Page 1 of 2 12 LastLast
Results 1 to 100 of 160
  1. #1
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059

    Monarch & IFP pressure change...

    I thought I'd seen mention of this by someone in the past, but it must be imbedded in another post, as a search didn't reveal it. I have a Monarch 4.2 rear shock in the off-the-shelf 7.5 X 2.0 size on my '08 Stumpjumper FSR. This increased travel from 120mm to about 137mm. The '08/'09 SJ FSRs have an oddball 7.25 X 1.75 Fox Triad air shock. I matched the rear to a 140mm RS dual air Revelation. The bike's geo is great with no weird handling traits.

    I know from the rebuild service info on the Monarch shock that the IFP chamber is user accessible with an adapter valve from RS. The adapter is priced reasonably. I bought a rebuild kit for this shock and obtained an adapter at the same time. RS initially uses nitrogen in the IFP chamber but states that using air from a shock is all that's necessary. We use straight air in many of our high end piggyback IFP chambers, so I'd have to agree.

    My SJ FSR has not achieved full travel since using the Monarch, and the small bump compliance hasn't been what I would have expected with the increased travel. I called RS tech and inquired about manipulating the IFP air pressure in the Monarch to better suit my bike and riding. The guy said that it was not the proper way to tune this shock, and that my IFP had probably mover out of spec which was causing my problem. OK...sounds reasonable, but since I was going to have to pull the shock down to reset the IFP position, I figured I couldn't lose anything by experimenting with the IFP pressure.

    Stock pressure in their info indicates a range of 250-300 PSI. Verbally the tech guy said that 250 was the correct pressure, as 300 was a bit much. I let the air out of the main chamber and removed the schrader valve. I released the IFP pressure and tried a couple of different pressures. At the 225 PSI mark, I got excellent small bump compliance and full travel with the same main chamber air pressure I was using before. Our trail has lots of rocky terrain with even some man-made features thrown in to get some small air. My sag is still good, the shock doesn't blow through its travel, small/mid bump compliance is highly improved, and I achieve full travel.

    I have owned/own several high end piggyback shocks that use pressure changes to the IFP to achieve different tuning goals. Am I missing something as stated by the RS tech about tuning the Monarch IFP pressure in this manner? I know most inline air shocks do not have as accessible a valve system for the IFP air pressure, but since the Monarch does, why not? Yes, one needs to be careful about stroking the shock and other issues just as you do with high end piggyback shocks with tuneable IFP chambers when you have the IFP chamber depressurized. I depressurized the main chamber during this process, because that's the condition of the shock in the sevice info when pressurizing the IFP chamber, which is logical from what I'm understanding of this shock's design. My damping is still spot on and did not change during this process.

    Anyone else try this or see the potential of performance issues with manipulating the IFP pressure on this shock in this manner?...despite RS's warning. I wasn't too worried about screwing anything up, as I had the rebuild kit in hand and would have had to open up the shock to reset the alleged faulty IFP location anyway. Right now the shock seems to be operating in synch with my bike's suspension design and rate for my riding, which I was never able to achieve by just tuning the main chamber.

  2. #2
    mtbr member
    Reputation: peternguyen's Avatar
    Join Date
    Dec 2007
    Posts
    1,172
    Thanks for the interesting write up.

    I also have a Monarch 4.2, although it is of the 6.5" length. And i also have a Revelation (2008 Dual Air), but i feel that the Monarch's small bump compliance isn't as good as the RVL, but i am not sure whether it may have something to do with the difference in travel. Would it be right to say that bump compliance of a shorter shock will be less than on a longer shock? That would seem to make sense, but i'd like to have confirmation.

    Also, what does the IFP pressure actually do. I can't find information on it's purpose.

  3. #3
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    peter, I don't claim to be a suspension guru...just dangerous enough to understand some basics...LOL! Shocks with an IFP are designed to keep the damping oil completely gas-free so that the damping control and quality through a shim or port-orifice damper is consistent. Generally, other shocks without an IFP are called emulsion shocks. The gas and oil can mix. IFP designs can also allow better tuning as one can set the IFP in different locations, allow pressure changes to affect shock stroke, and volume in an IFP chamber can change the nature of the compression stroke.

    Even in many of the sophisticated piggyback shocks out there that call the piggyback IFP tuning more of a bottomout element, in reality this piggyback tuning can affect small bump compliance and other factors depending on design and how much pressure you put in the IFP chamber. In most cases, everything in a shock design and its tuning can affect every other element in a shock's performance. Of course I'm speaking very generally here.

    Personally I think all bike shocks with an IFP should have the capability to tune the IFP pressure...and volume in the case of piggyback shocks. Since individual bike suspension designs vary so much, why would one IFP pressure be ideal for all of them? As an example, one could a specific off-the-shelf piggyback shock with a tuneable piggyback IFP chamber...like a DHX. That shock's IFP pressure and chamber volume would vary greatly between many different bikes...and even different riders on the same bike. I can't see why that wouldn't be the case with inline shocks either. Adjusting IFP volume on an inline shock is another issue, however, but the ability to tweak the IFP pressure sounds logical to me. The debate about nitrogen vs. air for tuning can also be an issue, but I don't think bike shocks are as critical in requiring nitrogen for most applications. Like I said, if someone sees a problem with my line of thinking on playing with the IFP pressure within reason on this Monarch, I'm all ears. I'll repeat that I'm definitelly not a suspension engineer.

  4. #4
    Cut Casing Whisperer
    Reputation: Mr.P's Avatar
    Join Date
    Feb 2005
    Posts
    5,424
    Hey TNC,

    Thanks for trying this, it was me that dug up the IFP pressure and adapter info when pouring through the rebuild instructions.

    Like you, I perceived the IFP as a tuning point as one would with a piggyback shock.

    I'll speculate that the tech was not hot on tuning via IFP as it has not been engineered to be user tunable, and perhaps as higher pressures are used greater greater chance of failure is possible.

    I was looking to this shock as it has some great tuning points, IFP pressure, air volume, in addition to the standard fare. But, IMHO, ultimate performance comes from the main piston, and I needed something that could damp some freeride. Tho, they are saying for next year they will have a more mid/high speed damping.

    Hats off the SRAM for posting full rebuild instructions as that kind of information puts the shock on the short list for me.

    Keep us posted on your tuning.

    P

  5. #5
    mtbr member
    Reputation: Vespasianus's Avatar
    Join Date
    Apr 2008
    Posts
    4,691
    Quote Originally Posted by TNC
    I thought I'd seen mention of this by someone in the past, but it must be imbedded in another post, as a search didn't reveal it. I have a Monarch 4.2 rear shock in the off-the-shelf 7.5 X 2.0 size on my '08 Stumpjumper FSR. This increased travel from 120mm to about 137mm. The '08/'09 SJ FSRs have an oddball 7.25 X 1.75 Fox Triad air shock. I matched the rear to a 140mm RS dual air Revelation. The bike's geo is great with no weird handling traits.

    I know from the rebuild service info on the Monarch shock that the IFP chamber is user accessible with an adapter valve from RS. The adapter is priced reasonably. I bought a rebuild kit for this shock and obtained an adapter at the same time. RS initially uses nitrogen in the IFP chamber but states that using air from a shock is all that's necessary. We use straight air in many of our high end piggyback IFP chambers, so I'd have to agree.

    My SJ FSR has not achieved full travel since using the Monarch, and the small bump compliance hasn't been what I would have expected with the increased travel. I called RS tech and inquired about manipulating the IFP air pressure in the Monarch to better suit my bike and riding. The guy said that it was not the proper way to tune this shock, and that my IFP had probably mover out of spec which was causing my problem. OK...sounds reasonable, but since I was going to have to pull the shock down to reset the IFP position, I figured I couldn't lose anything by experimenting with the IFP pressure.

    Stock pressure in their info indicates a range of 250-300 PSI. Verbally the tech guy said that 250 was the correct pressure, as 300 was a bit much. I let the air out of the main chamber and removed the schrader valve. I released the IFP pressure and tried a couple of different pressures. At the 225 PSI mark, I got excellent small bump compliance and full travel with the same main chamber air pressure I was using before. Our trail has lots of rocky terrain with even some man-made features thrown in to get some small air. My sag is still good, the shock doesn't blow through its travel, small/mid bump compliance is highly improved, and I achieve full travel.

    I have owned/own several high end piggyback shocks that use pressure changes to the IFP to achieve different tuning goals. Am I missing something as stated by the RS tech about tuning the Monarch IFP pressure in this manner? I know most inline air shocks do not have as accessible a valve system for the IFP air pressure, but since the Monarch does, why not? Yes, one needs to be careful about stroking the shock and other issues just as you do with high end piggyback shocks with tuneable IFP chambers when you have the IFP chamber depressurized. I depressurized the main chamber during this process, because that's the condition of the shock in the sevice info when pressurizing the IFP chamber, which is logical from what I'm understanding of this shock's design. My damping is still spot on and did not change during this process.

    Anyone else try this or see the potential of performance issues with manipulating the IFP pressure on this shock in this manner?...despite RS's warning. I wasn't too worried about screwing anything up, as I had the rebuild kit in hand and would have had to open up the shock to reset the alleged faulty IFP location anyway. Right now the shock seems to be operating in synch with my bike's suspension design and rate for my riding, which I was never able to achieve by just tuning the main chamber.
    Sounds like you have created a Stratos Helix Pro!

    I wonder if there are patent regarding this that are owned by Stratos

  6. #6
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    Quote Originally Posted by Mr.P
    Hey TNC,

    Thanks for trying this, it was me that dug up the IFP pressure and adapter info when pouring through the rebuild instructions.

    Like you, I perceived the IFP as a tuning point as one would with a piggyback shock.

    I'll speculate that the tech was not hot on tuning via IFP as it has not been engineered to be user tunable, and perhaps as higher pressures are used greater greater chance of failure is possible.

    I was looking to this shock as it has some great tuning points, IFP pressure, air volume, in addition to the standard fare. But, IMHO, ultimate performance comes from the main piston, and I needed something that could damp some freeride. Tho, they are saying for next year they will have a more mid/high speed damping.

    Hats off the SRAM for posting full rebuild instructions as that kind of information puts the shock on the short list for me.

    Keep us posted on your tuning.

    P
    Now I'm with you on this shock not being FR or even long travel AM suitable, but then at that point I'm totally in the camp that such bikes need piggyback shocks. I wouldn't consider using this shock on my Nomad, though I see it's supplied as an option. I just can't see how 6+ inch bikes can get optimal performance with most any inline shock when ridden the way they were intended. This shock does, however, fit my '08 SJ FSR excellently, and its intended use, and toning down the IFP pressure sure made a sweeter ride. As I always say, my opinion and $3.50 will get you a cup of coffee at Starbuck's.

  7. #7
    Cut Casing Whisperer
    Reputation: Mr.P's Avatar
    Join Date
    Feb 2005
    Posts
    5,424
    Quote Originally Posted by TNC
    Now I'm with you on this shock not being FR or even long travel AM suitable, but then at that point I'm totally in the camp that such bikes need piggyback shocks. I wouldn't consider using this shock on my Nomad, though I see it's supplied as an option. I just can't see how 6+ inch bikes can get optimal performance with most any inline shock when ridden the way they were intended. This shock does, however, fit my '08 SJ FSR excellently, and its intended use, and toning down the IFP pressure sure made a sweeter ride. As I always say, my opinion and $3.50 will get you a cup of coffee at Starbuck's.
    I'm not an expert, but I think inline shock should be Freerideable, within limits of course. I think the issue has been that the inline shocks have been built for wheels on the ground operation (pedalling efficiency and square edge compliance) which = threshold damping then blow through damping.

    It seems the new Fox BoostValve Float and Monarch are going to offer progressive damped shocks this next year, so hopefully that means more FR friendly shocks.

    One could hope. Especially with good fits like the Remedy, Nomad, Yeti Seven and others.

    P

  8. #8
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    Ves, believe or not I have a 7.25 X 2.0 Statos Helix Pro sitting in a drawer in my shop...LOL!

  9. #9
    "El Whatever"
    Reputation: Warp's Avatar
    Join Date
    May 2004
    Posts
    18,841
    Sorry to bring this one back up...

    TNC. how easy/difficult was to inflate the IFP with the RS adapter??

    Let me elaborate... with the Roco, using the Zoke inflation tool, it's a real chore. You have to be quick to remove the adapter from the port or you can lose the pressure or end up with whatever unknown pressure in the IFP as the seal on the adapter leaves the shock BEFORE the tip of the adapter disengages from the valve core.

    I just told myself not to get anything I can not service at home and the Monarch has me interested.

    Yeah, I'll pass on RP shocks from Fox... I want to strip the thing at home.

    Thanks!
    Check my Site

  10. #10
    mtbr member
    Reputation: retro83's Avatar
    Join Date
    Sep 2008
    Posts
    307
    Stock pressure in their info indicates a range of 250-300 PSI. Verbally the tech guy said that 250 was the correct pressure, as 300 was a bit much. I let the air out of the main chamber and removed the schrader valve. I released the IFP pressure and tried a couple of different pressures. At the 225 PSI mark, I got excellent small bump compliance and full travel with the same main chamber air pressure I was using before. Our trail has lots of rocky terrain with even some man-made features thrown in to get some small air. My sag is still good, the shock doesn't blow through its travel, small/mid bump compliance is highly improved, and I achieve full travel.
    Do you know what the minimum IFP pressure is?

    I can't find a technical manual for the shock online.

  11. #11
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    I was looking at this thread to learn more about the RS shock. Interesting to find other kindred spirits of in-the-garage shock tuning.

    Totally agree that all IFP's, inline or piggyback, need to be user tunable. I modded an old inline Vanilla R a few years ago with a custom schrader valve I machined. Totally did the trick for that shock.

    The Helix line was sweet. Mine worked perfectly for 4 years before I broke it.

    Just wanted to add for Warp: if you carefully drill out the tip of the adapter tool, you can make it so the needle is never depressed by the tool while engaged to the ROCO's IFP. This way, you can be sure that you hit the desired pressure and don't lose any on disconnect since the valve core will now act as a check valve. The only downside is that you can't bleed off pressure slowly through the pump. I've rebuilt my Roco's several times this way.
    "Adventure begins where good judgment ends."

  12. #12
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    Oh my...this is the first time I've looked on the suspension section of mtbr for some time...I hate to admit. Dirt motoring and just riding my MTB's have kind of overshadowed my mtbr time to a serious degree. However, a current rebuild on my '06 Van 36 got me motivated to look over here while I was changing the damper oil in my Van.

    Warp, manipulating the air pressure on the Monarch is easy. As to losing pressure on disengagement, there's none that I can tell, and RS doesn't address such in their IFP pressurization description. My Monarch acts just like the main chamber pressurization in that when/as you disconnect the pump, the shock and air needle don't seem to bleed pressure out of the chamber.

    Retro, on the minimum air pressure for the IFP in the Monarch, I have no idea. In fact RS doesn't recommend playing with the IFP pressure as a tuning method, but I think they really can't. People who know what they're doing can handle the job just fine, but the same pitfalls are present that exist with adjustable IFP piggyback shocks. A hamfister can let all the air out of the IFP and then ride or stroke the shock to a degree that lets air bleed into the damper oil...or run too low a pressure that yields the same result. So I see why RS doesn't recommend it on this shock. It's probably even more prone to allowing air into the damper oil due to how the IFP is designed and located in the shock body. Done correctly there shouldn't be any issue or one wouldn't even be able to do the home rebuild and IFP repressurization anyway. Just don't go too low. What's too low? Well, the same rules for adjustable IFP pressure in piggyback shocks should be somewhat of a guide. Most manufacturers say a minimum of 50 psi to prevent air bleeding past the piston. The Monarch isn't going to operate at anything much less than 200 psi from what I've experienced on the two linkage bikes I've used it on...that's 50 psi less than the original rebuild pressure recomendation. I can't see how one would ever get down to the low pressure levels of 50-100 psi where air bleed into the damper oil might even be a possibility. So while a minimum isn't recommended, I don't think you can get there from here...so to speak.

    I'm still loving this shock, and it's been bulletproof.

  13. #13
    "El Whatever"
    Reputation: Warp's Avatar
    Join Date
    May 2004
    Posts
    18,841
    Quote Originally Posted by HHMTB
    Just wanted to add for Warp: if you carefully drill out the tip of the adapter tool, you can make it so the needle is never depressed by the tool while engaged to the ROCO's IFP. This way, you can be sure that you hit the desired pressure and don't lose any on disconnect since the valve core will now act as a check valve. The only downside is that you can't bleed off pressure slowly through the pump. I've rebuilt my Roco's several times this way.
    Thanks for the recommendations, guys!! Don't quote me, but I think the Monarch and the Roco adaptors may be the very same. I think the threads match, but I'll doublecheck when I get home (that's more than a month from now). And as HHMTB mention, the difference is how the RS engages the valve stem. It makes sense now that you mention it.

    I agree with you. All shocks should have adjustable IFP pressures, but the prospect of an armchair engineer like me screwing up totally a perfectly good shock may scare manufacturers badly.
    Check my Site

  14. #14
    mtbr member
    Reputation: mullen119's Avatar
    Join Date
    Aug 2009
    Posts
    3,997
    Quote Originally Posted by Warp
    Thanks for the recommendations, guys!! Don't quote me, but I think the Monarch and the Roco adaptors may be the very same. I think the threads match, but I'll doublecheck when I get home (that's more than a month from now). And as HHMTB mention, the difference is how the RS engages the valve stem. It makes sense now that you mention it.

    I agree with you. All shocks should have adjustable IFP pressures, but the prospect of an armchair engineer like me screwing up totally a perfectly good shock may scare manufacturers badly.
    I believe the manitou adapter is the same as well. I dont have my bike here to check, But it looks identical.

  15. #15
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    Well, the schrader valve core design is owned by Schrader Bridgeport which as far as I know is the ONLY company that makes and sells the valve. Sweet gig if it's true.

    I know for a fact that the thread for the cores use a proprietary thread pattern that's different from any off the shelf tap. In fact, I had to buy the tap straight from them a few years ago. That being the case, I'd expect all the recessed schrader valve adapters, be it Marzo, Manitou, or whoever, will screw in fine. It's just a matter of depth to needle contact and the relative location of the o-ring seal on the tip.

    I wasn't aware that Manitou had an adapter. Got a picture Mullen?

    I just acquired a Monarch. I'll likely be tearing it apart soon. Any tips and tricks? Especially what the physical difference between "A" tune and "B" tune is?

    To TNC, you're pretty much on target with your shock observations. I just wanted to add a few things I've picked up in my tinkering. I don't run the IFP less than 100psi ever. Not only is it a nice round number to remember , it also gives you reasonable margin to prevent cavitation, avoid momentary vacuum at the main shaft seal during compression, and forces tiny air bubbles from an incomplete bleed to get dissolved into the oil.

    Also, try the Roco LO DC for an inline freeride shock. Feels amazing but has some maintenance issues. At speed, it's smoother than some coil shocks I've owned. At climbing speed, there's less motion than coil due to bigger swept area.
    "Adventure begins where good judgment ends."

  16. #16
    mtbr member
    Reputation: mullen119's Avatar
    Join Date
    Aug 2009
    Posts
    3,997
    Quote Originally Posted by HHMTB

    I wasn't aware that Manitou had an adapter. Got a picture Mullen?

  17. #17
    mtbr member
    Reputation:
    Join Date
    Jun 2009
    Posts
    252
    Hi guys,

    today I tried to play with the IFP pressure change but couldn' make my valve tool to engage the IFP core

    I can thread in the adapter enough (tried with some pliers, but was scared after a few turns that I could damage something) to get pressure readings inside the IFP chamber.

    This is the valve adapter/tool that I have:



    Is that the right adapter ?

    Thanks in advance

  18. #18
    mtbr member
    Reputation: retro83's Avatar
    Join Date
    Sep 2008
    Posts
    307
    Quote Originally Posted by Vuco
    Hi guys,

    today I tried to play with the IFP pressure change but couldn' make my valve tool to engage the IFP core

    I can thread in the adapter enough (tried with some pliers, but was scared after a few turns that I could damage something) to get pressure readings inside the IFP chamber.

    This is the valve adapter/tool that I have:



    Is that the right adapter ?

    Thanks in advance

    I had the same problem, and mine was the official adapter from RS

  19. #19
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    Quote Originally Posted by retro83
    I had the same problem, and mine was the official adapter from RS
    Guys, I'm not sure why you'd have a problem with accessing the valve for the IFP with the proper valve adapter. Now, for Mullen and retro83 I do see the problem. That valve does not have the "shoulder" required for the Monarch valve. In the pic here, the red valve is the Monarch adapter. The adapter attached to the pump is a Marz valve for the "SL" Marz air forks. The silver valve in the middle is an RS SID valve from the "old days". Notice carefully the "shoulder" on the red valve just past the o-ring as you go toward the pump end of the valve. The SID valve is machined smooth past the o-ring. The SID and Monarch adapters have the same thread pitch and diameter. The Marz valve is a bigger diameter by just a hair at the threaded portion, so it's obviously out of the game.

    That shoulder on the Monarch valve is required. It will not work without the shoulder. The valves pictured here by the other posters look the old SID adapter, even though they're not exactly like mine. The big difference is that shoulder on the red Monarch version. I wonder if RS made those Monarch valves red for a reason? I could see even the parts guy at RS getting confused in some instances about the difference in these two valves. Here's also a fuzzy pic of the end of the tips of the SID and Monarch valves. The Monarch valve has a larger inner diameter at the air passage, though I'm not sure how critical that is.
    Attached Thumbnails Attached Thumbnails Monarch & IFP pressure change...-3-valve-adapters.jpg  

    Monarch & IFP pressure change...-air-valve-tips.jpg  


  20. #20
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    Maybe this is a better pic taken from BBW's post.

    this? only 10$
    http://www.bikeparts.com/search_resu...p?ID=BPC132925
    __________________
    BBW. MS, RD of the Monarch valve.

  21. #21
    mtbr member
    Reputation:
    Join Date
    Jun 2009
    Posts
    252
    Thanks TNC, now I see the difference. I even think that somewhere wrote that my adapter is for RS forks, probably then for SID like you said.

    I'll try with some tools to make such a shoulder. Can loose anything by trying it.

    Anyway, thanks a lot.

  22. #22
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    Yup, TNC is right. There's a difference in the counterbore of these Monarch air valve ports. My Marzo adaptor will not engage as the shoulder hits. Crap. Time to modify. It seems too that the IFP schrader valve in mine loses air into the small space between the valve and the cap. I'm going to check the tightness of the valve but that's kind of shoddy work, RS.

    Also, I ran across a few posts about Monarchs leaking air out of the box. Mine did too. I just want to add to the group's knowledge that on mine it was the o-ring between the air can and the body and the two between the air can and the extra volume tube. Both are size -030. All three on mine were installed dry, as in no grease AT ALL. All three had significant compression set (likely due to age and/or no oxidation protection from being dry) and one was spiralled in its gland. I replaced and greased all of them and it holds air fine now. For good measure, I greased and installed the air can schrader valve. I've heard it can also be the swivel air fitting so check that too.
    "Adventure begins where good judgment ends."

  23. #23
    "El Whatever"
    Reputation: Warp's Avatar
    Join Date
    May 2004
    Posts
    18,841
    Quote Originally Posted by HHMTB
    Also, I ran across a few posts about Monarchs leaking air out of the box. Mine did too. I just want to add to the group's knowledge that on mine it was the o-ring between the air can and the body and the two between the air can and the extra volume tube. Both are size -030. All three on mine were installed dry, as in no grease AT ALL. All three had significant compression set (likely due to age and/or no oxidation protection from being dry) and one was spiralled in its gland. I replaced and greased all of them and it holds air fine now. For good measure, I greased and installed the air can schrader valve. I've heard it can also be the swivel air fitting so check that too.
    Thanks for the heads up!!

    Mine doesn't leak. Actually I was surprised to find it at proper sag after like 4mo.

    Anyway, due to past experiences with Marzocchi not properly lubing seals that would work OK for a few months and then suddenly crap out on you spectacularly, I will service the canister ASAP. I injected some 15wt fork oil into the canister and so far so good, but that's not even close to proper lubing.
    Check my Site

  24. #24
    mtbr member
    Reputation: Marmoto's Avatar
    Join Date
    Sep 2007
    Posts
    64

    How to convert an old SID adaptor to a MONARCH IFP adaptor

    I've tried hard to get an original (red ) IFP valve adapter here but I've failed. RS in Spain doesn't import the adaptor and all the on-line USA stores I've found have run out of stock

    But here is a solution I've tried... and it works!

    If you already have or have access to buy an old SID valve adapter, you can convert it to a fully functional Monarch IFP valve adapter. I did that yesterday and it took me less than haf an hour

    All you have to do is to shorten the threaded section of the SID valve adapter so you leave 3-4 threads (3,5mm). I've dremeled it easily. This allows the o-ring to enter in the IFP valve housing and air seal the adaptor properly.
    (see picture 1)

    Then, you have to increase the center port diameter to 2mm drilling it. This allows the rod of the schrader valve core to enter in the port so you don't loose pressure when you insert the adaptor (and also when you remove it)
    (see picture 2)

    I have setup the IFP air chamber pressure to 210 psi in my Monarch RT3 and now is really sweet with a much better small bump compliance and sensitivity.

    TNC, thanks for all the advise.
    Attached Thumbnails Attached Thumbnails Monarch & IFP pressure change...-sid-ifp-valve-adapter-1.jpg  

    Monarch & IFP pressure change...-sid-ifp-valve-adapter-2.jpg  

    Last edited by Marmoto; 01-14-2011 at 11:11 AM.

  25. #25
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    Good thinking, Marmoto. Yeah, the adapters are really close in size and design, and I can see some creativity allowing the SID adapter to work.

  26. #26
    mtbr member
    Reputation: Marmoto's Avatar
    Join Date
    Sep 2007
    Posts
    64
    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 11:15 AM.

  27. #27
    "El Whatever"
    Reputation: Warp's Avatar
    Join Date
    May 2004
    Posts
    18,841
    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.
    Check my Site

  28. #28
    mtbr member
    Reputation: mullen119's Avatar
    Join Date
    Aug 2009
    Posts
    3,997
    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.

  29. #29
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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."

  30. #30
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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."

  31. #31
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    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.

  32. #32
    "El Whatever"
    Reputation: Warp's Avatar
    Join Date
    May 2004
    Posts
    18,841
    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.
    Check my Site

  33. #33
    mtbr member
    Reputation: retro83's Avatar
    Join Date
    Sep 2008
    Posts
    307
    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..!)

  34. #34
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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"
    "Adventure begins where good judgment ends."

  35. #35
    mtbr member
    Reputation: retro83's Avatar
    Join Date
    Sep 2008
    Posts
    307
    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"

  36. #36
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    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.

  37. #37
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    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.

  38. #38
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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?
    "Adventure begins where good judgment ends."

  39. #39
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    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.

  40. #40
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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."

  41. #41
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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."

  42. #42
    mtbr member
    Reputation: Marmoto's Avatar
    Join Date
    Sep 2007
    Posts
    64
    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

  43. #43
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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.
    "Adventure begins where good judgment ends."

  44. #44
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    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.

  45. #45
    arc
    arc is offline
    mtbr member
    Reputation:
    Join Date
    Sep 2004
    Posts
    253
    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?

  46. #46
    arc
    arc is offline
    mtbr member
    Reputation:
    Join Date
    Sep 2004
    Posts
    253
    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.

  47. #47
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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."

  48. #48
    Dirty minded
    Reputation:
    Join Date
    Nov 2008
    Posts
    501
    Wow, good timing for this to pop up.
    Thanks to all!

  49. #49
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152

    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."

  50. #50
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    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.

  51. #51
    arc
    arc is offline
    mtbr member
    Reputation:
    Join Date
    Sep 2004
    Posts
    253
    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?

  52. #52
    arc
    arc is offline
    mtbr member
    Reputation:
    Join Date
    Sep 2004
    Posts
    253
    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?

  53. #53
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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.
    "Adventure begins where good judgment ends."

  54. #54
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    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?

  55. #55
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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...
    "Adventure begins where good judgment ends."

  56. #56
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    "Adventure begins where good judgment ends."

  57. #57
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    Great info, HH. I had no idea that PUSH was already pursuing the higher flow piston concept, but it's absolutely logical.

  58. #58
    arc
    arc is offline
    mtbr member
    Reputation:
    Join Date
    Sep 2004
    Posts
    253
    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.

  59. #59
    arc
    arc is offline
    mtbr member
    Reputation:
    Join Date
    Sep 2004
    Posts
    253
    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

  60. #60
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    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.

  61. #61
    arc
    arc is offline
    mtbr member
    Reputation:
    Join Date
    Sep 2004
    Posts
    253
    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.

  62. #62
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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."

  63. #63
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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.
    "Adventure begins where good judgment ends."

  64. #64
    mtbr member
    Reputation: joshdurston's Avatar
    Join Date
    Feb 2010
    Posts
    324
    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.

  65. #65
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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."

  66. #66
    mtbr member
    Reputation: vizsladog's Avatar
    Join Date
    Mar 2009
    Posts
    1,320
    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.

  67. #67
    mtbr member
    Reputation: joshdurston's Avatar
    Join Date
    Feb 2010
    Posts
    324
    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.)

  68. #68
    mtbr member
    Reputation: vizsladog's Avatar
    Join Date
    Mar 2009
    Posts
    1,320
    bump

  69. #69
    mtbr member
    Reputation:
    Join Date
    Jan 2006
    Posts
    35
    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

  70. #70
    kneecap
    Reputation:
    Join Date
    Dec 2003
    Posts
    1,560
    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?

  71. #71
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    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.
    "Adventure begins where good judgment ends."

  72. #72
    kneecap
    Reputation:
    Join Date
    Dec 2003
    Posts
    1,560
    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?

  73. #73
    "El Whatever"
    Reputation: Warp's Avatar
    Join Date
    May 2004
    Posts
    18,841
    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.
    Check my Site

  74. #74
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    1,196
    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...

  75. #75
    kneecap
    Reputation:
    Join Date
    Dec 2003
    Posts
    1,560
    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.

  76. #76
    mtbr member
    Reputation:
    Join Date
    Dec 2006
    Posts
    65
    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!

  77. #77
    mtbr member
    Reputation:
    Join Date
    Jun 2011
    Posts
    89
    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?

  78. #78
    Dirty minded
    Reputation:
    Join Date
    Nov 2008
    Posts
    501
    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.

  79. #79
    Dirty minded
    Reputation:
    Join Date
    Nov 2008
    Posts
    501
    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.

  80. #80
    Dirty minded
    Reputation:
    Join Date
    Nov 2008
    Posts
    501
    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.

  81. #81
    kneecap
    Reputation:
    Join Date
    Dec 2003
    Posts
    1,560
    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.

  82. #82
    mtbr member
    Reputation:
    Join Date
    Jun 2011
    Posts
    89
    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 09:36 AM.

  83. #83
    mtbr member
    Reputation: ktm520's Avatar
    Join Date
    Apr 2004
    Posts
    1,562
    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?

  84. #84
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    @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."

  85. #85
    mtbr member
    Reputation:
    Join Date
    Jun 2011
    Posts
    89
    [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 01:43 PM.

  86. #86
    Just the tip!
    Reputation: HHMTB's Avatar
    Join Date
    Aug 2006
    Posts
    152
    @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."

  87. #87
    mtbr member
    Reputation: mullen119's Avatar
    Join Date
    Aug 2009
    Posts
    3,997
    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.

  88. #88
    mtbr member
    Reputation:
    Join Date
    Mar 2004
    Posts
    1,011
    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.

  89. #89
    mtbr member
    Reputation: mullen119's Avatar
    Join Date
    Aug 2009
    Posts
    3,997
    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.

  90. #90
    mtbr member
    Reputation:
    Join Date
    Jun 2011
    Posts
    89
    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.

  91. #91
    mtbr member
    Reputation: ktm520's Avatar
    Join Date
    Apr 2004
    Posts
    1,562
    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.

  92. #92
    mtbr member
    Reputation: mullen119's Avatar
    Join Date
    Aug 2009
    Posts
    3,997
    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.

  93. #93
    mtbr member
    Reputation: ktm520's Avatar
    Join Date
    Apr 2004
    Posts
    1,562
    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.

  94. #94
    mtbr member
    Reputation: mullen119's Avatar
    Join Date
    Aug 2009
    Posts
    3,997
    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.

  95. #95
    mtbr member
    Reputation: ktm520's Avatar
    Join Date
    Apr 2004
    Posts
    1,562
    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.

  96. #96
    mtbr member
    Reputation: mullen119's Avatar
    Join Date
    Aug 2009
    Posts
    3,997
    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.

  97. #97
    mtbr member
    Reputation:
    Join Date
    Jan 2006
    Posts
    35
    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.

  98. #98
    kmc
    kmc is offline
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    293

    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.

  99. #99
    I work in .001 tolerances
    Reputation: HomegrownMN's Avatar
    Join Date
    Nov 2004
    Posts
    1,243
    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

  100. #100
    mtbr member
    Reputation: mullen119's Avatar
    Join Date
    Aug 2009
    Posts
    3,997
    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.

Page 1 of 2 12 LastLast

Members who have read this thread: 63

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •