Chain rubs on front mech for *part* of the time

Susec
Susec Posts: 15
edited August 2016 in Workshop
Hi, folks, I have a 2 month old Liv Thrive 1 hybrid. It goes back almost every ride to have the gears re aligned and I'm told it's fine each time. But I think there's a problem as the chain starts touching the front mech soon after taking it back. When I ride it or put it in my stand, you can hear that the chain isn't touching throughout its whole transit - only a section is really bad - it goes from nothing to bad gradually. It can't be frame flex given that it happens on the stand, too.
Am I right? Is there likely to be a problem? Any ideas what the problem might be?
I haven't had a single grinding noise free ride, yet, in 88 miles which spoils the enjoyment of getting back in the saddle, and the bike has been in the workshop as much as with me. I keep on getting told it's me as they re-adust the gears which then start to grind again after about 1 mile. I can adjust them, then they grind again a mile or so later. Repeat.
Any ideas??? Surely I don't have to live with this - it's tiagra, should work efficiently if not the best.
Thanks!!!! Sue

Comments

  • craigus89
    craigus89 Posts: 887
    Are you cross-chaining a lot? Where is it rubbing, on the outside of the mech or inside and on what ring?
  • arlowood
    arlowood Posts: 2,561
    Is the front mech a band-on type (ie it has it's own clamping ring around the seat tube) or is it a braze on type (fixes to a bracket either brazed or bolted in place on the seat tube)

    If it's the former then it's possible that the clamp is not tight enough and the mech is moving slightly after each time it is re-set and giving you the chain rub.

    However you say that it seems to rub only during part of the chain ring revolution which suggests that the chain ring may be out of alignment either due to a bent chain ring or a mis-aligned bottom bracket

    Maybe some pics or a video of the rubbing may clarify things better

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