RS Pike not right after loaning bike out- Mtbr.com
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  1. #1
    vbm
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    RS Pike not right after loaning bike out

    I have a RockShox Pike RCT 160mm that was OEM on my 2016 Mojo HD. With me weighing in at 150lbs, 55psi in the fork gave me 25% sag. Completely reliable for 3 years........ until last month.

    My cousin was coming in from out of state for a business trip. I haven't seen him in about 10 years. I thought it'd be awesome to go out riding with him, as the last time we rode was about 20 years ago. So I loaned him my Mojo. But he put on some weight. At 275 pounds I pumped up the fork and shock to set the sag on both. The Pike needed about 110psi IIRC. We only rode 4.5 miles, 1/2 that on road.

    But now it needs 82psi to sit at 25% sag instead of the 55psi it took before that ride. Also, it does not extend fully, only extends to 145mm. I did the zip tie trick and did hear the slight "whoosh" but I think that actually worsened the problem as far as the total travel goes.

    Aside from the decreased travel and the higher psi requirement, it seems to function just fine, though. The rear shock doesn't seem to have been affected at all, unlike the fork.

    Any thoughts? Thanks!

  2. #2
    ZSW
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    Increase the air pressure again until you can feel the negative and positive chambers equalize and pull the fork to full extension. Cycle the fork a few times then begin dropping the pressure down 15 psi at a time and compressing the fork 5-10 times each time. When you get to 0psi the fork should be able to be fully extended easily by hand, if it’s not then you have air trapped in the negative chamber. You can remove the valve core if you want to really be sure. Then do the zip tie trick for good measure. Next reinflate to desired pressure cycling the fork again every 10 psi or so. At this point you should have fixed the issue if nothing is blown out. You can try the zip tie trick again in a few hour and see if you have any built up pressure. If you do the lower seal head is likely bad

  3. #3
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    You've got a worn main air seal which is leaking air into the negative chamber and causing a partial stuck-down situation.

    It's not your cousins fault (this time anyway). It's just wear.
    Owner of www.shockcraft.co.nz, Mech Engineer, Tuner, Manitou, Motorex, Vorsprung EPTC, SKF, Enduro
    www.dougal.co.nz

  4. #4
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    Perhaps nothing is worn or damaged and you just need to equalize the negative chamber. Pump up to fully extended, gradually release pressure using the bleed button on the shock pump. If the fork starts to suck down, force it to fully extended a few times and continue.
    Do the math.

  5. #5
    vbm
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    Thanks for the tips. Inflating to 110psi or so extended it to full travel, then slow pressure release with manual/forced extension seemed to revive full travel again. BUT, it still needs about 20psi more than it did to run the proper sag. Feels nice and buttery smooth, though. May just do a full rebuild once the snow starts falling.

  6. #6
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    Quote Originally Posted by vbm View Post
    Thanks for the tips. Inflating to 110psi or so extended it to full travel, then slow pressure release with manual/forced extension seemed to revive full travel again. BUT, it still needs about 20psi more than it did to run the proper sag. Feels nice and buttery smooth, though. May just do a full rebuild once the snow starts falling.
    You said you did the tiewrap trick, and heard a slight 'woosh' sound. That trapped air pressure probably helped support your weight in the past, and took the place of that 20psi you now have to add.

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