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Over-engineered affordable classics episode 1: Citroën SM

In this new series of features, we’ll be exploring a number of over-engineered collector cars that won’t break the bank. The first is the Citroën SM — without doubt one of the most beautifully engineered cars of all time, as well as one of the most complex…

One thing to come from Citroën’s acquisition of Maserati was a new flagship model for the quirky French marque. The SM combined Citroën’s cutting-edge, self-levelling, hydro-pneumatic suspension with a Maserati V6 and futuristic styling. In fact, its drag coefficient of 0.26 would place it in the top 10 of all production cars, even today.

The aforementioned suspension gives the SM better ride quality than a new Rolls-Royce Phantom, and its innovative steering design — just two turns lock to lock — eliminated any torque steer. The brake pedal was incredibly light, and the headlights were self-levelling and swivelled with the steering — again, a feature 40 years ahead of its time. All this meant that, compared to its contemporaries, the SM’s dynamic qualities were outstanding.

Its performance grew from a 2.7-litre V6 fitted with three Weber carburettors that could produce 170hp to one that had been boosted slightly thanks to Bosch injection, pushing its horsepower to 178. By 1974, Citroën implanted a 3.0-litre engine from the Maserati Marek, but it was only in conjunction with a three-speed automatic transmission. This only added an additional two horsepower. Some owners have upgraded to the larger engine, while another alternative would be to buy a 3.0-litre automatic model and install a manual gearbox.

The SM’s dynamic controls are key to understanding its genius. You drive it with minimal steering input, making only small movements with your wrists, like a go-kart. And fifty years later, Ferrari has just implemented this into its latest models, such as the 812 Superfast. Strong servo assistance means the brakes require very little pressure and take some getting used to.

As such, the SM is not a car you just get in and drive — it takes a while to retune your senses to all these more sensitive inputs. But once your brain has recalibrated, any other car from the period seems pedestrian and feels heavy. Specialists, such as Brodie Engineering, have long mastered engine and reliability problems, and prices start as low as £10,000, while the best examples well exceed £50,000. If you work closely with a maintenance specialist, you should be able to find an excellent SM for well under £40,000. You won’t regret it. 

Photos: Historics at Brooklands

You can find this very 1971 Citroën SM, listed for sale with Historics at Brooklands, in the Classic Driver Market.