the 1971 European Car of the Year contest, trailing its stablemate Citroën GS, and won the 1972 Motor Trend Car of the Year award in the US in 1972.
961, Citroën began work on 'Project S' - a sports variant of the revolutionary Citroën DS. As was customary for the firm, many running concept vehicles were developed, increasingly complex and upmarket from the DS - eventually becoming a halo vehicle for the brand.
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The Citroën SM was a high performance coupé produced by the French manufacturer Citroën between 1970 and 1975. The SM placed third in the 1971 European Car of the Year contest, trailing its stablemate Citroën GS, and won the 1972 Motor Trend Car of the Year award in the US in 1972.
History
In 1961, Citroën began work on 'Project S' - a sports variant of the revolutionary Citroën DS. As was customary for the firm, many running concept vehicles were developed, increasingly complex and upmarket from the DS - eventually becoming a halo vehicle for the brand. Citroën purchased Maserati in 1968 with the intention of harnessing Maserati's high performance engine technology to produce a true Gran Turismo car, combining the sophisticated Citroën suspension with a Maserati V6 engine.
The result was the Citroën SM first shown at the Geneva Motor Show in March 1970. It finally went on sale in France in September of that year. All produced were left-hand-drive, although 3 official RHD conversions were done in the UK, and recently also Australia.
The origin of the model name 'SM' is not clear. The 'S' likely derives from the Project 'S' designation, the aim of which was to produce what is essentially a sports variant of the Citroën DS, and the 'M' perhaps refers to Maserati, hence SM is often assumed to stand for 'Sports Maserati', but others have suggested it is short for 'Sa Majesté' (Her Majesty in French), which aligns with the common DS model's nickname 'La déesse' (The Goddess).
The SM was Citroën's flagship vehicle, competing with other high performance GTs of the time from manufacturers such as Jaguar, Lotus, Ferrari, Aston Martin, Alfa Romeo and Porsche. It was also Citroën's way of demonstrating just how much power and performance could be accommodated in a front-wheel drive design.
The SM innovated a new type of variable assist power steering that has since spread throughout the vehicle population. DIRAVI as it was called, allowed great assistance to the motorist while parking, but little assistance at motorway speeds. The steering actually had the same "assist" at all speeds - the steering was hydraulically locked against steering movement of the wheels from the road ("feedback") up to the capacity of the unit. Hitting a pothole at high speed would not turn the steering wheel in the driver's hands. The reduction in 'assist' was achieved by a piston/roller pushing on a heart shaped cam geared to the steering shaft (hence the one turn to full lock), which was fed with system pressure so that as its pressure rose with increasing road speed, the steering assistance seemingly reduced and the steering centering effort rose. However, full steering wheel turning was available at all speeds, though considerable force was necessary to turn the steering wheel at high road speed. Enough pressure was admitted to the centering unit to return the wheels to the straight ahead position when the car was not moving. The centering pressure was regulated by a flyweight centrifugal governor driven by the pinion (secondary) shaft of the manual gearbox and by a proportioning valve connected to the fluid pressure in the automatic gearbox, which pressure was proportional to the speed of the output shaft. The pressure increased all the way to , and a subsidiary function of this feed was to turn off the air conditioning fans above .
Contemporary automotive journalists were most effusive about the SM's dynamic qualities, which were unlike anything they had experienced before. The SM provided a combination of comfort, sharp handling, and high performance not available in any other car at the time. Popular Science noted that the SM had the shortest stopping distance of any car they had tested. To this day this stopping distance remains outstanding.
The SM won its first competitive outing, the grueling 1971 Rallye du Maroc.
Unfortunately, the SM did not find a sufficient customer base in the European GT market, but much of the SM's technology was carried forward to the successful Citroën CX, launched in 1974 - the DIRAVI steering being the most obvious example. The same basic engine in enlarged 3.0 L form (some in Italy had 2.0 L) was used in Maserati's own Merak which, together with Maserati's Khamsin and Bora, used Citroën's high pressure hydraulics for some functions, and the Citroën gearbox in the Merak, during the Citroën-Maserati alliance.
Styling
The look of the car, although easily identifiable as Citroën, is quite distinct, with a shape that even today looks futuristic. Designed in-house by Citroën's chief designer Robert Opron, the SM bears a vague family resemblance to the DS, especially in retaining the latter's rear wheel spats. Seen from above though, the SM resembles a teardrop, with a wide front track tapering to a narrower rear track.
Many of the details reflect Opron's American background, notably the vestiges of 'fins' at the rear. Opron worked on aircraft body design and aerodynamics while in the USA, and the SM benefited from this experience. It was unusually aerodynamic for its era, with a very low drag coefficient of 0.26. The SM was one of the first production cars to benefit from extensive wind tunnel testing during its design phase, and as a result aerodynamic efficiency influenced the final design of many details including the shape of the side mirrors, the method of windshield sealing, and the underbelly of the car which featured active aerodynamics, effectively sucking the car to the road at high speed.
European critics marveled at the resulting ability to travel for hours at 200 km/h (120 mph) in comfort and with impressive fuel economy on the large 90 litre (20 US gal; 17 Imp. gal.) fuel tank.
With its distinctly Art Deco influence, the interior styling of the SM is as dramatic as the exterior. The small oval steering wheel is matched by oval gauges. The manual shift lever 'boot' is a highly stylized chrome gate. The seats are highly adjustable buckets with centre padding composed of many individual 'rolls'. High quality materials are used throughout. The bonnet is aircraft grade aluminum, while the external bright work is stainless steel, rather than ‘cheaper’ chrome (except for "plastichrome" "SM" trim at the rear base of the rain gutter).
The SM's design is timeless; the car was even used in a 1999 television advertisement for British Petroleum of Spain, where 'a futuristic car was required'. It placed eleventh on Automobile Magazine's 2005 "100 Coolest Cars" listing.
In 1970, it was a car of the future and the fastest front-wheel drive car to be made, with a factory quoted top speed of , and independent tests achieving as much as 235 km/h (145 mph). It was an example of the car as a symbol of optimism and progressive technology, similar to the SM's contemporary, the Concorde aircraft. The true distinction in speed of the SM is its ability to maintain 200 km/h (125 mph) from one fuel stop to the next. Many other cars will go faster for a dash, but most will not withstand long periods at such speed.
Technical innovations
The SM combines many unusual and innovative features, some of which are only just becoming commonplace on cars of today. It borrows heavily from the innovations introduced on the DS, by including hydro-pneumatic (oleopneumatic) self-leveling suspension, and self-leveling lights that swiveled with the steering (except in the USA where these were illegal at the time).
The steering is self-centering and fully-powered (as opposed to hydraulically assisted). This feature allows the front wheels to run near-zero caster, and means that there is no camber change as lock is applied, and also ensures that the maximum amount of tire area is in contact with the road at all times. The system also adjusts the hydraulic pressure on the steering centering cam according to vehicle speed so that the amount of steering feel remained almost constant at any speed, counteracting the tendency of manual and ordinary power assisted steering to feel light at high speed. Thus the car turns easily at low speed, emphasized by high gearing given two turns lock-lock, and relatively more effort is required at higher speed. Many contemporary reviewers remarked that this system would take at least of driving to become familiar, but once the driver is accustomed to the system traditional steering feels old-fashioned.
The wiper mechanism is 'sensitive' to rain, while the steering column is adjustable in both height and reach.
The braking system, adapted from the DS, employs disk brakes at all four corners (the DS has drums at the rear), with the front brakes being inboard, and cooled via large ducts on the front underside of the car. The hydraulic braking pressure front to rear balance is self-adjusting according to the weight in the rear of the car.
Standard wheels are steel with stainless trims, but a factory option was available for lightweight wheels made of composites. These wheels weigh less than half the standard weight and are possibly a unique application of composites on a production vehicle.
US exports
The main export market for the SM was the United States. In the US, the market for personal luxury cars was much larger than in Europe, with competitors like the Cadillac Eldorado, Lincoln Mark IV and Ford Thunderbird alongside a large selection of Italian, British, and German imports. Nevertheless, the unique design of the SM made quite a splash and won the Motor Trend magazine Car of the Year award in 1972: unheard of for a non-US vehicle at the time.
The SM's six headlight set up was illegal in the United States and consequently, US specification cars were fitted with four fixed round exposed lamps.
Despite initial success, US sales ceased suddenly - Citroën expected (but did not receive) an exemption for the 1974 model year bumper regulation imposed by the NHTSA. The integral variable height suspension of the SM made compliance impossible. The final batch of 134 now illegal 1974 US model SMs were shipped to Japan.
Interestingly, in 1977, Mercedes-Benz introduced a hydro-pneumatically suspended car to the U.S. market, the Mercedes-Benz 450 SEL 6.9, which cost as the equivalent of three SM's. This car did not "settle" when central system pressure bled off while parked, because it used a more complex suspension geometry that incorporated steel springs. The height adjustable feature the car had in other markets was disabled for the US,
This bumper regulation as written appeared not carefully thought through, and was repealed in 1981. The original intent was to address a fairly small economic concern, repair costs in low speed accidents. NHTSA attempted to address this issue by mandating a certain design and criminalizing any deviance from it. It called for bumpers to be an exact height off the ground at all times, yet according to the laws of physics, all cars (except the SM - its lateral front control arms' axes are angled forward to cancel this effect) dip at the nose on braking. Vehicles classified as trucks were always exempt.
Engines
The SM was sold with a small, lightweight engine in various forms, designed from scratch by Giulio Alfieri but capable of being assembled on existing V8 tooling. Because of this, the engine sported an unusual 90 degree angle between cylinder banks - a trait shared with the later PRV V6. It was a very compact and innovative design that allowed the use of just one pattern for the cylinder heads and an intermediate shaft extended out to drive the auxiliaries.
The engines - always mounted behind the front axle were:
- 2.7 L V6 with Weber 42 DCNF carburettors, "C114-1" (170 bhp) (1970-1972)
- 2.7 L V6 with Bosch D-Jetronic injection, "C114-03" (178 bhp) (1973-1976 - Not available in the US)
- 3.0 L V6 with Weber 42 DCNF carburettors, "C114-11" (180 bhp) (1971-1975 - US only in 1971, rest of the world, automatic only in 1974 & 1975)
The size of the 2.7 L engine was limited by French puissance fiscale taxation, which effectively banned large displacement vehicles. The engine was also used in the Maserati Merak from 1973 to 1982 (later versions for the Merak SS had much larger valves and a reputed 220BHP) and the Ligier JS2 sports car. The final SMs were produced in the Ligier factory in Vichy.
5 speed manual and 3 speed Borg Warner fully automatic transmissions were fitted early on, but with the rest of the world outside North America only getting the fully automatic in 1974 & 1975.
The C114 is a relatively sturdy unit, provided certain modifications are performed to eliminate weak points leading to catastrophic damage:
- Primary distribution chains and tensioners may wear out prematurely. This is commonly due poor lubrication of the chain and overloading from the air-conditioning system, which unlike modern cars has no safety cut-out fitted, a simple remedial. Modern timing chains should be fitted on overhaul as they have a considerably extended life. A curved fixed chain limiter and improved tensioner should be fitted to the primary chain, with if possible a spray lubrication hole as factory installed on I.E & 3.0L engines. If the timing is not kept perfect, the engine may "kick-back" when stopping, jerking the slack side of the main chain against the tensioner.
- The secondary chains should be tensioned regularly in compliance with the service book, and replaced when the tensioners reach the end of their travel. Valve timing is extremely critical as the normal valve-to-piston clearance is very close. There is little margin for error, and the change in valve timing due to normal chain wear uses much of the allowance.
- The sodium partly-filled exhaust valves may fail due to internal corrosion and drop into the cylinder. It is advisable to replace these valves immediately with externally dimensionally identical solid stem valves, certainly on the I.E. and 3.0L cars. Sodium filling gives no real advantage on highway cars not operated continually at full power. The theoretical advantage is realistically outweighed by the real possibility of a smashed engine from a piston cramming a broken-off valve head into the cylinder head or out the side of the cylinder liner.
- The backspacing of the crankshaft bore accepting the oil pump shaft is not controlled adequately. The oil pump drive shaft commonly falls into the crank and runs on a small area of its splines thus wearing rapidly. A simple fix is to add a compliant spacer (so as not to end-load the oil pump) in the splined hole in the crankshaft timing sprocket. Maserati beefed up the shaft in later versions, and this should be retrofitted if possible when not already present. Later shafts are longer, with longer splines, shorter necked-down central portions, and thicker central portions. Reports of broken oil pump drive shafts are known from revving the engine on start-up in cold weather. Though in 1970-75 the oil viscosity specification was 20W-50, modern engine oils do not need to be so heavy. Nevertheless, I started my early 2.7 litre engine, filled with 20W-50, in -17 °F (-27 °C) with no problem.
- It is a very quiet engine in good order, any noise should be investigated immediately. Only a slight "patter" from the cams and a little "buzz" from the timing chains, which are roller type, not the "silent" Morse-type chains common on USA cars, should come from an idling engine. Any "rattles" or "knocking" sounds should be corrected immediately! The engine, if properly updated and maintained, should be good for several hundred thousand miles before a total rebuild is needed.
Demise
After the 1974 bankruptcy of Citroën, Peugeot took ownership of the company and in May 1975, divested Maserati. Peugeot decided to stop building the SM, as sales were minimal in that year.
Observers often attribute the demise of the SM to the 1973 oil crisis and economic recession. While the oil shock certainly impacted sales, it is useful to note that many far more profligate cars were introduced at the same time the SM ceased production, like the Mercedes-Benz 450SEL 6.9. Peugeot even introduced a V6 powered car of similar displacement and fuel consumption in 1975, the 604. In the USA, the SM was actually an economical vehicle relative to its competitors. However, NHTSA imposed new automotive design regulations in 1974, effectively banning the Citroën from the US market.
As illustrated under production numbers, SM sales declined starting in 1972. This appears to be attributable to maintenance issues. The early ignition breaker cassettes are very unreliable, and the timing chains cause catastrophic engine failure if not adjusted at 60,000 km, faults that were corrected long after production ceased. The 90 deg engine timing was unfamiliar to mechanics in 1970s.
Most vehicles require only generalist maintenance, where any competent mechanic can properly maintain the vehicle. Certain vehicles, like Citroëns and Ferraris require specialist care due to their unique design. While a sturdy car if maintained rigorously, the SM did require two sets of specialist care - Citroën specialists, which are widespread in Europe, and a rarer Maserati specialist, to keep the engine in tune. Once potential buyers began to realize this, sales dropped precipitously.
Components of the SM lived on - in the Maserati Merak (engine, transmission) and the Lotus Esprit (transmission (both mirror image)). Nissan made a small three-door hatchback in the late 1970s which used many SM styling cues, including the tailgate. The successful Citroën CX carried forward most of the SM's dynamic qualities, including the trendsetting speed sensitive power steering.
Production numbers
A total of 12,920 SMs were produced during its lifetime. The production figures for individual years were:
- 1970: 868
- 1971: 4988
- 1972: 4036
- 1973: 2619
- 1974: 294
- 1975: 115
The North American market took 2,400 cars, in the years 1972 and 1973. Eliminating this impact, sales declined a dramatic 43% from 1971 to 1972 and a further 50% in 1973.
Variants
Coachbuilder Henri Chapron from Levallois-Perret produced a handful of convertibles (SM Mylord) and sedans (SM Opéra). French Presidents from Georges Pompidou to Jacques Chirac have enjoyed touring Paris in the two 4-door convertible Citroën SM présidentielle models, also converted by Chapron.
In 1971, Heuliez also produced 2 examples of a targa top convertible, the SM Espace.
Just before the SM's demise, Citroën produced several short-wheelbase racing versions with squared-off rear sections and highly tuned engines - known as the "breadvan" model.
The SM was never produced in right-hand drive although three official prototypes were constructed by Middleton Motors, a Citroën dealer in Hertfordshire, England. At least one of these prototypes still survives. Cars are currently being modified with RHD controls and dashboards for Australian sale.
Frua also proposed a concept car based on the SM, closely resembling the Merak.
SM World, a marque specialist in Los Angeles, California, has produced an extended SM pickup truck and a turbocharged SM, which set the land speed record for its class at the Bonneville Salt Flats, Utah - traveling 202 mph (327 km/h). These vehicles have both been memorialized in die-cast miniatures.
The Maserati Quattroporte II was a Maserati-badged, 4-door variant of the SM, with an angular body and lengthened floorpan. The six headlights were retained and the later 'SS' version of the engine fitted.
Appearances in art and famous owners
Like the Citroën DS, the SM has made prominent appearances in several films and TV series, and has had many celebrity owners. Emperor and religious icon Haile Selassie I of Ethiopia had an SM, while Ugandan strongman Idi Amin had seven of them. The Shah of Iran drove an SM. Actors Lorne Greene and Lee Majors, General Secretary of the Communist Party of the USSR Leonid Brezhnev, composer John Williams, author Graham Greene, soccer star Johan Cruijff, Cheech Marin,The Rolling Stones drummer Charlie Watts and Thomas Chong were among other prominent owners of the SM. In motorsport Mike Hailwood owned one and drove it to F1 meetings.
Burt Reynolds escapes a fleet of police cars behind the wheel of an SM in the 1974 film The Longest Yard. In the film, having driven the car to a quayside, Reynolds gets out of the car and nudges the car into gear, causing it to drive itself into the water. This is an amusing aspect of the film, as it required the use of an automatic-equipped SM, since this could not have been done with the manual transmission-equipped SM used in the rest of the chase sequence without either grinding the gears or stalling the engine. In real life, he liked the car so much that he gave an SM to his friend Dinah Shore.
Janet Jackson appears in an SM with a red leather interior in the music video for the 1998 hit song I Get Lonely from the Velvet Rope album.
Patrick McGoohan drives an SM in a 1975 episode of the American television series Columbo, while Gerry Anderson's 1971 television series The Protectors prominently featured a platinum blue SM.
Ben Stiller is kidnapped in a green SM in the 2001 film Zoolander, and an SM is also used in an attempted kidnapping in the 1975 Charles Bronson film Breakout.
While not bearing a resemblance to any other car on the market, the SM did resemble the vehicles featured on the 1970 science fiction television program UFO.
Sven Väth and Miss Kittin drive a modified Citroën SM in their video from the single Je T'Aime Moi Non Plus.
Comedian Jay Leno maintains a stock 1972 Citroën SM in his .
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