Products Road Racing

General How the shock works   View Larger Image   Technical Information How the shock works At low shaft speeds the damping oil is forced through an adjustable bleed valve in the main piston. The valve affects mainly rebound damping and has only a small effect on compression damping, see below. The adjuster is connected to the valve via an aluminium shaft, which runs inside the piston shaft. When the temperature in the shock increases the aluminium shaft extends, thereby closing the bleed valve gradually. This diminishes the influence of the oil viscosity changes due to temperature, keeping the flow through the valve virtually the same, regardless of temperature. With the second adjustable bleed valve, on the top of the reservoir, you can adjust the compression damping. The valve restricts the flow to the reservoir but not from it, thereby only influencing the compression damping, see below. At higher shaft speeds the damping forces are primarily controlled by the main piston and its compression- and rebound shim stacks. By changing the number, diameter, and thickness of the shims in the stack and by using different jets in the valves, your Öhlins shock absorbers are tailor-made for your car.   When you are driving 1. The oil flow in the shock absorber body and… On a smooth road When you are driving on a smooth road and the shock absorbers are compressed slowly (low shaft speed), the damping oil is forced only through the adjuster valve in the piston shaft, fig 1, flow 3. The oil displaced by the piston shaft is forced through the independent compression damping adjuster out into the external reservoir, fig 2, flow 3. 2. In the reservoir during a compression stroke. The floating piston in the reservoir is forced to move, compressing the gas behind it. When the shock absorber extends, the pressure behind the floating piston will force the oil through a one-way valve, and back into the shock absorber body, fig 3, flow 1 and 2. The oil beneath the piston returns through the adjuster valve in the piston shaft, fig 4, flow 3. 3. The oil flow in the reservoir and... Hitting a big bump When you are hitting a big bump the shock absorbers are compressed fast (high shaft speed). The oil can not be forced " fast enough" through just the valve in the piston shaft. The pressure on the compression side increases and opens the shim stack covering the compression orifices in the piston, fig 1, flow 2. Also, oil displaced by the piston shaft can not be forced through just the valve in the reservoir. The pressure increases and a shim stack, parallel to the valve, opens, fig 2, flow 1 and 2. 4. In the shock absorber body during a rebound stroke. The floating piston is forced to move, compressing the gas. When the shock absorber extends, the floating piston will force the oil through the one-way valve back into the shock absorber body, fig 3, flow 1 and 2. The pressure difference over the piston is still high and the flow can not be forced through just the valve in the piston shaft. The shim stack covering the rebound orifices in the piston opens and the oil returns, fig 4, flow 1.   External Adjusters The Öhlins 46HRC shock absorbers have the low speed compression adjustment knob located on top of the reservoir, both on McPherson front struts and on traditional shock absorbers. A low speed rebound adjuster is located in the bottom end of the McPherson front strut. Adjustments are made with a 3 mm Allen key. On traditional shock absorbers, the rebound adjustment knob is located at the upper end of the piston shaft. All the adjusters have a normal right-hand thread. Click position zero (0) is when the adjusters are turned clockwise to fully closed, and then opened to the first click. Some models of the Öhlins Racing shock absorbers features camber bushings that enable you to alter the front wheel camber. Depending on how you mount the bushings, with the eccentric hole facing the wheel or away from the wheel, different camber angles can be obtained Making adjustments Suspension settings are dependent on your car's weight, your driving style, track conditions etc. If you are not happy with our recommended settings, here are a few guidelines and ground rules how to make adjustments. To make improvements, it is important to understand the function of the shock absorbers and through testing learn how they affect the handling of your car. When making adjustments, always start with the Öhlins recommended settings. Keep notes, make adjustments one at a time... and in small steps. The adjusters should normally not be adjusted in steps of more than 2 clicks at a time and not outside the usable click range. When you think you have made an improvement, go back to what you started with and double check to be sure. Pay attention to changes in conditions like tires, temperatures, etc. In general, compression damping changes should be used to influence the car's stability and response, while rebound damping changes should be used to influence comfort and traction. When you need more damping force, you should mainly try to increase compression damping and use as little rebound damping as possible. This usually means that you gain comfort and handling performance.