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noMAD man
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Discussion Starter · #1 ·
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.
 

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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.
 

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noMAD man
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Discussion Starter · #3 ·
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.
 

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I dig trails!
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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
 

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TNC said:
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
 

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noMAD man
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Discussion Starter · #6 ·
Mr.P said:
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.:D
 

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I dig trails!
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TNC said:
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.:D
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
 

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"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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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.
 

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Just the tip!
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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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noMAD man
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Discussion Starter · #12 ·
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.:D

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

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"El Whatever"
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HHMTB said:
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!! :thumbsup: 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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Warp said:
Thanks for the recommendations, guys!! :thumbsup: 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.
 

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Just the tip!
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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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Orbea Occam 2020 M10 stock
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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
 

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Vuco said:
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
 

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noMAD man
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12,220 Posts
Discussion Starter · #19 ·
retro83 said:
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.
 

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