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How Does it work?

floats on fluid sticker

One of several technologically advanced features of the Morris 1100 design was the "Hydrolastic" Suspension. To explain and promote the benefits of this new system BMC used the slogan "It floats on fluid". Every Australian made 1100 had a teardrop shaped sticker fixed to the lower right hand corner of the rear window with the slogan on it.

So what exactly does "floats on fluid" mean?

You may well ask. As a small child in the seventies, I often found myself jostling for space in the back of a friend's mother's Mini or Morris 1100 and when I was old enough to read, I asked the friend's mum what the sticker meant. She replied: "Oh, I don't know dear - I expect the car would sink if I drove it into the ocean...". Commonsense had ruled out that meaning for me anyway, so I decided it must have been something to do with the car being economical on petrol !

Animated diagram of suspension operation

Many years later I discovered that it referred to the Hydrolastic Suspension. The Morris 1100 floats on fluid by means of interconnected rubber balloons filled with a solution of  equal parts alcohol and water, plus corrosion inhibitor and green dye.

When the front wheels hit a bump, fluid is displaced from the front balloon into the rear one causing the rear suspension to rise about the same amount as the front, thus keeping the car level. Conventional suspensions using metal springs and dampers (shock absorbers) cause a car to "pitch" first to the rear as the front wheel rides over the bump and then to front as the rear wheel does.

The Hydrolastic Suspension does not require separate dampers and, apart from an occasional "pump-up", requires little maintenance as the system is generally reliable and durable.

When BMC Australia released the Austin 1800 in late 1965 and the Mini Deluxe in 1966 they both featured Hydrolastic Suspension.