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  1. #1
    TNC
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    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
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    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
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    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
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    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
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    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
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    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
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    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
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    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"
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    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!
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  10. #10
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    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
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    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.
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  12. #12
    TNC
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    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
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    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.
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  14. #14
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    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
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    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.
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  16. #16
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    Quote Originally Posted by HHMTB

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

  17. #17
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    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
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    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
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    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
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    Maybe this is a better pic taken from BBW's post.

    this? only 10$
    http://www.bikeparts.com/search_resu...p?ID=BPC132925
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    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
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    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.
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  23. #23
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    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.
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  24. #24
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    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
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    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.

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

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

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

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

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

    I don't know if I've managed to explain my experience with my "rusty" English
    Last edited by Marmoto; 01-14-2011 at 11:15 AM.

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

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

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

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

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    Well F me sideways! On closer inspection, Marzocchi uses a two thread patterns in their recessed valve holes. The first one is to seat the schrader valve and the second, slightly larger one, to take the adaptor. This means that Marzo adaptors can't be modified to work on the RS or any port that uses the standard schrader valve thread form.
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    To build group knowledge:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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    Yup, no Curnutt/SPV valve in the Monarch.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

    Go easy on adding the oil. Like ~5-10 drops of oil at a time. Small changes here make big changes to the progressivity and you don't want to hydro-lock the shock.
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    HHMTB, I did something similar in my Monarch RT3 IFP chamber and it works perfect:
    - I removed the air/nitrogen from the IFP air chamber
    - I removed the IFP schrader valve core
    - I added 6 drops of 80W fully systetic gear oil into the IFP air chamber with a dual purpose: increase the IFP lubing and make it a little bit more progressive to counteract the side effects of the next step.
    - I inserted de IFP valve core and pumped 210 psi (it was 250-300 psi) to increase the small bump sensitivity. The bottom-out control didn't suffered.

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

    And is easy and cheap

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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    RP23 guts for those interested

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

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

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

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

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

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

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

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

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

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

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

    "Adventure begins where good judgment ends."

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

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