Hydropneumatic Suspension - History

History

Citroën first introduced this system in 1954 on the rear suspension of the Traction Avant. The first full implementation was in the advanced DS in 1955. Major milestones of the hydropneumatics design were:

  • During World War II, Paul Magès, an employee of Citroën, with no formal training in engineering, secretly develops the concept of an oil and air suspension to combine a new level of softness with vehicle control and self-levelling
  • 1954 Traction Avant 15H: Rear suspension, using LHS hydraulic fluid.
  • 1955 Citroën DS: Suspension, power steering, brakes and gearbox/clutch assembly powered by high pressure hydraulic assistance. A belt driven 7-piston pump, similar in size to a power steering pump, generates this pressure when the engine is running.
  • 1962 Morris Motors LImited introduces the BMC ADO16 ('1100') with hydrolastic suspension
  • 1964 Mercedes-Benz introduces the 600 with air suspension designed to avoid Citroën patents
  • 1965 Rolls-Royce licenses Citroën technology for the suspension of the new Silver Shadow
  • 1966 Mercedes-Benz introduces the 6.3 also with air suspension
  • 1967 The superior LHM mineral fluid is introduced
  • 1970 Citroën GS: Adaptation of the hydropneumatic suspension to a small car
  • 1970 Citroën SM: Variable speed auto-returning power steering, dubbed DIRAVI, and hydraulically actuated directional high beams
  • 1974 The Mercedes-Benz 450SEL 6.9 becomes the first hydropneumatic Mercedes-Benz automobile, with the pump driven by the engine's timing chain instead of an external belt. This adaptation was used only for the suspension. Power steering and brakes were conventional hydraulic- and vacuum-powered, respectively.
  • 1983 Citroën BX, built as a 4WD in 1990
  • 1989 Citroën XM: Hydractive Suspension, electronic regulation of the hydropneumatic system; sensors measure acceleration and other factors
  • 1990 Peugeot 405 Mi16x4: first Peugeot equipped with rear hydropneumatic suspension
  • 1990 JCB Fastrac high speed agricultural tractor uses this system for its rear suspension.
  • 1993 Citroën Xantia: Optional Activa (active suspension) system, eliminating body roll by acting on torsion bars. A Xantia Activa was able to reach more than 1g lateral acceleration
  • 2001 Citroën C5: Hydractive 3 removes the need for central hydraulic pressure generation; combined pump/sphere unit for the suspension only and with electric height adjustment sensors
  • 2005 Citroën C6: An improved version of the C5 system known as Hydractive 3+ (also fitted to some C5 models)
  • 2008 JCB Fastrac high speed 7000 series agricultural tractors now use this system for front and rear suspension.

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