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  1. #1
    No, that's not phonetic
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    Cool-blue Rhythm From the annals of Homer Bastardized R&D vol. 17: The FrankenFox

    The Problems: Too linear DHX Air; too progressive RP3.

    The Solution: Swap air canisters.

    I am a big fan of both DHX Air shocks and RP3s. The DHX Air requires very high air pressures on higher leverage bikes like the 6-Pack. The RP3 works great and can run lower air pressures but is thought not to be beefy enough for 6-Pack use. I swapped the air cans on my DHX Air and RP3, and took the DHX Air Lite out for a cruise today. First off, I ran it at about 20psi lower pressures than I would have with the standard DHX Air sleeve. I sort of spaced out and grabbed Barny's DHX Air for the conversion and didn't change her stock settings from full-out BO and 100psi BV. I normally turn the BO half way in and run 140psi BV. Despite the shock being way "softer" set up and less progressive (in BO) than I normally run, it exhibited admirable bottom out resistance. I will have more time to experiment over the next bunch of rides.





    Incidentally I am also riding Spot seat stays on the Pack presently. They are about 1/2" shorter in length than the stock Pack stays, so lower the back of the bike by about that much. Lower bb, slacker angles, couch on wheels ride. I dropped the oil volume in my Z1 FR1 by 10cc and bumped the air preload 5psi. Less sag and a somewhat less progressive stroke. Nice.
    My video techniques can be found in this thread.

  2. #2
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    This should be an entertaining thread. I can already hear it, "How come Push worked on Tscheezy's DHX-Air?, Will Darren Push mine too?"
    Oh, the drama.


    Glad to see that it fit.
    I stopped driving my bike into my garage - I'm now protected with Roof Rack Ranger app for my iPhone.

  3. #3
    not so super...
    Reputation: SSINGA's Avatar
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    very interesting and cool TS. Is the RP3 can smaller?
    Nothing to see here.

  4. #4
    No, that's not phonetic
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    Quote Originally Posted by SSINGA
    Is the RP3 can smaller?
    Exactly. That's why it "fixes" the DHX complaints in this case.
    My video techniques can be found in this thread.

  5. #5
    No, that's not phonetic
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    Quote Originally Posted by bikerx40
    Will Darren Push mine too?
    I have a whole sheet of Push stickers. What else do you want Pushed? RST shocks, anyone?
    My video techniques can be found in this thread.

  6. #6
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    Holy Hamsters; just look at all the cool things you can do with a Turner; bery creative. If this creation turns out to fix the problems of the DHX Air you'll be famous. Wait a minute, you're already famous Nice work.
    turtle

  7. #7
    Lay off the Levers
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    Mighty interesting. When you get down to da desert loan that puppy to El Ching and see if he can make it bark.

    The wheels are always turning eh TS?
    Faster is better, even when it's not.

  8. #8
    No, that's not phonetic
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    Quote Originally Posted by Bikezilla
    The wheels are always turning eh TS?
    Akshully I mentioned to someone in another thread that I had ridden an RP3 on a Rocky Mountain Slayer 50 which seemed to have a large volume DHX Air-style can on it (to that bike's detriment, ironically). BikerX40 PMed me and...

    Quote Originally Posted by BikerX40
    I read in some thread that you thought that the larger DHX-A air sleeve may be compatible with the RP3. With people complaining about the DHX-A needing a lot of added air pressure to fight excessive bottoming, wouldn't the smaller RP3 air sleeve possibly help achieve more ramp-up earlier in the shock stroke and allow lower main spring air pressure?
    The rest is wrenching (pun not intended ).
    My video techniques can be found in this thread.

  9. #9
    the 36 year old grom
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    Quote Originally Posted by tscheezy


    The rest is wrenching (pun not intended ).
    maybe I should try a DHX can on my motolite

  10. #10
    MK_
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    Cool. I thought of doing that as an alternative to filling the air sleeve with oil/grease to reduce the volume. I suspected that running the RP3 can would make the air spring too progressive, though. Sounds like it is working out for ya, though. Nice.

    _MK
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  11. #11
    No, that's not phonetic
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    Quote Originally Posted by demo_slug
    maybe I should try a DHX can on my motolite
    Yeah, I put the DHX air sleeve on Barny's 5-Spot's RP3. Hopefully that fixes the situation with that shock on her bike. Despite a Pushing and a lot of sag, she was not getting anywhere near the last inch of travel. She had been getting full travel with the DHX Air and a bit less sag along with a plush ride prior to the pushed RP3. If the DHX Air can doesn't make matters better, I'll put a full DHX Air back on her bike. It's hard to argue with success.
    My video techniques can be found in this thread.

  12. #12
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    There's a thread ayce started on the ventana forum and it looks like a rp3 air can on a dhx air there as well, with dhx air stickers on, but not the dhx air 5.0 stickers mine had, have fox started selling them with smaller air cans??

    DHX Air on X5...

  13. #13
    not so super...
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    Quote Originally Posted by Robbz
    There's a thread ayce started on the ventana forum and it looks like a rp3 air can on a dhx air there as well, with dhx air stickers on, but not the dhx air 5.0 stickers mine had, have fox started selling them with smaller air cans??

    DHX Air on X5...
    I think you're right.



    My DHx-A
    Last edited by SSINGA; 03-15-2006 at 08:46 AM.
    Nothing to see here.

  14. #14
    No, that's not phonetic
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    I don't know why they didn't just make the sleeve an option like the AVA on the old Floats. Seems to make perfect sense from a tuning flexibility standpoint.
    My video techniques can be found in this thread.

  15. #15
    FM
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    Quote Originally Posted by demo_slug
    maybe I should try a DHX can on my motolite
    That could be really cool. Darren at Push confirmed my suspicion that the motolite has a steep rising rate. It feels great with my stock rp3, but I think a more linear feeling shock might perform better on big hits.

  16. #16
    not so super...
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    Quote Originally Posted by FM
    That could be really cool. Darren at Push confirmed my suspicion that the motolite has a steep rising rate. It feels great with my stock rp3, but I think a more linear feeling shock might perform better on big hits.
    Wanna try a "can" swap?
    Nothing to see here.

  17. #17
    FM
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    Quote Originally Posted by SSINGA
    Wanna try a "can" swap?
    yeah that would be cool, but I'd like to wait just a bit. I'm currently on a borrowed Rp3 while mine is getting pushed. So I'd like to see what the pushed one feels like before I swap.

    based on my impressions of both bikes and shocks, I think that would be a win/win for us.

  18. #18
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    Hey Cheese-man...

    ...dumb question, but if the RP3 can is smaller in volume, why do you need less pressure for the same sag? I would have thought that the larger (DHX-A) can would mean lower pressures (high volume-lower pressure). I'm sure I'm missing something here
    Registered Dietitian, Cycling Coach, Ascend Nutrition and Coaching

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  19. #19
    not so super...
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    Quote Originally Posted by FM
    yeah that would be cool, but I'd like to wait just a bit. I'm currently on a borrowed Rp3 while mine is getting pushed. So I'd like to see what the pushed one feels like before I swap.

    based on my impressions of both bikes and shocks, I think that would be a win/win for us.
    Just let me know when/if you want to experiment.
    Nothing to see here.

  20. #20
    FM
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    Quote Originally Posted by tommyrod74
    ...dumb question, but if the RP3 can is smaller in volume, why do you need less pressure for the same sag? I would have thought that the larger (DHX-A) can would mean lower pressures (high volume-lower pressure). I'm sure I'm missing something here
    RP3 = smaller air chamber = less volume = ramps up quicker

    DHX-air= larger air chamber = more volume = more linear spring rate, requires more pressure to prevent bottom-out.

    SSinga, give me about 2 weeks. I will throw in some incentive for you when the time comes!

  21. #21
    No, that's not phonetic
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    Once you start compressing the smaller volume of air (RP3 can), the pressure increases faster than with the larger air reservoir the bigger can (DHX) provides. Note that the piston on the DHX Air does not span inside the entire diameter of the air can, but rather there is a sleeve within a sleeve. The piston pushes on the contents of the inner sleeve, which is allowed to expand into the outer sleeve via a small air exchange port. You could run a lower pressure in the DHX Air if the piston was as wide as the outer sleeve, but it's not. Large diameter pistons and cylinders equals low pressure. Volume (which would seem to come from diameter, but not in this case) is not really applicable here.
    My video techniques can be found in this thread.

  22. #22
    not so super...
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    Quote Originally Posted by FM
    SSinga, give me about 2 weeks. I will throw in some incentive for you when the time comes!
    That works for me since I'll be in south Florida all next week
    Nothing to see here.

  23. #23
    Baked Alaskan
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    the mad scientist strikes again!!!!!

    Quote Originally Posted by tscheezy
    The Problems: Too linear DHX Air; too progressive RP3.

    The Solution: Swap air canisters.
    You just keep topping yourself. I'm surprised the detailed instructions with photos hasn't been posted. Nice job though.

    So this is what happens when you live on an island in Alaska.

    I'm going to crack open my RP3 and DHX for a lube-job when the Spot and RFX traingles are getting PC'd. This should be fun.
    The red couch has moved from Alaska to Florida...

  24. #24
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    Quote Originally Posted by tscheezy
    Yeah, I put the DHX air sleeve on Barny's 5-Spot's RP3. Hopefully that fixes the situation with that shock on her bike. Despite a Pushing and a lot of sag, she was not getting anywhere near the last inch of travel. She had been getting full travel with the DHX Air and a bit less sag along with a plush ride prior to the pushed RP3. If the DHX Air can doesn't make matters better, I'll put a full DHX Air back on her bike. It's hard to argue with success.
    tscheezy, I was having the same problem as Barney, but for different reasons. This higher volume sleeve that came off of a Blur shock fixed my travel problems.

    With the standard RP3 sleeve, I was only seeing 3.75-4" of consistent travel from my Ventana built frame. This while also running excessive sag. Now I'm in the 25-30% range, and am getting full travel from the shock.


  25. #25
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    Chad answered that was how the DHX Air came with the smaller sleeve.

  26. #26
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    Quote Originally Posted by tscheezy
    Yeah, I put the DHX air sleeve on Barny's 5-Spot's RP3. Hopefully that fixes the situation with that shock on her bike. Despite a Pushing and a lot of sag, she was not getting anywhere near the last inch of travel. She had been getting full travel with the DHX Air and a bit less sag along with a plush ride prior to the pushed RP3. If the DHX Air can doesn't make matters better, I'll put a full DHX Air back on her bike. It's hard to argue with success.
    So in general the full DHX Air is good on a 5-spot?

  27. #27
    No, that's not phonetic
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    I dig it, so does Barny.
    My video techniques can be found in this thread.

  28. #28
    Not dead yet, just playin
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    soo 2005

    I thought you did this about a year ago



    spooky...



    op
    www.msmtb.org - Mississippi Mountain Biking

  29. #29
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    ...FYI, I just ordered up an air sleeve (RP3) to try this out & cost is $35 from Fox direct. CS from Fox leaves MUCH to be desired, however


  30. #30
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    ...Tscheezy, have you experienced any harsh topout with the RP3 can? I have been running the RP3 can on the DHX air in 5" rear mode to compare the difference with a lower leverage rate....so far the smaller can seems to exhibit some serious topout. It is at the very end of the stroke & the majority of the return is well damped & controlled...however, if I only compress .5" or so & release, there is an audible topout *clunk*.


  31. #31
    No, that's not phonetic
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    Yes, if I get much lube in the negative chamber. The chamber is tiny and any amount of lube reduces the volume to a nearly useless size.
    My video techniques can be found in this thread.

  32. #32
    MK_
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    No harsh/loud topout for me.

    EDIT: Also, any excess lube in the negative chamber out to get purged out within a few rides due to the design of the Fox seals, so I don't think you can blame reduced air volume of the negative chamber.

    JNC, when I disassembled my DHXair to perform the can swap, I had no pressure in the negative chamber, maybe your shock has the same problem. Without any pressure in the negative, there's not much there to slow down the topout.

    _MK
    Last edited by MK_; 04-24-2006 at 12:06 PM.
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  33. #33
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    Mr. T,

    are those Spot seat stays as beefy as the RFX? They look pretty similar in the photos...is the only diff the shorter lenght?

    JW
    Beer has food value. Food has no beer value.

  34. #34
    No, that's not phonetic
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    Quote Originally Posted by MK_
    Also, any excess lube in the negative chamber out to get purged out within a few rides due to the design of the Fox seals, so I don't think you can blame reduced air volume of the negative chamber.

    JNC, when I disassembled my DHXair to perform the can swap, I had no pressure in the negative chamber, maybe your shock has the same problem. Without any pressure in the negative, there's not much there to slow down the topout.
    If you run your shock "upside down" (shaft up, damper down), then the runny lube (like I use- straight fork oil*) would drain away from the air exchange dimple and would make its way out of the neg chamber. If you run your shock "right side up", runny lube will puddle down on the piston head and get sucked into the dimple when it appears at the piston seal near topout, and lube can fill the neg chamber.

    MK, why do you think air is not getting into your neg chamber?

    *Non-runny lube, like grease, would just get pushed aside and sit there uselessly, and pretty much put you back with the wipe-aside lube Fox seems to use which contributes to stuck-down in the first place.
    My video techniques can be found in this thread.

  35. #35
    MK_
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    Quote Originally Posted by Biker75
    Mr. T,

    are those Spot seat stays as beefy as the RFX? They look pretty similar in the photos...is the only diff the shorter lenght?

    JW
    While I'm not the high priest Mr T., I've owned a RFX briefly and the stays are definatelly beefier.

    _MK
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    -- Einstein, Albert

  36. #36
    No, that's not phonetic
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    Quote Originally Posted by Biker75
    are those Spot seat stays as beefy as the RFX?
    No, the tubing is narrower gauge. The yoke is similar and the dropouts are the same as far as I can tell.
    My video techniques can be found in this thread.

  37. #37
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    Quote Originally Posted by MK_
    JNC, when I disassembled my DHXair to perform the can swap, I had no pressure in the negative chamber, maybe your shock has the same problem. Without any pressure in the negative, there's not much there to slow down the topout.

    _MK
    ...how exactly do you resolve such an issue? It didn't seem to have the same amount of neg. pressure after I installed the RP3 can because the shock didn't really try & stay compressed without any pressure in the pos. chamber. Is air escaping past the wiper/ lip seals as I am pressing the can on? With no adjustment for the neg. pressure, it seems like a crap shoot to get a consistent feeling shock.


  38. #38
    MK_
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    Quote Originally Posted by tscheezy
    If you run your shock "upside down" (shaft up, damper down), then the runny lube (like I use- straight fork oil*) would drain away from the air exchange dimple and would make its way out of the neg chamber. If you run your shock "right side up", runny lube will puddle down on the piston head and get sucked into the dimple when it appears at the piston seal near topout, and lube can fill the neg chamber.

    MK, why do you think air is not getting into your neg chamber?

    *Non-runny lube, like grease, would just get pushed aside and sit there uselessly, and pretty much put you back with the wipe-aside lube Fox seems to use which contributes to stuck-down in the first place.
    Air is getting to my negative chamber now, but when I was replacing the air cans, there was definatelly no air down there. When I was unscrewing the air can, instead of it shooting off like usual, it was stuck in the up position and it took quite a bit of force to get it off, due to the vacuum in the negative chamber. I am not sure why, but that was the case.

    As of stuff purging from the negative chamber; when I rebuilt my air sleeve, I squirted a bit of float fluid in the negative chamber and the shaft of my shock was moist for a few rides until, I am guessing, all that float fluid finally got purged out of there, so now it is dry.

    All this is speculation as there are no windows in the air cannister, but putting a few bits of info together (like the fact that the Fox scraper seals will grab stuff on the inside and dump it out, while not allowing things to enter the shock) makes me arrive at this conclusion.

    _MK
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    -- Einstein, Albert

  39. #39
    MK_
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    Quote Originally Posted by jncarpenter
    ...how exactly do you resolve such an issue? It didn't seem to have the same amount of neg. pressure after I installed the RP3 can because the shock didn't really try & stay compressed without any pressure in the pos. chamber. Is air escaping past the wiper/ lip seals as I am pressing the can on? With no adjustment for the neg. pressure, it seems like a crap shoot to get a consistent feeling shock.
    I think it is a complete crap shoot. I am not a big fan of how Fox is doing their negative chamber pressure, although I must admit, at first I thought the idea was brilliant. If you get those seals moist when you slide the air can on, I think you have a better chance of trapping a good amount of air.

    _MK
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  40. #40
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    Quote Originally Posted by tscheezy
    No, the tubing is narrower gauge. The yoke is similar and the dropouts are the same as far as I can tell.
    ...according to DT, it is the same gauge (material thickness) between models. The RFX does have a bigger diameter/ box section...but the tubing gauge is the same.


  41. #41
    No, that's not phonetic
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    Oops, that's what I meant. RFX = larger diameter (dunno on thickness- go with JNC on that one).
    My video techniques can be found in this thread.

  42. #42
    No, that's not phonetic
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    Quote Originally Posted by MK_
    When I was unscrewing the air can, instead of it shooting off like usual, it was stuck in the up position and it took quite a bit of force to get it off, due to the vacuum in the negative chamber. I am not sure why, but that was the case.
    Gotcha. FWIW, even when my shock is not stuck down, I also experience that suction effect and have to pull my sleeve off. I've never, ever had one shoot off.
    My video techniques can be found in this thread.

  43. #43
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    Quote Originally Posted by tscheezy
    If you run your shock "upside down" (shaft up, damper down), then the runny lube (like I use- straight fork oil*) would drain away from the air exchange dimple and would make its way out of the neg chamber. If you run your shock "right side up", runny lube will puddle down on the piston head and get sucked into the dimple when it appears at the piston seal near topout, and lube can fill the neg chamber.

    MK, why do you think air is not getting into your neg chamber?

    *Non-runny lube, like grease, would just get pushed aside and sit there uselessly, and pretty much put you back with the wipe-aside lube Fox seems to use which contributes to stuck-down in the first place.
    You have made this theory several times and I've corrected you before. I have taken two floats apart several times now with main chambers lubed with shock oil and the negatives were not "filling" with oil. I previously pointed out that the lower main chamber seals are designed "one way" so oil/lube can drain out of it.

    Use shock oil.

  44. #44
    No, that's not phonetic
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    Oh, I must have missed that before. So how does air get in but not oil?
    My video techniques can be found in this thread.

  45. #45
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    Ha, the oil can weep out the wiper, as it has been designed. Good try in "misunderstanding". You have not been able to provide much more than an opinion on a theory that there will be harsh top out due to hydraulic lock, which is not the case and will not happen, as I, as well as others have worked with the method I outlined with success. The lower end seals are designed with notches to bypass oil one way out of the shock.

    Sometimes Tscheezy has to suck it up that he's not the be all know all and sometimes he can be wrong or not have all the information about everything bike related. It's a tough pill to swallow, but you're not right all of the time.

  46. #46
    No, that's not phonetic
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    Quote Originally Posted by Jerk_Chicken
    Good try in "misunderstanding".
    Geeze, good job at copping at attitude. I just asked a simple question. No wonder you are so popular around here.

    So, you are saying the shaft wiper (the one at the lower end of the air can body, that seals the neg chamber from the outside environment) acts as a sump pump?
    My video techniques can be found in this thread.

  47. #47
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    As I said before, you can't take being wrong. Look at the notching on the inner circumference.

    You have just a few toys left to throw out of your sandbox.

  48. #48
    MK_
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    Quote Originally Posted by tscheezy
    Gotcha. FWIW, even when my shock is not stuck down, I also experience that suction effect and have to pull my sleeve off. I've never, ever had one shoot off.
    That is interesting, because each time I have serviced me old RP3, the thing would come off by itself with a pop. And it wasn't stuck down. First time I serviced my DHX air sleeve it poped off as well. The last time I serviced it, I was holding on to the air sleeve with a firm grip, in preparation for the usual pop, but it never came. I thought of it as strange. Then I remembered that my small bump compliance was not the greatest with that shock, out on trail. I previously assumed that it was due to rather high pressures I was running, but it must have been due to the lack of air in the negative.

    Since when you trap air when you slide the sleeve on there, I would assume that you create pressure in the negative chamber at all time while the sleeve is on the shaft. Only when the sleeve is ready to come off is the pressure equalized to atmospheric. Therefore, it would seem, that the sleeve poping off is natural and I accepted it as such. But I could be wrong here. I don't know.

    _MK
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  49. #49
    No, that's not phonetic
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    Quote Originally Posted by Jerk_Chicken
    Look at the notching on the inner circumference.
    It seems to me like we are talking about different things. In my experience, air (and also oil) from inside the main air chamber passes through the pressure equalization dimple into the neg chamber near topout. I think you are saying that that lube subsequently passes back out of the neg chamber past the lower air can seals. Did I get that right?
    My video techniques can be found in this thread.

  50. #50
    No, that's not phonetic
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    Here's a little diagram to show how I am picturing the situation. Feel free to heap your righteous indignation on me.

    The color red depicts an area of higher air pressure, yellow is equal air pressures, and green is lower air pressures.

    In "A", the shock is partially compressed due to weight on the suspension (or whatever). The higher air pressure above the piston (relative to the lower air pressure in the negative chamber below the piston) causes the shock to want to extend.

    In "B", the shock has been allowed to "relax" (extend until the air pressure in the pos and neg chambers equalize) and at this point the piston head straddles the chamber equalization dimple. This allows the chambers to exchange air (and oil). Since the negative chamber has a very small volume, tiny changes in the piston position will cause large changes in neg chamber pressure. A small movement in the piston head will cause air (and oil) to rush in or out of the neg chamber as long as the dimple straddles the piston seal (and this is probably a tiny range of movement). This air exchange is absolutely essential to the operation of the shock, and how the negative spring is automatially set.



    In "C", the shock has now extended beyond a relaxed state and the air trapped in the negative chamber is now compressed, causing the shock to want to shrink a little. This would be the case if you held the rear wheel down and pulled up on the seat. The shock if left to its own devices would shrink until the pressures equalized (this is different than "sag," btw, where an external weight is compressin the shock). A relaxed state, straddling the dimple, is by definition the point where the air exchange can occur.

    A stuck-down shock has the problem of air escaping from the positive to negative chamber NOT via the equalization dimple, but rather at some deeper point in compression. The higher than normal volume of air now trapped in the negative chamber makes it very hard to extend the shock to the normal "resting" state where the chambers would equalize normally.

    Any thoughts?
    Last edited by tscheezy; 04-25-2006 at 02:06 PM.
    My video techniques can be found in this thread.

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