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  1. #26
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    I forgot to put some important information regarding the use of a SID adapter converted to a IFP valve adapter (ModA from now on)

    1- When the ModA is threaded in the Monarch IFP valve, the rod of the schrader valve core is not pressed, so it remains closed and you can't have any reading in the pump pressure gauge. You can only have a correct reading if you pump more pressure than the one that was already present in the IFP chamber, but the problem is that you don't know how much is it.

    2- To overcome this, what I did was first to empty the IFP air chamber by pressing the schrader valve with a small screwdriver. You can hear how an small amount of air (or nitrogen ) blows out.

    3- Now I know I have 0 psi in the IFP chamber . So, when I start pumping, the pressure that reads the gauge is the real pressure that I'm putting in the IFP chamber.
    In other words: you can increase and measure the increasing IFP air pressure in the pump but you cannot decrease it from the pump because you will only evacuate the air in the pump and hose.

    4- Because the schrader valve remains closed when you are not pumping, to remove the ModA and the pump without loosing any pressure is straightforward. Unthread it without taking any particular precaution. It doesn't matter if you do it fast, slow, drinking a beer... you will not loose any IFP chamber pressure.

    I don't know if I've managed to explain my experience with my "rusty" English
    Last edited by Marmoto; 01-14-2011 at 10:15 AM.

  2. #27
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    Quote Originally Posted by Marmoto
    I don't know if I've managed to explain my experience with my "rusty" English
    You've done it perfectly.

    Thing is, there is a market for those DIY's for a proper filling adapter. One you can screw in, then when you want the core of the schrader depressed, you give the adapter a half turn or press a button and then do the opposite to remove the adapter with the core depressed. No air loss, proper readings, no hassle.

    It doesn't take a rocket scientist to figure one out.

    Better yet... make shock mfg's to put goddamned schrader valves on all IFP's.
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  3. #28
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    The IFP adapter I have from Manitou has a little rod in the center of it that floats. when screwed onto the shock only, it rests against the core in the shock. When the pump is added, the rod pushes down on the schrader core in the shock, allowing access. Its a nice feature. Its literally impossible to loose any pressure when unscrewing the adapter.

  4. #29
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    Well F me sideways! On closer inspection, Marzocchi uses a two thread patterns in their recessed valve holes. The first one is to seat the schrader valve and the second, slightly larger one, to take the adaptor. This means that Marzo adaptors can't be modified to work on the RS or any port that uses the standard schrader valve thread form.
    "Adventure begins where good judgment ends."

  5. #30
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    To build group knowledge:

    Ok, so I made an adapter and found out the IFP schrader core was leaking slightly. I pulled it out and found a few slivers of aluminum on the tapered seal seat on the core. Cleaned that off, reinstalled and it holds air now. Bad Rockshox! No donut!

    Because it was never holding properly high pressure, the shock felt like it had ingested some air. So I took it apart and refilled it (real simple, just a vise and crescent wrench). Bleeding is a breeze with the bleed port on the seal head, but it means I don't know what my IFP depth truly is. I just cycled the shock on my hand dyno while bleeding out oil until it felt right. The next time I take it apart, I'll be sure to measure it. I think rebuilding it fully submerged will also work just fine.

    After charging the IFP to ~220psi, it no longer has bad bottom out characteristics and feels smooth throughout the stroke. For reference: this is a Monarch 2.1, "A" tune, 190x50, on a 2.5:1 linear frame.

    An observation: at full bottom out, this shock's air can scraper seal actually rides past the end of the shaft. I.E. it pushes the travel indicator O-ring completely off and then some. Do yours do that too? Seems like a bad design feature for seal life.
    "Adventure begins where good judgment ends."

  6. #31
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    Quote Originally Posted by HHMTB
    To build group knowledge:

    Ok, so I made an adapter and found out the IFP schrader core was leaking slightly. I pulled it out and found a few slivers of aluminum on the tapered seal seat on the core. Cleaned that off, reinstalled and it holds air now. Bad Rockshox! No donut!

    Because it was never holding properly high pressure, the shock felt like it had ingested some air. So I took it apart and refilled it (real simple, just a vise and crescent wrench). Bleeding is a breeze with the bleed port on the seal head, but it means I don't know what my IFP depth truly is. I just cycled the shock on my hand dyno while bleeding out oil until it felt right. The next time I take it apart, I'll be sure to measure it. I think rebuilding it fully submerged will also work just fine.

    After charging the IFP to ~220psi, it no longer has bad bottom out characteristics and feels smooth throughout the stroke. For reference: this is a Monarch 2.1, "A" tune, 190x50, on a 2.5:1 linear frame.

    An observation: at full bottom out, this shock's air can scraper seal actually rides past the end of the shaft. I.E. it pushes the travel indicator O-ring completely off and then some. Do yours do that too? Seems like a bad design feature for seal life.
    Someone on another Monarch post kind of railed against the idea of altering the IFP pressure to achieve a better tune. This attached Velonews link I just found looks like Fox uses the same technique to tune their RP shocks to fit different suspension designs and such. Look down in the article to the section on Boost Valve and IFP pressure on the RP shocks. Looks like 200-300 psi is safe for the RP series shocks, and I doubt that it's much different for the Monarch.http://velonews.competitor.com/2009/...ry-scene_90761

    On the o-ring getting pushed down, The Fox shocks will do the same thing in the right conditions. Just adjust your main air can pressure up incrementally or juggle the IFP and main spring pressure until you get all the travel and find your sweet spot.

  7. #32
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    Quote Originally Posted by TNC
    Someone on another Monarch post kind of railed against the idea of altering the IFP pressure to achieve a better tune. This attached Velonews link I just found looks like Fox uses the same technique to tune their RP shocks to fit different suspension designs and such. Look down in the article to the section on Boost Valve and IFP pressure on the RP shocks. Looks like 200-300 psi is safe for the RP series shocks, and I doubt that it's much different for the Monarch.http://velonews.competitor.com/2009/...ry-scene_90761

    On the o-ring getting pushed down, The Fox shocks will do the same thing in the right conditions. Just adjust your main air can pressure up incrementally or juggle the IFP and main spring pressure until you get all the travel and find your sweet spot.
    Boost Valve is Fox's name for an SPV valving. It's a little more refined than what Progressive and Manitou did in the past, but same thing. A spring loaded valve that reacts to damper pressure by closing some ports.

    The Monarch is a more conventional shim-based shock.
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  8. #33
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    Quote Originally Posted by HHMTB

    An observation: at full bottom out, this shock's air can scraper seal actually rides past the end of the shaft. I.E. it pushes the travel indicator O-ring completely off and then some. Do yours do that too? Seems like a bad design feature for seal life.

    Same problem with mine, and it over-stroked too. Since tolerances are tight on my frame, this meant the rockers hit the frame on full compression. Not good.

    Quote Originally Posted by TNC
    On the o-ring getting pushed down, The Fox shocks will do the same thing in the right conditions. Just adjust your main air can pressure up incrementally or juggle the IFP and main spring pressure until you get all the travel and find your sweet spot.
    Not in my experience of the 2010 RP23 (heavily falling rate frame tends to show up bad bottom-out characteristics..!)

  9. #34
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    Yup, no Curnutt/SPV valve in the Monarch.

    I disagree with the statement in the article that all the bottom out functions are now shifted to the damper. It's always a summation of the damper and spring characteristics and the IFP pressure is a huge variable we should have access to with or without the Curnutt.

    I don't think the Monarch is over stroked in that it gets what it's supposed to get (2") but when it does, the scraper runs off. I've never seen a Fox do that either. When the O-ring comes off on those it's usually because of inertia from a fast hit and the o-ring is old/cracked and not gripping the shaft as well.

    Huh huh... "gripping the shaft"
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  10. #35
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    Quote Originally Posted by HHMTB
    I don't think the Monarch is over stroked in that it gets what it's supposed to get (2") but when it does, the scraper runs off. I've never seen a Fox do that either. When the O-ring comes off on those it's usually because of inertia from a fast hit and the o-ring is old/cracked and not gripping the shaft as well.
    Yeah, but measure the exposed stanchion, it was well over the claimed 51mm on mine, and like yours the o-ring gets pushed right off the end - so it definitely uses the whole amount


    Quote Originally Posted by HHMTB
    Yup, no Curnutt/SPV valve in the Monarch.
    Huh huh... "gripping the shaft"

  11. #36
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    Not trying to cause controversy here, but I work in a shop and have seen and owned plenty of Fox air shocks that get the o-ring knocked off...everything from the DHX Air to the Float series. If the shock body is designed to have pretty much most of the exposed shock stanchion used up in the travel, with too soft an air spring pressure you can knock the o-ring off. Some of the Fox air shocks aren't designed by length or travel requirements to use relatively all the stanchion, and so you'll never see that happen...or if you run high air pressures...or your bike's suspension design doesn't challenge the end of stroke travel...or other variables. With many of the air shocks, Fox or otherwise, that are having the o-ring knocked off, just raise the pressure. Unless there are other internal issues with the shock, this is not too uncommon. I'm surprised some haven't heard of this before.

  12. #37
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    Quote Originally Posted by Warp
    Boost Valve is Fox's name for an SPV valving. It's a little more refined than what Progressive and Manitou did in the past, but same thing. A spring loaded valve that reacts to damper pressure by closing some ports.

    The Monarch is a more conventional shim-based shock.
    True, boost valve or not, it's the IFP pressure that Fox is using as a tuning element just like some of us are doing with our Monarchs.

  13. #38
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    Good to know, TNC. I just hadn't run across that configuration of Fox shock I guess. Still seems shoddy to me that that can happen. Marzocchi doesn't do that in my experience. Can you tell me offhand which sizes do that? I've deflated and fully compressed 6.5x1.5, 7.5x2, and 7.875x 2 Floats and RP23's without seeing this. Not trying to pick a fight, just curious.

    In any case, I don't think that the proper solution is to just up the pressure until you can't access all available stroke. I mean, what's the point of paying for a 2" stroke shock when realistically if you use all 2" you risk damaging the main seal? The right solution is to design the shock so that bottom out doesn't compromise things.

    The exposed stanchion on mine is right at 2"/50.8mm. More QC issues with yours Retro, maybe?
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  14. #39
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    Quote Originally Posted by HHMTB
    Good to know, TNC. I just hadn't run across that configuration of Fox shock I guess. Still seems shoddy to me that that can happen. Marzocchi doesn't do that in my experience. Can you tell me offhand which sizes do that? I've deflated and fully compressed 6.5x1.5, 7.5x2, and 7.875x 2 Floats and RP23's without seeing this. Not trying to pick a fight, just curious.

    In any case, I don't think that the proper solution is to just up the pressure until you can't access all available stroke. I mean, what's the point of paying for a 2" stroke shock when realistically if you use all 2" you risk damaging the main seal? The right solution is to design the shock so that bottom out doesn't compromise things.

    The exposed stanchion on mine is right at 2"/50.8mm. More QC issues with yours Retro, maybe?
    No offense taken or given...just discussion. You can't achieve this by just deflating the shock and cycling it in the bike or by hand. I'm not sure what bottomout medium is used in the Fox...usually a rubber bumper in most...but it almost always take a bottomout under actual operation of the bike to achieve this.

    As to what models of Float series shocks do this, I know it's on some Treks and Spec models. It was also very common on the DHX Air's that came on Nomads and RP23's on the BLT2. The point I was making about adding air is only that you're getting a clear indication that your air spring is insufficient if you're knocking off the o-ring. Just adding air in small increments until you find that spot where you get full stroke without knocking off the o-ring isn't robbing you of potential travel. When you find that air pressure, you know that's your benchmark from then on.

  15. #40
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    Hmmm... I'll let you know what the bottom out medium is. I've got a buggered ~08 RP23 sitting on my desk right now that's gonna get autopsied soon-ish.

    FYI, no bumper in the Monarch. O-ring on the hydraulic shafts of Roco air shocks, though the O-ring squashes to nothing almost imperceptibly. I think it's just there to prevent metal on metal.
    "Adventure begins where good judgment ends."

  16. #41
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    By the way, since I don't think anyone else addressed it in this thread, you CAN easily adjust the IFP chamber size in an inline shock. Just take out the valve core and add some oil. I've been doing this for a few years now and not only does it increase your tuning options, it also helps with IFP seal life since both sides of the seal are now lubricated with oil.

    Go easy on adding the oil. Like ~5-10 drops of oil at a time. Small changes here make big changes to the progressivity and you don't want to hydro-lock the shock.
    "Adventure begins where good judgment ends."

  17. #42
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    HHMTB, I did something similar in my Monarch RT3 IFP chamber and it works perfect:
    - I removed the air/nitrogen from the IFP air chamber
    - I removed the IFP schrader valve core
    - I added 6 drops of 80W fully systetic gear oil into the IFP air chamber with a dual purpose: increase the IFP lubing and make it a little bit more progressive to counteract the side effects of the next step.
    - I inserted de IFP valve core and pumped 210 psi (it was 250-300 psi) to increase the small bump sensitivity. The bottom-out control didn't suffered.

    Now is really sweet: the shock provides in the rear the same feeling as my RS Revelation in the front, really "equalized". It is very plush (which is good for my IBIS Mojo DW-Link) and has the right bottom-out control for my riding style (aggressive trail riding but with few jumps)

    And is easy and cheap

    I love this forum

  18. #43
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    Hey, TNC. So the bottom out element in this RP23 (7.875x2.0) is an O-ring that's .10" thick (section diameter) and mounted on the .375" hydraulic shaft.

    Very nicely made inside, I might add. I am a little perturbed that the main compression stack is actually belleville washer loaded. I wouldn't expect a whole lot of tuning resolution from that.
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  19. #44
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    Quote Originally Posted by HHMTB
    Hey, TNC. So the bottom out element in this RP23 (7.875x2.0) is an O-ring that's .10" thick (section diameter) and mounted on the .375" hydraulic shaft.

    Very nicely made inside, I might add. I am a little perturbed that the main compression stack is actually belleville washer loaded. I wouldn't expect a whole lot of tuning resolution from that.
    I wonder what PUSH does to the RP23? Good to know on the o-ring bottomout.

  20. #45
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    Quote Originally Posted by HHMTB
    Hey, TNC. So the bottom out element in this RP23 (7.875x2.0) is an O-ring that's .10" thick (section diameter) and mounted on the .375" hydraulic shaft.

    Very nicely made inside, I might add. I am a little perturbed that the main compression stack is actually belleville washer loaded. I wouldn't expect a whole lot of tuning resolution from that.

    Darren from Push calls those things disc springs and says they are a minor contributor to total damper flow, and were something related to propedal. The ports are huge but that plate is not allowed to move far enough to flow a large amount of oil. I'm not sure if it affected propedal directly or if its there to take the edge off of the bumps while the propedal plunger opens.

    I think the o ring slams the compression stack shut before it plays mechanical end stop on the RP23. Is the monarch built as nicely as the Fox stuff?

  21. #46
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    Quote Originally Posted by TNC
    I wonder what PUSH does to the RP23? Good to know on the o-ring bottomout.
    They had a picture of the new internals on their website. Looks like new piston and shim stacks. The disc washer stuff is replaced by a real HSC shim stack. I'll bet the high speed rebound flows a bunch more.

  22. #47
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    The way it looks to me, in this '08 RP23, is that there are two compression flow paths. The one that has the Bellevilles (fancy name for disc spring) is the first circuit which is built on the piston face the way I'm used to seeing and this never gets blocked.

    The second circuit is behind the main piston and receives its flow from oil passing through the specially machined shaft end nut. This circuit gets blocked by the Propedal pop off valve when the PP lever is engaged. The PP valve is spring loaded and this spring preload is what you're adjusting when you turn the PP selector in the 3 settings. Thus, with Propedal engaged, only the first circuit is active until you hit a big enough bump to unseat the Propedal pop off which then allows flow to the second circuit.

    Without plugging it into a dyno, I don't know what the relative circuit contributions are to the overall compression damping performance, but I would guess it's close to 50/50? It should be noted that the second circuit has a traditional shim stack so that's probably how Fox achieves fine tuning of the compression. If and when I figure out how to upload pictures on the forums, it'll make much more sense.

    The bottom out O-ring can't do anything to the damping since it's not in the oil. It's outside the damper on the shaft. It's like the bottom out bumper on a coil over.

    The Monarch seems nice as well, but their assembly techs need to do a better job as I alluded to above. The 2.1 that I'm looking at is also a much simpler, straight forward shock with no fancy stuff going on. For reference, the Monarch uses a 9mm shaft which I think gives the IFP less bottom out effect as compared to Fox's 9.52mm shaft or Marzo's 10 or 12.7mm. At least that's my theory for now.
    "Adventure begins where good judgment ends."

  23. #48
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    Wow, good timing for this to pop up.
    Thanks to all!

  24. #49
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    RP23 guts for those interested

    Ok, I kinda sorta promised TNC some pictures of the RP23 innards a while back so here they are. I know this is a Monarch thread, but this is where the conversation started.

    First picture shows the bottom out O-ring that TNC and I were wondering about. Nothing particularly special. The shiny disc behind it is a flat washer/shim to prevent the O-ring from expanding over the stub that the shaft screws into when smashed on a full bottom out. The Marzocchi Roco air shocks I've seen don't have this shim so the O-ring can over-expand and then no longer work as a bottom out softener.

    Second and third pictures show the piston assembly more or less in its assembled state. That cross shaped, ninja star thing above the piston is a ring that protects the shim stack from damage on top out.

    Fourth picture is the the piston/shim stack/Pro-Pedal assembly exploded. I laid it out from the top row left to right and then bottom row left to right. I laid them out the same way except for the one part that is marked flipped because the detail would have been obscured. As it's too ambiguous to describe the orientation of how I removed a shim and put it on the table, you'll have to figure it out by looking at the actual piston relative to picture two.

    The fifth picture shows Pro-pedal on/off pop off valve next to the shaft end nut that it seats on. It's this pop off valve you are moving when you switch the blue lever. The PP level knob governs the preload on the spring.

    I was surprised when I took this thing fully apart for the pictures that there seems to be a two stage rebound setup. That's what the "flipped" part does. Everything else is as described in my previous message as far as I can tell.

    Hope that helps someone. If not, it'll help me when I forget
    Attached Thumbnails Attached Thumbnails Monarch & IFP pressure change...-p1030105.jpg  

    Monarch & IFP pressure change...-p1030106.jpg  

    Monarch & IFP pressure change...-p1030107.jpg  

    Monarch & IFP pressure change...-p1030108.jpg  

    Monarch & IFP pressure change...-p1030110.jpg  

    "Adventure begins where good judgment ends."

  25. #50
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    Excellent HH. Am I also seeing 2-stage compression? I'm used to seeing dirt motor shocks like the KYB and Showa, but I wasn't sure if a couple of those parts in the compression stack interact with Propedal in some way. It's way more complicated and sophisticated than the KYB on my Kawasaki. Thanks for posting this disassembly...very informative. I can see why PUSH has a lot to work with here to improve this shock. I am usually not impressed with how most of these feel on the bikes that come through the shop, but man...there should be lots of potential here. Thanks for posting this up. I didn't go into my Monarch's damper components at all to just change oil. Makes me wonder what's in there.

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