The Citroën SM is a high-performance coupé produced by the French manufacturer Citroën from 1970 to 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.
History In 1961, Citroën began work on 'Project S' – a sports variant of the Citroën DS. As was customary for the firm, many running concept vehicles were developed, increasingly complex and upmarket from the DS. At some stage in the 9-year project, it evolved from developing a faster variant of the 1955 DS to developing an entirely new, thoroughly engineered car – in terms of engineering effort, a replacement for the high volume DS model. Citroën purchased Maserati in 1968 with the intention of harnessing Maserati's high-performance engine technology to produce a true Gran Tourer car, combining the sophisticated Citroën suspension with a Maserati V6.
The result was the Citroën SM, first shown at the Geneva Motor Show in March 1970. It went on sale in France in September of that year. Factory produced cars were all left-hand-drive, although RHD conversions were done in the UK and Australia.
This car was unusual for France – production of luxury cars was heavily restricted in the country by post-World War II puissance fiscale horsepower tax, so France had not had a production vehicle in this market sector since before World War II. The SM had an engine of only 2.7 liters owing to these regulations; it was the first response to the luxury/performance sector since the export oriented Chrysler Hemi V8 engine Facel Vega in the late 1950s. Citroën's flagship vehicle competed with high-performance GTs of the time from other nations and manufacturers, such as Jaguar, Ferrari, Aston Martin, Alfa Romeo, Mercedes-Benz, Porsche and Maserati's Merak.
The origin of the model name 'SM' is not completely clear. The 'S' may derive 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 "Systeme Maserati" or "Sports Maserati". Another common alternative is Série 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 did not find a sufficient customer base in the small 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 (1,800 units) and later with some modification in the Biturbo (40,000 units). The Merak, Khamsin, and Bora, used Citroën's high-pressure hydraulics for some functions, and the Citroën gearbox in the Merak, during the Citroën-Maserati alliance.
Performance Contemporary automotive journalists were 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 braking not available in any other car at the time. CAR Magazine 1972 The magazine Popular Science reported that the SM had the shortest stopping distance of any car they had tested.
Automotive journalists marveled at the resulting ability to travel for hours at in comfort. In 1972 Motorsport (U.K.) noted ..."that rare quality of being a nice car to be in at any speed, from stationary to maximum." The touring range based on the SM's fuel economy and the large fuel tank made long, fast, relaxing journeys possible.
Because the SM had a smaller engine than competitors, the acceleration was adequate rather than exemplary – some competitors were quicker. Some owners have fitted the similar sized Maserati Merak SS engine, which does improve the driving experience considerably. The fuel consumption compared favorably to its competitors.
+Performance against competitorsMake & modelPower 'SAE net'Top speedAcceleration 0 to 60 mph (0–97 km/h)Fuel economy Citroën SM 8.5 sec Jensen Interceptor 7.5 sec Alfa Romeo Montreal 7.5 sec BMW 3.0CS 7.9 sec Mercedes-Benz 450 SLC 9.5 sec Jaguar XKE Series III V12 6.8 sec Continental Mark IV 10.8 sec Cadillac Eldorado 9.7 sec
Technical innovations The SM combined many unusual and innovative features, some of which were only becoming commonplace on cars manufactured many decades later. It borrowed heavily from the innovations introduced on the DS, by including hydro-pneumatic (oleo pneumatic) self-leveling suspension, and self-leveling lights that swiveled with the steering (except in the United States, where these were illegal at the time).
The SM was Citroën's means of demonstrating just how much power and performance could be accommodated in a front-wheel drive design. This was novel, and many technical issues needed to be overcome, especially related to torque steer, where excessive steering feedback affects control of the vehicle.
A solution was found – no road feedback at all – the driver points and goes, regardless of what the driven wheels are experiencing. Hitting a pothole at high speed would not turn the steering wheel in the driver's hands.
This new type of variable assist power steering was later fitted to the Citroën CX in large numbers and its basic principle has since spread throughout the vehicle production. DIRAVI as it was called, allowed great assistance to the motorist while parking, but little assistance at motorway speeds. The system 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.
If the driver released the steering wheel, then the steering would center back to the straight ahead position. It was geared for minimal steering input – with two turns from lock to lock, it is often described as go kart-like.
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, then traditional steering feels old-fashioned.'Wheel December 1970
This steering was controversial at the time – the exaggerated, strong-arm steering inputs required in contemporary cars could cause abrupt manoeuvres in the SM. When the SM was cast as a TV series regular on The Protectors (1972), the lead actress refused to drive it, because of the familiarization required from the steering.
The DIRAVI 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 tyre area is in contact with the road at all times.
The wiper mechanism, when on the "low speed" setting, is 'sensitive' to rain, by measuring the current needed to drive the wiper motor, while the steering column is adjustable in both height and reach.
The braking system, adapted from the DS, employs disc 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, so on hard braking the entire car lowers evenly.The Longest Yard – Lockdown Edition DVD, selection 02638, Paramount Home Entertainment, 2005.
Standard wheels are steel with stainless trims, but for the rigors of off-road racing, Michelin developed a unique solution – a lightweight fiberglass wheel, which became a factory fitted option. These plastic wheels weigh less than half the standard weight and were decades in advance of similar applications. Hemmings and others are wrong when mentioning Michelin's "Roues Resin" as carbon fiber wheels, the wheels contain glass fibers, not carbon fibers. This is very clear when seeing the backside of the rims. Jalopnik also wrongly states that the wheels are made with carbon fibers.
Styling Designed in-house by Citroën's chief designer Robert Opron, the SM bears a family resemblance to the Citroën CX and Citroën GS, and to some extent the Maserati Mistral. Like the CX, the SM retains the rear fender skirts, and seen from above, the SM resembles a teardrop, with a wide front track tapering to a narrower rear track.
The SM was unusually aerodynamic for its era, with a Kamm tail and low drag coefficient. At launch, Citroën claimed a drag coefficient of 0.26,'Motor Trend' magazine (USA), May 1970 issue although it later published a revised figure of 0.339. The ventilation intake is located in a "neutral" area on the hood, which makes the ventilator fan regulate the interior ventilation at all road speeds.
With its distinctly modernist 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).
In 1970, it was the fastest front-wheel-drive car, with a factory-quoted top speed of , and independent tests achieving as much as . 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 SM's design placed eleventh on Automobile Magazines 2005 "100 Coolest Cars" listing.
US exports
The main export market for the SM was the US, where the market for personal luxury cars was much larger than in Europe. Competitors included the Cadillac Eldorado, Lincoln Mark IV and Ford Thunderbird alongside Italian, British, and German imports. The unique design of the SM made quite a splash and won the Motor Trend magazine's Car of the Year award in 1972, unheard of for a non-US vehicle at the time.Motor Trend February 1972
The SM's system of six replaceable-bulb composite halogen headlamps with swivelling high beams was illegal in the US, where regulations at the time required all vehicles to have two or four round sealed-beam headlamps on fixed mounts and with no lens or other covering in front of them. SMs for the US market were fitted with four exposed round non-swivelling sealed beams.
Despite initial success, US sales ceased suddenly when Citroën did not receive an expected exemption for the 1974 model year bumper regulation imposed by the NHTSA. The integral variable height suspension of the SM made compliance impossible. The 1974 SMs built for the US market (134 cars), could not be supplied to Americans due to the effective date of the bumper regulation, so were sold in Japan instead.
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 the existing tooling for the Maserati V8 engine. Because of this, the engine sported an unusual 90° 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 engine was aluminum, weighing just , and was always mounted behind the front axle.