suspension maintenance

Discussion in 'Shop Talk' started by beartooth, Dec 14, 2018.



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  1. SnakeCharmer

    SnakeCharmer iMTB Hooligan

    Location:
    Crescenta Valley
    Name:
    Mike, aka "Ssnake"
    Current Bike:
    2018 Trek FEX
    Of course I will. I was just giving you a hard time (like always). :D
     
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  2. mtnbikej

    mtnbikej J-Zilla

    Location:
    Orange
    Name:
    J M
    Current Bike:
    SC Chameleon SS, SC Hightower
    When was the last time it was serviced?

    The RL damper is pretty simple, and to me it seems like it always makes noise.

    You may have grease blocking the dimple on the air spring side, so perhaps there is too much air trapped in the negative spring. You may also have a bad o-ring on the piston head. The o-ring on the damper/rebound side may have failed, allowing oil down into the rebound side of the lowers.

    Does the lockout still work?
     
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  3. SnakeCharmer

    SnakeCharmer iMTB Hooligan

    Location:
    Crescenta Valley
    Name:
    Mike, aka "Ssnake"
    Current Bike:
    2018 Trek FEX
    The lockout does not completely lock the fork out. It's been sitting for over a year.
     
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  4. mtnbikej

    mtnbikej J-Zilla

    Location:
    Orange
    Name:
    J M
    Current Bike:
    SC Chameleon SS, SC Hightower

    I'd drop the lowers and see if the damper fluid migrated into the lowers.
     
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  5. Ebruner

    Ebruner Well-Known Member

    Name:
    Erik Bruner
    Current Bike:
    SC Hightower, Kona Hei Hei
    Bingo. The motion control dampers work by having the bottom of the compression damper submerged into the bath oil (on the damper side obviously). When RS dictates an oil volume or oil height for the open bath oil, what they are doing is dictating a volume and by extension, a height so that the end of the motion control damper is ~10mm submerged.

    What can happen, as @mtnbikej pointed out, is that the lower seal head on the damper side can fail, or leak, which would cause some of that open bath oil to leak into the lowers. This means that the bottom of the motion control damper is no longer submerged. This would cause the initial sink down feeling you are describing. In addition, the motion control dampers also function based on the flexing of the perforated plastic tube, and that is a big factor in their compression performance but an even bigger factor in the lockout. Without sufficient oil volume in that side of the leg, you can't create the hydraulic lockout pressure needed to sustain a true lockout.

    Fortunately, the damper side service for an open bath RS fork is literally no more difficult then the air side service. All you really need in the way of special tools is a wood dowel rod of about 18" or so, or a way to measure suspension fluid/oil to an accuracy of 1-2ml. Open bath RS forks are where I cut my teeth learning MTB suspension service, and they are a great place to start. It also doesn't hurt that these forks are like cockroaches. The only real thing that kills them is the bushings in the lowers wearing out and causing stiction and stanchion wear. Short of that, they are always just a 2 hour rebuild away from feeling brand new.

    Screenshot_1.jpg
     
  6. SnakeCharmer

    SnakeCharmer iMTB Hooligan

    Location:
    Crescenta Valley
    Name:
    Mike, aka "Ssnake"
    Current Bike:
    2018 Trek FEX
    Thanks @mtnbikej and @Ebruner. I don't have the time to service this fork but I want to sell it as functional. Would either of you be willing to service it for me if I brought it to you?
     
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  7. mtnbikej

    mtnbikej J-Zilla

    Location:
    Orange
    Name:
    J M
    Current Bike:
    SC Chameleon SS, SC Hightower
    In that amount of time, you could do it yourself.
     
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  8. SnakeCharmer

    SnakeCharmer iMTB Hooligan

    Location:
    Crescenta Valley
    Name:
    Mike, aka "Ssnake"
    Current Bike:
    2018 Trek FEX
    Mechanically, I have no doubt but availability, I have none.
     
    DangerDirtyD likes this.
  9. blixet

    blixet Well-Known Member

    Location:
    San Gabriel Valley
    Name:
    Tom
    Current Bike:
    Bronson
    Took my 2013 Rockshox Recon Silver TK 29er fork apart yesterday and did a full service on both sides uppers and lowers. Replaced all the seals and other stuff that came in the full service kit, cleaned inside and out, inspected all parts, replaced the oil in the solo air can and the lowers. Everything looks good. Was planning on upgrading the damper from the low end turnkey that only has lockout function, no compression dampening, with an argyle moco that is supposed to fit with some oil level adjustment. All went well except the delivery guy didn't show up with the Argyle until around 5 pm which was a couple hours after I had everything else completed. I just left the damper top tube open and covered (so no crickets or whatever could end up down in there overnight) and will finish it up later this morning. It may end up being putting lipstick on a pig but it was a good exercise and will be interesting to see if any improvement in performance is noticeable.
     
  10. blixet

    blixet Well-Known Member

    Location:
    San Gabriel Valley
    Name:
    Tom
    Current Bike:
    Bronson
    4 months into this upgrade. Riding it regularly every week. Nothing too hard core, just my regular trail riding. The Argyle moco is a definite improvement. The fork works well considering it is a low end model fork with a still pretty weak damper. I originally used some 5wt Lucas Oil suspension fluid for the damper since it was cheap and handy. Didn't know if there was any reason to get a hold of more Rockshox/Maxima that the service instructions called for since I was running low and needed 130 ml. Seemed fine. Probably no difference, but I got the bug up my butt to see for sure. So today I drained it and added 5 wt. Maxima Plush. According to the respective tech sheets, although all 3 are nominally 5 wt, Lucas has a cSt@40 of 25.3, Maxima Performance weighs in at 16.2 (pretty big difference, but not sure if it really matters) while the Plush sits at 18.6. Just riding it around the street dropping off curbs and stuff, seems fine. I think any difference is negligible all things considered. But I'll put it through the paces tomorrow morning and see what I can feel if anything.
     
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