Shock Absorber rear Polini 290mm Aprilia / Yamaha

Shock Absorbers

Basic Function

Whether motocross, scooter, moped, or motorcycle, shock absorbers have a very simple and fundamental function: they dampen impacts and vibrations to make riding more comfortable and safe. Without shock absorbers, it would be impossible to reach higher speeds, as the wheels would barely maintain contact with the ground.

Since shock absorbers ensure contact with the road and are therefore one of the main safety features of a vehicle, they must be serviced regularly and always be in perfect working condition.

How do I recognize a defective shock absorber?

A shock absorber must absorb impacts, but it must not behave only like a spring, otherwise you'd have a “catapult effect”.

If the shock absorber rebounds too quickly after being compressed, sticks, squeaks, or shows oil residue (oil leak), it must be repaired or replaced immediately.

For motocross bikes, where shock absorbers are technically complex and correspondingly expensive, there are repair kits. However, you need a certain level of technical know-how and special tools to carry out these repairs.
For 50cc scooters, mopeds, and gear bikes, complete shock absorbers are more commonly available, allowing full replacement.

OEM, Adjustable, Racing

Gas pressure or hydraulic, simple shock units or complex systems – there are many different types of shock absorbers.
An important factor is suspension travel, which determines how intensively the vehicle can be used. Depending on the model, there are also various adjustment options.
There are simple models, such as most stock shocks on scooters. Shock absorbers can also feature various adjustment options that allow the handling to be adapted to the rider, purpose, and conditions. These include shock absorbers with adjustable spring preload, high/low shock absorbers with adjustable compression damping for low and high speeds, and shock absorbers with adjustable rebound damping found on motocross bikes.
Racing shock absorbers are the most advanced models; they include all the adjustment options mentioned above, are made from high-quality materials, and often feature special surface finishes (e.g. the popular “Kashima coating”).

How to find the right shock absorber?

In general, most shock absorbers for 50cc scooters are very similar and have a 20 mm wide lower mount and a 10 mm “eye” at the top. Scooters with Piaggio engines have a 34 mm wide lower mount and a threaded pin at the top. There are, of course, exceptions.

The length of the shock absorber can be adjusted by 2–3 cm to modify seat height or handling according to personal preference. A longer shock absorber provides slightly sportier handling.

Standard factory shock lengths

• 250mm : Yamaha BW's, Axis, MBK Booster, Malaguti F10, F12, Rieju First

• 260mm : Suzuki AJ50, Sepia, Honda Ruckus, Zoomer, PGO PMX

• 270mm : Peugeot Speedfight 1/2, CPI, Keeway, Generic, Chinese 2-stroke

• 280mm : Yamaha Aerox, Neo's, Jog R, BW's 100, Peugeot Vivacity 1&2, TKR

• 290mm : Aprilia SR50 -99, Sonic, Rally, Kymco Super9, Agility / Vitality 2T

• 310mm : Peugeot Ludix, Kisbee, Streetzone, Kymco People, Dink

• 300-340mm : GY6 / Chinese 4-stroke scooters

• 300-340mm : Piaggio, Gilera, Aprilia with Piaggio engine

Replacing a shock absorber