Hydrolastic

Hydrolastic is a type of automotive suspension system used in many cars produced by British Motor Corporation (BMC) and its successor companies.

Invented by famous British rubber engineer Alex Moulton, and first used on the 1962 BMC project ADO16 under designer Alec Issigonis (of Mini fame), later to be launched as the Morris 1100.

Moulton attempted to replicate the hydropneumatic suspension of the Citroën DS in a cheaper format. The aim was to provide decent ride quality in a small, lightweight vehicle - an ongoing challenge for automakers.

Description

The system replaces the separate springs and dampers of a conventional suspension system with integrated, space efficient, fluid filled, displacer units, which are interconnected between the front and rear wheels on each side of the vehicle.

Each displacer unit contains a rubber spring, and damping is achieved by the displaced fluid passing through rubber valves. The displaced fluid passes to the displacer of the paired wheel, thus providing a dynamic interaction between front and rear wheels.

The system was not popular with home mechanics, as it had to be re-pressurized after a chassis or subframe replacement. Even welding the sub-frame to repair rust damage typically required the system to be drained. The only way to re-pressurize was to pay a properly equipped mechanic, usually at a BMC dealer. Inevitably the charge for this service was higher than many cared to pay.

Cars

Cars using the Hydrolastic suspension system:

• BMC 1100
• Mini (from 1964 to 1971)
• Austin 1800
• Austin Maxi
• Austin 3-Litre

Evolution

The Hydragas system was a development of this system.