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  1. #51
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    Quote Originally Posted by HHMTB
    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.
    I had one of the early RP23 aftermarket shocks and it didn't have the second rebound stage. It was tuned for medium compression and rebound.

    The RP2 that came on my Specialized Pitch has the second stage. I think that shock was tuned medium compression, light rebound. The RP2 looked the same internally as the RP23 except for the extra rebound circuit and the propedal needle didn't have the intermediate positions.

    I think the additional rebound stage and the number of disc springs in the HSC valve is how Fox gets their different tunes for the shock.

    It's been a while since I had either shock apart and they're both retired but do those HSR ports look normal or are they awfully small?

  2. #52
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    Quote Originally Posted by HHMTB
    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.
    If you make the IFP chamber smaller to make the shock progressive, the pressure at full compression will be higher. Seems to me the IFP pressure and the damper oil pressure should be equal, but is there any operating condition where the seals or piston could be damaged? Is there an upper limit to IFP pressure? Any drawbacks to damper performance?

  3. #53
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    Yep, TNC, that's a two stage compression. With ProPedal on, the little shaft plunger closes off the shaft end bolt and compression flow only goes through the Bellevilles. With PP off, flow goes through the center of the shaft bolt through the side ports of the bolt and through the pyramid shim stack.

    I too am not a fan of the feel of the RP23's stock. I think it simply can't flow enough oil through the center of the shaft bolt for the pyramid stack to dominate. That means the Belleville PP circuit would dominate which equals dooky performance. At least that's my opinion from looking into it more.

    Now I didn't bother to undo the shaft bolt on the Monarch when I rebuilt it, but I would expect at the most there's only a dished piston or preloaded shim stack. It was pretty basic in appearance and that's why I didn't bother to take it all apart. Not that "basic" is bad, mind you, I like stuff that is simple and bulletproof, but I just didn't think I'd learn anything from taking it apart. Maybe the next time I open the Monarch I'll do that.

    For ARC, I haven't yet run into the upper pressure limit, but I assume there must be one. I will say I've gone as high as 300psi in a Roco LO DC, which probably means it was upwards of 400 at bottom out, without issue.

    Where the limit is would be a function of how good the shaft seal and shaft-to-guide bushing fit are. I.E. rudimentary O-ring will likely blow faster whereas a honest to goodness directional lip seal ought to seal harder as the pressure gets higher. Again, just my thinking. You may be able to feel more stiction as pressures go up because of the lip seal thing, but the swept area is small so probably not.
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  4. #54
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    HH, on the possible inability to flow enough oil, maybe it's something like you encounter in some dirt motor shocks. Race Tech has made a ton of money with their Gold Valve system which flows more oil more effectively through the shim stack of many shocks. It was a dramatic improvement on my Kawasaki dirt bike with a KYB shock. Many compression pistons/valve don't flow enough oil to give optimum performance through the shim stack. I wonder if PUSH replaces the main piston along with shim stack modification to achieve what seems to be real performance increases on the RP series?

  5. #55
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    An appropriate comparison. From what I've heard, Push and Race Tech founders are friends, or at the very least know each other well. Hearsay, I know, but it makes sense if true.

    I know that the original generations of Push upgrade occurred when Propedal made its entrance ~2003 and the upgrade included a High Flow Piston to facilitate better tuning resolution.

    I don't know what goes into RP23's now (and keep in mind the one I show dissected is an 08, not the current Curnutt Boost Valve versions) but their website says they install the "VxRII High Flow Piston." I can only assume that they do this to remove the Belleville's and replace them with preloaded shims so as to create a better PP transition?

    If anyone wants to donate a Pushed RP23, I'll be happy to find out...
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  6. #56
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    "Adventure begins where good judgment ends."

  7. #57
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    Great info, HH. I had no idea that PUSH was already pursuing the higher flow piston concept, but it's absolutely logical.

  8. #58
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    When Push started up there was a lot of internet chat going around, I recall reading somewhere that the Race Tech guy was a mentor for Push.

    If you look through Push's website there's pictures of shock internals. Seems the shocks always get new a piston with new shimmed LSC, HSC, and HSR. Its probably easier for them from a tuning standpoint, regardless of shock brand or model you can have the same size ports and IFP pressure. All you have to do then is match the shim stack to the application.

    In my experience with the RP2 and RP23, compression flow was not as big a problem as high speed rebound flow. I think mine were always packing down a bit and you ended up riding too much in the wrong part of travel. Also the rebound portion of a fast square edge hit was worse than the compression.

    I ended up drilling the HSR ports to .047, and tossing one of the disc springs. IFP was 2.13" and about 150psi before bleeding. Turns out the IFP was too big or not enough pressure, it blew through travel so fast I had to compensate with an extra 20psi in the air can. The ride was lively and smooth, didn't notice any compression spiking. Traction was outstanding, perfect for fast singletrack riding as long as you were careful to get your weight back fast on downhill turns and didn't do anything resembling a jump. The RP23 was my first attempt and that bike got retired. I tried putting a schraeder valve in the RP2, but the schreader got bent and pulled some threads out while riding.

    HHMTB, can you see any path for low speed rebound oil flow with propedal engaged? As I see it, the propedal plunger blocks it off to hold the bike at sag height to help manage bobbing. If the HSR circuit was more active it would reduce the propedal effect. I think propedal is active on compression and rebound, the HSR on the RP floats got constrained for that reason.

  9. #59
    arc
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    Quote Originally Posted by TNC
    Great info, HH. I had no idea that PUSH was already pursuing the higher flow piston concept, but it's absolutely logical.
    They've been pushing that since they started. Did you see this?

    http://www.pushindustries.com/2009/i...OTO%20Services

  10. #60
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    Quote Originally Posted by arc
    They've been pushing that since they started. Did you see this?

    http://www.pushindustries.com/2009/i...OTO%20Services
    Sometimes it's hard to tell the difference between marketing hyperbole and actual engineering. Darren's association with Paul Thede tells me he pursues the real deal...as well as the PUSH'd Fox RC I had done to my Nomad more than two years ago. Frankly it wasn't until I did the Race Tech revalve on my dirt motor shock myself last year, that I truly grasped how important the main piston flow design could be. I mean, you'd think these guys designing and building these shocks could get something as important as the main piston oil flow correct. I thought anything could be fixed with proper shimming...if it had shims, of course...but if the main piston flow is insufficient, the shim stack never achieves full performance. If KYB, Showa, and some others could screw up on the main piston oil flow in some applications, I can see how the MTB guys could follow suit. Anyway, it seems Darren follows a similar trend as Race Tech and some other moto suspension companies...OK, maybe nothing earth shattering here...but that gives me even more faith in PUSH's efforts.

    I had already done some fairly extensive shock and fork servicing such as oil change, o-ring, piston ring, and main seal repairs. I had even experimented, somewhat successfully, with IFP position to manipulate travel characteristics. However, it wasn't until I did that Race Tech revalve on my own for my moto fork and shock that I really got the "full" picture.

  11. #61
    arc
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    Quote Originally Posted by TNC
    Sometimes it's hard to tell the difference between marketing hyperbole and actual engineering.
    Didn't mean for my comment to be taken that way. Perhaps I should have used the word advertising instead of pushing. No knocking Darren Murphy from me. I've learned a lot reading his posts, and its easier for me to attempt some shock tuning knowing that if I screw it up badly I can always send it to Push.

    The high flow piston has been there from the beginning. Push has always followed Race Tech's approach, custom high flow piston and shim stacks. I thought since you ride dirt bikes, you'd find Push getting into moto tuning interesting.

  12. #62
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    Hi, ARC. I think you are right that the LSR port of the shaft bolt gets closed when PP is switched on. However, I think that's why the second stage rebound circuit exists. The flutes and cross drills on the bolt itself allow flow through the second stage.

    Will it be different from the rebound with PP off? Absolutely. So your observation looks right to me: PP affects both compression and rebound.

    TNC: I agree, it makes way more sense to have excessive flow that you can choose to block off with shims than to never be able to achieve enough flow. Like most things in life, it's better to have too much and be able to say "no," than to hunger for more and not be able to get it... food, money, sex, etc
    "Adventure begins where good judgment ends."

  13. #63
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    I wanted to amend something I said back in December. I rebuilt a Roco Air R shock recently and came to a "no duh" realization. This shock had a big air bubble in it. The last time I rebuilt it, I put 140psi in the piggyback and 145 in the air chamber. The "no duh" part is that in an air shock it's the air chamber that acts against the main shaft seal and not atmospheric pressure. So having the air spring set higher than the IFP will allow air in past the main seal causing the big bubble effect.

    So my comment above saying I consider minimum IFP pressure to be 100psi does not apply to air shocks. Always set the IFP higher than your air chamber pressure will ever reach. As the IFP pressure raises much more quickly during compression than the main air chamber, I don't think a huge differential is needed. I've rebuilt with IFP at 170, air can at 140 and all seems well for the last few weeks.

    Sorry if I screwed anyone up in my prior post.
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  14. #64
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    Good thread. I still don't see how the IFP pressure affects anything other than effective total spring rate in the Monarch or Pre Boost Valve RP shocks. There is nothing "pressure" sensitive in the damping, it is all velocity or flow sensitive. I can see how a smaller IFP volume or higher pressure will cause the pressure to ramp up on compression, but couldn't you acheive the same boost by shimming the air can or more air pressure?

    The new BV RP23 should be a different animal, and I suspect they are very sensitive to IFP pressure.

    Could someone elaborate on how the rebound circuit is affected by PP position on RP shocks? I have not been happy at all with the rebound (or compression) on my 2011 RP23 BV, and I always run PP off on my Mach 5. Could I see an improvement in rebound damping with PP on? The bike always kicks me going over dips and g-outs even set to full slow rebound. I've switched to a Monarch Plus which is a million times better, but would like to now how to achieve better performance with the RP shock.

  15. #65
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    In my experience, changes to IFP pressure and, more importantly, position have a drastic effect on the shape of the spring curve that is harder to achieve than just by altering the volume of the air can. Basically, if you want minute changes to spring progressivity, yes, what you said is true. However if you need a lot more or a lot less bottom out resistance (especially in a non-position sensitive shock) your options are to re-shim, change oil viscosity, or alter the IFP pressure/position.

    This, by the way, is indictive of what I think are two schools of thought in suspension. On one end are people that don't like a lot of damping and rather depend on spring rate and shape to control bottom out and attitude. On the other end are people who tend to have softer, more linear spring rates and depend on more sophisticated damping to provide bottom out and attitude control. In my opinion, this was the difference between Marzocchi and Fox products. For me, I'm in the first group so being able to tweak IFP becomes quite important.

    I haven't taken apart a position sensitive RP23 yet as I'm still waiting for someone to donate one . I would venture to guess that the fact you can't get the feel you want no matter what your rebound setting is indicates that it's not the rebound that's the problem. My reason for generally not preferring fox air shocks is that to me they feel overly compression damped even in the softest tune. Further, DW bikes like yours work better with very little compression damping. Maybe in your particular situation it's just not able to use enough travel to adequately absorb the energy. Basically, you probably need a lighter compression revalve, or better yet, stick with your Monarch.

    To more directly answer your question, if the rebound circuit architecture in the current models is anything like the one I took apart and posted pictures of, turning on PP will turn off one of the rebound flow paths resulting in less rebound control (faster rebound). This correlates with what I've felt in the few RPs that I've ridden. It will also increase your low speed compression damping resulting in less trsvel used.

    Wanna donate your 2011 RP23 to me to experiment on?
    "Adventure begins where good judgment ends."

  16. #66
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    I have a rt3 with m/m on the can assuming it's a mid volume mid tune. With the ifp set at 250 it gets about 60% of it's full travel. set to 210 it's suppler and gets a little more travel but still not full travel.

    My bike has 3.5 inches of travel and a stroke of 38mm so it's leverage ratio is 2.3

    i guess i need a re tune or a lower leverage ratio shock.

  17. #67
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    Quote Originally Posted by HHMTB View Post
    Wanna donate your 2011 RP23 to me to experiment on?
    I'm super curious what's inside, but I'm thinking of getting the RP23 Pushed this winter (unless the aftermarket Monarch tuning finally arrives.)

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    bump

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    This thread is great - informative and motivating. In fact, it's motivated me enough to pick up the adapter valve to start messing with IFP pressure. But before I do, I want to make sure I understand the procedure.

    For the record, I have a Monarch Plus RC3 on a Trek Scratch. I spent a good amount of time on my '09 Commencal Meta 6 messing with Fox Float R air can volume using various plastic shims to get the best combination I was able of "proper" sag, big hit firmness and small hit compliance. It may not be perfect, but I like the feel better than that on my new ride, and I'm hoping I can make similar improvements on the Monarch.

    So I remove the IFP access cap with the Schrader core removing tool. I fit the adapter to the end of my shock pump, and thread this whole unit into the IFP valve. Do I empty the air from the air spring chamber first? Any other step I'm missing?

    I see Rock Shox specs 250 PSI for the IFP. There seems to be some debate about an ultimate lower limit - is there a consensus on a conservative lower limit? Is there a relationship between air spring pressure and IFP pressure, i.e. a ratio I should shoot for? Does IFP pressure affect sag?

    Thanks for any and all help,

    Forrest

  20. #70
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    Quote Originally Posted by vizsladog View Post
    I have a rt3 with m/m on the can assuming it's a mid volume mid tune. With the ifp set at 250 it gets about 60% of it's full travel. set to 210 it's suppler and gets a little more travel but still not full travel.

    My bike has 3.5 inches of travel and a stroke of 38mm so it's leverage ratio is 2.3

    i guess i need a re tune or a lower leverage ratio shock.
    My rt3 on a giant trance, tuned softer by a local tuner, with 200 lbs in the ifp chamber still won't get full travel unless pushed very hard on a cross country ride. It's harsh on compression even @ 35% sag. I gave up on it & had the stock float tuned by push, & the bike flows much better at the rear. I don't understand all the great praises for the monarch, perhaps for heavy weight riders on longer travel bikes?

  21. #71
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    Ok, I'll try to help. But please post anything new you learn so we all get better knowledge.

    Completely deflate the main air can. If there's any significant pressure in there and you let out all the IFP pressure, you'll get a big bubble in the oil as air forces its way around the main shaft seal. If after letting all the air out of the main air can, the shock compresses a little due to negative air spring interactions, it'd probably be best to unscrew the air can off the shock completely.

    Ok, so now you're ready to play with IFP. What you wrote, "So I remove the IFP access cap with the Schrader core removing tool. I fit the adapter to the end of my shock pump, and thread this whole unit into the IFP valve." is correct.

    I usually dump all the existing IFP pressure first just to make sure that that valve is still functioning. In the case of my report, it wasn't so I had to pull it out and clean crap off the sealing face. After you're satisfied that it's all mechanically in order, start pumping.

    As I mentioned in a post a short while back, set that IFP higher than your main can by some good amount. I used 30 or so psi greater, but you'll have to be the judge of your own comfort level. On a coil over, I'd say anything over 100 is good, but given an air shock, I'm staying above 170 psi on the IFP for this reason.

    Yes, IFP pressure affects sag to a small degree. However it affects mid stroke and bottom out more as does actual IFP volume. I can't point you to a magic ratio as it varies from shock model to shock model due to dimensional differences. Also, you may like something entirely different from what I like.

    Generally speaking, the higher the IFP pressure, the greater its effect on bottom out the more support you'll get mid stroke so you can lower the main air can pressure. It's a reasonable way to combat a wallowy shock up to a certain point. If you reach that limitation, you'll have to actually vary the IFP chamber volume. Less volume = more bottom out resistance/spring progressivity which can actually make the wallowing feeling worse in some cases.

    Anyway, that's all I got time for now. Post your findings please and we'll talk some more.
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  22. #72
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    OK, maybe I'll give it another shot.
    I thought I had read that 200 was the min. psi?
    You're saying I could drop it down to 170 lbs without any adverse affects?

  23. #73
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    Quote Originally Posted by kneecap View Post
    OK, maybe I'll give it another shot.
    I thought I had read that 200 was the min. psi?
    You're saying I could drop it down to 170 lbs without any adverse affects?
    He's saying that your IFP pressure ideally should be higher than your main chamber pressure, otherwise the air will migrate from the main chamber to the damping oil.

    You don't mention what your main chamber pressure is, so hard to tell what pressure will work for you.

    Try going down in decrements of 20psi. If you go too low, the shock will start fading due to cavitation. There are no adverse effects other than having to bleed the damper if you run it low in IFP pressure for short periods of time (I am NOT recommending it either!). It's long term operation in this mode that can damage seals and internals.

    Also, the shock will also have weaker mid-stroke and will be easier to bottom as you go down in pressure.
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    Make sure there is enough ifp pressure to keep the rebound side from cavitation on a fast hit. The easier the oil flows through the piston, the less ifp pressure needs to be on a coil shock. My swinger air shock can run as low as 50 lbs in the ifp. It uses an oring on the shaft and is not directional, so I'm not sold on the fact that the ifp needs to be higher than in the can on all air shocks. I do not know what type of shaft seal the Monarch uses. Just remember, the shock needs enough pressure in the ifp to get the oil through the piston without cavitation of the oil on the rebound side.

    Edit..late on my post I see...

  25. #75
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    Thanks warp, I think I have the main PSI set to around 100 lbs, (I'm 150 lbs suited up), so apparently I could drop the IFP down as low as 150 lbs if needed.
    I need a weaker midstroke & closer to bottom out would be fine.

  26. #76
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    Quote Originally Posted by retro83 View Post
    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.



    Not in my experience of the 2010 RP23 (heavily falling rate frame tends to show up bad bottom-out characteristics..!)
    Not sure if above is related to an RP3/23 or Monarch but my RT3 has 2.5" exposed stanchion, as did the 4.2 it replaced, both pushed the o-ring off the end, both are supposed to be 200mm x 51mm shocks, the only difference is the RT3 lets the wheel move so far the tyre now hits my seat tube when I bottom the shock out, I can't remember the 4.2 doing this and I'm running the same tyres albeit with less tread.

    I've increased the IFP pressure to 300psi (The IFP Valve comes with the Vivid Spanner if you're struggling to find one) would putting a couple of drop's of oil in there help at all or am I way off with this?

    As I side note I doubt it would be under warranty since I filled the HV Sleeve with the foam rings RS sell so sending it back probably isn't an option - plus I do like tinkering!

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    Great thread here, very informative. So after reading all of this I decided to order the adaptor for the IFP pressure valve and get to tweaking. I am not a tech, but it all sounded so straight forward that I figured I would try it myself, but it appears I am having some technical issues now. When I screw the adaptor on to the pump and thread it to the IFP chamber it immediately starts to bleed air pressure. There is no way to not have the shock lose all its pressure so I cannot fill the chamber with air and now cannot use the shock. Has anyone experienced this?

  28. #78
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    Quote Originally Posted by oli h View Post
    Not sure if above is related to an RP3/23 or Monarch but my RT3 has 2.5" exposed stanchion, as did the 4.2 it replaced, both pushed the o-ring off the end, both are supposed to be 200mm x 51mm shocks, the only difference is the RT3 lets the wheel move so far the tyre now hits my seat tube when I bottom the shock out, I can't remember the 4.2 doing this and I'm running the same tyres albeit with less tread.

    I've increased the IFP pressure to 300psi (The IFP Valve comes with the Vivid Spanner if you're struggling to find one) would putting a couple of drop's of oil in there help at all or am I way off with this?

    As I side note I doubt it would be under warranty since I filled the HV Sleeve with the foam rings RS sell so sending it back probably isn't an option - plus I do like tinkering!
    soundit is like it is either the wrong size (2.5"=64mm) or f'd up pretty good.

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    Quote Originally Posted by los05 View Post
    Great thread here, very informative. So after reading all of this I decided to order the adaptor for the IFP pressure valve and get to tweaking. I am not a tech, but it all sounded so straight forward that I figured I would try it myself, but it appears I am having some technical issues now. When I screw the adaptor on to the pump and thread it to the IFP chamber it immediately starts to bleed air pressure. There is no way to not have the shock lose all its pressure so I cannot fill the chamber with air and now cannot use the shock. Has anyone experienced this?
    screw the adaptor onto the pump first, before connecting it to the shock.

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    Quote Originally Posted by kneecap View Post
    My rt3 on a giant trance, tuned softer by a local tuner, with 200 lbs in the ifp chamber still won't get full travel unless pushed very hard on a cross country ride. It's harsh on compression even @ 35% sag. I gave up on it & had the stock float tuned by push, & the bike flows much better at the rear. I don't understand all the great praises for the monarch, perhaps for heavy weight riders on longer travel bikes?
    i have to ask...
    isn't a trance a 5" trail bike? if so, I would expect that it would have to be pushed VERY hard on a cross country ride to use up all 5" of travel.
    I can figure on a 4' drop and a rough landing before I use up 5" of travel.

  31. #81
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    Well, I'm just under 150 lbs, & what most would consider age challenged, ha. I ain't a leaper.
    I wanted the set up on my trance for the nearby cross country trails, some rock gardens & natural drops of maybe a foot or two. With the pushed float I still have a little rear travel to spare after most rides.
    I think you should be able to set up almost any bike within preferred desired suspension parameters.
    & I have a 6.7" travel reign for the knarley stuff.

    As a response to los05, I remember that almost all the IFP psi is lost when the sdaptor/pump is installed, but when I pumped it back to desired pressure it held. (but some psi is probably lost on disconnect) Maybe your pump leaks or the adaptor isn't tight in the pump head? Also, there's supposed to be an o ring on the adaptor just above the threads.

  32. #82
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    Quote Originally Posted by dimitrin View Post
    screw the adaptor onto the pump first, before connecting it to the shock.
    Quote Originally Posted by kneecap View Post
    Well, I'm just under 150 lbs, & what most would consider age challenged, ha. I ain't a leaper.
    I wanted the set up on my trance for the nearby cross country trails, some rock gardens & natural drops of maybe a foot or two. With the pushed float I still have a little rear travel to spare after most rides.
    I think you should be able to set up almost any bike within preferred desired suspension parameters.
    & I have a 6.7" travel reign for the knarley stuff.

    As a response to los05, I remember that almost all the IFP psi is lost when the sdaptor/pump is installed, but when I pumped it back to desired pressure it held. (but some psi is probably lost on disconnect) Maybe your pump leaks or the adaptor isn't tight in the pump head? Also, there's supposed to be an o ring on the adaptor just above the threads.

    Upon further inspection, my buddy noticed that the O-Ring was a little chewed up on the valve adapter. I swapped it with the one on the valve cover for testing purposes and was able to pump in air and make it stay, so problem solved there.

    Now it brings me to my second issue. Now when I unscrew the adaptor from the shock, (pump attached) it bleeds a lot of air. I am filling the shock with about 220 PSI and when I remove it and put it back on to see how much was lost, the reading is at about 140psi. Which is an issue because I am not going to be able to get an acurate reading on the shock. Any ideas?
    Last edited by los05; 11-07-2011 at 08:36 AM.

  33. #83
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    I have an RT3 on a Salsa Spearfish. I recently dropped the IFP to 210 and it seem to add a little plushness on the square edge stuff. I pulled the air can last night to lube the seals, and the can seals where completely dry.

    The issue I had was when I added air back to the shock, I set the ifp at 190 and spring at 155. The shock would not compress and seemed to be locked. Finally, I ended up putting the IFP back at 210 and the shock worked as normal. I have no idea how the shim stack preload works on the RT3, but I don't see how the differential between IFP and spring pressure would have any affect on the action of the shock. What am I missing here?

  34. #84
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    @los05:
    Cool, I was just about to suggest you check your O-ring for cuts. Glad that's working.

    As for the disconnect. Assuming you've got a correctly made adapter (no reason to suspect that something's wrong), then the adapter comes off of the valve needle before the O-ring comes out of the port. That means the hiss you hear on disconnect is that small volume of air you got trapped between the needle and the O-ring which is at your ~220psi.

    When you reconnect, you are now tapping the very small IFP chamber into your pump. Because the internal volume of your pump (basically the hose all the way to the gauge) is a significant fraction of the IFP chamber size, the pressure drops by the time it gets to the gauge.

    Think of it this way: Let's say you have a gas tank in your car that holds 15 gallons and is completely full. You decide to install a 20 gallon gas tank and put all your gas in that tank. Your new tank now looks 3/4 full. Your total amount of gas isn't different, but your reference volume has changed.

    The same goes for your shock situation. By measuring the system, you have changed the system. The fact that you still see 140psi when you reconnect tells me that it's probably fine. If you repeat what you've described a couple of times and always arrive at ~140psi, I'd say you're definitely fine.

    BTW, you experience the same effect on the air can as well. But because the air can is a much larger volume compared to pump volume, you only see a few psi difference.

    @ktm520: No idea, man. To my knowledge, there isn't any pressure sensitive valving in the RockShox line, but I don't own all of them nor have I opened all of them so I could be wrong. But that's the only way I can see what you're describing happening.
    "Adventure begins where good judgment ends."

  35. #85
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    [QUOTE=HHMTB;8608164]@los05:
    Cool, I was just about to suggest you check your O-ring for cuts. Glad that's working.

    As for the disconnect. Assuming you've got a correctly made adapter (no reason to suspect that something's wrong), then the adapter comes off of the valve needle before the O-ring comes out of the port. That means the hiss you hear on disconnect is that small volume of air you got trapped between the needle and the O-ring which is at your ~220psi.

    When you reconnect, you are now tapping the very small IFP chamber into your pump. Because the internal volume of your pump (basically the hose all the way to the gauge) is a significant fraction of the IFP chamber size, the pressure drops by the time it gets to the gauge.

    Think of it this way: Let's say you have a gas tank in your car that holds 15 gallons and is completely full. You decide to install a 20 gallon gas tank and put all your gas in that tank. Your new tank now looks 3/4 full. Your total amount of gas isn't different, but your reference volume has changed.

    The same goes for your shock situation. By measuring the system, you have changed the system. The fact that you still see 140psi when you reconnect tells me that it's probably fine. If you repeat what you've described a couple of times and always arrive at ~140psi, I'd say you're definitely fine.

    BTW, you experience the same effect on the air can as well. But because the air can is a much larger volume compared to pump volume, you only see a few psi difference.

    __________________________________________________
    First of all, thanks for the reply...

    Logically speaking that makes sense, and I can see how that can happen. However, if that in fact that is the case and if I am understanding your comment correctly, then that would mean that I could never get an accurate pressure reading after I initially disengage the valve correct? Therefore one would always have to depressurize the entire chamber if you wanted to modify/verify the pressure at a later time? For example, I fill it to ~220psi today, and then next week I decide I want to set it at 240psi. Could I just add 20lbs to the current reading of 130psi to make it 160psi or do I bring the reading all the way to 240psi which would technically be adding an additional 100psi?

    BTW, I am always getting the same reading after I remove the pump and put it back on.

    Please excuse my ignorance; I am just very new to all this tweaking and trying to understand this correctly so that I don't damage the shock by not having it setup properly.
    Last edited by los05; 11-07-2011 at 12:43 PM.

  36. #86
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    @los05:
    Don't feel compelled to apologize for ignorance. Without asking questions, how is one supposed to learn?

    I'll try to be as not confusing as possible by starting from the top and posing this in a quiz format.

    Let's say your IFP is complete discharged. I.E. If you press the needle, nothing comes in or out. The IFP is at atmospheric pressure. You attach your pump with adapter and pump to 220psi. You disconnect. What's in the IFP? Ans:220

    You reattach the pump and adapter. Because the hose and gauge were at atmospheric (0 psi) before you attached, the air that was in the IFP must fill that space before it can give a reading on the gauge. Once it does this, your gauge says 140psi because when a given amount of gas expands to fill a larger volume the pressure drops (PV=nRT if you remember chemistry). If you disconnect the pump and adapter right now, what's in the IFP? Ans: 140

    If instead of disconnecting when you see the 140 on the gauge, you instead pump back up to 220 and then disconnect, what's in the IFP? Ans: 220

    What's the take away of this story? After you connect and everything stabilizes, what's on the gauge is what's in the IFP. The only way that's not true is if you have an adapter that doesn't physically depress the needle, but what you're describing does not indicate that to be the case.

    So what does this mean from a verification standpoint? Well, you can't verify without having to pump back up. And verification is reliant on using the same pump/adapter every time and knowing what kind of pressure drop you would expect to see if the initial pressure were correct. In other words, pump up to 220, disconnect, reconnect, take reading, pump up to 220, repeat several times. The results should be repeatable. That's your expected pressure drop for that given IFP volume. If you ever adjust IFP volume, you'll need to redo this to find your new pressure drop expectation.

    In reality, barring some stupid leak in your system (check that the valve is greased and seated right unlike mine was), you'll rarely need to verify the IFP setting once you have confidence in your pump/adapter/disconnect technique.
    "Adventure begins where good judgment ends."

  37. #87
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    Quote Originally Posted by HHMTB View Post
    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
    So I took apart my Monarch 2.1 last night and my internals are very similar to what you have posted.(even though its a fox) My goal is to reshim it to my liking. I am having a hard time wrapping my head around what each shim stack actually does. I know that the two stacks on the main(blue) piston are compression(shaft side) and high speed rebound (under side). Those are obvious to me from tuning my forks. The smaller piston (under the main piston) and larger piston( on top) leave me scratching my head though. Im also confused on where the oil that passes through the rebound free bleed goes. Any insight would be appreciated.

  38. #88
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    The two smaller piston shim stacks are the comp and rebound check valves for the low speed circuits. The low speed compression circuit is from the preloaded poppet valve in the middle of the shock shaft, around the square edges of the piston bolt,, and out the check valve. Flow is controlled by the amount of preload on the poppet valve. The rebound circuit is through the hole in the shock shaft (below piston), around the square piston bolt, and out the check valve on top of the piston. Flow is controlled by a needle that closes the hole in the shock shaft.

  39. #89
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    Quote Originally Posted by Scotth72 View Post
    The two smaller piston shim stacks are the comp and rebound check valves for the low speed circuits. The low speed compression circuit is from the preloaded poppet valve in the middle of the shock shaft, around the square edges of the piston bolt,, and out the check valve. Flow is controlled by the amount of preload on the poppet valve. The rebound circuit is through the hole in the shock shaft (below piston), around the square piston bolt, and out the check valve on top of the piston. Flow is controlled by a needle that closes the hole in the shock shaft.
    That helps. What I was missing is that that bolt is square, allowing oil to pass on the sides of it and not just through the center. Thanks for the help.

  40. #90
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    Quote Originally Posted by HHMTB View Post
    @los05:
    Don't feel compelled to apologize for ignorance. Without asking questions, how is one supposed to learn?

    I'll try to be as not confusing as possible by starting from the top and posing this in a quiz format.

    Let's say your IFP is complete discharged. I.E. If you press the needle, nothing comes in or out. The IFP is at atmospheric pressure. You attach your pump with adapter and pump to 220psi. You disconnect. What's in the IFP? Ans:220

    You reattach the pump and adapter. Because the hose and gauge were at atmospheric (0 psi) before you attached, the air that was in the IFP must fill that space before it can give a reading on the gauge. Once it does this, your gauge says 140psi because when a given amount of gas expands to fill a larger volume the pressure drops (PV=nRT if you remember chemistry). If you disconnect the pump and adapter right now, what's in the IFP? Ans: 140

    If instead of disconnecting when you see the 140 on the gauge, you instead pump back up to 220 and then disconnect, what's in the IFP? Ans: 220

    What's the take away of this story? After you connect and everything stabilizes, what's on the gauge is what's in the IFP. The only way that's not true is if you have an adapter that doesn't physically depress the needle, but what you're describing does not indicate that to be the case.

    So what does this mean from a verification standpoint? Well, you can't verify without having to pump back up. And verification is reliant on using the same pump/adapter every time and knowing what kind of pressure drop you would expect to see if the initial pressure were correct. In other words, pump up to 220, disconnect, reconnect, take reading, pump up to 220, repeat several times. The results should be repeatable. That's your expected pressure drop for that given IFP volume. If you ever adjust IFP volume, you'll need to redo this to find your new pressure drop expectation.

    In reality, barring some stupid leak in your system (check that the valve is greased and seated right unlike mine was), you'll rarely need to verify the IFP setting once you have confidence in your pump/adapter/disconnect technique.
    Yeap, makes perfect sense.. Thanks so much man, I've been racking my brain with this trying to figure out what the hell was going on with thing. Thanks for putting it in layman's terms as well... Greatly appreciated.

  41. #91
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    Quote Originally Posted by mullen119 View Post
    So I took apart my Monarch 2.1 last night and my internals are very similar to what you have posted.
    Could you posts some pics if you get a chance? I'm trying to wrap my head around why my shock hydraulically locked when I lowered the IFP.

  42. #92
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    Quote Originally Posted by ktm520 View Post
    Could you posts some pics if you get a chance? I'm trying to wrap my head around why my shock hydraulically locked when I lowered the IFP.
    I put it back together already, But have no had a chance to test it yet to see if I like the new shim stacks. There is a good change I will take it back apart to tinker with it again, and I post pictures. It looks exactly like the picture above though, Only a few minor differences.

  43. #93
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    No problem. I'd be curious to see what changes you made if you don't mind sharing. I've always wanted to play with re-shimming a fork/shock, but have never had the chance/time. I'm planning to tear into my RT3 this winter.

  44. #94
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    Quote Originally Posted by ktm520 View Post
    No problem. I'd be curious to see what changes you made if you don't mind sharing. I've always wanted to play with re-shimming a fork/shock, but have never had the chance/time. I'm planning to tear into my RT3 this winter.
    The interesting thing is that when I took it apart, It was slippery (from the oil) and I dropped it. The shims and what came apart and I never got to see what the stock shim stacks consisted of(although I have a general idea). So I wrote down what my stacks are currently and will have to use that as my starting point. I have tuned many forks, but this is the first rear shock, So im excited to see what I can do with it.

  45. #95
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    Mullen, that sounds like something I'd do :-) Keep us updated. I've done a few shim shuffles on dirtbike forks, but no bike stuff. What characteristics of the shock are you looking to change?

    I played with the ifp some more today and couldn't re-create the hydraulic lock it experienced the other night after lubing the air seals. So I dropped the ifp from 210 to 190, main at 155, and it got even more plush on the Spearfish, maybe a tad too much. I will probably run it like this for the 6hr race this weekend for the comfort factor. I typically like a firmer mid stroke.

    This shocks is working so good, I don't know what I'd change.

  46. #96
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    My bike has a very low 2:1 leverage ratio and I find the "D" tune to be a little harsh over all and a little sluggish from being over damped. Im playing around with having a two stage stack for HSC. Im looking for it to open slightly on smaller hits to give better small bump sensitivity,. Then have the second stage be pretty stiff for good control on bigger hits. Im hoping to get a ride in here shortly if I can find the time.

  47. #97
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    On my first ride after messing with my IFP pressure, I snapped both chain stays in half. So I didn't get a whole lot of data that ride, and I've only had a couple of rides since putting the bike back together. I checked out of this thread after my breakage - thank you for the response.

    I want to say that lowering my IFP from 250 psi to 200 psi (main can at 150 psi) has improved small bump compliance, which is what I am after, but I think I have changed too many variables to say right now. When I replaced my chain stays, I replaced all the bearings in the swing arm and rocker, so everything in the back end is new and clean and low friction. I can't decide if the bike feels so nice due to this or my shock tuning or both - more data needed. Ideally, I'd like to do some shuttles on the same trail, changing IFP between runs.

    I do enjoy how easy it is to play with this component on the Monarch. On my old Fox Float, it took some experienced help and much more effort to get inside and change some things.


    Quote Originally Posted by HHMTB View Post
    Ok, I'll try to help. But please post anything new you learn so we all get better knowledge.

    Completely deflate the main air can. If there's any significant pressure in there and you let out all the IFP pressure, you'll get a big bubble in the oil as air forces its way around the main shaft seal. If after letting all the air out of the main air can, the shock compresses a little due to negative air spring interactions, it'd probably be best to unscrew the air can off the shock completely.

    Ok, so now you're ready to play with IFP. What you wrote, "So I remove the IFP access cap with the Schrader core removing tool. I fit the adapter to the end of my shock pump, and thread this whole unit into the IFP valve." is correct.

    I usually dump all the existing IFP pressure first just to make sure that that valve is still functioning. In the case of my report, it wasn't so I had to pull it out and clean crap off the sealing face. After you're satisfied that it's all mechanically in order, start pumping.

    As I mentioned in a post a short while back, set that IFP higher than your main can by some good amount. I used 30 or so psi greater, but you'll have to be the judge of your own comfort level. On a coil over, I'd say anything over 100 is good, but given an air shock, I'm staying above 170 psi on the IFP for this reason.

    Yes, IFP pressure affects sag to a small degree. However it affects mid stroke and bottom out more as does actual IFP volume. I can't point you to a magic ratio as it varies from shock model to shock model due to dimensional differences. Also, you may like something entirely different from what I like.

    Generally speaking, the higher the IFP pressure, the greater its effect on bottom out the more support you'll get mid stroke so you can lower the main air can pressure. It's a reasonable way to combat a wallowy shock up to a certain point. If you reach that limitation, you'll have to actually vary the IFP chamber volume. Less volume = more bottom out resistance/spring progressivity which can actually make the wallowing feeling worse in some cases.

    Anyway, that's all I got time for now. Post your findings please and we'll talk some more.

  48. #98
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    ifp adapter?

    Anyone know who has got these red adapters in stock? I have looked everywhere.

    Just got a Monarch RT3 for my 2009 Racer X and am not impressed so far. Can't get it to use its full travel and even at 30 percent sag the small bump compliance is pretty harsh. Got the shock directly from Titus and they assure me it is the right tune for the bike (MM).

    I am going to ride it a bit more to let it break in then try to mess with the ifp chamber. If that does not work, off to Push it goes.

    Thanks.

  49. #99
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    Quote Originally Posted by kmc View Post
    Anyone know who has got these red adapters in stock?.
    Just ordered mine from Universal Cycles this past monday & the adapter was waiting for me when i got home last night.

    ^ That's been tapped

  50. #100
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    Quote Originally Posted by kmc View Post
    Anyone know who has got these red adapters in stock? I have looked everywhere.

    Just got a Monarch RT3 for my 2009 Racer X and am not impressed so far. Can't get it to use its full travel and even at 30 percent sag the small bump compliance is pretty harsh. Got the shock directly from Titus and they assure me it is the right tune for the bike (MM).

    I am going to ride it a bit more to let it break in then try to mess with the ifp chamber. If that does not work, off to Push it goes.

    Thanks.
    Push currently doesnt tune Monarchs that are sent in. They only sell their version. Kinda silly but its the way it works for now. I hope the IFP tool works for you.

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