Leaking FOX DHX-AIR???- Mtbr.com
Results 1 to 14 of 14
  1. #1
    mtbr member
    Reputation: BlueRidgeRider's Avatar
    Join Date
    Dec 2004
    Posts
    148

    Leaking FOX DHX-AIR???

    I purchased a Fox DHX-Air shock for my 04 Kona Coiler approximately a month ago and have been on several big mountain rides including some very technical downhill’s to test it out. I noticed that the shock is leaking a lot of oil from the area around the rebound adjuster valve. I currently have 210 PSI in the main chamber, 125 PSI in the reservoir, bottom out adjuster set to max and the Pro Pedal adjuster maxed out. The biggest drop so far was about three feet to flat with no problems. Climbing is a chore because the shock is still extremely active while pedaling even with the current settings. I only weigh about 200 pounds with all my gear on. I think something's wrong with the shock but I wanted to get some other opinions before I send it back to Fox.
    Thanks
    Attached Images Attached Images

  2. #2

    Reputation:
    Join Date
    Jun 2005
    Posts
    710
    Quote Originally Posted by BlueRidgeRider
    I purchased a Fox DHX-Air shock for my 04 Kona Coiler approximately a month ago and have been on several big mountain rides including some very technical downhill’s to test it out. I noticed that the shock is leaking a lot of oil from the area around the rebound adjuster valve. I currently have 210 PSI in the main chamber, 125 PSI in the reservoir, bottom out adjuster set to max and the Pro Pedal adjuster maxed out. The biggest drop so far was about three feet to flat with no problems. Climbing is a chore because the shock is still extremely active while pedaling even with the current settings. I only weigh about 200 pounds with all my gear on. I think something's wrong with the shock but I wanted to get some other opinions before I send it back to Fox.
    Thanks
    First of all don't tell Fox you put 210psi in there. Isn't 200 the Max?

    I would take a guess and say you blew your shock, which is obvious by the oil leaking.

    I would get it fixed and either keep riding it (feeling lucky?) or sell it and buy a used DHX coil for less. The coil ones have been pretty reliable.

    With the propedal turned all the way up, you should be feeling a change. Not locked out feeling, but considerable less bobbing. Seems your damper could be shot, or not working right due to the oil leaking.

  3. #3
    3 "fiddy" for short
    Reputation: be350ka's Avatar
    Join Date
    Dec 2004
    Posts
    2,739
    200 is the max value for the boost valve. The main chamber on the other hand.... Not sure what the max value is but have heard of others with 300 PSI.

  4. #4

    Reputation:
    Join Date
    Jun 2005
    Posts
    710
    Quote Originally Posted by be350ka
    200 is the max value for the boost valve. The main chamber on the other hand.... Not sure what the max value is but have heard of others with 300 PSI.
    Yes you are correct. Manual says 300psi MAX.

  5. #5
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059
    If that oil around your rebound knob has been coming out on a fairly consistent basis, then there is a problem. Even if it's just a little bit, and you've been wiping it off, but it continues to seep there...there's a problem. Your comment on the very active mid-stroke plushness appears to be norm from most reports on the site here. Your boost chamber pressure sounds a little low and your Propedal sounds high. Mk on this suspension forum outlined some very good tuning info for this shock in some recent posts. I think Mk, Renegade, and some others have had theirs for some time and have sorted out some issues with this shock. I have one on a Bullit and found their info to be pretty spot on. Look down for some various posts on this shock and some that mention air shocks in general. There's some good design description also which may help in understanding why you're making the changes you need and do. Your oil problem there, however, sounds like more than a tuning issue. Sometimes it's not unusual to have some oil in odd places on a newly shipped shock or fork, but if you've wiped it down and the bleeding continues, it needs to go back for service. I had to send mine back for a stuck down condition after two days of use. It happens.

  6. #6
    mtbr member
    Reputation: BlueRidgeRider's Avatar
    Join Date
    Dec 2004
    Posts
    148
    Thanks for the info, I've been wiping the oil off since I noticed it. I think I may send it back after one or two more rides. I want to increase the boost valve pressure a bit first. This is the first problem I've had with a Fox product, I currently have a DHX-A on my son's Coiler, a 2002 Float RLC; that's never been serviced, a DHX-C no Pro Pedal on a RM7 and several other rear Fox rear shocks including a Fox Float R 130mm front fork...not one single issue with any of their products I've tried. I figure I just got a bad one this time.

  7. #7
    MK_
    MK_ is offline
    carpe maana
    Reputation: MK_'s Avatar
    Join Date
    Nov 2004
    Posts
    7,278
    If you're losing oil out of the rebound, you're also losing oil out of the damper. It makes your shock more active and there's less control of it's motion. It definatelly needs to be sent back. When you start leaking oil, you're also introducing air into the damper, and that's not good. As of the setup, I've noticed that there is a small window of the boost valve pressures for a given main spring pressure. I have 165psi in main chamber and 140psi in boost valve. My BV volume is about half way turned in and my propedal knob is all the way at 0. ProPedal is essentially a coil assist to the air spring pressure in the BV. The problem is that if you have the coil assisting the air pressure, you make the shock less compliant on the small bumps. If you only control it by air pressure, you have a smoother stroke. Volume of the BV controls the bottom out and helps a bit with mid stroke, but at the tail end of it, only. Main thing is to adjust for sag with the main spring, keeping the BV pressure within a certain % below the main spring pressure. I don't know what that percentage is, I would say about 20% off the top of my head, but that's purely on what works for my weight (~170lb) on my frame (Turner 5 Spot which has a ~2.5 ratio of shock stroke to total travel).

    _MK

    "The things you get fired for when youre young are the same things you get Lifetime Achievements for when youre old."

  8. #8
    mtbr member
    Reputation: stoked's Avatar
    Join Date
    Mar 2004
    Posts
    428
    I have somewhat of a different problem w/ DHX A on my spot. When I was riding up until Friday w/ 120 in BV and 120psi in main with 1/3 sag the shock was great. Does cold air do a number on this shock because now in 30-40 degrees temps I have the main set up at 200 and sag is almost 1/2. I have 2 assumptions at this point , 1st being that shock was in break-in period and now I have to use very high psi or 2nd it is busted and have to send it back soon and performance will go downhill from here on. I weigh 180 with gear.

    MK_ , how do you setup psi? dou you pump BV to 140 psi and remove the pump and ride or do you compensate for the fact that shock loses 30-40 psi when you remove the pump and reattach. When I pump 140 remove/reattach psi is at 110 in BV. when I do 180psi and remove/reattach it is at 140. I have been using sag on my other shocks but DHX is a bit more complex.

  9. #9
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059

    That's interesting.

    Quote Originally Posted by stoked
    I have somewhat of a different problem w/ DHX A on my spot. When I was riding up until Friday w/ 120 in BV and 120psi in main with 1/3 sag the shock was great. Does cold air do a number on this shock because now in 30-40 degrees temps I have the main set up at 200 and sag is almost 1/2. I have 2 assumptions at this point , 1st being that shock was in break-in period and now I have to use very high psi or 2nd it is busted and have to send it back soon and performance will go downhill from here on. I weigh 180 with gear.

    MK_ , how do you setup psi? dou you pump BV to 140 psi and remove the pump and ride or do you compensate for the fact that shock loses 30-40 psi when you remove the pump and reattach. When I pump 140 remove/reattach psi is at 110 in BV. when I do 180psi and remove/reattach it is at 140. I have been using sag on my other shocks but DHX is a bit more complex.
    Interesting because you're not the first to have a problem with a fairly new DHX A during a cold snap. Now obviously this could just be coincidence as most of us are getting cooler/colder weather this time of year. However, mine did just about the same thing on a Bullit during the second day's ride. The first day was about 70, but the second day started out at 40 when the shock failed. It didn't go completely into a 100% stuck down condition, but it was at least halfway stuck down regardless of the pressure I put into the main air chamber. Air from the main chamber migrated to the negative chamber for some reason, and no matter what things I tried, the air remained in the negative chamber. It had to go back to Fox.

    You really don't lose any appreciable air from your main chamber or boost chamber when disconnecting the pump if you're doing it properly and your pump valve is in good shape. You shouldn't be having to estimate how much air you believe you're losing.

  10. #10
    mtbr member
    Reputation: stoked's Avatar
    Join Date
    Mar 2004
    Posts
    428
    Quote Originally Posted by TNC
    You really don't lose any appreciable air from your main chamber or boost chamber when disconnecting the pump if you're doing it properly and your pump valve is in good shape. You shouldn't be having to estimate how much air you believe you're losing.
    You're right. Main chamber is fine but secondary loses 30-40 psi after pump removal. I tested it few times. I am going to call FOX today for this cold air hick-up.




    Does anyone know if this shock supposed to be run at high psi? Owner's manual does not have recommendations besides using sag.

  11. #11
    MK_
    MK_ is offline
    carpe maana
    Reputation: MK_'s Avatar
    Join Date
    Nov 2004
    Posts
    7,278
    Quote Originally Posted by stoked
    You're right. Main chamber is fine but secondary loses 30-40 psi after pump removal. I tested it few times. I am going to call FOX today for this cold air hick-up.

    Does anyone know if this shock supposed to be run at high psi? Owner's manual does not have recommendations besides using sag.
    You have your psi measurements a bit confused. You don't lose any air when you detach the hose. What you hear is air escaping from the hose, not from the shock. When you reattach the pump, air from the chamber escapes into the hose, to equalize the pressue and that's why you observe a reduced pressure. The best pumps to use are the ones that have a split design for the head and one piece threads on the valve to keep the air seal tight and then another piece threads in and depresses the valve core. I use one of those and I thread on the first piece and pump up the pressure in the hose to roughtly what is in the chamber, then thread in the piece to engage the valve core. The reason why you lose 30-40psi from the BV versus almost nil from the main chamber is the size of the air volume. BV is tiny so you lose a greater % of the air when you attach the pump.

    As of why your sag is all wrong, I would guess that because of cold temprerature the seal around the air sleeve, which separates the negative chamber from the positive, must have shrunk enough to let air past it, so now you have a lot of pressure in the negative chamber. This is what is commonly referred to as a stuck down shock. Let all the air out of the shock, cylce a few times, let all of it out again, then put the weight of your body on the seat, so you fully compress the shock and unscrew the air sleeve. A rag on top of the sleeve will be a good idea in case it pops. Then unbolt the shock from the frame and do the recommended air sleeve maintenance.

    _MK

    "The things you get fired for when youre young are the same things you get Lifetime Achievements for when youre old."

  12. #12
    TNC
    TNC is offline
    noMAD man
    Reputation: TNC's Avatar
    Join Date
    Jan 2004
    Posts
    12,059

    Got mine back today.

    Quote Originally Posted by MK_
    You have your psi measurements a bit confused. You don't lose any air when you detach the hose. What you hear is air escaping from the hose, not from the shock. When you reattach the pump, air from the chamber escapes into the hose, to equalize the pressue and that's why you observe a reduced pressure. The best pumps to use are the ones that have a split design for the head and one piece threads on the valve to keep the air seal tight and then another piece threads in and depresses the valve core. I use one of those and I thread on the first piece and pump up the pressure in the hose to roughtly what is in the chamber, then thread in the piece to engage the valve core. The reason why you lose 30-40psi from the BV versus almost nil from the main chamber is the size of the air volume. BV is tiny so you lose a greater % of the air when you attach the pump.

    As of why your sag is all wrong, I would guess that because of cold temprerature the seal around the air sleeve, which separates the negative chamber from the positive, must have shrunk enough to let air past it, so now you have a lot of pressure in the negative chamber. This is what is commonly referred to as a stuck down shock. Let all the air out of the shock, cylce a few times, let all of it out again, then put the weight of your body on the seat, so you fully compress the shock and unscrew the air sleeve. A rag on top of the sleeve will be a good idea in case it pops. Then unbolt the shock from the frame and do the recommended air sleeve maintenance.

    _MK
    Hey, MK, my DHX A came to the shop today, and I'll try it out again tomorrow. The repair info says it was a failed Q-Ring, quantitiy 1...and yeah, that's Q, not O. It's typed in about 3 places on 2 sheets of paper, so I guess it's not a typo. What a Q-Ring is...it isn't coming to me yet...LOL!

  13. #13
    mtbr member
    Reputation: stoked's Avatar
    Join Date
    Mar 2004
    Posts
    428
    Quote Originally Posted by MK_
    You have your psi measurements a bit confused. You don't lose any air when you detach the hose. What you hear is air escaping from the hose, not from the shock. When you reattach the pump, air from the chamber escapes into the hose, to equalize the pressue and that's why you observe a reduced pressure. The best pumps to use are the ones that have a split design for the head and one piece threads on the valve to keep the air seal tight and then another piece threads in and depresses the valve core. I use one of those and I thread on the first piece and pump up the pressure in the hose to roughtly what is in the chamber, then thread in the piece to engage the valve core. The reason why you lose 30-40psi from the BV versus almost nil from the main chamber is the size of the air volume. BV is tiny so you lose a greater % of the air when you attach the pump.

    As of why your sag is all wrong, I would guess that because of cold temprerature the seal around the air sleeve, which separates the negative chamber from the positive, must have shrunk enough to let air past it, so now you have a lot of pressure in the negative chamber. This is what is commonly referred to as a stuck down shock. Let all the air out of the shock, cylce a few times, let all of it out again, then put the weight of your body on the seat, so you fully compress the shock and unscrew the air sleeve. A rag on top of the sleeve will be a good idea in case it pops. Then unbolt the shock from the frame and do the recommended air sleeve maintenance.

    _MK
    Good info with air getting into hose on 2nd time. Appreciate it. I decided to call FOX and have them open it up for me. I was going to follow suggestions from you and Tscheezy but I don't want to mess it up. It might be a Q-ring thing or bad assembly, who knows. Fox will give their blessing 1st. I have a backup bike in the mean time. Its not a Spot but it will do.

  14. #14
    MK_
    MK_ is offline
    carpe maana
    Reputation: MK_'s Avatar
    Join Date
    Nov 2004
    Posts
    7,278
    Quote Originally Posted by TNC
    Hey, MK, my DHX A came to the shop today, and I'll try it out again tomorrow. The repair info says it was a failed Q-Ring, quantitiy 1...and yeah, that's Q, not O. It's typed in about 3 places on 2 sheets of paper, so I guess it's not a typo. What a Q-Ring is...it isn't coming to me yet...LOL!
    Heh. Yeah, hopefully that will do the trick. Have fun playing with it.

    _MK

    "The things you get fired for when youre young are the same things you get Lifetime Achievements for when youre old."

Members who have read this thread: 0

Posting Permissions

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

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2019 VerticalScope Inc. All rights reserved.