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| Compression Stroke |
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| 1.
The oil flow in the shock absorber body and… |
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| 2.
In the reservoir during a compression stroke. |
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| Rebound Stroke |
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| 3.
The oil flows into the reservoir and... |
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| 4.
In the shock absorber body during a rebound stroke. |
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To
show you what is happening in a Öhlins shock absorber when
you are riding we have chosen a shock with a double-acting,
rebound/compression damping adjuster in the piston shaft and
an independent compression damping adjuster in the external
reservoir.
The principle illustrated here is the
same for all types of Öhlins shock absorbers. Just disregard
the adjusters that your shock absorber does not have and you
can still understand how it works!
On a smooth road
When you are riding on a smooth road and the shock absorber
is compressed slowly and only a small amount (low shaft speed
and short stroke), the damping oil is forced through the double-acting
rebound/compression adjuster 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.
The floating piston in the reservoir
is forced to move, compressing the gas behind it.
When the shock absorber extends the
gas pressure behind the floating piston will force the oil through
a one-way valve, past the compression adjuster and back into
the shock absorber body, fig 3 flow 1 and 2.
The oil under the piston returns through
the double-acting rebound/compression adjuster in the piston
shaft, fig 4 flow 3.
Hitting a big
bump
When you hit a big bump the shock absorber is compressed quickly
and almost totally (high shaft speed and long stroke).
The oil can not be forced " fast
enough" through just the valve in the piston shaft. The
pressure in the shock absorber increases and force open the
shim stack (thin steel washers stacked as a pyramid) covering
the compression orifices in the piston, fig 1 flow 2.
Also, oil displaced by the piston shaft
can not be forced " fast enough" 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.
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 is still high in the shock
absorber 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.
All
are tailor made
By changing the number, diameter, and thickness of the shims
in the stacks and by using different jets in the valves, your
Öhlins shock absorber is tailor-made for your bike. The
set-ups are not guesswork but the results of true tests with
a bike exactly like yours! |
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