Fox 34 Rhythm - grease in air chamber- Mtbr.com
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  1. #1
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    Fox 34 Rhythm - grease in air chamber

    3 month old 2018 YT Jeffsy, stock fork.

    So I was curious about whether or not I had any volume spacers...and it doesn't. Questions as follows...

    1. there is quite a bit of grease all gooped in the bottom of the air chamber. Is this normal? Seems like I read something about that perhaps blocking air to the negative circuit or something?

    2. With the bike on the stand, front wheel off the ground, when I released the air pressure from the air chamber, the fork actually sucked up and reduced it's travel, just by releasing the air?? Seems it should have just fallen completely slack. Is this related to question 1? Like you can't pull the fork down by hand with the air cap completely off...it will just suck back up.

  2. #2
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    That's absolutely normal for any fork to suck into it's travel when you let all the air out. As to the grease, far as I know the new air springs use grease instead of oil, or at least when I did the upgrade to my friends F34 from 2015 and installed the new air shaft that's what the Fox install instructions called for.
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  3. #3
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    Quote Originally Posted by LyNx View Post
    That's absolutely normal for any fork to suck into it's travel when you let all the air out. As to the grease, far as I know the new air springs use grease instead of oil, or at least when I did the upgrade to my friends F34 from 2015 and installed the new air shaft that's what the Fox install instructions called for.
    So what's making it "suck" in? Again, it seems like it should go completely slack.

  4. #4
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    Quote Originally Posted by escrowdog View Post
    So what's making it "suck" in? Again, it seems like it should go completely slack.
    Edit: Lynx explained it better than I did.

  5. #5
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    Basically the negative chamber equalizes from the positive when you fill it, but when you release the air from the positive, the negative stays charge, so it has greater pressure than the positive side, which thereby contracts into itself from the vacuum created and neg pressure, or there abouts

    Quote Originally Posted by escrowdog View Post
    So what's making it "suck" in? Again, it seems like it should go completely slack.
    Quote Originally Posted by Harold
    You're doing mtbr wrong, you're supposed to get increasingly offended by the implications that you're doing ANYTHING wrong.

  6. #6
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    I guess what's perplexing is watching the service videos, NO other forks exhibit this. They just fall totally slack. I'm just trying to understand why it's not "equalizing" back OUT. :-)

  7. #7
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    Quote Originally Posted by escrowdog View Post
    I guess what's perplexing is watching the service videos, NO other forks exhibit this. They just fall totally slack. I'm just trying to understand why it's not "equalizing" back OUT. :-)
    If you want to slide the lowers off easily keep the air valve depressed. Allowing air to enter releases the vacuum.

    From my understanding (which could be wrong), when you release some pressure the fork slides up and the air piston seal no longer sits in the bypass port, so it creates a vacuum and can't equalize the pressure.

    https://www.youtube.com/watch?v=03pdywBkuNQ

  8. #8
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    Quote Originally Posted by GoldFly View Post
    If you want to slide the lowers off easily keep the air valve depressed. Allowing air to enter releases the vacuum.

    From my understanding (which could be wrong), when you release some pressure the fork slides up and the air piston seal no longer sits in the bypass port, so it creates a vacuum and can't equalize the pressure.

    https://www.youtube.com/watch?v=03pdywBkuNQ
    Awesome vid! Literally worth a 1000 words!

    So that's what has me stumped, the top cap is off but there is a LOT of pressure in the negative chamber effectively compressing the fork.

    So I guess letting air out of the schrader slowly and perhaps pulling up on the forks to full extension would keep the negative air chamber more equalized at that "bypass" at the top of the stroke?

  9. #9
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    My 2018 pike sucked all the way down to almost zero travel at the end of my ride today. It was a pain to fix. Zip ties, cracked the lower bolts, pump to 170, stand on bars and pull like heck several times till I could get her back to full extension. Pop sound and magically they extended on there own to full travel.
    I have 42 hours of clean riding according to my gps. I just ordered everything for a lower service, guess Iíll check for excessive grease.
    I thought they had this sorted out. I wondered why I had some pedal strikes, lol.
    99 SJ Pro FSR XC
    15 SJFSR Comp EVO 650b
    18 YT Jeffsy 27 CF

    Former United States Marine.
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  10. #10
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    Quote Originally Posted by RyeThomas View Post
    My 2018 pike sucked all the way down to almost zero travel at the end of my ride today. It was a pain to fix. Zip ties, cracked the lower bolts, pump to 170, stand on bars and pull like heck several times till I could get her back to full extension. Pop sound and magically they extended on there own to full travel.
    I have 42 hours of clean riding according to my gps. I just ordered everything for a lower service, guess Iíll check for excessive grease.
    I thought they had this sorted out. I wondered why I had some pedal strikes, lol.
    Sounds like somehow you lost negative chamber pressure and didn't balance out...which has to happen at full extension. I doubt it has anything to do with the grease. More likely a seal.

    FYI...I moved on to an MRP Ribbon coil fork. It's nirvana and no air to mess with.

  11. #11
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    Thanks for the response, I had read grease can block the chamber. Iíll service it and check things out. Ugh, if itís a seal itís going back for warranty. Problem with that is what seems normal is itís gone for a few weeks. No Bueno during riding season.

    Iím not ready to drop that kind of coin on a fork when this one is new, that said that looks like a really good fix! Lol.
    99 SJ Pro FSR XC
    15 SJFSR Comp EVO 650b
    18 YT Jeffsy 27 CF

    Former United States Marine.
    ďBoredom is self inflictedĒ

  12. #12
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    Quote Originally Posted by RyeThomas View Post
    Thanks for the response, I had read grease can block the chamber. Iíll service it and check things out. Ugh, if itís a seal itís going back for warranty. Problem with that is what seems normal is itís gone for a few weeks. No Bueno during riding season.

    Iím not ready to drop that kind of coin on a fork when this one is new, that said that looks like a really good fix! Lol.
    I scored my Ribbon coil used. I just watch for stuff used I'd like to have and wait it out.

    Ya, grease could maybe block the port, but that's a LOT of pressure for a blob of grease to hold back. Air forks are weird. I'm used to dirt bike suspension, so the coil was a natural move for me. All the suspension take some fiddling and desire to tune to make it better, if not great. Some riders have NO desire to mess with it and I get that too. But man there is some great stuff out there if you're willing to experiment.

  13. #13
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    Quote Originally Posted by escrowdog View Post
    I scored my Ribbon coil used. I just watch for stuff used I'd like to have and wait it out.

    Ya, grease could maybe block the port, but that's a LOT of pressure for a blob of grease to hold back. Air forks are weird. I'm used to dirt bike suspension, so the coil was a natural move for me. All the suspension take some fiddling and desire to tune to make it better, if not great. Some riders have NO desire to mess with it and I get that too. But man there is some great stuff out there if you're willing to experiment.
    Thatís a very valid point on the pressure, might be more too it. Well itís holding now, if it happens again itís going in for service. At that point I will be forced to pick up a new/used one from someone on one of these sites and get it shipped to me. That way I donít have a lot of down time and I can try out something else....mwahhhhhh.
    Thanks for the thoughts, Rye.
    99 SJ Pro FSR XC
    15 SJFSR Comp EVO 650b
    18 YT Jeffsy 27 CF

    Former United States Marine.
    ďBoredom is self inflictedĒ

  14. #14
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    Rode a 6 miles today, fork was spot on. I bet I had signs of negative pressure but Iím a big dumb animal and tend to not pay attention. Iíll keep a much better eye on my sag indicator percentage marks, o-ring, etc.
    Odd the 2018 fork had the Debonair upgrade on it and wasnít supposed to be an issue, from what Iíve read....Iím no expert.
    99 SJ Pro FSR XC
    15 SJFSR Comp EVO 650b
    18 YT Jeffsy 27 CF

    Former United States Marine.
    ďBoredom is self inflictedĒ

  15. #15
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    Quote Originally Posted by RyeThomas View Post
    Rode a 6 miles today, fork was spot on. I bet I had signs of negative pressure but Iím a big dumb animal and tend to not pay attention. Iíll keep a much better eye on my sag indicator percentage marks, o-ring, etc.
    Odd the 2018 fork had the Debonair upgrade on it and wasnít supposed to be an issue, from what Iíve read....Iím no expert.
    I think what got me messing with my suspension was arm fatigue. I just felt like with a modern full sus bike I shouldn't be getting pounded by the front end with 150mm of travel! It's hard to take the time, but definitely do some test runs back to back over the same section, adding faster rebound by 2 or 3 clicks or more so you can see how it responds. I started out with recommended settings for rebound and it's fine on slower rocks/roots but certainly a LOT better with faster rebound once I was going faster. Just tracks and corners better.

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