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Theroy behind IC springs

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Whats the basic theroy behind the IC springs in the twin chamber showa's?

Ive messed with lighter springs, oil levels etc. and after a multitude of changes and settings, I ended up back at the stock IC spring rate with a .49 spring rate with my own subtank set up. And itworks awesome.

It seemed to be under sprung with the .49's and the 1.61 IC springs. What I didnt expect was the impact the IC's have on the overall spring rate of the fork...

Anyone have any thoughts?

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Shawn,

The way it looks to me is that the IC spring functions somewhat the way N2 pressure does in the shock. It supplies pressure against fluid in the IC via the floating piston at the top of the inner chamber.

When the rod moves into the IC and displaces fluid, the IC spring resists against the floating piston, pressurizing the fluid.

A lighter spring rate would provide less resistance to the fluid displacement, like a lower N2 pressure in the shock.

I haven't tried to figure it out but I imagine you could calculate its overall effect via a hydraulic ratio, like a car lift in a shop.

I may be all wet, but does this make any sense?

:thumbsup:

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well in a very simple form what they are trying to end up with is a shock set up just like the rear------where you have a shock in the rear and two shocks in the ft ------now granted there are other needs in the ft --i.e. no rising rate ---1 to 1 ratio of movement (not 3 to 1) and must have outter chamber to control oil height for botteming--------and more -----but basically it is trying to be like the bladder in your shock and keep the fluid from emulsing and mixing with air like an older kyb to keep more consistant damping like a shock-------so now you can see how kool they really are and it does work way better, and i think it is way easy to tune ,-----and so did kyb there stuff in 05 is this three shock set up also.

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You have to remember that the ics spring rate is added to the current spring rate in your forks.

Effectivly your .49s could be up to 5.0's with a heavier ics.

Changing ICS has very little effect and is more of a marketing gimmick. Your better off working with the stock setup.

Like the guys said, you have a shock inside your fork!

nice!

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The ICS helps reduce or I should say control cavitation in the inner chamber. By applying pressure to the fluid, it helps refill the cartridge during rebound action. When cavitation is reduced during the rebound stroke the active valving(midvalve) with have a more consistent body of fluid for damping (more fluid and less air).

The IC spring adds about .01-.02kg/mm of spring tension. Although not a significant amount, we cant dismiss it entirely as not having impact on the overall spring rate. When we install lighter Ic springs, not only are we reducing the overall spring rate slightly, but we are also reducing the positive aspects of a twin chamber fork. The twin chamber fork will give the rider more feedback as to what the front is doing, this increased feedback will allow an aggressive rider to push the front end to the limits of traction, unfortunately, feedback can be perseived as harshness.

Take a look at the top ten during a national motocross, they are all usually armed with twin chamber forks of some type.

Take Care, John

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The IC spring adds about .01-.02kg/mm of spring tension.

This explains a lot to me. I wasn't aware the impact was that great.

When I put the lighter IC's in there I ended up at my old settings that I used with the .47 springs. Which bugged the heck outa me...since I felt like I was chasing my tail to a point... :thumbsup:

Given that, when I replaced the 2.1's with the 1.61's in I probably almost negated entirely the spring rate increase from .47 to .49, not to mention the corresponding difference in the flow rates of the stacks :devil:

And I dodged all that initial harshness with my subtank setup... :lol:

Before I had my C-clickers cranked in all the way to 4-out to control the bottoming, but it was nasty harsh. But since I put the stock IC's back, with my sub tank setup, and the oil hieght at 400cc, Ive been able to back the clickers out to 8 or 9 with almost no (harsh) bottoming an its nice and plush over foot high braking bumps.

I so happy :lol:....Id better becareful though, I could hurt a shoulder patting myself on the back.... :D

Id also like to thank John Curea, ShocDoc, Dave J and the others for coming over to visit TT. Its nice to talk to folks that know what they're talking about...acutal suspension tuners, instead of shim jockeys :D:awww:

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