Metro / MGF Hydragas Links on this site

Hydragas is a type of automotive suspension system used in many cars produced by British Leyland and its successor companies.

Invented by famous British automotive engineer Alex Moulton, Hydragas is an evolution of the previous Hydrolastic system, and was first introduced in 1973 in the Austin Allegro. Both systems attempt to address the ride-handling compromise of car suspension by interconnecting the suspension of the front and rear of the car in some way. Hydragas attempted to perform the same function and advantages as the famous hydropneumatic system developed by Citroen, but without its attendant complexity.

The heart of the system are the displacer units, which are pressurised spheres containing nitrogen gas. These replace the conventional steel springs of a regular suspension design. The means for pressurising the gas in the displacers is done by pre-pressurising a hydraulic oil, and then connecting the displacer to its neighbour on the other axle, unlike the Citroen system, which uses hydraulic fluid, continuously pressurised by an engine-driven pump, and regulated by a central pressure vessel.

Despite early teething problems (the Allegro version of Hydragas was found seriously wanting), it was gradually developed into a very effective and efficient alternative to steel springs on later BL/Rover Group models such as the Austin Metro and MGF.

Hydragas Mini world Magazine article
Hydragas comparison of different displacers (MGF Trophy is the same body as MGF standard)
research on Hydragas Suspension English language article German translation
blown hydragas unit at my early MGF
the second blew
The pump (Different suppliers and .... How to build your own Hydragas Pump ) ;-)
Cut displacer unit (MGF)
Metro racing Mods
recharging hydragas displacers Link to ARO Website (MAXI )
Sir Alex Moulton article from 'MiniWorld'
Suspension explanations at Car Bible
Rideout, D.G., and Anderson , R.J. (2003) "Experimental Testing and Mathematical Modeling of the Interconnected Hydragas Suspension System." SAE Journal of Passenger Cars – Mechanical Systems

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