BMW's 1200GS gets (very) serious!

The air spring strut comes with three sequential air chambers, connected to one another by ducts. An aluminium cylinder forms the two upper chambers, separated from one another by a piston. Longitudinal movement of the separating piston compresses air within the cylinder, the air thus acting as a kind of spring. At the same time a defined volume of air flows into the other chamber via plate valves - or slot throttles - and, through their throttling effect, dampens sudden wheel travel.

The lower air chamber is formed by a gas-tight rolling gaiter made of rubber tissue, giving the damper freedom of movement and seals the spring strut to the outside, avoiding the need for a piston rod seal, which would merely increase friction within the system. The resistance built up by the rubber gaiter when rolling over a specially shaped cone supplements the progressive effect of the system.

Outside, the spring strut is fully sealed and air-tight. Any leakage which might occur can be compensated by topping up the air through a valve. External variation of internal pressure also permits simple adjustment of seat height by adding or discharging air as required, although spring travel is reduced with the seat set to a lower position, making this setting more appropriate for moderate riding conditions.

Adjusting the system to different load conditions is a very simple operation requiring only a small change in air pressure. A small inspection balance on the rear frame allows the rider to read the normal setting of the motorcycle.

To adjust the system while travelling, the R 1200 GS HP2 comes fitted with a high-pressure pump complete with a pressure gauge – which is also suitable for pumping up the tyres after having reduced tyre pressures when riding in rough terrain.

A unique feature of the air/spring damper system is the option to vary the damping effect as a function of frequency, achieved by adapting the inner flow system with the slot throttles to suit rider preferences.

A major benefit of this unique system is a significant improvement in rear-wheel traction on undulating surfaces. The range of damping effect is factory-configured in the frequency bands of the swinging arm system operating on bumpy surfaces, enabling the wheel to follow uneven surfaces and maintain optimum ground contact.

This means even better traction when accelerating flat-out, as well as extra safety in applying the brakes, for even greater riding pleasure.

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