Air in Pike lowers: a PSA- Mtbr.com
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  1. #1
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    Air in Pike lowers: a PSA

    I realize there is a huge thread on the Pike in this forum, but given that I am subscribed to it and failed to realize this was an issue, I thought I'd make a new post.

    Short version: The seals at the top of the lowers on the Pike are very good, and they can trap a substantial amount of air pressure. In some cases, this can completely ruin the performance of your fork. Bleed the air by emptying the air chamber and sliding a thin piece of plastic in between the stanchion and dust wiper until you hear a hiss.

    Long version: I loved my Pike when I first got it, but over time, and especially lately, had been experiencing a significant loss of enthusiasm about it. This culminated in a trip to Mammoth where I really just couldn't believe the level of arm fatigue I was getting. I chalked it up to being out of shape and that my Tallboy LTc just wasn't cut out for park riding. Cut to a few weeks later, I remember something about this air trapping issue and decide to check it out. There was significant resistance to compression even with the air cap removed, so I executed the cable tie bleed technique and released quite a bit of pressure.

    I had thought it curious that I only needed ~72 psi to get desired sag (~25%) out of the Pike even though I'm 220 lbs geared to ride. After bleeding the lowers, I had to up the pressure to 90 psi in order to have a rideable fork! (Much closer to what Rock Shox recommends for my weight.) On the subsequent ride, my fork was back to it's good old self with the excellent small bump compliance and mid-stroke support I remembered. I'm super happy about this.

    So if you own a Pike or took a ride on one and are disappointed, consider that this may be the issue. I was absolutely blown away by the effect it had on the performance of the fork, and I think the air pressure change I had to make speaks for itself. It's a fantastic fork, as long as air trapped in the lowers isn't creating an undesired spring rate that completely alters its behavior.

  2. #2
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    I had the same experience but with a Talas 34. I removed the lowers because they were riding harsh, and pressure was released when I knocked loose the shaft. Like you, I had to increase the pressure and they are working much better.
    Thanks for the ziptie-under-the-wiper suggestion, I didn't think of that as an alternative to unbolting the shafts.

  3. #3
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    Can you post some pictures or a link to it? I've been having the same issues and it's driving me nuts! Thanks in advance.

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    huh. While i haven't had any complaints about the Pike's performance, I was a bit mystified at running 65 PSI for correct sag. Sure enough, I tried the air bleed, and when I re-set the sag it is right at RS's recommended pressure (~80 psi).

    Thanks for the tip.

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    Quote Originally Posted by Vhom View Post
    Can you post some pictures or a link to it? I've been having the same issues and it's driving me nuts! Thanks in advance.
    Basically, at the seals where the stanchions enter the lowers, there is a dust wiper and then underneath that, the actual seal. You need to insert something in between to temporarily break the seal and release the air. The thinner the better, and nonmarring so you don't scratch the stanchion. The thin end of a small cable tie works great. Just stick in in between the dust wiper and stanchion and keep inserting till you hear a hiss. Then you are done.

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    I checked youtube and here's a short clip. RockShox Pike Burp BikeCo - YouTube

  7. #7
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    Re: Air in Pike lowers: a PSA

    Quote Originally Posted by hillharman View Post
    Basically, at the seals where the stanchions enter the lowers, there is a dust wiper and then underneath that, the actual seal. You need to insert something in between to temporarily break the seal and release the air. The thinner the better, and nonmarring so you don't scratch the stanchion. The thin end of a small cable tie works great. Just stick in in between the dust wiper and stanchion and keep inserting till you hear a hiss. Then you are done.
    So this should be done on both sides...

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    Now, if someone would come up w/ a way to inject some grease into that tiny space/channel between the seals...

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    Quote Originally Posted by jazzanova View Post
    So this should be done on both sides...
    Yes.

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    Why would you need to air down to do it? You want to equalize when it's topped out.

  11. #11
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    Quote Originally Posted by GH28 View Post
    Why would you need to air down to do it? You want to equalize when it's topped out.
    Yeah that's fair. You just need to air down to see the effect of it (i.e. the inability to compress the fork and have it stay down).

  12. #12
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    OMG...that was stupid easy.....Thanks!

  13. #13
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    I'm at 68psi and still only around 20% sag... RS says I need to be 75-85psi.

    I swear I've heard a "pssssssst" on the last ride or two... Trying this tonight.
    I like 'em long, low, slack and playful

  14. #14
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    Thanks for posting this!

  15. #15
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    I have this problem on my SID. Seems like the negative air chamber must be leaking into the lowers. I replaced my seals but the problem came back in ~2 months. Would be nice to get to the bottom of the issue.

  16. #16
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    Fixed the problem and can't be happier. I was going to have the LBS do service on it, but I only have about 13 hours on it. Thanks for the tip!

  17. #17
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    You're the man! So simple, thank god.

  18. #18
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    Yep, it works. 13 psi higher now
    I like 'em long, low, slack and playful

  19. #19
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    I think I may have had a double whammy with the lowers pressure and an overfilled damper.

    With the fork at full extension, I pulled out the LSC snap ring and adjuster and it gave up a few cc's of damper fluid. I think the bladder was hitting the walls of the stanchions at full compression.

  20. #20
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    If you opened the damper while you still had pressure built up in the legs, it likely wasn't overfilled. That was most likely built up lower leg pressure acting on the bladder. There is no static force on that bladder except for ambient air pressure within the leg.

    The only way, that I know of, to tell if it's overfilled is by installing the damper into the upper leg (lowers off), and cycle all the way to see if the bladder hits the ID of the stanchion and restricts any more displacement. It's not like a MX cartridge where you have a big spring instead of a bladder and can feel for top-out force if it's overfilled.


    This air burping trick works for any fork as well, not just the Pike. Fox, X-Fusion, Zoke, etc. Film negatives work great too.

    With how quickly this happens, and how customer complaints about forks over the last decade or so have almost all related to compliance and arm pump, I find it astonishing that quick bleeders are NOT standard features on all high-end forks now.

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    Ah, well, easy fix if that is that is the case. My buddy had success cramming a mixmizer syringe in the adjust port for a bleed, so I'll give that a go.

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    Quote Originally Posted by GH28 View Post
    If you opened the damper while you still had pressure built up in the legs, it likely wasn't overfilled. That was most likely built up lower leg pressure acting on the bladder. There is no static force on that bladder except for ambient air pressure within the leg.

    The only way, that I know of, to tell if it's overfilled is by installing the damper into the upper leg (lowers off), and cycle all the way to see if the bladder hits the ID of the stanchion and restricts any more displacement. It's not like a MX cartridge where you have a big spring instead of a bladder and can feel for top-out force if it's overfilled.


    This air burping trick works for any fork as well, not just the Pike. Fox, X-Fusion, Zoke, etc. Film negatives work great too.

    With how quickly this happens, and how customer complaints about forks over the last decade or so have almost all related to compliance and arm pump, I find it astonishing that quick bleeders are NOT standard features on all high-end forks now.
    Definitely. It's something I'll do every ride from here on out.

  23. #23
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    I've been playing with ride characteristics when you equalize when the fork is topped out vs. bottomed out and I noticed:

    When equalized with ambient pressure topped out, I still can't bottom out the fork at 25% sag.

    When equalized with ambient bottomed out, I can get full travel, but sag sits at 5% when the fork is unweighted. So, I think it creates a vacuum when you equalize bottomed out and then put air in the positive chamber.

    Maybe compromise by equalizing at 50%?

  24. #24
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    Quote Originally Posted by Pau11y View Post
    Now, if someone would come up w/ a way to inject some grease into that tiny space/channel between the seals...
    Couldn't you pull the lowers and schlube 'n lube it up? Obviously not the same as simply injecting, but would maybe work for a while?
    I like 'em long, low, slack and playful

  25. #25
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    BTW:

    I know understand why X-Fusion puts "Neutra-Valves" on their HLR forks:

    X-Fusion RV1 HLR DH fork review - BikeRadar

    We used the pressure releasing ‘Neutra Valves’ (two small valves on the lower legs to remove air pressure built up inside) while in Spain. When air pressure did build when at altitude, the Neutra Valves proved to work effectively.
    I like 'em long, low, slack and playful

  26. #26
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    Quote Originally Posted by hokiebrett View Post
    Couldn't you pull the lowers and schlube 'n lube it up? Obviously not the same as simply injecting, but would maybe work for a while?
    Too much work. I was hoping for something like this:

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  27. #27
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    Quote Originally Posted by Pau11y View Post
    Too much work. I was hoping for something like this:

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    Sounds great... let us know how it works
    I like 'em long, low, slack and playful

  28. #28
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    thanks for the information.....FYI, this worked wonders for my 2015 Fox 36 Float RC2, mucho gracias !

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    Quote Originally Posted by half_man_half_scab View Post
    I've been playing with ride characteristics when you equalize when the fork is topped out vs. bottomed out and I noticed:

    When equalized with ambient pressure topped out, I still can't bottom out the fork at 25% sag.

    When equalized with ambient bottomed out, I can get full travel, but sag sits at 5% when the fork is unweighted. So, I think it creates a vacuum when you equalize bottomed out and then put air in the positive chamber.

    Maybe compromise by equalizing at 50%?
    I'd stick to equalizing when topped out, if at all. If you want to use more of your travel @ 25% sag, remove one or two tokens, depending on how much bottom out reserve you want.

    A setup method that takes the least amount of work and gives the same result over and over would be best. I just do not see why this equalising should be done with the fork compressed: it's designed to have a certain amount of air in the lowers. Adjusting sag with a guessed amount of vaccuum? No way for me . If you equalize the pressure in the lowers with the outside air, all the normal adjustments of the fork are sufficient to get the characteristics you want.

  30. #30
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    Why? The air is only on one side. Trapped air from compressions?

    Interesting find for sure.

  31. #31
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    It's on both sides. Completely independent of air spring air pressure.
    I like 'em long, low, slack and playful

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    Originally Posted by JeroenK
    I'd stick to equalizing when topped out, if at all. If you want to use more of your travel @ 25% sag, remove one or two tokens, depending on how much bottom out reserve you want.
    Quick question for clarification: When we say "topped out", do we mean fork legs fully extended with the fork aired up to a particular riders required pressure before equalizing?
    Last edited by challybert; 09-11-2014 at 08:46 AM.

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    Quote Originally Posted by JeroenK View Post
    I'd stick to equalizing when topped out, if at all. If you want to use more of your travel @ 25% sag, remove one or two tokens, depending on how much bottom out reserve you want.
    Well I'm running 26", so there were never any tokens installed to begin with. I have no other avenue to get the travel I want at the sag I want. Equalizing at bottom out feels a lot better to me, so I think I'll stick with it. It still ramps up at the end, but it's not like I'm hitting a wall in the last inch, and the high speed circuits seem to handle the bottom out characteristics better.

    The best solution would be for the manufacturers to engineer pores that are always open and equalizing with ambient pressure, with some kind of filter to prevent loss of fluid and incursion of dust.

  34. #34
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    OK, is the air equalizing better to do with air in the fork? What is the difference?

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    Quote Originally Posted by jazzanova View Post
    OK, is the air equalizing better to do with air in the fork? What is the difference?
    With air in the forks there is no vacuum but additional air pressure from the air trapped in the lowers as you compress them. With no air in the forks when you pump them up you will get a vacuum as it extends and need to extend the fork little possibly to allow the air to equalise in a solo air fork due to the vacuum keeping the fork lower in its travel. Make of it what you will.

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    It's seems most probable that the fork is designed to operate with 1 atm of pressure in the legs (i.e. no pressure differential between the outside and inside of fork leg at full extension).

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    After riding it for a few days I lost the vacuum generated from equalizing bottomed out. So, from a practical perspective, I don't care to empty the positive chamber of air, bottom out the fork, and equalize every ride. So I've reversed my initial opinion, and am equaling with it topped out now.

  38. #38
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    Air in Pike lowers: a PSA

    Makes one wonder why not more forks using little air bleeders like on the Fox 40... Seems like the trick highlighted in this thread is accomplishing the same thing...



    https://www.pinkbike.com/photo/8449370/

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  39. #39
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    I did this before yesterday's ride. I didn't get any "equalizing" or "pss" coming out of mine, nor did it seem to change anything with how the fork rides (which is pretty damn good). I figured I probably shouldn't keep inserting zip-ties in between the fork and the stanchion, as I live in a pretty wet, muddy and mucky environment and I don't want those loosening up.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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  40. #40
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    Quote Originally Posted by LCW View Post
    Makes one wonder why not more forks using little air bleeders like on the Fox 40... Seems like the trick highlighted in this thread is accomplishing the same thing...


    Fox 40 RAD Prototype at Fox 40 RAD Prototype in Deep Cove, British Columbia, Canada - photo by fraserbritton - Pinkbike
    Or why Fox didn't include these on their new '15 MY Float 36

  41. #41
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    Air in Pike lowers: a PSA

    Quote Originally Posted by Idaho View Post
    Or why Fox didn't include these on their new '15 MY Float 36
    Good point as the rest of the 2015 36 lowers are very 40-like (the arch, the pinch bolt system)

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  42. #42
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    Or why these MOFOs making these semi-bath forks don't include valves in the footnuts that allow you to quickly change the semi-bath fluid without taking apart the fork?

    Probably a good reason for that, they wouldn't sell as many forks, seals, and replacement stanchion-steerer assemblies.
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    Quote Originally Posted by Pau11y View Post
    Too much work. I was hoping for something like this:

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    Pretty sure needles for grease guns are fairly available. I bought one at AutoZone once. They're basically the size of a largish hypodermic needle (can't remember gauges), so you could easily slide it down beside the seal and inject grease.

  44. #44
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    I've started doing this with my 2010 Revelations and get the hssst noise when I compress the fork and then really smooth buttery movement.

  45. #45
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    Unless there is a defective seal in the air cartridge allowing high pressure air to leak into the lowers, there is no reason to purge air out of the lower legs.

    Any oil bath fork, coil or air, when assembled, has a sealed lower leg. The oil seal at the top and the crush washers or O-rings at the foot nuts form a sealed chamber. When the stanchion tubes are inserted, at the top, air is trapped in the lower tubes. When the fork compresses and the stanchion tubes travel into the lower legs, the stanchions take up volume, and the air in the lower legs is compressed. Yes, this results in a slight ramp up of pressure in the lower legs. This is normal and inevitable. It does not pose an impediment to performance because at the top of the travel you are starting at 0 PSI and the amount of pressure built up at the approach of bottoming out is just a slight cushion. Depending upon your riding weight and style, the effect will vary, but that is why you adjust the air spring pressure for your particular situation rather than just going by a shock chart.

    You can absolutely compensate for this slight air cushion by adjusting your air spring pressure and damping accordingly.

    The video that was posted showing the zip tie "procedure" is a horrible example of how to "solve" a problem that does not exist. Worse, it's a good way to create a problem. Notice that the air being "purged" is at the bottom of the stroke. They are venting out the air pressure as the stanchions compress the air. This means when the air spring is charged and the fork extends, the lower legs will be in a vacuum. All this does is provide the temporary effect of having a negative air spring. Sure, it feels plush for a bit, but it needs to be repeated later. Why? Because the vacuum gets filled. In other words, the air gets sucked back into the lowers. Depending on where you are riding, guess what else gets sucked into the lowers? Moisture, dust, or whatever.

    I can't see the point in running a zip tie past the seals on regular basis to get some temporary gimmicky effect while risking damaging the seals and contaminating the oil. Simply accept that fact that a slight ramp up occurs inside the lower legs and adjust the air spring and damping accordingly. Then, ride your bike and stop wasting time performing unnecessary "procedures."

    Again, if significant air pressure is building in the lowers, that would be different and would indicate a loss of air from a pressurized part of the fork to the lower leg. This calls for a repair of the problem, not a quick zip tie purge.

  46. #46
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    Quote Originally Posted by Chris2fur View Post
    Unless there is a defective seal in the air cartridge allowing high pressure air to leak into the lowers, there is no reason to purge air out of the lower legs.

    Any oil bath fork, coil or air, when assembled, has a sealed lower leg. The oil seal at the top and the crush washers or O-rings at the foot nuts form a sealed chamber. When the stanchion tubes are inserted, at the top, air is trapped in the lower tubes. When the fork compresses and the stanchion tubes travel into the lower legs, the stanchions take up volume, and the air in the lower legs is compressed. Yes, this results in a slight ramp up of pressure in the lower legs. This is normal and inevitable. It does not pose an impediment to performance because at the top of the travel you are starting at 0 PSI and the amount of pressure built up at the approach of bottoming out is just a slight cushion. Depending upon your riding weight and style, the effect will vary, but that is why you adjust the air spring pressure for your particular situation rather than just going by a shock chart.

    You can absolutely compensate for this slight air cushion by adjusting your air spring pressure and damping accordingly.

    The video that was posted showing the zip tie "procedure" is a horrible example of how to "solve" a problem that does not exist. Worse, it's a good way to create a problem. Notice that the air being "purged" is at the bottom of the stroke. They are venting out the air pressure as the stanchions compress the air. This means when the air spring is charged and the fork extends, the lower legs will be in a vacuum. All this does is provide the temporary effect of having a negative air spring. Sure, it feels plush for a bit, but it needs to be repeated later. Why? Because the vacuum gets filled. In other words, the air gets sucked back into the lowers. Depending on where you are riding, guess what else gets sucked into the lowers? Moisture, dust, or whatever.

    I can't see the point in running a zip tie past the seals on regular basis to get some temporary gimmicky effect while risking damaging the seals and contaminating the oil. Simply accept that fact that a slight ramp up occurs inside the lower legs and adjust the air spring and damping accordingly. Then, ride your bike and stop wasting time performing unnecessary "procedures."

    Again, if significant air pressure is building in the lowers, that would be different and would indicate a loss of air from a pressurized part of the fork to the lower leg. This calls for a repair of the problem, not a quick zip tie purge.
    Chris I'm not sure you are understanding the issue. I agree that purging the air at the bottom of the stroke does seem like a bad idea. For whatever reason, air pressure does in fact build up in fork legs, such that even at full extension, there is significant pressure in the fork leg. The anecdotal evidence in this thread suggests it happens on a range of models, and of course, many DH forks have a provision to bleed air out of the fork lowers. You could probably account for why this happens better than I could, but it definitely is an issue than can amount to a dramatic alteration of the spring rate of the fork.

  47. #47
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    Some additional information for my specific case: I live around 900' above sea level but routinely drive up to 5000' feet to ride and occasionally 8000'+ (Mammoth). I've wondered if frequent altitude changes exacerbate the issue.

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    Quote Originally Posted by hillharman View Post
    Chris I'm not sure you are understanding the issue. I agree that purging the air at the bottom of the stroke does seem like a bad idea. For whatever reason, air pressure does in fact build up in fork legs, such that even at full extension, there is significant pressure in the fork leg. The anecdotal evidence in this thread suggests it happens on a range of models, and of course, many DH forks have a provision to bleed air out of the fork lowers. You could probably account for why this happens better than I could, but it definitely is an issue than can amount to a dramatic alteration of the spring rate of the fork.
    Hillharman: Thanks for zeroing in a very specific aspect. If air is actually building up inside the non-air spring lower leg of a fork, it cannot be due to a leak from a pressurized part of the fork. Hence your inferred question: Where is it coming from? The only rational explanation would be that somehow the main seal design is such that air is being "grabbed" during extension and then remains trapped and slowly builds up. I'm guessing something along the lines of what was happening with the Fox air chambers that were filling up with oil from the lower leg. The U-Cup seal was doing something similar with the oil. Anyway, that's the best guess I have for that specific situation. I've not had any reports of such air build up with our seals, but would certainly like to know if it is a seal-specific issue.

    My main concern was that every fork will compress air in the lowers on the downstroke and that is not a problem. It's not going to be a good thing if everyone is shoving cable ties past their seals as part of normal "maintenance."

  49. #49
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    This happens on all forks, not just Pike, especially when you go from low elevation to high elevation. They do it on some DH forks because they figure people are riding lifts all day at higher elevation. Trail bikes not so much. And what would your lowers look like if you were smooshing grease into them every ride for that extra plushness, eventually it would just be a ****y mess inside your fork. Nasty. No fork company in their right mind is going to incorporate that, warranty nightmare
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  50. #50
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    Quote Originally Posted by Chris2fur View Post
    Hillharman: Thanks for zeroing in a very specific aspect. If air is actually building up inside the non-air spring lower leg of a fork, it cannot be due to a leak from a pressurized part of the fork. Hence your inferred question: Where is it coming from? The only rational explanation would be that somehow the main seal design is such that air is being "grabbed" during extension and then remains trapped and slowly builds up. I'm guessing something along the lines of what was happening with the Fox air chambers that were filling up with oil from the lower leg. The U-Cup seal was doing something similar with the oil. Anyway, that's the best guess I have for that specific situation. I've not had any reports of such air build up with our seals, but would certainly like to know if it is a seal-specific issue.

    My main concern was that every fork will compress air in the lowers on the downstroke and that is not a problem. It's not going to be a good thing if everyone is shoving cable ties past their seals as part of normal "maintenance."






    In this particular case, the root of the problem needs to be pinpointed and corrected because the last thing you need is your fork pulling outside elements into the lower leg.
    I think we are on the same page. The only explanation that made sense to me was that it was somehow easier for air to enter the fork leg (past the seals) than for it to exit, resulting in a gradual build up. I agree that compromising the seals in order to solve the problem is a really bad solution, but it was to the point where my fork felt like garbage. I was running ~15 psi less than I was initially and it was still extremely harsh and only using ~80% of the travel. Equalizing the fork legs at full extension instantly brought me back to the out of the box feeling and more reasonable air pressures in the air spring.

  51. #51
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    Quote Originally Posted by hillharman View Post
    I think we are on the same page. The only explanation that made sense to me was that it was somehow easier for air to enter the fork leg (past the seals) than for it to exit, resulting in a gradual build up. I agree that compromising the seals in order to solve the problem is a really bad solution, but it was to the point where my fork felt like garbage. I was running ~15 psi less than I was initially and it was still extremely harsh and only using ~80% of the travel. Equalizing the fork legs at full extension instantly brought me back to the out of the box feeling and more reasonable air pressures in the air spring.
    Well, if you ever want to see if it's seal-specific, let me know. Since you have the problem consistently, you'd be a great test candidate.

  52. #52
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    Quote Originally Posted by Chris2fur View Post
    Unless there is a defective seal in the air cartridge allowing high pressure air to leak into the lowers, there is no reason to purge air out of the lower legs.

    Any oil bath fork, coil or air, when assembled, has a sealed lower leg. The oil seal at the top and the crush washers or O-rings at the foot nuts form a sealed chamber. When the stanchion tubes are inserted, at the top, air is trapped in the lower tubes. When the fork compresses and the stanchion tubes travel into the lower legs, the stanchions take up volume, and the air in the lower legs is compressed. Yes, this results in a slight ramp up of pressure in the lower legs. This is normal and inevitable. It does not pose an impediment to performance because at the top of the travel you are starting at 0 PSI and the amount of pressure built up at the approach of bottoming out is just a slight cushion. Depending upon your riding weight and style, the effect will vary, but that is why you adjust the air spring pressure for your particular situation rather than just going by a shock chart.

    You can absolutely compensate for this slight air cushion by adjusting your air spring pressure and damping accordingly.

    The video that was posted showing the zip tie "procedure" is a horrible example of how to "solve" a problem that does not exist. Worse, it's a good way to create a problem. Notice that the air being "purged" is at the bottom of the stroke. They are venting out the air pressure as the stanchions compress the air. This means when the air spring is charged and the fork extends, the lower legs will be in a vacuum. All this does is provide the temporary effect of having a negative air spring. Sure, it feels plush for a bit, but it needs to be repeated later. Why? Because the vacuum gets filled. In other words, the air gets sucked back into the lowers. Depending on where you are riding, guess what else gets sucked into the lowers? Moisture, dust, or whatever.

    I can't see the point in running a zip tie past the seals on regular basis to get some temporary gimmicky effect while risking damaging the seals and contaminating the oil. Simply accept that fact that a slight ramp up occurs inside the lower legs and adjust the air spring and damping accordingly. Then, ride your bike and stop wasting time performing unnecessary "procedures."

    Again, if significant air pressure is building in the lowers, that would be different and would indicate a loss of air from a pressurized part of the fork to the lower leg. This calls for a repair of the problem, not a quick zip tie purge.
    Makes sense to me. It makes a strong argument for reintroducing adjustability of the negative air spring. The increase in small bump sensitivity was pretty nice with the vacuum.

    So, with the Enduro seals you get a little bit of air trapped as well?

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    Quote Originally Posted by half_man_half_scab View Post
    Makes sense to me. It makes a strong argument for reintroducing adjustability of the negative air spring. The increase in small bump sensitivity was pretty nice with the vacuum.

    So, with the Enduro seals you get a little bit of air trapped as well?
    Yes, as far as initial air trapped during installation with pressure at "0" fully extended and ramping up slightly on compression that should happen with any seal that is actually sealing, including the Enduros.

    As far as the "pumping up" effect described by some in this thread, where the air pressure builds up to where it exceeds the air pressure outside the fork--I have not seen that happen with the Enduros. On the other hand I have not had first hand experience with this phenomenon with any fork I have rebuilt.

    The only fork I've opened had the lowers almost shoot off due to excess air pressure int the lower leg was due to a leaking postitive/negative air spring assembly. Magura sent out a new assembly and that took care of it.

    I'd like to have someone that has a fork with this problem try a set of our seals and see if the pressure build up goes away.

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    I'm in over my head here... but the question I beg to ask is, why then to achieve 30% sag after "equalizing" the fork with the zip-tie method, does the air spring increase by nearly 20psi over the previous "pre zip-tie" air spring?

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    The pike would have to have some pretty amazing seals IMO to stay pumped up like that and base on my tear downs, it doesn't. Not like older marzocchis with the oil seals that seal harder the more pressure that's applied.
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    I have been experiencing a slow decrease in small bump sensitivity and overall performance from my Pike. I've had it six months so I decided it was probably a good time for some maintenance. After pulling the damper I immediately noticed a problem, air in the system. Did a bleed and added at least 10cc's of fluid. Not sure if it leaked out or was not filled fully from the factory, kinda strange. Put the fork back together with some fresh bath oil and seals and holy buttery smoothness. Most suspension components really do benefit from routine maintenance, and I know many riders skimp on it, including me. So if your fork isn't feeling like it used to, it could be time for a rebuild.

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    Quote Originally Posted by Chris2fur View Post
    Well, if you ever want to see if it's seal-specific, let me know. Since you have the problem consistently, you'd be a great test candidate.
    Its got to be a side effect of how well the seals work at holding in grease/oil. They are good enough to keep grease from passing allowing the upper stanchions to remain dry when extended, id assume air is getting in when the seal is being pushed against the dry upper and then trapped when the seal pushes back down as air cant get past the grease coated stanchion seal surface on the inside.

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    Quote Originally Posted by Krause View Post
    Its got to be a side effect of how well the seals work at holding in grease/oil. They are good enough to keep grease from passing allowing the upper stanchions to remain dry when extended, id assume air is getting in when the seal is being pushed against the dry upper and then trapped when the seal pushes back down as air cant get past the grease coated stanchion seal surface on the inside.
    This was basically my thought as well. One side of the interface is better lubricated than the other.

  59. #59
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    Quote Originally Posted by Krause View Post
    Its got to be a side effect of how well the seals work at holding in grease/oil. They are good enough to keep grease from passing allowing the upper stanchions to remain dry when extended, id assume air is getting in when the seal is being pushed against the dry upper and then trapped when the seal pushes back down as air cant get past the grease coated stanchion seal surface on the inside.
    Definitely something like that. Only thing is, the seal is not supposed to be a one-way device. We've found someone that's consistently having the problem with the OE seals that is going to switch to our RS 35mm kit and we'll see what happens.

  60. #60
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    So before this ride, I did the equalization at full compression... Which this thread says that would've put my lowers under vacuum and made my small numb über plush... Which it did.

    This thread also says that my fork would "pumped" back up and lost small bump and sag during a ride... Which it did. I could feel the Pike stiffening up during the descent.

    I feel the moral of my story is to equalize at full extension.
    I like 'em long, low, slack and playful

  61. #61
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    I thought most of this was jibberish until I rode at altitude this weekend. Something was way wrong and jgusta points out my Pike is way stiff for my weight. Sure enough, the zip tie thing worked. It definitely has something to do with going up in altitude (more than 5,000 feet).

    Have FUN!

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    People at the top of shuttle drop offs wonder what I'm doing with my zip tie and fork. Think I'm crazy, I always hear a loud pssshhhh
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    I wonder if this is just normal pressure and temperature variations. Do a DH run, entire fork heats up, stick zip-tie in there, sure enough it's going to PSSST a little. When it cools down, it will be slightly negative to the outside ambient pressure, so at some point it will suck in a little more air to equalize, but eventually you'll heat it up a gain and the process will repeat itself. Then think about cold/hot cycles and pressure variations due to altitude and other factors, I have to wonder if this is really varying all that much or just a normal thing that can't be controlled. I guess it would be optimal to equalize it for every condition, at the beginning of ever ride/run, but I'm not sure mine traps the pressure like this, so I wonder also if it's just limited to some forks that seem to seal better than others?
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  64. #64
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    Ever hear a half empty plastic water bottle start to crunch when driving down the canyon couple thousand feet, same thing..
    video=youtube;][/video]...

  65. #65
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    Quote Originally Posted by Jayem View Post
    I wonder if this is just normal pressure and temperature variations. Do a DH run, entire fork heats up, stick zip-tie in there, sure enough it's going to PSSST a little. When it cools down, it will be slightly negative to the outside ambient pressure, so at some point it will suck in a little more air to equalize, but eventually you'll heat it up a gain and the process will repeat itself. Then think about cold/hot cycles and pressure variations due to altitude and other factors, I have to wonder if this is really varying all that much or just a normal thing that can't be controlled. I guess it would be optimal to equalize it for every condition, at the beginning of ever ride/run, but I'm not sure mine traps the pressure like this, so I wonder also if it's just limited to some forks that seem to seal better than others?
    Re-thinking this, the air space in the lowers goes up at altitude unless it gets released past the upper stanchion seal. Maybe the Fox and Enduro seals are better at releasing that pressure build as you state?

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  66. #66
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    This is absolutely a real phenomenon.
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    When saying you do the equalize at full extention,you mean that you put the zip-tie inside the seals without compressing it at all?
    Do you remove the air from the fork before doing it?
    Please help!!

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    ^^ Correct, full extension; and no, do not remove the air!

    Have FUN!

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    Quote Originally Posted by blade72 View Post
    When saying you do the equalize at full extention,you mean that you put the zip-tie inside the seals without compressing it at all?
    Do you remove the air from the fork before doing it?
    Please help!!
    I asked the same question and never got a response. That said, from reading the more recent posts, it should be done at "full" extension (not compressed) and with air in the fork. If you have the issue and air releases, you should re-check your sag settings.

  70. #70
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    I am not sure if this is related, but I will ask anyway.
    Since I have done the zip-tie air release, the fork started to behave differently. It's mostly noticeable on climbs and on jumps when the fork extends. I can feel a slight movement, it almost feels like the fork is loose in the headset. It is very minor and no sound when it happens.
    On climbs when the front wheel lifts and the fork extend I can feel it through the handlebars.
    How I said, I am not sure if this is related in any way though...

  71. #71
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    Quote Originally Posted by NoahColorado View Post
    This is absolutely a real phenomenon.
    Not to put you on the spot, but have you seen this happen with the Stage?

  72. #72
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    Quote Originally Posted by jazzanova View Post
    I am not sure if this is related, but I will ask anyway.
    Since I have done the zip-tie air release, the fork started to behave differently. It's mostly noticeable on climbs and on jumps when the fork extends. I can feel a slight movement, it almost feels like the fork is loose in the headset. It is very minor and no sound when it happens.
    On climbs when the front wheel lifts and the fork extend I can feel it through the handlebars.
    How I said, I am not sure if this is related in any way though...
    Sounds like "top out." Typically there's a small spring inside to minimize that but you may just need a slight bit more rebound damping.

  73. #73
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    Re: Air in Pike lowers: a PSA

    Quote Originally Posted by Chris2fur View Post
    Sounds like "top out." Typically there's a small spring inside to minimize that but you may just need a slight bit more rebound damping.
    Yep. My Pike has done this from the get go. Just like Chris2fur said, a few clicks of rebound damping and it is much less noticeable.

  74. #74
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    Funny to run across this today. I've been complaining about the small bump compliance on my Fox 100mm 32 29er for a couple months now. This morning I decided to pop the seals and add a bit of float fluid thinking it couldn't hurt. There was a big hiss of pressure relieved on both sides as I pulled the seals, which I thought was very odd. After putting the fluid and seals back I saw this thread, so I did the zip tie just to make sure all the pressure was out. It will be interesting to see what it rides like. Speaking of plastic soda bottles, I'll bet a small piece of one would make a good "bleeder". Thinner than a zip tie, less likely to damage the seals.

  75. #75
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    Re: Air in Pike lowers: a PSA

    Quote Originally Posted by Chris2fur View Post
    Sounds like "top out." Typically there's a small spring inside to minimize that but you may just need a slight bit more rebound damping.
    Thank you. I will try it out.

  76. #76
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    Quote Originally Posted by hillharman View Post
    Not to put you on the spot, but have you seen this happen with the Stage?
    Yup, I do this routine when I travel to/from widely varying elevations.
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  77. #77
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    Mini zip-ties are great for this, but my fave tool so far is a filleted straw. The ones in small cardboard orange juice boxes especially!
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  78. #78
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    I've been disappointed with the lack of full extension from day one on my pike.

    I gave this a good read and burped my fork at full extension with the zip tie and viola! My left leg sucked in some fresh air and the fork extended the missing 15mm and now I get a nice full extension with a light tap on the top out bumper! Nice!

    Now I just need to keep an eye on it and see if it was just a vacuum created during assembly or a reoccurring theme I'll need to tend to from time to time.

    The other issue that has been frustrating is occasional blockage in the negative air chambers bypass groove. I've been able to clear it when necessary by forcing the legs down with a good jerk but i kinda miss my dual air Revelation set up. Never had an issue with the air chambers on that and it was nice to be able to tune with the Neg air pressure.

  79. #79
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    Re: Air in Pike lowers: a PSA

    Quote Originally Posted by hillharman View Post
    Yeah that's fair. You just need to air down to see the effect of it (i.e. the inability to compress the fork and have it stay down).
    For some reason I can't release any air with the fork with air. The zip tie just hits something inside (about an inch in) but no air comes out.
    It works only when I take all the air out. Than the zip tie releases the accumulated air...

  80. #80
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    Quote Originally Posted by jazzanova View Post
    For some reason I can't release any air with the fork with air.
    Because it's already equalized with ambient air pressure

    Quote Originally Posted by jazzanova View Post
    For some reason I can't release any air with the fork with air. The zip tie just hits something inside (about an inch in) but no air comes out.
    That's the upper bushing, if you've made it that far, there is no pressure build up.

    Quote Originally Posted by jazzanova View Post
    It works only when I take all the air out. Than the zip tie releases the accumulated air...
    By equalizing with the fork bottomed you create a vacuum, which increases small bump sensitivity when aired up, but is lost over the course of a ride in my experience.

  81. #81
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    I have a defective PIKE. Nothing is wrong with it. I waiting for it to go break, I even proactively zip tie it just to see what happens. Nothing, zilch, nada (knocking on anything made of wood right now). I'm about to do a routine service on it. Crap, given my luck I may just let it go. Surely, as soon as I take it apart problems will begin.

  82. #82
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    Thanks for the thread. Some random thoughts. If altitude seems to be a factor in causing this issue, would it be reasonable to expect that any fork shipped via air could have issues? could this explain some of the high infant mortality rates reported by users?

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    I am leery of trying the zip tie, and was thinking a thin book marker might work, too?

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    Is it not an inherent design flaw that needs remedying by the manufacturers? Seem that if compromising the seal is a fix...well it's really not solution...if needing to remove the lower bolt frequently to equalize is a fix....well it's really not solution. Seems like the solution lies in the manufacturers actually fixing the poor design causing it.

    Hey, Challybert, we know your car stalls on occasion. It's not a problem though... you just need to put a small tear in your air filter and it shouldn't stall anymore. Don't do it too often or you'll ruin your airfilter. If that doesn't work remove your drivers side tire and bounce it two times on the ground and the car won't stall anymore. Hey, thanks for the tip.

  85. #85
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    Quote Originally Posted by challybert View Post
    Is it not an inherent design flaw that needs remedying by the manufacturers? Seem that if compromising the seal is a fix...well it's really not solution...if needing to remove the lower bolt frequently to equalize is a fix....well it's really not solution. Seems like the solution lies in the manufacturers actually fixing the poor design causing it.
    What problem? Have you established that there really is a problem?
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    Ok, I tried this last night, and wanted to make sure I am doing it correctly? FWIW - I have a Pike 29 Solo Air 120 mm travel.

    -I let out almost all of the air pressure out of the top valve
    -Slid a zip tie end into the seal, and pressed down on the fork until it bottomed out.
    -I heard a small hiss come out, and did the same for the other side.
    -I then pumped it back up to the recommended PSI

    That's it? Small bump should be better?

    I am lost at equalize -- does that apply to this situation, or is that something else?

    Thanks!

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    Quote Originally Posted by Jayem View Post
    What problem? Have you established that there really is a problem?
    yes

  88. #88
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    This is a testament to better seals and better bushings. Manufacturers have improved the sealing so much that another problem was created, namely trapped air. I like the idea of a small threaded hole into the groove where the foam ring sits. Remove the screw once in a while and put in a few drops of oil, that is when the trapped air will come out!

  89. #89
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    Re: Air in Pike lowers: a PSA

    You should do it with the air in the fork.
    When there is no air, you create a negative pressure when you use the zip tie once you add air. It will make the fork super plush and sensitive on small bumps. You will also have to run higher psi in order to have the same sag as you had before the zip tie trick.
    This plush effect is only temporary. The negative pressure created inside the fork will suck in the air after riding it and the fork will be even stiffer then before because you now run the extra psi. Also, more junk will get inside with the sucked air.

  90. #90
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    Quote Originally Posted by ziprace View Post
    This is a testament to better seals and better bushings. Manufacturers have improved the sealing so much that another problem was created, namely trapped air. I like the idea of a small threaded hole into the groove where the foam ring sits. Remove the screw once in a while and put in a few drops of oil, that is when the trapped air will come out!
    The pike doesn't have those kind of seals (hydraulic oil seals that seal better as more pressure is applied).
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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    Sounds like 2 opposite things are going on here.

    Some forks are getting a build up a too much air in the lowers.

    Other forks are getting major negative pressure in the lowers, sucking the fork down in its travel - I assume that is not suppose to happen. Was happening bad with my fork. Called RS and they told me to open the air spring side lower fixing bolt - which I did and tapped it and a whole lotta air sucked _in_. Put it back and pumped it up, and quickly got what seemed too much neg air spring back. Pulled the loweres and did a seals change on the entire air spring side. So far the isssue has not returned. Maybe a worn out seal/o-ring needed replacing?

  92. #92
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    I think it's much better to click the bike upside down and undo the bolt to let the air out/in. I do not want to slip things in past my seals.

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    Folks, i have been riding a Pike 2014 for about 6 months now and for the past few weeks it's feeling ultra-stiff. I am running about 30% sag, 2 clicks LSC and a mid-rebound setting; going over moderate roots the front feels shaky and stiff, the fork is not using travel at all, even when riding on a fire road there's no real bump absorption.

    As i have never self-serviced any forks for now can someone explain to me what the problem might be? the fork is not a year old, maybe sending it in for a service would do the trick?


    Thanks

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    Craig, at Avalanche, said to replace or at least rotate(turn it 90/180 degrees) the Piston head o-ring with every 50hour service. The dimple causes a distortion (groove) in the o-ring over time. Just throwing it out there.

    Air in Pike lowers: a PSA-pike.png

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    Hmm, ok - is this a manageable task for an "average" bike self-servicer? Or do i need special tools??

  96. #96
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    try to find some youtube videos of how it is done. that is how I learned to service my fox fork.

  97. #97
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    Quote Originally Posted by challybert View Post
    Craig, at Avalanche, said to replace or at least rotate(turn it 90/180 degrees) the Piston head o-ring with every 50hour service. The dimple causes a distortion (groove) in the o-ring over time. Just throwing it out there.

    Click image for larger version. 

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    Good to know and that could certainly explain the excess negative air chamber pressure problem that some are experiencing, like Miker J pointed out, but it does not explain the air entrapment in the lowers.

    Have FUN!

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  98. #98
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    Quote Originally Posted by Mudguard25 View Post
    I think it's much better to click the bike upside down and undo the bolt to let the air out/in. I do not want to slip things in past my seals.
    You think??? On what basis? The anodized stanchions are MUCH harder than any nylon zip tie and cannot be scratched as such by a zip tie. The seals are urethane - again, good luck damaging a urethane seal - the most resilient flexible plastic on the planet. You'll do more damage by the hammering out those lower bolts as the friction will cause metal loss/wear at the press fit of the lower shafts into the fork lowers, not-to-mention damaging the plastic crush washers on the lower bolts.

    To each their own...

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  99. #99
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    Quote Originally Posted by Gman086 View Post
    You think??? On what basis? The anodized stanchions are MUCH harder than any nylon zip tie and cannot be scratched as such by a zip tie. The seals are urethane - again, good luck damaging a urethane seal - the most resilient flexible plastic on the planet. You'll do much more damage by the bashing out those lower bolts as the friction will cause metal loss/wear at the press fit of the lower shafts into the fork lowers, not-to-mention wearing out the plastic oil seals on the lower bolts.

    To each their own...

    G MAN
    Every time you push something through a seal (like a zip-tie) you push some contaminants through the seal with it.

    There is no bashing or damage going on to vent a lower bolt and no metal loss either. Crush washers aren't expensive.
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  100. #100
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    Glad I found this thread. I'm having a similar issue with a new Reba fork, that felt great for the first few rides, but has now lost all its plushness and small bump sensitivity.

    I've also had the same issue with SID, felt amazing after I serviced it, but after about a month of riding, it went back to its old harsh ways. I really hope this fix works.

    As a thought, because any pressure in the lower chamber is in a cylinder of bigger diameter / cross sectional area, then it'll take less air pressure to have a noticeable affect on the spring rate. Same as how an Air spring with bigger diameter, needs less pressure than an air spring with small diameter to achieve the same feel / spring rate. If that makes any sense?
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  101. #101
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    Tried this on my 2014 Reba RL Solo, and 2008 Reba RL duel air.

    Has worked a treat with both. Has completely transformed the ride.
    Funny it seems like this is affecting the fork more than just increasing the positive spring pressure - maybe just because of the inbalance between +ve and -ve air.

    This could also account for why many people preferred to run more air in the -ve chamber, than in the +ve chamber on duel air forks.

    An easy way to tell if you do have air in the lowers, is to let all the air out from the valves, and then see if the fork is still sprung. My fork felt as though it had 20 - 30 psi still in it.

    Would be interesting to know how much pressure builds up over a typical ride?
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  102. #102
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    Quote Originally Posted by jazzanova View Post
    You should do it with the air in the fork.
    When there is no air, you create a negative pressure when you use the zip tie once you add air. It will make the fork super plush and sensitive on small bumps. You will also have to run higher psi in order to have the same sag as you had before the zip tie trick.
    This plush effect is only temporary. The negative pressure created inside the fork will suck in the air after riding it and the fork will be even stiffer then before because you now run the extra psi. Also, more junk will get inside with the sucked air.
    I did the burp with air totally out. How can I correct this now? By slipping a zip tie in at full length now? Thanks!

  103. #103
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    Quote Originally Posted by Chris2fur View Post
    Definitely something like that. Only thing is, the seal is not supposed to be a one-way device. We've found someone that's consistently having the problem with the OE seals that is going to switch to our RS 35mm kit and we'll see what happens.
    Did you find out anything more about this? Did the Enduro seals remedy the problem?

    I only found this thread yesterday, after taking a ride on my Pike that had been stationary for a while, only to find it very stiff, and being unable to get more than 7-8mm of sag out of it. It had held it's pressure in the positive chamber, so I don't know where the pressure had been coming from, but there was enough air pressure in the left lower leg (air side) alone to give me less sag than I normally do with 50psi in the positive and negative chambers, with the top cap OFF the left leg.

    I'm gonna be keeping an eye on this, but if a simple seal swap to something that's not air tight can fix it, it'd be good.

    Wouldn't adding some kind of blowoff valve to the seals be an option. just a rubber flap releasing at a given pressure, or something? (Maybe I should apply for a patent? Stupider things has been sold, I'm sure!)

  104. #104
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    I just recently drilled and tapped my Pikes lowers to install a pressure release valve used in the Moto industry and the Fox 40s. Went well. I haven't put it all back together yet though. I'm waiting on a custom tuned Avy damper to put it all together. My stock damper cavitated a ton of air regardless of the bladder system.

    I'll post pics when I get a chance.

  105. #105
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    Quote Originally Posted by BMJ View Post
    I just recently drilled and tapped my Pikes lowers to install a pressure release valve used in the Moto industry and the Fox 40s. Went well. I haven't put it all back together yet though. I'm waiting on a custom tuned Avy damper to put it all together. My stock damper cavitated a ton of air regardless of the bladder system.

    I'll post pics when I get a chance.
    Cool. Where did you buy the valve?

  106. #106
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    Many valve options online.

    I went with the Mition Pro Micro Bleeders. Nice and compact.
    Attached Images Attached Images  

  107. #107
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    Thanks. Looking forward to the pics.

  108. #108
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    My Mod.

    Heres what my mod looks like. Just waiting for the Avy Damper to put it back together.

    Bad timing to order a custom damper. 3 week back log.
    Attached Thumbnails Attached Thumbnails Air in Pike lowers: a PSA-photo-1.jpg  

    Air in Pike lowers: a PSA-photo-2.jpg  


  109. #109
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    I have serious doubts that the venting of the lowers is actually a solution.

    The lower leg oil volume is very sensitive. On the rebound side, I've seen main seals pop off when you load 10ml of oil instead of 5ml. That said, you can imagine the difference in compression resistance there is between the two levels. When a rebound damper leaks oil into the lower leg, you get the same effect. Yes, collapsing the fork and venting the air addresses the compression resistance a bit, but that is not a solution. You should be checking oil levels and rebuilding the rebound seal head as necessary.

  110. #110
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    My issue is a vacuum of air in the lowers that was actually pulling the fork down into it's travel. Too much neg air affect. Once i did the zip tie thing, it rose up and rides higher in it's travel. Now i can set the sag properly.

    The problem now is that I've noticed the pressure change within the lowers depending on the temperature of the day. Bleed it on a hot day and ride it on a cold and the air shrinks and pulls it back down. Bleed it on a cold day and ride it on a warm and the air expands and rides too high. I even had a ride that started cold and rapidly warmed up through the day and the fork rode harsher and harsher until i zip tie bled it again.

    A quick blip of an easy access bleed valve like on the Fox 40's would have easily solved the pressure difference pre ride or even during.

  111. #111
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    Applying the zip tie method described here on my DPA 27,5" 160mm PIKE completely transformed the fork.

    It feels far more plush now and the hard topout when pulling up the front wheel is gone. I only compressed the fork halfway when doing the zip tie venting and still have full travel - seems like a good compromise to me

    Thanks a lot for everyone who contributed to this thread and raised the issue in the first place!

  112. #112
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    I have also had this same issue with my 150mm Pike RCT3. I did the zip tie trick and that fixed the issue. Rode again about 20-30 miles. Same issue once again. Has anyone talked to someone with Rockshox/Sram to find out why this is happening and what should be done to fix the issue. (I dont want to drill holes in my $1k fork). Thanks in advance.

  113. #113
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    Quote Originally Posted by Steel Calf View Post
    Applying the zip tie method described here on my DPA 27,5" 160mm PIKE completely transformed the fork.

    It feels far more plush now and the hard topout when pulling up the front wheel is gone. I only compressed the fork halfway when doing the zip tie venting and still have full travel - seems like a good compromise to me

    Thanks a lot for everyone who contributed to this thread and raised the issue in the first place!
    unfortunately the positive effect after applying the zip tie method lasted only a few days. Damn... Now I understand why people above my post started drilling holes in their fork.

  114. #114
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    Everyone is content with drilling holes in their $800+ fork? Air in the lowers may indicate a leak in the main chamber that is filling the lowers. Are people checking that?
    It is the Right of the People to Alter or to Abolish It.

  115. #115
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    Just found this today. Wow, what a difference!!

    Quote Originally Posted by hillharman View Post
    I realize there is a huge thread on the Pike in this forum, but given that I am subscribed to it and failed to realize this was an issue, I thought I'd make a new post.

    Short version: The seals at the top of the lowers on the Pike are very good, and they can trap a substantial amount of air pressure. In some cases, this can completely ruin the performance of your fork. Bleed the air by emptying the air chamber and sliding a thin piece of plastic in between the stanchion and dust wiper until you hear a hiss.

    Long version: I loved my Pike when I first got it, but over time, and especially lately, had been experiencing a significant loss of enthusiasm about it. This culminated in a trip to Mammoth where I really just couldn't believe the level of arm fatigue I was getting. I chalked it up to being out of shape and that my Tallboy LTc just wasn't cut out for park riding. Cut to a few weeks later, I remember something about this air trapping issue and decide to check it out. There was significant resistance to compression even with the air cap removed, so I executed the cable tie bleed technique and released quite a bit of pressure.

    I had thought it curious that I only needed ~72 psi to get desired sag (~25%) out of the Pike even though I'm 220 lbs geared to ride. After bleeding the lowers, I had to up the pressure to 90 psi in order to have a rideable fork! (Much closer to what Rock Shox recommends for my weight.) On the subsequent ride, my fork was back to it's good old self with the excellent small bump compliance and mid-stroke support I remembered. I'm super happy about this.

    So if you own a Pike or took a ride on one and are disappointed, consider that this may be the issue. I was absolutely blown away by the effect it had on the performance of the fork, and I think the air pressure change I had to make speaks for itself. It's a fantastic fork, as long as air trapped in the lowers isn't creating an undesired spring rate that completely alters its behavior.

  116. #116
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    Quote Originally Posted by BMJ View Post
    Heres what my mod looks like. Just waiting for the Avy Damper to put it back together.

    Bad timing to order a custom damper. 3 week back log.
    Any long term review on this hack?

  117. #117
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    Quote Originally Posted by cmarshack View Post
    Any long term review on this hack?
    Subscribing to the thread since I just got a pike and notice this.

    Do we have a definitive reason why this happens? Someone suggest air leaking from the air chamber into the lowers, but I dont think so because that would be the same total amount of air pressure in the fork and would not be stiffer.

    Maybe the air gets sucked in when the fork is working hard or perhaps friction is heating the air up increasing the pressure.

    So is the best solution to always zip tie and check air chamber before every ride?

  118. #118
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    The most likely explanation is air leaking past the seals on the spring side. I rebuilt my air spring and the problem went away. I didn't even touch the seals for the stanchions as a experiment to see if they were the issue. Also important to note is they revised the seal head on both sides.

    If you you think about the idea that air is getting "sucked in" as the fork cycles that would mean that a pressure differential would have to exist in which pressure was greater outside of the fork than inside the fork. That differential is not there. As the fork compresses pressure in the lowers rises and as it extends it goes back down but its not going to create a pressure lower than whats outside the fork.

    I could see the pressure in the lowers being different than outside due to heat, altitude, barometric pressure change but I just can't see how air could get sucked in when there is no pressure differential where pressure is greater outside the fork to make that happen.

  119. #119
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    Any walkthroughs available on how to rebuild or service the air spring?

    The fact that Noah from MRP does this trick makes me think that it isn't a hack, instead that there is some benefit to the zip-tie burp.
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  120. #120
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    I have just installed an Avalanche open bath cartridge in my Pike.
    I also equalized the air pressure (pulling on the fork and fully extending it while the air cap was removed)
    After I was finished and added air, the fork doesn't extend fully. Its about 1/3" in.
    Anything I should try?

  121. #121
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    Quote Originally Posted by jazzanova View Post
    I have just installed an Avalanche open bath cartridge in my Pike.
    I also equalized the air pressure (pulling on the fork and fully extending it while the air cap was removed)
    After I was finished and added air, the fork doesn't extend fully. Its about 1/3" in.
    Anything I should try?
    Hmm, now when I think about it, it might be related to the air piston swap. I installed the piston with the fork compressed, which igjt have created vacuum...

  122. #122
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    I was getting 30% sag with 50 psi in my 150mm solo air with 1 token. Tried the zip tie, didn't hear anything. But,....I now get 30% sag at 65 psi. wtf.

    anyone tested how long it stays well behaved? days?

  123. #123
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    Feedback on Avy Damper?

    Quote Originally Posted by BMJ View Post
    Heres what my mod looks like. Just waiting for the Avy Damper to put it back together.

    Bad timing to order a custom damper. 3 week back log.
    Considering ordering an Avy damper. Thoughts so far?

    Anyone tried the MRP Ramp Control and have a review?

  124. #124
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    Quote Originally Posted by aavallon78 View Post
    Considering ordering an Avy damper. Thoughts so far?

    Anyone tried the MRP Ramp Control and have a review?
    Whenever I ride the Lyrik with Avy cart I'm always amazed/impressed at the support and stability it gives in rough terrain/at speed. Big braking bumps just go away and you laugh as you ride over them or other super chunky terrain because the fork sucks it up and remains so stable, like whatever it was isn't even there. I recommend it for sure. If you get it tuned like I have, it has a lot of damping, compression and rebound, but the faster you go, the smoother it gets and when you aim at a big rock or root complex at speed, it just takes it all in stride. At slower speeds it's not harsh, but it is somewhat firm, good for your compression support and not diving through the travel.
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  125. #125
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    Quote Originally Posted by Jayem View Post
    Whenever I ride the Lyrik with Avy cart I'm always amazed/impressed at the support and stability it gives in rough terrain/at speed. Big braking bumps just go away and you laugh as you ride over them or other super chunky terrain because the fork sucks it up and remains so stable, like whatever it was isn't even there. I recommend it for sure. If you get it tuned like I have, it has a lot of damping, compression and rebound, but the faster you go, the smoother it gets and when you aim at a big rock or root complex at speed, it just takes it all in stride. At slower speeds it's not harsh, but it is somewhat firm, good for your compression support and not diving through the travel.
    Thanks!

  126. #126
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    Was your question answered? I too was confused - I'm thinking that 'topped out' means internal air spring pressure - when I insert a zip tie I push the stanchions in some which I thought would help squeeze air out - it also helps to get the zip tie a little further in past the seals. thanks.

    Quote Originally Posted by challybert View Post
    Quick question for clarification: When we say "topped out", do we mean fork legs fully extended with the fork aired up to a particular riders required pressure before equalizing?

  127. #127
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    (I thought this post was going to appear directly below the post I was asking about but it appears at the end of the thread, so I reposted.)
    Last edited by rshalit; 10-05-2016 at 05:55 AM. Reason: post did not appear where I wanted it

  128. #128
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    (ok well that didn't work, so this is a response to BMJ's 04-21-2015 post #108)

    Hi - I would like to do this to my 2016 Fox 27.5/36/160 RC2 - if you had time, I'd really like to know more details - it looks like you've drilled approximately where the foam oil ring would be on my Fox - I don't know how similar the Pike is, as I've never had one.
    I could probably do this myself, or with a friend at a shop, but I've never actually tapped anything.

    -Is it obvious what size drill bit to use to accommodate the Mition Pro Micro Bleeders, and also the size of the tap to use?
    -Is the location of the drill sites crucial - just somewhere between the bottom of the dust wipe seal and above the foam ring seat?
    -What size and type of drill bit did you use for the Mition Bleeders?
    -Did you use a drill press? I'm not sure I'd trust myself using a handheld drill.

    Have there been any problems at all since you did this a year and a half ago?

    I'm really tired of doing the zip tie thing - sometimes that doesn't work and I have to remove air spring top cap/transfer shaft, and as soon as I pull the shaft out I hear a significant release of air pressure - but that's even more of a pain of course.

    thanks in advance!

  129. #129
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    I haven't done the mod but have drilled and tapped thousands of holes so can answer those questions.

    You need to know the thread size (diameter and pitch) for the bleeders. There will be a corresponding tap for that and a smaller diameter drill bit specifically for that tap size. Given the tap size (diameter and pitch) you can look up the bit size in tables. These bits are generally odd sizes.

    With practice and experience, you could do this by hand. Get an old fork from a bike shop and practice. It wouldn't be perfect but it could be acceptable. Personally, I'd use a drill press or a milling machine with the part fixtured in the machine. These bleeders have an o ring that seals against the surface of leg so I'd first mill a small flat for that o ring to seal against, then use a centering drill, then drill the hole. I also prefer to use the mill or drill press to hold the tap so that it's coaxial with the hole, at least for starting it. You can essentially do a perfect job this way.

    As to where to put it, I'd have to pull the fork apart and decide what's the best spot where there's enough material thickness, nothing will be interfered with, and there's preferably a clear shot to the gap between the stanchion and leg. The best position/orientation might not be radial to the stanchion axis.
    Do the math.

  130. #130
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    many thanks. Might have a machine shop do the milling for o-ring, but I can see myself also asking how much to do the drill and tap, too...

  131. #131
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    If you do have a shop machine the flats, you might as well have them drill and tap the holes because once it's fixtured to do the flats, drilling and tapping the holes will be very quick and easy.
    Do the math.

  132. #132
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    I'm still a little confused on if there is a need to bleed the lowers constantly, I've been testing this over the past couple of weeks, and here is what I've experienced.
    First time doing it (fork is about months old), I didn't hear a hiss when bleeding with air in the fork, emptied it, then heard a big hiss from both sides. Refilled and it was indeed more plush and needed more air for 20% sag.
    Two rides later, same result, but still had 20% sag, and did not notice the for was harsh. (but still get the loud hiss from the lower when venting with no air in the chamber).
    Tried it last night after only one ride (23 miles or so), but forgot to check sag before venting, fork still didn't feel harsh yet.

    Here is a video showing how much vents: https://youtu.be/oUnTx3CqA3k


    I'd like to hear what other have found over time.
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  133. #133
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    Quote Originally Posted by bbqmike View Post
    I'm still a little confused on if there is a need to bleed the lowers constantly, I've been testing this over the past couple of weeks, and here is what I've experienced.
    First time doing it (fork is about months old), I didn't hear a hiss when bleeding with air in the fork, emptied it, then heard a big hiss from both sides. Refilled and it was indeed more plush and needed more air for 20% sag.
    Two rides later, same result, but still had 20% sag, and did not notice the for was harsh. (but still get the loud hiss from the lower when venting with no air in the chamber).
    Tried it last night after only one ride (23 miles or so), but forgot to check sag before venting, fork still didn't feel harsh yet.

    Here is a video showing how much vents: https://youtu.be/oUnTx3CqA3k


    I'd like to hear what other have found over time.
    You really want to stop doing it.

  134. #134
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    Quote Originally Posted by bbqmike View Post
    I'm still a little confused on if there is a need to bleed the lowers constantly, I've been testing this over the past couple of weeks, and here is what I've experienced.
    First time doing it (fork is about months old), I didn't hear a hiss when bleeding with air in the fork, emptied it, then heard a big hiss from both sides. Refilled and it was indeed more plush and needed more air for 20% sag.
    Two rides later, same result, but still had 20% sag, and did not notice the for was harsh. (but still get the loud hiss from the lower when venting with no air in the chamber).
    Tried it last night after only one ride (23 miles or so), but forgot to check sag before venting, fork still didn't feel harsh yet.

    Here is a video showing how much vents: https://youtu.be/oUnTx3CqA3k


    I'd like to hear what other have found over time.
    This is a fairly well documented issue with the Pike and while some forks seem to exhibit the issue consistently, other forks do not. There doesn't seem to be a clear explanation for exactly why it happens though. I have a newer Pike that has never built up excessive pressure inside the lowers.

    I think one thing that confuses the situation is that depending on how you "burp" your fork you will end up with different results like you do in your video. If you burp your fork fully extended you are releasing any excess air pressure that has built up as a result of riding. If you do it with no air in the fork and with the fork compressed you are actually getting somewhat of a false positive.

    When you compress the fork you compress the air that's already inside the lower legs of the fork so you will get a hiss of air when you do it that way even if there hasn't been any excessive buildup. If you left the zip tie in and pulled the fork back to full extension you would likely hear air sucking back into the fork as a slight vaccum is created in the lowers. It seems like some people are burping their Pike at full compression which essentially makes the area in the lowers into a big negative air spring. This will make the fork feel softer in the first part of the travel than it would normally but it's not really the way the fork is intended to work.

    I have experimented with this phenomenon seeing if you can tune the amount of negative pressure in the lowers when I have serviced my fork. I've tried setting the "equilibrium" point at around the 25% sag point just to see how the fork would behave and if it makes any difference. I found that at the pressure I normally run (65psi) doing this made the fork not return all the way to full travel so I stopped.

    So I would recommend burping at full extension, unless you like the extra "negative spring effect". Also, it doesn't matter if you let the air out of the fork or not since the main air spring is completely sealed and unaffected by the "burping" process.

  135. #135
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    Burping when fully extended gives necessery midstroke support, bottom out resist and feelable difference between min and max of LSC.

    I'd not recommend burping without air in fork.

  136. #136
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    Just so I understand the process since I haven't rebuilt the pike yet, if I were to remove the lowers for service, the same thing would happen, is there a proper way to air the fork back up after disassembly, or does it just work itself out after you ride it?
    5010v3 @mikerides.mtb

  137. #137
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    It doesnt. If you want the same performance air lowers up while fully extended. Anyway if you assemble fork back it should get enough air to be in "normal" state. Just do not create underpressure in lowers.

  138. #138
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    Quote Originally Posted by bbqmike View Post
    Just so I understand the process since I haven't rebuilt the pike yet, if I were to remove the lowers for service, the same thing would happen, is there a proper way to air the fork back up after disassembly, or does it just work itself out after you ride it?
    It doesn't have anything to do with the air spring. There's nothing you need to do differently when airing the fork up. It's about how much air ends up trapped inside the lowers. The positive and negative air spring chambers are inside the left stanchion tube and are sealed off from the lowers. Basically if you slide the lowers back on and attach the air spring and damper shaft bolts at full extension you are good.

  139. #139
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    In my description air up means put a zip tie between stanchion and dustseal when fork fully extended.

  140. #140
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    Quote Originally Posted by nikon255 View Post
    In my description air up means put a zip tie between stanchion and dustseal when fork fully extended.
    If you do the service correctly there is no need to do anything with a zip tie. The only time you may need to do that is if extra air is building up in the lowers as a result of riding your bike. You can't get any extra air in the lowers by servicing it.

  141. #141
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    correctly is a big word for some people. It is possible to do underpressure during assebling by mistake. Thats why I said if you want the same performance zip tie it. But in general you are right.

  142. #142
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    rshalit,

    The zip ty must pass 2 seals, the first (outer) is de dust seal and inside there is a 2nd oil seal. Once you get passed both it must deflate every time.

    BMJ,

    Very nice mod! Are those vents or vavles? I would really like the idea of a permanent vent so the lowers can't even build up pressure and the fork stays the same. But ofcourse it isn't a big deal to press the vavles every run.
    Amplify Your ®ide!

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