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• Upside-down fork Upside-down fork

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technology & future

Upside-down fork

Upside-down fork
Upside-down fork

The inverted telescopic fork system, in which the upper tubes (stanchions) have a larger diameter than the lower (immersion or sliding tubes), is almost as old as the motorcycle itself.

02/25/2003

The upturned telescopic fork system, in which the upper tubes (stanchions) have a larger diameter than the lower (immersion or sliding tubes), is almost as old as the motorcycle itself. This system was also used for the mopeds of the 1950s. Only in a very primitive and cheap version.

Instead of hydraulic damping, there was only a grease filling to lubricate the slide bearing points. The system has been consistently further developed by White Power, a Dutch manufacturer of dampers and telescopic forks. The advantages of the upside-down fork are obvious. The large diameter of the stanchions increases the torsional stiffness, at the same time they cannot twist in the fork bridge.

Because the tube and fork bridge are made of aluminum, which means that the surfaces interlock under pressure. However, the unsprung masses are no less than with the conventional fork. The internal immersion tubes in the upside-down system have a smaller diameter than the usual immersion tubes, but are made of heavy steel. That is why the weight is almost the same, in some cases even higher than the aluminum or even magnesium of the conventional forks. The decisive advantage results from the very long guidance of the immersion tube through the standpipe.

Sensitive response even under high loads and maximum stability enabled the White Power fork to make a breakthrough in motocross. Until the construction was stable, there were a number of problems with the sealing. That is why other manufacturers were reluctant to venture into developing their own upside-down forks. Another advantage in off-road sports is the greater ground clearance of the dip tubes. With upside-down forks, this ends at the axle mount. But the qualities of the new concept are also convincing in road racing. The super-light 80s and 125s racers in particular require extremely precise, responsive suspension, which is why the world champions use the upside-down fork here too.

The upside-down construction ensures stable wheel guidance and sensitive response.
1. Triple clamps
2. Axle mount
3. Immersion or sliding tube
4th. Standpipe

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