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Woods suspension: best valving route to fork compliance without bottoming ?

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Lets assume we are working with twin chamber cartridge forks.  Say Yamaha SSS forks for discussion purposes.

 

What is the best way to get excellent compliance on small, sharp hits from roots, ruts and rocks while keeping the forks up in the stroke and not bottoming off small jumps ?

 

- softer base valving ?

- softer mid valving ?

- dual stage base valving ?

- dual stage mid valving ?

- increase mid valve float ?

- overall soft damping, compensate with strong springs and high oil level ?

- mix and match of these ?

 

How does the ICS spring play into this ?

 

Do the stock Yamaha pistons have enough flow area for good high speed damping ?

 

Thanks

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They flow enough for sure , to get plush you need the right amount of spring and damping, what is right us the question

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All those or a combination of those could all work. I have tried many stacks that others have liked/suggested and didnt care for them. You really need to just experiment on your own to find out what you like.

The biggest time saver I found is to make radical changes. I did too many revalves where I changed just a single shim. I am not good enough to tell a difference. Instead of testing more float with a .1mm change, I should have tested .3mm of change. Or if I wanted to test a soft base, I should have removed 6 32mm shims instead of 2. Those major changes gave me a clear idea or feeling of what more float or a softer base felt like. Then it became obvious - either I liked it or I didnt.

Then once I knew I was heading in the direction I liked, I then made small changes to fine tune.

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There isn't some straightforward answer to this. If there was, we'd all just do it, and we wouldn't be on here talking about different setups all the time.

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You compromise

 

If having a setup that handles roots and rocks is the most important then you tune for that and make small compromises for the jumps.  Those compromises are either in the suspension or in how they are ridden.

 

The other option you have is to go faster.

Edited by kan3

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The other option you have is to go faster.

Isnt that the truth! I used to ride with an A class HS racer who kept his MX valving and was perfect for him.

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Comments on this stack ?   Not the actual shim sizes, but the number of shims, progression in sizes, etc.

 

BASE VALVE
24.1 x 3
16.1
24.1
22.1
20.1
18.1
17.1 (take out )
16.1
14.1
12.1
9.3
16.25

MV
12.1
20.1 x 3
18.1
16.1
10.2
11.1
Float 0.7mm

REB
20.1 x 3
12.1
16.1
14.1
13.1
12.1
10.3
14.25

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Taking one shim out won't make any noticeable difference

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Comments on this stack ?   Not the actual shim sizes, but the number of shims, progression in sizes, etc.

 

Without any context, there's not a whole lot that anyone can say about a shim stack.  It's like posting up a set of jetting without knowing the carb, bike, mods, elevation, and terrain, and asking people to comment on the jetting, it just doesn't make sense.  Suspension is even more complicated than this because it is more dependent on rider weight, skill, and terrain than jetting.

 

If it's in a traditional OC USD fork (such as early-2000s YZ/WR stuff), or Showa conventional cartridge (DRZ, RM) or some others, it's probably a woods-oriented stack.  There's not much more to say...

 

I'm not a huge fan of bleed shims on the mid, personally.

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Its from a 2012 KTM 300 XC(W?).

 

KT: Read through your DRZ suspension thread last night.  Probably the best thread I've seen on suspension anywhere.  Loved your simulations and discussion.  Have you done a similar thread on a bike that has a mid valve ?

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Thanks, but I don't think that thread is particularly groundbreaking.  It's the same info that's lots of other places on here, just consolidated into one place (and for a bike that, IMO, had previously been mostly ignored).  I'm not sure what a "similar thread for a bike with a midvalve" would be.  There is some midvalve stuff in there, and while the stacks are mostly specific to that bike, midvalves are midvalves.

 

With regard to that stack, it looks like a woods stack, given the bike.  Beyond that, there isn't a lot that you can say.  Some people like 2-stage, some don't.  Some people like midvalve bleeds, some don't. :excuseme:

 

What, exactly, are you trying to ascertain?

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What, exactly, are you trying to ascertain?

 

 

Thread title? =]

Could be wrong though

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Thanks, but I don't think that thread is particularly groundbreaking.  It's the same info that's lots of other places on here, just consolidated into one place (and for a bike that, IMO, had previously been mostly ignored). 

 

The fact it was all that and it had Restackor graphs and there was lots of discussion about the how and why of it, when you are starting out in this stuff, is huge.  There are lots of revalving threads where someone posts a stack and someone else replies with a recipe to fix it with no explanation why and certainly no Restackor graphs to back anything up.

 

 

 

I'm not sure what a "similar thread for a bike with a midvalve" would be.  There is some midvalve stuff in there, and while the stacks are mostly specific to that bike, midvalves are midvalves.

 

The result you obtained was great, but there was a lot of discussion about "what if" if a midvale would have been used.  I know one member ended up using a midvalve, but if the entire thread had included midvalves in the solution, it would been better.

 

The thing I don't quite understand yet is how much damping should be put on the BV and how should be put in the MV and why (and when).

 

I have a question about Restackor.   Your DRZ had a compression BLEED stack, right ?   You mentioned that and you also had graphs for low speed response for it.   How does one model a bleed stack in Restackor ?  My WR450F has a compression bleed stack as well.   I'd like to model it in Restackor.

 

I have a bunch of Restackor questions, but I'll leave it at that for now and this is also probably not the right thread for it either.

 

Aside: I ordered a set of progressive ICS springs for my WR450F today.  (ie Merge Racing RSS springs.)  I'm not 100% sure that they are going to do what I want, but if they do anything to allow me to have plushness over rocks and roots and yet not bottom, I'll be happy.

Edited by MidlifeCrisisGuy

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Regarding the stack example I gave, there are a number of things that intrigued me that I would love to hear comment on.

 

BASE VALVE
24.1 x 3
16.1
24.1
22.1
20.1
18.1
17.1 (take out )
16.1
14.1
12.1
9.3
16.25

 

I found it interested that there were 3 face shims (24.1x3) separated by a single 16.1 pivot, followed by a tapered stack, with a small 9.3 clamp shim in the bottom valve.  On the WR the base stack is a single taper and the clamp shim is much larger.   Did they design the example stack like this for good high speed flow ?

 

MV
12.1
20.1 x 3
18.1
16.1
10.2
11.1
Float 0.7mm

 

I don't understand that the face shim is a 12.1 on the MV stack and that the float is so high.   The face shim probably isn't going to cover all of the ports on the MV piston, right ?  So the mid valve is an orifice of sorts, semi covered by a tapered stack.  Why ?  And how does this play into how the BV is set up ?

 

REB
20.1 x 3
12.1
16.1
14.1
13.1
12.1
10.3
14.25

 

I thought the rebound stack was pretty unique too.  Thee 20.s for the face shims, then a 12.1 pivot and then a 16mm stack tapering down to 10.3 clamp.  Its kind of like a 2 stage rebound stack ?  Why ?  Are there situations where the rebound gets kicked or something where the return force would be higher than what the spring would provide ?   I thought that because the rebound force was pretty uniform, ie the spring, that rebound stacks were pretty plain.

 

Comments ?

Edited by MidlifeCrisisGuy

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Would the 2 stage rebound allow a faster return when the fork is deeply compressed and yet slow down for when its only slightly compressed ?   Would that be a good thing ?  For what conditions ?

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I have a question about Restackor.   Your DRZ had a compression BLEED stack, right ?   You mentioned that and you also had graphs for low speed response for it.   How does one model a bleed stack in Restackor ?  My WR450F has a compression bleed stack as well.   I'd like to model it in Restackor.

 

DRZs do not have compression bleed stacks.  There is not a (straightforward) way to model them in Restackor, but the effect is fairly subtle, so I wouldn't sweat it too much.  Once you get your setup a lot closer to where you want, then you could experiment with the bleed stack.

 

I found it interested that there were 3 face shims (24.1x3) separated by a single 16.1 pivot, followed by a tapered stack, with a small 9.3 clamp shim in the bottom valve.  On the WR the base stack is a single taper and the clamp shim is much larger.   Did they design the example stack like this for good high speed flow ?

...

I don't understand that the face shim is a 12.1 on the MV stack and that the float is so high.   The face shim probably isn't going to cover all of the ports on the MV piston, right ?  So the mid valve is an orifice of sorts, semi covered by a tapered stack.  Why ?  And how does this play into how the BV is set up ?

...

I thought the rebound stack was pretty unique too.  Thee 20.s for the face shims, then a 12.1 pivot and then a 16mm stack tapering down to 10.3 clamp.  Its kind of like a 2 stage rebound stack ?  Why ?  Are there situations where the rebound gets kicked or something where the return force would be higher than what the spring would provide ?   I thought that because the rebound force was pretty uniform, ie the spring, that rebound stacks were pretty plain.

 

FYI, nothing in these stacks is uncommon or super-fancy.  This is a pretty generic woods setup.

 

The 16.1 shim in the base is a crossover.  That's a standard 2-stage stack.  The crossover just lets the face shims bend more easily as low pressure (velocity).  Once the crossover closes, it behaves just like a single stage stack, albeit at an overall reduced damping level because of the crossover.  The intent is to reduce the low speed damping proportionally more than highspeed, making the stack less digressive or more progressive.

 

The 12.1 on the face of the mid is a bleed shim.  It makes it so that the mid can never fully closed; it's equivalent to having a (much) larger bleed hole or clicker port.  It doesn't really "play into" the BV valve any more than any other setup, it just makes the mid softer (and what that implies for the base depends on what you're trying to achieve).

 

2-stage rebound, not uncommon.  Same intent as the 2-stage stack on the base.  Rebound force is consistent, not uniform; the force is proportional to spring force, so it can vary quite a bit depending on stroke.  The intent of a 2-stage rebound, ostensibly, is to give the suspension faster response on small chop.  Of course, you can make the opposite argument too, and some dampers (Sachs shocks on Huskies, for example) run a preloaded stack, which is much more digressive and basically the opposite of a staged stack.

 

Would the 2 stage rebound allow a faster return when the fork is deeply compressed and yet slow down for when its only slightly compressed ?   Would that be a good

thing ?  For what conditions ?

You have it backwards. Faster return when slightly compressed (compared to not having a crossover, not compared to when deeply compressed).

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