Wheel trajectory curve

Schematic diagram of the wheel trajectory curve

Determination of the wheel trajectory curve

In addition to the position of the virtual pivot point, the wheel trajectory curve also has a crucial influence on the mountain bike kinematics. The wheel trajectory curve is determined by a straight line for the instant centre, which passes through the virtual pivot point and the axis of the rear wheel. The wheel trajectory curve is always perpendicular to the line of the instant centre. It therefore describes the horizontal change in length of the rear swing arm across the vertical compression process in the rear-wheel axle.

Illustration of the wheel trajectory curve

Wheel trajectory curve in detail

In our optimization steps, we subdivide the wheel trajectory curve into two regions, where we concentrate on the first of these, the sag range (20-30% of the entire suspension travel). At this point, the remaining suspension travel only plays a secondary role and is essentially determined by the transmission ratio of the rear suspension.

The aim of optimizing the kinematics in the first range of the suspension travel is to minimize the rocking of the rear suspension. If the rear swing arm is lengthened in this region, the force arising from the chain tension and applying tangentially to the wheel trajectory curve is only able to pull the rear suspension apart, i.e. the rear swing arm extends, so that an additional positive anti-squat effect occurs. This results in a reduced tendency of the rear suspension to rock with respect to the chain tension. 

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