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| Ok, so we took this from the STI article but you can’t illustrate or explain this any better. The low speed rebound damping is controlled mostly by the piston on the end of the shock rod. Turning the rebound adjusting knob located on the top of the shaft screws the tapered metering rod “V” up and down varying the size of the orifice. The low speed fluid flow is represented by the green arrows. At higher shaft speeds the mid and high speed circuit kicks in, the high speed fluid flow is shown by the blue arrows. The hydraulic pressure deflects the metering disc shown in yellow for mid speed damping and higher velocities allow the spring loaded blow off of the disc to open. |
In grassroots motorsports or street cars where you don’t have a large pit crew, being able to quickly and easily adjust the damping is important. The Clubsport’s easy to reach external adjustments make dialing in the chassis a lot easier. The Clubsport’s have a large adjusting range which is very handy for the serious grassroots suspension tuner. A big range of adjustment means that a big range of spring rates can be used without having to revalve the shocks.
The Clubsports damping curve can be tailored from mildly digressive to heavily digressive. A digressive damping curve means that there is more damping at low piston speeds. At higher piston velocities, the valving blows open bypassing fluid to where there is less overall damping. Digressive curves give good body platform control while still allowing a decent ride and minimizing traction reducing tire shock and hop.
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| Here we go from the Subie article again. In rebound, the shocks foot valve located on the bottom of the shock, simply acts like a one way check valve allowing fluid displaced by the shock shaft to flow into the outer tube and the hydraulic accumulator. |
Typically, a twin tube shock simply has a volume of air or gas in the outer tube at the top of the fluid to allow for shaft displacement. This works ok, but under hard use the gas can get mixed with the fluid and the frothy mix has less damping than non-emulsified fluid. This mixing of air and oil is the primary cause of shock fade in hard use.
Another disadvantage of a standard twin tube is that usually only a low gas pressure can be used if the shock is indeed gas pressurized. Pressurization is good because it reduces fluid cavitation through the valves at high piston speeds. Cavitation is localized boiling in low pressure zones like the backside of shock valves. Cavitation also causes the fluid to foam and lose damping ability.
The Clubsports have a remote accumulator to eliminate this issue. The accumulator is like a remote reservoir found in some super high end race shocks. On the Clubsports this accumulator is a canister with a rubber bladder that is pressurized with nitrogen gas. Oil from the outer tube can flow back and forth from the outer tube to the accumulator. The bladder inside the accumulator gives the fluid displaced by the volume of the shock shaft as it goes in and out of the shock body a place to go. The rubber flexes and the gas compresses giving the incompressible fluid room, preventing the shock from getting hydraulic lock. The bladder keeps the gas and oil from mixing, eliminating foaming.
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| The low speed compression damping adjustment is mostly handled by the foot valve. The low speed fluid flow is shown in green. When the adjusting knob is turned, the spring preload on the needle valve controlling low speed fluid flow is increased, this increases the initial force needed to open the valve. When high speed flow needs to be controlled, like when hitting a big bump, the much larger compression blow off valve opens, its fluid flow is shown in blue. This allows the shock to react and absorb the impact. Thus you can have both good control via external adjustability and decent ride. |
