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Derailleur having trouble shifting to largest rear sprocket.

JamesHavillJamesHavill Posts: 14
edited February 2018 in MTB workshop & tech
I have an XT RD-M8000 1x11 full drive train with 11-42 XT cassette
The problem is that i can get it to shift into the largest sprocket but it is very hard to and jumps down most times. My limit screws are not making contact with anything, so it should be able to shift up. The top pulley is half inline with the 42t and 37t and i cant allign it any better using limit screws or b screws. When i try to adjust it by using the barrel adjuster, it can shift up alot easier but then has trouble downshifting. The cable tension is very tight. Just to clarify it can shift up but has trouble staying there or else will not go up at all.

Posts

  • ed1973ed1973 Posts: 182
    Hi
    Did you convert it into a 1x11? I only ask as I did the same with mine (but to 1x10) and I needed to get a hanger extender. I bought a goatlink, but you can get cheaper copies from eBay but a word of warning, I bought a cheap version first and it didn’t fit my hanger as MTB hangers are different from road bikes. Anyway as soon as I put this on my shifting worked like a charm and I didn’t need to mess about with b-screw much.
  • The RookieThe Rookie Posts: 27,748
    It does sound like the L-screw is impeding it, can you push it further towards the spoke by hand?

    Unless you have a whacky frame (hanger location) and wheel combo I've never heard of a mech doing as you describe.

    By the way I think you have your terminology out (or it makes even less sense), shifting 'up' is up (numerically) through the gears towards the smallest sprocket, shifting down is towards the largest sprocket
  • ed1973 wrote:
    Hi
    Did you convert it into a 1x11? I only ask as I did the same with mine (but to 1x10) and I needed to get a hanger extender. I bought a goatlink, but you can get cheaper copies from eBay but a word of warning, I bought a cheap version first and it didn’t fit my hanger as MTB hangers are different from road bikes. Anyway as soon as I put this on my shifting worked like a charm and I didn’t need to mess about with b-screw much.
    Nope i did not convert it, it has the stock drivetrain used to work fine until a muddy enduro race. I cant remember the name but most shimano derailleurs come with a goatlink type piece already attached and most bikes have then unless the hanger already has an extension. I may try swap the spacer around to be on other side of the shimano goatlink thing so it will push the derailleur further towards the wheel so it should be able to align better and be able to make the shift. Thanks
  • The Rookie wrote:
    It does sound like the L-screw is impeding it, can you push it further towards the spoke by hand?

    Unless you have a whacky frame (hanger location) and wheel combo I've never heard of a mech doing as you describe.

    By the way I think you have your terminology out (or it makes even less sense), shifting 'up' is up (numerically) through the gears towards the smallest sprocket, shifting down is towards the largest sprocket
    Nope the wheels, frame, hanger, shifter and cassette are all stock as a rock on my giant reign. The screw is not making contact so it wont be impending it. I can push it up a tiny bit but cable tension is as tight as i can get it. Thanks
  • JBAJBA Posts: 2,708
    I may try swap the spacer around to be on other side of the shimano goatlink thing so it will push the derailleur further towards the wheel so it should be able to align better and be able to make the shift. Thanks

    Why do that?
    If the gearing worked fine before the muddy race the spacer is in the correct place.

    Suggest you disconnect the gear cable from the mech and do a complete gear index. Plenty of guides on the web/YouTube.
    If you have no adjustment left on the barrel adjuster it is possible that the gear cable has slipped a bit.
    “Life has been unfaithful
    And it all promised so so much”

    Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Bird Zero Mk1 ¦ Giant Revolt Advanced 2 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 2009
  • cobbacobba Posts: 282
    I cant remember the name but most shimano derailleurs come with a goatlink type piece already attached and most bikes have then unless the hanger already has an extension. I may try swap the spacer around to be on other side of the shimano goatlink thing so it will push the derailleur further towards the wheel so it should be able to align better and be able to make the shift. Thanks

    Shimano calls this 'goatlink type piece' a bracket axle unit, it's also commonly known as a b-link.

    The bracket axle unit can rotate clockwise on the derailleur hanger if knocked, if this happens, you will need to turn it anticlockwise to the position where it is supposed to be. If it's been knocked out of position, it can affect the shifting.

    Page 8 of the Shimano dealer manual shows what I'm talking about:
    http://si.shimano.com/#/en/DM/RD0004
  • JW599JW599 Posts: 30
    The cable tension is very tight. Just to clarify it can shift up but has trouble staying there or else will not go up at all.

    I had this problem, cable tension was too tight, there was not enough slack to make the full range of movement from the shifter.

    Can you get to the biggest sprocket by releasing the cable from the pinch bolt and pushing the rear mech by hand?
  • The RookieThe Rookie Posts: 27,748
    Either as cobba describes or maybe there is a lump of dried mud or similar inside the paralellogram acting as an early Low stop.

    jw599 you seem to have missed that when he says 'up' he means 'down' to the biggest sprocket.
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