Motorcycle suspension

Some manufacturers (e.g. Greeves) used a version of the swinging arm for front suspension on their motocross designs.

They allow the front wheel to react to imperfections in the road while isolating the rest of the motorcycle from that motion.

Some fork tubes, especially on early roadsters and off-road motorcycles, are enclosed in concertina plastic/rubber protective "gaiters".

This USD arrangement has two advantages: (i) it decreases the unsprung weight of the motorcycle; and (ii) it increases torsional stiffness, which can improve handling.

Pre-load is used to adjust the initial position of the suspension with the weight of the motorcycle and rider acting on it.

Total sag is set to optimize the initial position of the suspension to avoid bottoming out or topping out under normal riding conditions.

Some motorcycles allow adjustment of pre-load by changing the air pressure inside the forks.

[7] Damping at low slider speeds is controlled by a much smaller orifice, but damping at higher slider speeds is controlled by a system of flexible shims, which act as a bypass valve for the fork oil.

Some of the shims (or "leaf springs") lift with little force allowing fluid to flow through the orifice.

For a detailed explanation and a sample calculation, see the braking section of the Bicycle and motorcycle dynamics article.

This shortening of the forks causes the front end of the bike to move lower, and this is called brake dive.

However, all of these changes make the motorcycle less pleasant to ride on rough roads, since the front end will feel stiffer, in the 1980s various manufacturers attempted to get round this by methods of anti-dive such as: With the advent of cartridge forks, which allow more low speed damping and less high speed damping than the previous damping rod forks, separate anti-dive mechanisms have generally fallen out of use.

Some fork designs mitigate dive, eliminate it, or even reverse it without affecting the front suspension adversely.

Leading link front forks, such as used on some Ural motorcycles, can also be designed either to reduce or eliminate dive.

The Saxon-Motodd (marketed as Telelever by BMW) has an additional swingarm that mounts to the frame and supports the spring.

Hub-center steering is characterized by a swingarm that extends from the bottom of the engine/frame to the centre of the front wheel instead of a fork.

[13] Notable manufacturers of motorcycles with plunger suspension include Adler, Ariel, BMW, BSA, Indian, MZ, Saroléa, Norton, Cossack/Ural and Zündapp.

Although plunger suspension could be sophisticated, with springing and damping in both compression and rebound, it had three disadvantages (compared to the almost universal swingarm that succeeded it), as follows: (i) wheel travel was limited, (ii) the wheel could move out of the required vertical axis, and (iii) it was more expensive to produce and maintain.

The long sides are connected to the motorcycle's frame or rear sub-frame with one or two shocks with coil-over springs.

In 1981 BMW introduced the single sided swingarm (mono lever) to motorcycles on their R 80 GS model.

Single-sided swingarms make rear-wheel removal easier, though they generally increase the unsprung weight of the rear suspension.

This is due to the additional material required to give identical torsional rigidity to a conventional (two-sided) swingarm setup.

[citation needed] On many shaft-drive motorcycles the drive shaft is contained in one of the long sides of the swingarm.

The hydraulic shock absorbers used on the rear suspensions of motorcycles are essentially the same as those used in other vehicle applications.

During the late 1970s and 1980s, motorcycle rear suspension design and performance underwent tremendous advances.

At the end of this period, most of these motorcycles had rear wheel travel of approximately 12 inch (30 cm).

Typically this lone shock absorber is in front of the rear wheel, and uses a linkage to connect to the swing arm.

[15] In 1972, Yamaha introduced the Mono-Shock single shock absorber rear suspension system on their motorcycles competing in the Motocross World Championships.