Page 1 of 2 1 2 LastLast
Results 1 to 25 of 34
  1. #1
    g3h6o3
    Reputation: PissedOffCil's Avatar
    Join Date
    Oct 2007
    Posts
    3,708

    RS Reba Team Dual Air : The dreaded positive oil leak!

    Hello, this thread is the pursuit of a leak I'm experiencing with my 08 RockShox Reba and that has been going on for over a year. The process has started in the o-ring thread but given the o-ring sizes can be safely ruled out, I thought of starting a new thread.

    The problem is that I lose all oil from the positive chamber during a ride of more or less an hour. It leaks to the negative chamber and if I keep on riding the fork when it lost all it's oil, I pressures in both chambers will equalize.

    So, up to now, the fork has received a new CSU since there seemed to have some minor scratches inside the stanchion. Since this didn't help, a brand new dual air piston assembly was installed without curing the problem. There is not much left to investigate but I'm also close to giving up so if you have any idea of what I could try then let me know!

    Thanks
    Check out my SportTracks plugins for some training aid software.

  2. #2
    g3h6o3
    Reputation: PissedOffCil's Avatar
    Join Date
    Oct 2007
    Posts
    3,708
    Since there aren't many place the oil can leak from, I just worked on one of them. I removed the valve stem with a 9mm socket and replaced the o-ring at it's base with a 4mm x 2mm (close enough to the original).

    I might go for a 2nd ride today to test this...
    Check out my SportTracks plugins for some training aid software.

  3. #3
    nocturnal oblivion
    Reputation: stumblemumble's Avatar
    Join Date
    Mar 2006
    Posts
    2,309
    It's not the top cap if its leaking to the neg. Try thicker oil on top the positive piston. Could be caused be those scratches of course, which you could test by seeing if it leaks to the neg. just while sitting with the positive at 100psi and the negative empty. If it doesn't leak then, it's the scratches.
    "...like sex with the trail." - Boe

  4. #4
    mtbr member
    Reputation: dh_swing's Avatar
    Join Date
    Sep 2006
    Posts
    45
    Same problem on an '09... No air loss, but oil always moved to the negative chamber as evidenced by it squirting out whenever checking the neg air pressure.

    Recently bought an '11 RLT for another bike, and when taking out the 20mm spacer, low and behold, there was NO oil in the air spring chamber at all. Just a blob of grease on the top of the positive piston, with all seals well greased. Referring to the the Reba 2011 Tech Manual, page 7, turns out they no longer spec oil for the air piston -- grease only.

    I guess that solved a nagging problem for them . I then disassembled my '09 fork, and set it up the same way. Problem solved.

  5. #5
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    7,688
    What weight oil are you using?

  6. #6
    g3h6o3
    Reputation: PissedOffCil's Avatar
    Join Date
    Oct 2007
    Posts
    3,708
    Quote Originally Posted by stumblemumble View Post
    It's not the top cap if its leaking to the neg. Try thicker oil on top the positive piston. Could be caused be those scratches of course, which you could test by seeing if it leaks to the neg. just while sitting with the positive at 100psi and the negative empty. If it doesn't leak then, it's the scratches.
    There are no scratches, I replaced the whole CSU.
    I did try 80W gear oil without success.
    I can only assume it's leaking in the neg. Ther doesn'T seem to be a leak in the Shrader valve and when I disassemble the fork there is always oil in the neg. With that said, there is always oil everywhere when disassembling a fork so it could be an false impression.

    Quote Originally Posted by bad mechanic View Post
    What weight oil are you using?
    Spectro 15W in the + chamber.
    Check out my SportTracks plugins for some training aid software.

  7. #7
    g3h6o3
    Reputation: PissedOffCil's Avatar
    Join Date
    Oct 2007
    Posts
    3,708
    I rode the fork tonight but it wasn't a big or intense ride as it was the 2nd of the (12:15 to 1:30 & 5:15 to 6:15) day and I wasn't too energetic. I did push it hard at times but it wasn't as harsh as usual. To top it off, my rear brake had a layer of dirt "cooked" on the pads so they didn't brake well and it wasn't helping my confidence.

    I will try to give it another go tomorrow.
    Check out my SportTracks plugins for some training aid software.

  8. #8
    g3h6o3
    Reputation: PissedOffCil's Avatar
    Join Date
    Oct 2007
    Posts
    3,708
    Quote Originally Posted by dh_swing View Post
    Same problem on an '09... No air loss, but oil always moved to the negative chamber as evidenced by it squirting out whenever checking the neg air pressure.

    Recently bought an '11 RLT for another bike, and when taking out the 20mm spacer, low and behold, there was NO oil in the air spring chamber at all. Just a blob of grease on the top of the positive piston, with all seals well greased. Referring to the the Reba 2011 Tech Manual, page 7, turns out they no longer spec oil for the air piston -- grease only.

    I guess that solved a nagging problem for them . I then disassembled my '09 fork, and set it up the same way. Problem solved.
    Interesting...
    Check out my SportTracks plugins for some training aid software.

  9. #9
    nocturnal oblivion
    Reputation: stumblemumble's Avatar
    Join Date
    Mar 2006
    Posts
    2,309
    Quote Originally Posted by PissedOffCil View Post
    I can only assume it's leaking in the neg. Ther doesn'T seem to be a leak in the Shrader valve and when I disassemble the fork there is always oil in the neg. With that said, there is always oil everywhere when disassembling a fork so it could be an false impression.
    Again for effect:
    An example if you run 100psi positive and 70psi negative and both chambers end up at 80psi, then it's the positive piston o-ring.
    The positive piston is a one piece white dome cap with an o-ring around the edge, there's nowhere else the air could get down to the negative chamber from.
    If the above is happening it's not the schrader or top cap.
    Like I mentioned, try putting 120psi or so in the positive and put no pressure in the negative. After a day of sitting if the negative has pressure when you thumbnail the negative schrader, you know it's the positive piston o-ring. If the negative doesn't have pressure, but the positive lost pressure, it'd be the top cap assembly (which you'd probably see oil seeping/bubbling from).
    There's only two culprits, the positive piston o-ring or the top cap o-ring or schrader.

    If you do the above experiment and no air is lost from the positive, your fork is either fine or it only loses positive air to the negative when the fork is cycled. The latter would indicate an inner stanchion scratch causing air to pass the o-ring when the piston passes over it, which seeing how you replaced the stanchions shouldn't be the issue.
    Good luck!
    "...like sex with the trail." - Boe

  10. #10
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    6,901
    I wasn't impressed by the durability of my Rockshox Pike's Dual AIr. I went to a Dual Air U-turn in my 2010 Reba - no air loss issues but I had a nasty top out clunk. RS waranted the assembly but I have not had a chance to install. The U-turn Dual Air is an enclosed cartridge isolated from the stanchions.

  11. #11
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    7,688
    The problem is grease simply isn't the best lubricant to use there. Oil stays on top of the o-ring, while the grease will eventually be pushed away. The problem is Rock Shox is trying to use one o-ring to seal two chambers. It's cheaper, lighter, with less stiction, but it doesn't doesn't work all the well unless you have a tight fit. What Rock Shox really needs to do is go to either a quad-ring, or go with two separate (hopefully lip) seals. While I like what they're doing, RS makes are seriously head scratching engineering decisions.

    Try and heavy weight synthetic gear oil in the air chamber instead of the 15w. The gear oil will lubricate just as well, but the higher viscosity should help keep it from leaking past the o-ring.

  12. #12
    g3h6o3
    Reputation: PissedOffCil's Avatar
    Join Date
    Oct 2007
    Posts
    3,708
    Quote Originally Posted by bad mechanic View Post
    Try and heavy weight synthetic gear oil in the air chamber instead of the 15w. The gear oil will lubricate just as well, but the higher viscosity should help keep it from leaking past the o-ring.
    As mentionned 80W gear oil did not help.
    Check out my SportTracks plugins for some training aid software.

  13. #13
    g3h6o3
    Reputation: PissedOffCil's Avatar
    Join Date
    Oct 2007
    Posts
    3,708
    Quote Originally Posted by stumblemumble View Post
    Again for effect:
    An example if you run 100psi positive and 70psi negative and both chambers end up at 80psi, then it's the positive piston o-ring.
    The positive piston is a one piece white dome cap with an o-ring around the edge, there's nowhere else the air could get down to the negative chamber from.
    If the above is happening it's not the schrader or top cap.
    Like I mentioned, try putting 120psi or so in the positive and put no pressure in the negative. After a day of sitting if the negative has pressure when you thumbnail the negative schrader, you know it's the positive piston o-ring. If the negative doesn't have pressure, but the positive lost pressure, it'd be the top cap assembly (which you'd probably see oil seeping/bubbling from).
    There's only two culprits, the positive piston o-ring or the top cap o-ring or schrader.

    If you do the above experiment and no air is lost from the positive, your fork is either fine or it only loses positive air to the negative when the fork is cycled. The latter would indicate an inner stanchion scratch causing air to pass the o-ring when the piston passes over it, which seeing how you replaced the stanchions shouldn't be the issue.
    Good luck!
    I disassembled the fork about 40-50 times while investigating this issue and fully understand how it works. I could do your overnight test with air but I can tell you oil is only lost when riding. I believe it's the same for air as I did store the bike after riding only to realize days later that I had no oil in the pos. chamber yet the pressures had remained where I left them.

    So as mentioned, I could do the test specifically but I doubt air leaks when stored and I believe it only leaks on hard impacts after all oil has spilled out. In fact, it's not uncommon to hear a hissing sound on a hard impact.
    Check out my SportTracks plugins for some training aid software.

  14. #14
    mtbr member
    Reputation: shapirus's Avatar
    Join Date
    Jun 2009
    Posts
    488
    I have successfully solved the same issue with my Dual Air fork by using some very thin grease instead of oil. Ended up mixing about 4 parts of Fox Float fluid with 2 parts of Slickoleum (aka Slick Honey). The resulting mixture is very thin, yet does not drip.

    Using the Fox Float fluid alone didn't work well: even though it is very viscous, it would still leak to the negative chamber eventually.

    It is possible that the Slickoleum alone would work fine too (it's fairly thin anyway), but I didn't try that and went with a mixture right away.

  15. #15
    g3h6o3
    Reputation: PissedOffCil's Avatar
    Join Date
    Oct 2007
    Posts
    3,708
    I could try mixing PrepM with the Spectro oil.

    However, if it doesn't drip, it means that it sticks to the stanchions and at one point there might be no grease left to seal the o-ring, no?
    Check out my SportTracks plugins for some training aid software.

  16. #16
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    7,688
    Quote Originally Posted by shapirus View Post
    I have successfully solved the same issue with my Dual Air fork by using some very thin grease instead of oil. Ended up mixing about 4 parts of Fox Float fluid with 2 parts of Slickoleum (aka Slick Honey). The resulting mixture is very thin, yet does not drip.

    Using the Fox Float fluid alone didn't work well: even though it is very viscous, it would still leak to the negative chamber eventually.

    It is possible that the Slickoleum alone would work fine too (it's fairly thin anyway), but I didn't try that and went with a mixture right away.
    I like your solution.

  17. #17
    mtbr member
    Reputation: shapirus's Avatar
    Join Date
    Jun 2009
    Posts
    488
    Quote Originally Posted by PissedOffCil View Post
    However, if it doesn't drip, it means that it sticks to the stanchions and at one point there might be no grease left to seal the o-ring, no?
    This sounds reasonable, however, I've had absolutely no issues for the 80 hours of riding since the last fork service. It is smooth and doesn't lose air. And it is time to service it again anyway, so the piston will get re-lubed.

    Also, check the service manuals for the 2011+ RS forks: they tell to use grease rather than oil to lubricate the air piston now. So I guess it shouldn't cause any troubles.

  18. #18
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    7,688
    Even if it doesn't drip, it can still flow, which is what you're looking for. You want something which is just thin enough to flow back down the wall of the stanchion.

  19. #19
    g3h6o3
    Reputation: PissedOffCil's Avatar
    Join Date
    Oct 2007
    Posts
    3,708
    It's worth the try.
    Check out my SportTracks plugins for some training aid software.

  20. #20
    mtbr member
    Reputation:
    Join Date
    Jun 2009
    Posts
    229
    EDIT...

    didn't read the thread, wrote completely wrong stuff. My bad.

  21. #21
    mtbr member
    Reputation:
    Join Date
    Aug 2009
    Posts
    27
    Quote Originally Posted by PissedOffCil View Post
    As mentionned 80W gear oil did not help.
    80W gear oil is not all that heavy. For instance Castrol VMX80 has a viscosity of 59.2 cSt at 40 degC, which is equivalent to some 15WT fork oils.

  22. #22
    mtbr member
    Reputation:
    Join Date
    Sep 2011
    Posts
    3
    Just found out I have the same problem. Although its just air and not oil thats leaking from positive to negative. Should I grease the o-ring myself, drop some oil in the pos side, or take it to a LBS for warranted service? It was a mail order Sette Razzo, so the LBS would probably charge for labor which I assume isn't included by the RS warranty.

  23. #23
    meow, meow.
    Reputation: J. Random Psycho's Avatar
    Join Date
    Apr 2008
    Posts
    3,063
    Quote Originally Posted by shapirus View Post
    I have successfully solved the same issue with my Dual Air fork by using some very thin grease instead of oil. Ended up mixing about 4 parts of Fox Float fluid with 2 parts of Slickoleum (aka Slick Honey). The resulting mixture is very thin, yet does not drip.

    Using the Fox Float fluid alone didn't work well: even though it is very viscous, it would still leak to the negative chamber eventually.

    It is possible that the Slickoleum alone would work fine too (it's fairly thin anyway), but I didn't try that and went with a mixture right away.
    Have you ever tried to use Rock N Roll Super Slick grease for that?

    I'm currently in the Float Fluid / full synthetic viscous oil camp, but that stuff doesn't last long in too many (RS and Manitou) forks that I encounter, so I'm trying to find out which o-ring grease is better.
    26" faithful.

  24. #24
    ballbuster
    Reputation: pimpbot's Avatar
    Join Date
    Dec 2003
    Posts
    12,627
    If all else fails, you can convert it to coil spring. If the inner tubes are scored, no seal in the world is is going to seal it.

    I basically got a used Reba SL 29er fork for super mega cheap (as in, cheaper than the shipping to get it to my house) on the knowledge that it probably needed a full rebuild... and even that might not bring it back. Well, new seals, and it still leaked down.

    So, I converted it to coil using a Pike U-Turn coil for $45. Add another $25 if you actually care about having a U-Turn knob on the top.

    The fork is now pretty heavy, but man, it feels pretty amazing.

    Now, the damper leaks out the top a bit. It's not show stopping. It's just some seepage, but I don't wanna spend real money on fixing it.

  25. #25
    meow, meow.
    Reputation: J. Random Psycho's Avatar
    Join Date
    Apr 2008
    Posts
    3,063
    Quote Originally Posted by pimpbot View Post
    Now, the damper leaks out the top a bit. It's not show stopping. It's just some seepage, but I don't wanna spend real money on fixing it.
    FWIW, some RS MC dampers have such leak from new.
    26" faithful.

Page 1 of 2 1 2 LastLast

Similar Threads

  1. 05 Reba Team -ve Chamber Leak
    By navioh in forum Shocks and Suspension
    Replies: 0
    Last Post: 07-04-2009, 06:30 PM
  2. New Reba Team 29er oil leak
    By pushinpixels in forum SRAM
    Replies: 2
    Last Post: 06-27-2009, 08:04 PM
  3. Oil leak on my Reba Team
    By bozack in forum Shocks and Suspension
    Replies: 6
    Last Post: 10-16-2008, 09:38 PM
  4. Aaarrrgh-the dreaded Reba clearance issue
    By Fett in forum 29er Bikes
    Replies: 13
    Last Post: 11-30-2006, 01:08 PM
  5. Reba Team positive air
    By metacycle in forum SRAM
    Replies: 4
    Last Post: 01-17-2006, 06:05 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •