Öhlins Shock Absorber ST 44 Owners Manual
Öhlins Shock Absorber ST 44 Introduction
All of Öhlins advanced suspension products are adepted to the brand and model. This means that length, travel springaction and damping characteristics, are tested individually just for the vehicle that you have decided to fit with Öhlins suspension.
Öhlins Racing AB can not be held responsible for any damage whatsoever to suspension or vehicle, or injury to persons, if the instructions for fitting and maintenance are not followed exactly. Similarly, the warranty will become null and void if the instructions are not adhered to.
Öhlins Shock Absorber ST 44 Table of Contents
Tuning the suspension .................................... 3
Design .......................................................... 3
Function ........................................................ 4
Settings ........................................................ 4
Setting your vehicle ........................................ 6
Inspection and maintenance ............................ 7
Öhlins Shock Absorber ST 44 Design
The Öhlins suspensions type ST 44 is of the De Carbon type. The fluid is put under gas pressure and the gas and the fluid are kept apart by a separating piston. The gas and the separating piston are fitted in separate fluid reservoir, connected by hose or fixed direct on top of the shock absorber (piggyback). Pressurization of the fluid is made with nitrogen. The pressurization prevents cavitation of the fluid and the shock absorbing action is therefore more even. The external fluid chambers also contribute to better cooling of the fluid, giving longer service life for both the fluid and components.
Öhlins shock absorbers have integrated temperature compensation. As the temperature increases and the fluid flows more easily the flow is controlled accordingly. The shock absorbing effect is therefore independent of the temperature. Öhlins shock absorbers provide the possibility for adjustment, making them adaptable to most vehicles, drivers and ranges of use.ST 44 models permit individual adjustment of compression damping and rebound damping, and also certain adjustment of the length of the shock absorber. The ST 44 can be equipped with highand low speed compression damping.
- External reservoir with hose connection
- External piggyback reservoir
Öhlins Shock Absorber ST 44 Tuning the suspension
Road holding qualities
All vehicles are designed with a suspension geometry that includes wheel movemnets and angles. The changing of components can affect this and it is therefore essential that both the rear and the front ends match each other. Changing to Öhlins suspension gives optimum performance only when both the front and the rear suspension interact properly.
Everything must harmonize
Incorrect spring action can affect the road holding abilities in a negative way. This in turn can give a tendency for oversteering or understeering, which could seriously affect the road holding characteristics of the vehicle. It´s important that the springs are checked for correct lenght and stiffness when Öhlins shock absorbers are mounted.
Öhlins Shock Absorber ST 44 Function
The function, in principle, is that fluid is forced through needle valves at a low rate of flow (Fig.1) and through a number of apertures in the piston at a high rate of flow (Fig.2). The flow through these apertures is regulated by shims (thin steel washers) that at high pressure are deflected to open for the fluid. On some models the needle valves can be set individually. By altering the size of the shims-stack (ie, number, thickness, diameter) (Fig. 3) the characteristics of the damping action can be varied (this shall only be done by Öhlins authorized service workshops).
When movement of the vehicle causes compression in the shock absorber, the fluid flows through the needle valve (combined compression and return valve) in the piston rod. If velocity of the piston is high, ie, in the case of rapid compression, this will not be sufficient and consequently the shims underneath the piston will open to allow a greater rate of flow. The fluid that is displaced by the volume of the piston rod is forced into the external fluid chamber via a separate compression valve. Even this valve is fitted with shims that open at high piston velocity. The separating piston is displaced, thus increasing the gas pressure.
When the spring presses the shock absorber out again, the fluid flows back through the needle valve in the piston rod. The fluid flowing into the chamber is forced by the pressure of the gas back into the shock absorber via a separate nonreturn valve (illustration). If velocity of the piston is high, the shims on top of the piston will also open to allow the fluid to flow though.
Öhlins Shock Absorber ST 44 Settings
Always ensure that the basic setting made by the Öhlins dealer is correct.
Öhlins Shock Absorber ST 44 Setting the spring preload
Preload on the spring/springs is very important, because it affects the height of the vehicle and the wheel angles. Consequently, road holding characteristics can be changed, even negatively. Adjustment is made with the ring on the shock absorber.
Öhlins Shock Absorber ST 44 Setting the damping
The adjusting possibilities of Öhlins shock absorbers facilitate fine setting. You can optimize adjustments to suit your own vehicles weight and equipment, your individual way of driving and the condition of the track. To be able to improve the road holding qualities it is of the utmost importance that you fully understand the functioning of the shock absorbers. Then you can learn by trial and error how they affect the vehicle. they increase the damping action and anticlockwise they reduce it. The knobs have definite positions with a noticeable “click”, so it is easy to count to the right setting.
Rebound damping action affects the characteristics of the vehicle most. The setting knob is at the bottom on the piston rod (Fig.4). It can be adjusted in about 40 steps. The compression damping knob is on the top of the cylinder (Fig.5). This can be adjusted in about 25 steps.
Öhlins Shock Absorber ST 44 Inspection and maintenance
Keep the shock absorbers clean and always spray them with oil (QS 14, WR40 or CRC 5-56) after washing the vehicle.
- Check ball joints for possible excessive play.
- Check the piston shaft for leakage and damage.
- Check the shock absorber body and for external damages.
- Check the external reservoir for damages that can restrict the floating piston from moving freely.
- Excessive wear of rubber components
- Fastening to the vehicle
• Check the hose equipped models for leaks in hose and inlet plugs.
Preventive maintenance and regular inspection reduces the risk of functional disturbance. If there is any need for additional service, please get in touch with an authorized Öhlins service workshop. There they have the necessary tools and know-how for whatever you need.
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