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Old 02-09-2013, 11:25 AM   #46
slackmeyer OP
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I just had a sweet 900 mile "test ride swap" with a Husqvarna 610 supermoto with redone suspension. Obviously, my bike is not going to ever feel like a 300 lb supermoto with sticky rubber on the front, but it sure did make me realize that I still want more feeling at the front wheel.

I think I'll go back and try to follow Javier's advice on the midvalve a bit more- I reused the original shims (4 x 0.1mmx24mm), even though they were worn out. I'm going to replace those with some 0.15x24mm shims, and try to drop the float on the midvalve down to a bit less than 1 mm. (I think I'm at 1.05mm now, I'll aim for around 0.8mm). With the fork springs out, moving the damping rod up and down, it seems like I can move it quite fast before I feel the base valve starting to work.

Anybody else playing around with shim stacks this winter?
Man, with all the suspension threads going now, I looked back on this thread, and realized that I kind of left things hanging after I made the last round of changes. I just thought I'd come back to say that those changes made the bike much better again. The changes were mainly just adding a thicker face shim to the midvalve, and reducing float to about .8mm. It finally brought my 950 up to the suspension quality of my 640, and a bit beyond (though the 640 still has the weight advantage in a big way).

I try to keep in mind the mx idea that you should bottom out your suspension once per lap- on steep downhill bumps offroad, my forks will still get within a couple cms of bottoming out, but most of the time they stay quite a bit higher in the stroke. I can't remember if I mentioned it earlier, but I'm running .56 springs, and I leave my preload all the way in (tight). I should probably make some spacers so that I can have the preload in the middle of the range, but I haven't done that yet.
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Old 02-10-2013, 05:18 AM   #47
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Hi Zak,

Thanks for including this update to your spreadsheet. Looks like your setup favors a firmer ride.
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Old 02-10-2013, 07:02 PM   #48
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Well the shims on my 2011 990 matches yours.

Zac you're running the stock valves with no modifications correct? The reason I ask is because the Race Tech Gold Valve sure is different. So different in fact that I just ordered the Rebound Valve off of Amazon. Race Tech Rebound Gold Valve Fork Kit FRGV 2302
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Old 02-10-2013, 09:50 PM   #49
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Well the shims on my 2011 990 matches yours.

Zac you're running the stock valves with no modifications correct? The reason I ask is because the Race Tech Gold Valve sure is different. So different in fact that I just ordered the Rebound Valve off of Amazon. Race Tech Rebound Gold Valve Fork Kit FRGV 2302
Correct. I'm really interested to see what you think of the Gold Valves and their setup. I probably should have sprung for that, but I'm pretty cheap, and I think that the WP valve bodies should be good enough for me. . . I think most suspension tuners change shim stacks, and only modify valve bodies when they really customize forks.

I talked to Racetech about a gold valve kit for the shock, they said they had one but they wouldn't sell it to me; the only way to get it was to send the shock in and have them R and R it. Hopefully that changes at some point.
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Old 02-11-2013, 02:18 AM   #50
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Correct. I'm really interested to see what you think of the Gold Valves and their setup. I probably should have sprung for that, but I'm pretty cheap, and I think that the WP valve bodies should be good enough for me. . . I think most suspension tuners change shim stacks, and only modify valve bodies when they really customize forks.

I talked to Racetech about a gold valve kit for the shock, they said they had one but they wouldn't sell it to me; the only way to get it was to send the shock in and have them R and R it. Hopefully that changes at some point.
I'm going to input the stock shim stacks with both the RaceTech and stock valve specs and then I'm going input your other stacks and the one that the Hipster gave me along with what Racetech recommended into the Restacker program and see what they all look like.
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Old 02-26-2013, 04:07 PM   #51
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Hey Zak what did you end up with for float on your midvalve? The restacker software is showing .6 to .8 as the sweet spot.



Oops, just saw the answer on post #48 and it's around .8. Any opinion of it being even lower?

Thanks, Tim.
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Old 02-26-2013, 05:52 PM   #52
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Hey Zak what did you end up with for float on your midvalve? The restacker software is showing .6 to .8 as the sweet spot.



Oops, just saw the answer on post #48 and it's around .8. Any opinion of it being even lower?

Thanks, Tim.
Hey Tim-
My first mods brought the float down to around 1 mm, which I wasn't happy with, my second round brought it to .8. The research I did pointed me towards that also, most other KTMs with this fork come with a float around there. I haven't tried any less float, so I can't comment on that, except to say that in theory, having no float (a clamped midvalve) just doesn't sound right to me: the float on the midvalve really lets you have a bit of relatively plush travel while having plenty of compression damping to keep bigger hits from bottoming the forks.

What does the restacker software say about float? And when you say sweet spot, how can you tell what that is?

Thanks,
Zak
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Old 02-27-2013, 02:48 AM   #53
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Hey Tim-
My first mods brought the float down to around 1 mm, which I wasn't happy with, my second round brought it to .8. The research I did pointed me towards that also, most other KTMs with this fork come with a float around there. I haven't tried any less float, so I can't comment on that, except to say that in theory, having no float (a clamped midvalve) just doesn't sound right to me: the float on the midvalve really lets you have a bit of relatively plush travel while having plenty of compression damping to keep bigger hits from bottoming the forks.

What does the restacker software say about float? And when you say sweet spot, how can you tell what that is?

Thanks,
Zak

Well it's kind of cool to look at since it computes the damping force of the base valve, mid-valve and the combined system. Since the combined damping force of the base and mid-valve produces three distinct regions with this software I get to see a graph that shows all 3 and the influence of each valve in each region and where the system transitions from one region to the next.

So what I'm seeing is that modifying the mid-valve float influences damping in the low speed range and the velocity where the suspension transitions to mid-speed with lower values transitioning earlier. Seems to me that for offroad this would be what you'd want thus (My sweet spot).
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Old 04-02-2013, 07:46 AM   #54
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990 Forks + shock

I just stretched my forks to 'S' specs and revalved with Race Tech valves. I just put 'em back on the bike yesterday. They should be somewhat stiffer, less prone to bottoming and plusher. I'll give a ride report soon. I'm stretching the shock next (obviously) but that's a right PITA and I think over my head due to the need for nitrogen recharge. If anyone has a bead on a good suspension guy on the East coast I'd love to hear about it.
BTW, I had a running email conversation with Jeff Slaven (one of the suspension gurus) and he told me Race Tech stuff is basically crap. He called them the Walmart of bike aftermarket. Thanks Jeff - where were you six weeks ago? Too late now. He said there was little wrong with the stock valves that couldn't be worked around and they were better quality anyway.
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Old 04-02-2013, 09:56 PM   #55
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BTW, I had a running email conversation with Jeff Slaven (one of the suspension gurus) and he told me Race Tech stuff is basically crap. He called them the Walmart of bike aftermarket. Thanks Jeff - where were you six weeks ago? Too late now. He said there was little wrong with the stock valves that couldn't be worked around and they were better quality anyway.
My wild ass guess is that Race tech stuff with valving that works well for you is going to be way better than WP (or Ohlins, or Penske, or whatever) hardware with valving that is all wrong for what you're doing. I started this thread hoping to shake loose a little knowledge out in the community about revalving with the stock hardware, and to put down my experimentation, since it's hard to find the information. I think it worked out well, but Racetech is the other alternative for people to work on their own suspension without feeling totally alone in the wilderness without a map. . .
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Old 04-02-2013, 10:40 PM   #56
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From my experience with the RT stuff compared OEM WP stuff, I'd have to say that the WP stuff is pretty decent. There are things that can easily be done to the WP valve bodies to improve them, or at least make me feel better that I have "touched" them..... if it really make a difference I have no real data. I hand lap the valve mating surfaces, hand blend the edges and chuck them in the lathe to re-leave some of the edge restrictions. The "Gold valves" that I have installed into standard orifice forks help make things better, not sure if there is much improvement over OEM WP valve sets.

One of the things that I find rather confusing about what I have seen in my WP suspensions and some RT stuff too, is that the valve bodies have zero transitioning from the sealing surface and the shim.... like a good modern 7 or 9 angle valve cut on a engine cylinder head can make a significant difference in flow performance (and output HP too). Long are the days gone where a "three angle valve job" is the hot setup.... Why not suspension valve bodies too?
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Old 04-02-2013, 11:01 PM   #57
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I wonder if its because the hydraulic fluid does not compress, but gases like air do.. Liquids usually your fighting cavitation, which is aggravated by surface changes.. Hmm good question..

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Old 09-23-2013, 09:08 PM   #58
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From my experience with the RT stuff compared OEM WP stuff, I'd have to say that the WP stuff is pretty decent. There are things that can easily be done to the WP valve bodies to improve them, or at least make me feel better that I have "touched" them..... if it really make a difference I have no real data. I hand lap the valve mating surfaces, hand blend the edges and chuck them in the lathe to re-leave some of the edge restrictions. The "Gold valves" that I have installed into standard orifice forks help make things better, not sure if there is much improvement over OEM WP valve sets.

One of the things that I find rather confusing about what I have seen in my WP suspensions and some RT stuff too, is that the valve bodies have zero transitioning from the sealing surface and the shim.... like a good modern 7 or 9 angle valve cut on a engine cylinder head can make a significant difference in flow performance (and output HP too). Long are the days gone where a "three angle valve job" is the hot setup.... Why not suspension valve bodies too?
Pushing this thread back to the top.

Hey Ken, all the above has the assumption that you want maximum possible flow when the valves are open. It's possible to use the orifice restrictions of these valves as a last ditch extreme damping to prevent it blowing through the travel on extreme hits. Orifice damping goes up to the square of the velocity, where the valves are more linear.
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Old 09-23-2013, 09:20 PM   #59
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Pushing this thread back to the top.

Hey Ken, all the above has the assumption that you want maximum possible flow when the valves are open. It's possible to use the orifice restrictions of these valves as a last ditch extreme damping to prevent it blowing through the travel on extreme hits. Orifice damping goes up to the square of the velocity, where the valves are more linear.
Absolutely.

Let me just say that there are a few complaints about these forks that I've seen from time to time, but that I never felt for myself-

That they suffer from too much stiction- Never thought that, it seemed like the stock forks would start moving over the smallest pavement seams. Seemed cool at first, like it was doing something important, but I've discovered that I much prefer more initial damping, so that small bumps don't upset the bike.

That the stock forks don't flow well enough- kind of related to above, I felt like the reason that the forks were not absorbing big hits is because they were already way down in the stroke, and I was starting to get an air spring effect (I'm sure there's a better way of saying that).

Anyway, I'm really very happy with the work I did and the way the bike handles now- of course, I can't compare it to every possible fork mod, but I'd say that changing the shim stack and using all stock components can transform these forks, and going further than that (modifying valves) would introduce more variables, and be a lot less reversible than playing with shim stacks.
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Old 09-24-2013, 08:08 AM   #60
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Pushing this thread back to the top.

Hey Ken, all the above has the assumption that you want maximum possible flow when the valves are open. It's possible to use the orifice restrictions of these valves as a last ditch extreme damping to prevent it blowing through the travel on extreme hits. Orifice damping goes up to the square of the velocity, where the valves are more linear.
shim stack suspension is (in my mind) effectively 'orifice' damping, its just dynamic orifice. It of course messes with a fixed calculation for a fixed orifice size by being dynamic :)

I am a believer in freedom of flow, independent of the fluid flowing, and that induced restriction (and this restriction can become a significant dynamic factor) from turbulence from poor transition areas is a bad thing and can be very difficult to resolve..... Can I back this up with data? No. Do I have a doctorate in fluid dynamics? No.

HOWEVER.... based upon what I have seen in simple testing and what I have read in some heady physics books, reduction in turbulence, specifically where induced by valve body 'should' reduce heat and sheer of the fluid passing. It also should reduce cavitation.

I believe that making the mid valve as 'slippery' as possible through blending of edges and smooth transitions from support structure to valve seating area would be a good thing. Any high speed damping requirements should be able to be applied through shim stack configurations.

Getting the suspension to stay 'up in its stroke', in my mind comes from a series of things. 1. correct spring rate 2. compression 'float' 3. rebound setting.

So.... if the spring is too soft and the float is too much, then the forks will tend to be down in the stroke which then leads to 'harshness' from the air gap spring effect (the effective spring rate is non linear).

I set my suspension up such that occasionally, when riding hard and hitting big G-outs or doubling whoops the suspension does bottom, I want it too. The key is to set it so that it doesn't 'CLANK' bottom, but 'click' bottom. I get this through fine tuning the effect of the bottoming cup (I drill 3 relief holes to soften the 'anti bottoming' of the cup... and then set air gap to refine further, starting with 110mm and I think the last setup ended up somewhere around 100mm by the time I was done messing with it, but this was also 'my' valve setup and a .60 spring and my FatAzz (260lb geared rider).
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