Ghost Shifting Under Load - '08 Trek Fuel EX8- Mtbr.com
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  1. #1
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    Ghost Shifting Under Load - '08 Trek Fuel EX8

    Driving myself nuts on this one...

    I've replaced everything BUT the rear derailleur. That's probably my next move but wanted to check here first.

    New cables, new cassette, new chain. I understand how the RD works...and everything seems lined up fine. It cycles through all the gears flawlessly with no load.

    Soon as I start a climb - POP! - slides down to a lower gear. I'm on my third chain now.

    What the hell am I missing? It's definitely happening on the rear cassette so I don't think it's a worn chain ring. The shifter seems to be functioning fine so the only thing left is the RD.

    Thoughts?

  2. #2
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    Is your shifter working ok? It can be that it cannot maintain the tension in the cable. Also, RD can play a major role if it is banged up. How's the RD hangar looking like?
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  3. #3
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    Have you checked for a bent derailleur hanger? Also cable housing being short can cause ghost shifting on a dual suspension bike while riding and you don't catch that on the work stand.

  4. #4
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    The hanger looks fine to me. I'll take a closer look when I get a chance. There's quite a bit of side to side play when I grab the cage and give it a wiggle. I'm starting to think the RD has been my problem all along.

  5. #5
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    If by under load you mean suspension compression then it's most likely your housing and cable routing or length.

    If by under load you mean chain tension, it could be the rear derailleur or a combo of that and the above. Post a pick of your cable routing.

  6. #6
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    Oh yeah, and drop all of the air out of your rear shock and test the shifting while the suspension is fully compressed. Reduce your rebound all the way to give you some added time to shift thru the gears with the suspension compressed.

  7. #7
    > /dev/null 2&>1
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    Also check if there is play in your rear triangle due to loose pivots. If you have a loose lower pivot, chain tension tends to pull the triangle to the left, at which point it's pulling at a slight angle, catching the helper ramps on the cassette on the lower gear.

  8. #8
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    ^this too!!

  9. #9
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    Check the hanger. It is not something you can eyeball; you need a tool to check it. I would say that or an adjustment in cable tension are to blame

  10. #10
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    Quote Originally Posted by heybrady View Post
    Check the hanger. It is not something you can eyeball; you need a tool to check it. I would say that or an adjustment in cable tension are to blame
    Truth. Do this.

  11. #11
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    Check to see if it is due to the cable housing being too short by removing all the air from the rear shock and compressing the rear end while watching for derailleur movement. If the derailleur moves inward while you compress the rear suspension you've found your culprit.
    Keep the rubber side down

  12. #12
    rebmem rbtm
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    I've grenaded a hub that behaved this way as well, but given you said the deraileur had wiggle it seems pretty straight forward at this point.

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