Citroën DS, Different From The Rest
The hydro-pneumatic system, introduced with the DS in 1955, distinguished Citroën for decades and was one of the hallmarks of an original and innovative brand. For better and for worse, Citroën did not do things like the others.
Since the invention of the automobile, if there is one to which the adjective “revolutionary” can be applied, it is the Citroën DS. Among its many qualities there are two that stand out: the originality of the design and its hydropneumatic system.
By combining air springs (nitrogen-filled spheres with an elastic membrane) with a pressurized hydraulic system, another advantage for the suspension is achieved: constant height and independent of static load. When the springs are compressed, the hydraulic pump adds fluid to the system until the body returns to its working height. Thanks to this, the wheels always work from the same position, whatever the load.
It is hard to imagine the impression it would make on those who saw it for the first time at the Paris Motor Show in October 1955. It was as if a prototype of the future had been put up for sale.
Some manufacturers used the same suspension as Citroën or something similar. Rolls-Royce tried to create one to realize that they couldn’t beat Citroën’s, so they reached an agreement to implement it from the 1965 Silver Shadow. Mercedes-Benz offered a similar system as an option for the 450 SEL 6.9 (W 116) from 1975, the S-Class from 1980 (W 126) and the E-Class (W 124), although in the latter case only as a self-leveling system on the rear axle.
Citroën made the decision to offer a simpler and less expensive version: the 1957 ID. It retained the hydropneumatic suspension, but without the rest of the hydraulic circuit elements: the steering did not initially have optional assistance since 1963), there was a gearbox manual gearbox with clutch pedal and a specific hydraulic circuit for brakes, but without assistance of any kind and with a normal pedal.