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Chainline line reduced, but front mech won't reach middle chainring - what have I done wrong?!

93supervee93supervee Posts: 33
edited August 2018 in MTB workshop & tech
I've transferred my entire XT/LX/Deore mix triple group from a 2007 Cannondale Rush to a Giant Anthem X3 (Rush was a bit small). Chain line on the Rush was 49mm, on the Anthem it is 43mm. External cup Hollowtech BB on the Rush, press fit on the Anthem. Cranks went straight on no bother, though I was surprised not to need a spacer/wave washer or similar due to the difference in chain line.

On fitting the front mech (FD-M510 band on with shims removed to fit 34.9), I found the cage was fouling the Anthem swing arm; no worries once set up I thought, but with no cable attached and limit screws wound out, the mech did not have enough travel to get past the middle ring. I aligned and cabled up regardless assuming my daft error would make itself known, but to no avail. I had to wind in the lower limit screw almost all the way to get the cage close to the chain when on the granny ring and so much travel was taken up that not enough was available to shift up.

I'm not convinced about the cable routing, but it has no bearing on the position issue as moving the cage by hand finds the same limes of movement (and I emphasise that limit screws are out).

The thing I cannot get my head around is that surely going to a narrower chain line, the rings should be closer then they were on the previous Rush setup and that the mech mounting would effectively be centred on the chainline anyway?

I really hope someone points out my idiot mistake here because I am utterly foxed. I can never remember how to link pics but I'll try these.https://imgur.com/a/njs4VSu

Posts

  • steve_sordysteve_sordy Posts: 2,239
    I am by no means any sort of expert on this, but.....

    If you remove the limit screw limitations by winding them out of the way, can you move the mech-arm by hand to give you what you want?

    If you can, then a physical solution is there to be found. If you can't then maybe the mech mount you have transferred across is the wrong one. :(
  • steve_sordysteve_sordy Posts: 2,239
    But of course the answer is staring you in the face!

    Go 2x at least instead of your current 3x. :D
  • 02GF7402GF74 Posts: 1,294
    From your photos, the cage moves more than enough to shift chain to granny...

    Can you post photo with cage at maximum position away from the seat tube, I. E as when trying to put chain on the big ring, when you do that, put chain the big ring. Having it on the granny like you have m stops the cage from moving.
    .
  • Thanks for the responses - in order:

    Limit screws are wound right out - even when moved by hand, the cage cannot move far enough.

    The mount type could well be an issue - for clarity, the overall travel of the mech seems normal, it's just that it starts and stops in the wrong place, suggesting that either the mount is too close to the centreline or the rings are too far away from it, but I can't see how how moving to a narrower chainlink frame would result in the cage being further away from the outer ring. This exact setup worked fine on my Rush.

    Would consider 2x with a bash but cage won't even shift to the middle!

    The issue is not that it won't shift in to the granny, it's that it won't shift up and out of it - photo 4 shows position with no tension (fouling the swing arm) and photo 3 shows maximum travel.

    Still feeling like an idiot, still scratching head...
  • whyamiherewhyamihere Posts: 7,465
    Take the chain off, disconnect the cable and try pushing it across by hand to see what makes contact first and stops it from moving any further. It could be something like the outside of the cage touching the outer ring.
  • whyamihere wrote:
    Take the chain off, disconnect the cable and try pushing it across by hand to see what makes contact first and stops it from moving any further. It could be something like the outside of the cage touching the outer ring.
    Result!

    I knew it wasn't fouling on the rings, but took the mech off the bike "to see what makes contact first" in the mech travel. Looks like I put the cable retention clamp on the wrong way round and the L-shaped tab having bent out a bit was fouling on the body - only 1mm but enough to make a dead stop. Tab off, full travel.

    Thank you people - happy idiot again!
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