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Valving/Shim Info
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Posted by: MX823---------------------
Are there any specific articles, videos , that go in to specifics on valving , shim stacks and arrangements. Including how to? I know Eric Gorr has the suspension maintenance video but it did not go indepth on shim arrangements. I am not looking for any shops secrets valving specs etc, but I am looking for pricipals and how and whys? Also the shim sizes what do they mean ? the O.D. x I.D. ?
Posted by: JTT---------------------
OD = outer diameter
ID = inner diameter
Stick around here and search past posts, you will find lots of info, but be patient, it's not something to learn overnight 
Posted by: MX823---------------------
Thanks JTT, I know what OD and ID stand for but I was looking for more along the lines which size I.D.are the shims on current model bikes , and the effectiveness of the O.D. ?[is next 1 up or down a huge diference?]
Basic info, but not that basic, lol!
I also have done some searches unfortunate it has been bits of info more pertaining to a specific need.
Posted by: JTT---------------------
Sorry, didn't mean to to condescending :confused:
The ID varies from model to model and application somewhat. You need to check for a specific application.
As for the OD...humm...well, think of it like a leaf spring in your car. Larger diameter creates a longer lever arm and effects characteristiics accordingly. Shims also come in a variety of thicknesses, also effecting their "flex" characteristic.
Have you actually seen a piston and valve stack apart? If not, I highly recommend that you take a close look. You will get a much better understanding by actually seeing (at least I do). The shims area arranged in a pyamid shape, usually, with larger shims facing the piston. As noted above, this creates that "leaf spring" effect. By varying the diameters, thickness and stack configuration, you can alter the damping characteristics. It becomes a WAY complicated subject beyond this
Hope this helps more :think , and keep asking questions, there are lots of very smart people around here (not me 
)
Posted by: MX823---------------------
Condesending not at all, It was a vague question,
Looking at the shim stack it goes from low speed to high speed with transition shims between the two. Now by larger OD shims you obstruct the rate at which the oil passes by the shims and into the piston orffaces. The effect slows down the travel, making a more plush. {if we were looking at a perfect pyramid].
Is that right so far?
Now if we look at a model of an hour glass, well 2 stacked on top of each other, we see the low /mid/ high stacks, varying the size [shape] of each will dettermine the effect the oil travels through that phase .
is that correct?
So if that is correct then to soften or stiffen a section of the travel , addition or subtraction of shim saze will vary. I assume Larger od shiims slow so the travel is held up through that part, and small OD will speed the travel through that part too.
SO a bike that is plush on small bumps but blows through the mid to last part of travel would benefit from using a larger OD shim in the mid and High speed.
I know there is not one shim to a section and transitioning is needed but that is the general concept??
Am I off on this, or even close?
Posted by: JTT---------------------
Quote:
Originally posted by MX823
Now by larger OD shims you obstruct the rate at which the oil passes by the shims and into the piston orffaces.
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Actually the oil is flowing through the piston and out past the shims. The shims deflect or flex away from the piston seat to allow the oil to pass through. This is the reason for the analogy of the leaf spring, the shims are actually acting as a spring of sorts (or torsion bar) and flexing. This flexing or bending is how they meter flow.
Make any sense?
Posted by: MX823---------------------
I gotcha! thanks ! the analogy does make sense now
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