The SM was one of the most severely compromised designs ever to be put into production by Citroën.
The engine was a V8 with two cylinders lopped off which meant that the angle of the V was wrong, resulting in uneven firing impulses at low engine speeds.
The problems with the intermediate shaft which drives the hydraulic pump, air conditioning and alternator were admirably covered by Andrew Brodie in SE MAN TECHS in the August issue.
Powerful front wheel drive cars suffer from torque steer unless careful attention is paid to the front suspension and steering geometry. The SM employed the DS suspension geometry. Although ride quality was improved, the car's resistance to dive and squat was greatly impaired and severe handling problems beset early prototypes. The answer was not a fundamental redesign of the suspension but a powered steering system with powered return to mask torque steer, roll oversteer in extremis and strong understeer when driven reasonably. The front suspension geometry results in a slightly harsh low speed ride but as any D owner will tell you, this disappears as momentum increases. More important still, the SM set up has inherent anti dive characteristics which assists braking by ensuring tyre contact with the tarmac.
The dashboard was fitted with oval instruments because round ones would have been too small to read. To kid you that this was an integral part of the design, the steering wheel was also made ovoid.
The control rods linking the lights to the steering and suspension (necessary in the case of the levelling link due to the aforementioned soft suspension with zero anti-dive/anti-squat) were a Heath Robinson affair which ensured that your lights regularly went out of alignment. The lessons of the DS were ignored here.
The SM was too big and heavy, underpowered, noisy and thirsty. As an example of what engineers can do when freed from commercial restraints, the SM is a tour de force. As a means of transport (and after all, this is the raison d'être of the beast) the SM, when new, was impractical and difficult to drive until one had been acclimatised -and this could take days, if not weeks.
That having been said, the SM offered, indeed offers an unparallelled driving experience. Compared to its peers, it has aged very well. Yes, it is a product of its time and certain of the styling detailing now looks old fashioned but, like the E Type, the 2CV, the VW Beetle and the Morris Minor, its purpose is self-evident; just by looking at it, you can see that it was intended as a high speed luxury cruiser. Twenty years on, it's a classic...
Just imagine what the SM might have been however; powered by a Wankel trirotor or V8 or even V12, equipped with anti-roll suspension incorporating anti squat and anti dive, with headlamp levelling/steering connected to the suspension and steering rack via high pressure hydraulics...
|This article was originally published in the Citroënian, the monthly magazine of the Citroën Car Club .|