1973 Citroen SM
Join us as we visit with the owner of this beautiful 1973 Citroen SM.
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 U.S.
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 Citroen 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 2 turns from lock to lock, often described as like a go kart.
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.
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