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Suspension valving & shim stacks explained


nobleswood
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Ages ago I re-valved the shock on my DR 350 with help from a friend. I was amazed at how beautifully simply the concept of valving really was. I assume they have gotten more sophisticated but the basic premise should still be the same. In the Jeep world a high end step up is bypass shocks, where you add bypasses so some of the shock oil can bypass the piston valving. Then by controlling the flow of oil through the bypasses, and having different bypasses between different parts of the shocks travel you can change the dampening in different parts of the stroke. As I recall KTM put a lot of effort into figuring out how to have variable dampening over the length of the stroke so they could run a progressive spring and no linkage.

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1 hour ago, GuzziMoto said:

Ages ago I re-valved the shock on my DR 350 with help from a friend. I was amazed at how beautifully simply the concept of valving really was. I assume they have gotten more sophisticated but the basic premise should still be the same. In the Jeep world a high end step up is bypass shocks, where you add bypasses so some of the shock oil can bypass the piston valving. Then by controlling the flow of oil through the bypasses, and having different bypasses between different parts of the shocks travel you can change the dampening in different parts of the stroke. As I recall KTM put a lot of effort into figuring out how to have variable dampening over the length of the stroke so they could run a progressive spring and no linkage.

How does all this compare to the V11 Marzocchi internals, @GuzziMoto ?

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19 hours ago, docc said:

How does all this compare to the V11 Marzocchi internals, @GuzziMoto ?

Well, I revalved the rear shock on the DR 350, while I assume you are referring to the front forks on the Guzzi. The shock was made to be easily opened up and revalved. Where as cartridge forks can be harder to open up as at least some of them aren't made to be revalved. In some cases the cartridge is crimped together, and that can be tricky to open up and close when done. The cartridge works much like a shock, it has a piston that moves up and down through it with valving stacks to regulate dampening. The cartridge on the wife's red frame V11 (early forks) had two bypass holes in the cartridge that allowed oil to bypass the valving in the piston. All I did to the forks on the wife's V11 was close off one of the two bypass holes so that more oil was forced to go through the valving stack. That was actually enough. Not only did it increase dampening, it made the adjuster useful as you can now feel a difference when you turn the adjuster. Before the mod the adjuster only made a difference in the last inch or so of travel, after the piston had gone past the first bypass hole. But if I could buy a replacement cartridge I would do that. Right now I am busy doing a number of things, including acquiring the required parts to set the TPS and run GuzziDiag (we have made it this far with that bike without needing either, but it seems I should finally bite the bullet). Maybe when that is done I will dig deeper into the forks, but it is hard to justify when they actually work pretty well with the bypass mod.

On a side note, anyone feel like helping an old fart learn new tricks? Free Beer....

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