BikeAdvice Informative Series: We discuss motorcycle suspension, its working and maintenance in this story…
With a suspension geometry that consists of fork angle and height, motorcycles are designed. Changing of components from the suspension geometry of motorcycles can affect the geometry; therefore, it is advisable that the front and rear ends of motorcycles must be in sync with each other. When the front and rear shock absorber components interact properly, the optimum results can be achieved.
Design of motorcycle shock absorbers:
The shock absorbers of motorcycles are pressurized under gas pressure, the fluid is put and the fluid and the gas pressure are kept apart from each other with the help of a piston. On the top of the shock absorber, this separating is directly fixed or it is kept in a separate reservoir.
There is another type of shock absorber found in motorcycles in which everything is fitted in the main cylinder tube. This tube is also called as internal gas reservoir.
Nitrogen is used for making the pressurization of the fluid. This pressurization prevents the cavitation of the fluid which is useful for making the shock absorption more even. The external reservoirs assist in controlling the temperature of the fluid, which increases the service life of both the components and the fluid.
In the motorcycle shock absorbers, there is integrated temperature compensation. The fluid starts to flow more easily with the increasing temperature of the fluid, but this flow of fluid is controlled inside the absorbers. Therefore, the effect of shock absorption is quite independent of the temperature.
In some modern motorcycle shock absorbers, the individual- adjustment of rebounding damping and compression damping is possible. There is also adjustable either mechanical or hydraulic pre-loading system found in the motorcycle shock absorbers.
Fluid flow in motorcycle shock absorbers:
The fluid of the shock absorbers is forced through the needle valves at a slow rate. It can also be forced through a number of other apertures, which are present in the piston. The shims regulate the flow of fluid. The shims are the steel washers. At high pressure of fluid flow, the shims are deflected from their position. The features of the damping action can be altered by changing the thickness, number or diameter of the shims.
When the shock absorbers of motorcycles get compression due to the movement of the motorcycles, through the needle valves (combination of return valves and compression valves), the fluid starts to flow in the piston road. During rapid compression, when the velocity of the piston is high, the needle valves are not sufficient for the flowing of the fluid. In this case the fluid starts to flow through the shims, which are present just beneath the piston. The fluid is forced into the external fluid chamber, which is displaced through the piston rod. A separate compressive valve is used through which the fluid is forced into the external fluid chamber. This valve is attached with the shims which open during the high piston velocity.
Setting of shock absorbers in bikes & motorcycles
- Place the bike or the motorcycle on its stand.
- To keep the suspension of the vehicle in full extended position, raise the rear end of the vehicle.
- Either from the lower edge of the rear mud guard or from any point just above the rear wheel axle marked by a piece of tape, the distance is measured.
- Similar measurement is done on the front axle also. (Between bottom of the upper fork crown and the front wheel axle)
- For applying load on the springs, the motorcycle or the bike is allowed (With our rider). The measurement process is repeated.
- In this step, take the measurements but this time the measurement is taken with rider.
Inspection & maintenance of two-wheeler shock absorbers:
- Soft detergent can be used for external wash of these shock absorbers. Compressed air can also be used for this purpose.
- The place used for cleaning the shock absorbers should be clean.
- The bump rubber should also be lifted, while cleaning it. Frequent oil spray should be applied on these shock absorbers and these should keep clean.
- Detergent should never be used for cleaning because they may erode the external surface.
- Brake cleaner and thinner can be used for quick drying-up of the surface of these absorbers.
- Normally, the pressure of gas of the absorbers should not be changed of altered.
- Some special purpose equipments can be used for altering the gas pressure of these absorbers.
- For more frequent and smoother play, the ball joints should be checked regularly.
- For preventing any leakage and damage, the piston shafts of the absorbers should be checked.
- The external reservoirs of the absorbers must also be checked.
- Prevent the excessive wear and tear of different rubber equipments present within the absorbers.
- Ensure the secure and tight fastening of the shock- absorbers in the two- wheelers.
Ride safe, wear a helmet. Take care
– Pritam Dhamde