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Front mech trim help

redvisionredvision Posts: 2,519
edited April 2015 in Workshop
Hi,

I have an annoying problem with the front mech on my race bike. Its full shimano 105 but the trim doesnt seem to hold. Every time i adjust the trim using the barrel adjusters i get it perfect and it holds until i change down to the small ring and back up, then its as if the trim resets and 8/9/10 rub constantly against the chainset.

I have checked the front mech, gear cable (installed a new one), cable housing, shifter etc but just cant get to the bottom of it.

Anyone had this before? Could it be the spring in the front mech gone? Any simple solution?

Thanks for your help

Posts

  • sungodsungod Posts: 12,211
    the 105 shifter has a trim setting, make sure it's at the full tension setting when adjusting cable tension

    adjust for correct shifting to big ring as shown in the shimano instructions

    what are "8/9/10" ?

    if these are the larger three sprocket postions then depending on frame size etc. it's not uncommon to get chain rub using the larger sprockets when on the big ring, which is why the shifter has the trim position
    my bike - faster than god's and twice as shiny
  • redvisionredvision Posts: 2,519
    Thanks for your reply.

    Yes, 8/9/10 were in regards to the cassette sprockets.

    I removed the front mech last night and reinstalled - issue still there.
    I adjusted the limit screws and then used the barrel adjusters to get it perfect (including the trim) on the workstand. BUT, i then watched closely and as soon as you change down and then back up its as if the tension is lost in the front mech and the trim disappears completely.

    I tried adjusting the limit screw but found that if i moved it out any further the chain was thrown over the big ring.

    I think its got to be something to do with the spring in the front mech.

    Is there anything else i can try? or should i just take to my lbs?

    Thanks
  • deswellerdesweller Posts: 5,271
    I reckon you've wound the barrel adjuster fully out of the frame stop and have actually run out of adjustment. Pop the chain onto the big ring, then operate the shifter as if going to the small ring; that will release the cable tension so you can inspect the barrel adjuster and make sure you still have it fully engaged with the frame stop.
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  • sungodsungod Posts: 12,211
    ^this or similar

    it's not due to the spring, the mechanics are that the cable drags the cage out to the big ring, so if it isn't moving that far you simply didn't get enough tension on it (or possibly the shifter is faulty and slipping under tension or something else is giving way such as faulty outer or flexy cable stop etc.)

    the adjuster is for fine tuning, not for getting initial tension correct

    when setting cable tension, set the adjuster to minimum tension

    undo cable clamp, then move the cage to the correct position and drag on the end of the cable hard until the tension holds the cage in place, then clamp it - you may find it easier if someone helps hold things while you do it

    this way you have the full range of adjustment remaining for final tweaking
    my bike - faster than god's and twice as shiny
  • trailflowtrailflow Posts: 1,311
    Which derailleur do you have 5600 ,5700 ,5800 ?

    You can check how smooth the action is and how much tension is in the FD spring by un-doing the cable and moving the FD by hand. If it is returning from the big ring to the small ring fast then the spring is working normal.

    The trim is determined by the shifter internal mechanism. So that could be at faullt.

    Are you clicking the left shifter into its lowest postion when clamping the cable ?

    If you have a cable guide running under the bottom bracket. Check that it is secure and not moving around.

    Check the cable is clamped in the right positon. You could also be pulling the cable too tight or too loose when clamping.

    Also screw the barrel adjuster all the way in before clamping the cable.
  • redvisionredvision Posts: 2,519
    Thanks for the replies.
    trailflow wrote:
    Which derailleur do you have 5600 ,5700 ,5800 ?

    You can check how smooth the action is and how much tension is in the FD spring by un-doing the cable and moving the FD by hand. If it is returning from the big ring to the small ring fast then the spring is working normal.

    The trim is determined by the shifter internal mechanism. So that could be at faullt.

    Are you clicking the left shifter into its lowest postion when clamping the cable ?

    If you have a cable guide running under the bottom bracket. Check that it is secure and not moving around.

    Check the cable is clamped in the right positon. You could also be pulling the cable too tight or too loose when clamping.

    Also screw the barrel adjuster all the way in before clamping the cable.

    The mech is a 5700, as is the whole groupset. Its also under 2 months old (bought the bike new in Feb).
    I have made sure the barrell adjuster is screwed in all the way, and have also checked the height of the mech but the issue is still occuring.

    I move the chain to the big ring and a quick push of the shifter again to move the mech out for the trim and it works and is perfect. BUT when i change down to the small ring, as soon as i change back up to the big ring the trim doesn't work. You can see the mech moving out but it doesn't hold it in the correct position and its back to square one.

    I think its either something i'm doing or perhaps it could be a faulty shifter. Either way, im going to drop it off later at my lbs so will post back what they find.

    Thanks again for your help.
  • styxdstyxd Posts: 3,234
    I thought the trim position on Shimano was on the inner ring, not the outer?
  • mamba80mamba80 Posts: 5,086
    redvision wrote:
    Thanks for the replies.

    I move the chain to the big ring and a quick push of the shifter again to move the mech out for the trim and it works and is perfect. BUT when i change down to the small ring, as soon as i change back up to the big ring the trim doesn't work. You can see the mech moving out but it doesn't hold it in the correct position and its back to square one.

    the trim is nt for the smallest cassette sprockets, its for the bigger sprockets, so if 10 is the smallest, then say you were to change to the 3rd largest(and you r on the outer chainring) and the chain rubs on the FD, then you d just touch the inner left hand shifter and the FD would move inwards a small amount... no rubbing.

    Have a read of the shimano tech docs for FD 5700, its the SI pdf.
  • sungodsungod Posts: 12,211
    I move the chain to the big ring and a quick push of the shifter again to move the mech out for the trim and it works and is perfect. BUT when i change down to the small ring, as soon as i change back up to the big ring the trim doesn't work. You can see the mech moving out but it doesn't hold it in the correct position and its back to square one.

    looking that the st-5700 info, the trim feature is available on both rings, see...

    http://si.shimano.com/php/download.php? ... 02-ENG.PDF

    ...are you following this for set-upand operation?

    because as mamba80 says above, this statement is wrong...
    move the chain to the big ring and a quick push of the shifter again to move the mech out for the trim

    ...on the big ring selecting the trim would move the mech *in* not out
    my bike - faster than god's and twice as shiny
  • deswellerdesweller Posts: 5,271
    When the OP says 'trim' he/she does not mean trim in the conventional sense. They're talking about the cable tension adjuster in the frame stop.

    To the OP: the system is very simple. The derailleur position is governed by the available length of cable, which you fine-tune by lengthening or shortening the path it has to take via the barrel adjuster. If the adjustment is not consistent then that suggests that the cables may not be correctly seated or something of that ilk.
    - - - - - - - - - -
    On Strava.{/url}
  • redvisionredvision Posts: 2,519
    Thanks for the responses.

    I decided to have one last crack at it last night before going to the lbs.
    I took off the front mech and fitted yet another brand new cable. I spent ages reinstalling the mech, being very conscious about the height/position etc. Also made sure the barrel adjuster was fully in.

    And its worked! it was pretty much perfect the very first time :D
    I had to adjust the limit screw a tad (1/4 turn on the inner) but it seems absolutely perfect!
    The trim is there and there is no rubbing at all, across all ratios!

    Thanks so much for all the help. Saved me a few quid by sorting it myself.

    :D
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