Citroen by Lance Cole

Author:Lance Cole
Language: eng
Format: epub
ISBN: 9781847976604
Publisher: Crowood

SPORTING SUSPENSION

To exceed the DS saloon handling qualities, SM needed changes to its suspension. So pressure rates in the system were altered, mounting angles changed, and roll centres lowered. The ride was stiffer but the roll less noticeable than in the DS, and given the correct technique, the car could be steered and pointed as a fast sporting car with higher abilities than the DS-derived suspension might suggest.

With all-round independent suspension within a typical Citroën hydro-pneumatic set-up the SM had the expected leading arms up front (but with rally-inspired trailing pivot arms), and DS-type trailing arms to the rear. There were reinforcements to metal gauges where suspension components were mounted to ensure torsional rigidity and handling consistency – the hull did not flex and upset the handling. Internal pressures in the spheres were raised, and a notable difference in front and rear tyre pressures – 32psi and 29psi respectively – meant that the SM’s handling was excellent and predictable – once you had learned how to drive it. There was no ‘snap’ understeer-oversteer reaction or transition, nor ‘tailwagging’ when pushed. Lift off the power mid bend, and the SM would tuck in.

The fully powered steering design was called Direction à Rappel Asservi – ‘DIRAVI’ – or latterly in Britain, branded in capitals as ‘VARIPOWER’. This was the DS-derived super-sensitive steering with just two turns of the steering wheel across the lock, which meant that those not used to it would lurch all over the road. The system gave full assistance at low speeds, and leaned off the assistance at higher speeds. A monitoring of a gearbox shaft speed was used to calibrate the system ‘live’. At rest with the engine running, a driver could be ‘hands off’ the wheel and the car would steer itself straight. Jean-Claude Pajot was a lead technician in creating SM’s steering system, and worked with Marcel Le Breton (who had worked for Panhard) on the project. Jean-Claude Janes worked on the SM’s complex electrical system and dashboard, and an engineer by the name of M. Joly, working with Chausson, was consulted.

All this is commonplace now, but in 1970 it was sensational. For a glider or fighter pilot, the minimal steering inputs required were normal, while everyone else had to learn how to steer and brake the sensitive SM; but once mastered, rapid, sweeping progress could be made with the greatest of ease. Only the strange ‘button’-type brake pedal really needed continuous vigilance, but this was Citroënism in the pure – and after all, you didn’t have to buy one...

SM on the road: Italian, Milano-registered SM gets going during the 2013 European SM Club tour.

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