Rear suspension

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Rear suspension

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Rear suspension

Rear suspension
Rear suspension

The first motorcycles had a rigid rear suspension. Since bumps in the road were introduced directly into the frame via the rear wheel, driving comfort was poor on uneven stretches.

02/25/2003

The first motorcycles had a rigid rear suspension. Since bumps in the road were introduced directly into the frame via the rear wheel, driving comfort was poor on uneven stretches.

The purpose of the spring connected between the wheel and the frame is to convert the kinetic energy that the wheel absorbs on uneven road surfaces into deformation energy. The so-called straight-line suspension initially prevailed on the rear wheel. The rear wheel with its axle is bolted directly to the spring struts. The shock absorber also takes on the task of guiding the wheel. The wheel is raised and lowered vertically. The spring travel that could be achieved in this way was limited. With chain drives, the distance between the sprocket and the chainring changed significantly. It was therefore only possible to select correspondingly low chain tensions in order not to overload the chain.

A cardan drive required two joints. The spring hub was a special design of the rear suspension. The two-part hub was connected by rubber elements so that the wheel bearing could move in relation to the wheel in the event of bumps in the road.

These designs were replaced by the rear swing arm. One strut is hinged to each of the two swing arms and the frame. With the one or two-armed swing arm, the wheel is guided in an arc around the swing arm bearing. Here, too, changes in length occur, but these can be reduced if the pivot point of the rocker moves as close as possible to the drive pinion.

In the case of the drive train swing arm, the motor-gear unit is screwed to the swing arm and thus takes part in its rotation without being sprung. This special construction can be found in scooters. The transmission ratio of the spring depends on the inclination and articulation of the suspension struts.

With increasing power, motocross motorcycles required ever greater suspension travel in order to ensure good ground contact even at high speeds on undulating slopes. In conventional designs with two struts, the spring travel is limited by the length of the struts and the installation space.

The first step towards realizing large suspension travel was the Yamaha cantilever swingarm. The rear wheel movement is transferred to a single spring strut via a triangular swing arm. The deflection causes a much shorter path on the strut than on the wheel axle. In the original arrangement with two struts and in the Yamaha cantilever design with one strut, the force required to compress the spring by a certain distance remains almost constant over the entire spring travel.

However, what is desired is a progressive spring rate with a significantly higher force increase per unit of travel at the end of the spring travel. The suspension can therefore respond sensitively to minor bumps. This also prevents the suspension from bottoming out in the event of major impacts and when fully loaded. A progressive spring rate can be achieved, for example, by specially winding the spring.

However, the Japanese high-volume manufacturers took a different path. At first they developed a spring system only for cross motorcycles, later also for road machines, in which a deflection with levers is connected between the shock absorber and the swing arm. By choosing the lever lengths, the transmission ratio can be varied as desired, and the arrangement of the levers influences the characteristic curve (measure of the displacement-force ratio) of the suspension.

The shock absorber is usually placed vertically in front of the rear wheel. The systems of the Japanese manufacturers are very similar in their structure. They only differ in the position and articulation of the levers on the rocker arm or on the frame. This means that every company has its own patent and a special company name.

With straight-line suspension, the strut is rigidly screwed to the frame at both ends. It takes over the wheel suspension and guidance.


Rear suspension

The conventional swing arm takes over the guidance of the wheel, the two struts take over the suspension.


Rear suspension

Despite the single shock absorber, the BMW Monolever construction works without progression.


Rear suspension

In the case of the drive train swing arm, the motor and gearbox are screwed to the swing arm in an unsprung manner.


Rear suspension

With the Yamaha cantilever swing arm, long spring travel can be achieved, but progression is hardly achievable.


Rear suspension

In modern central spring strut systems, the spring strut is linked to the frame or swing arm via levers.


Rear suspension

The transmission ratio between wheel and spring movement changes in the course of the compression.


Rear suspension

The Honda single-arm construction enables quick wheel changes in connection with progressive suspension.

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