Forum home Road cycling forum Workshop

Mech Problems

LycraVirginLycraVirgin Posts: 55
edited February 2013 in Workshop
I’m trying to set up my front and rear mechs on a new bike I bought off the internet. I have followed the Bike Radar video for this procedure but am having some problems.
The chain rubs the cage of the front mech when on the big ring and rear three sprockets. When I turn the stop anti clockwise to move the cage away from the chain nothing happens. If i turn it clockwise it will move towards the frame. I set the stop on the small ring first, then attached the cable before moving onto the above mentioned. Any ideas what I’m doing wrong? The only way I can see to move the mech further out is to pull the spring across and put the cable under a lot of tension. But having posted similar questions in the beginners forum I’m assured this is wrong. Given the bike arrived brand new with this problem is it possible something on the mech is broken and it was sent to me after a mechanic failed to adjust it properly? I can’t really see what can go wrong with a front mech between a PDI check and arriving at my house. Thanks in advance for any comments.

Posts

  • nicklousenicklouse Posts: 81,520 Lives Here
    as said in your earlier post it is cable tension. adjust a 1/4 at a time you will feel the bumps.

    read the how to on Parktools.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Are you talking about a front or rear mech? The screws or ‘high low stops’ make the adjustment I’m talking about for the FRONT mech. I have played with the barrel adjustment but it does not move the cage away from the chain. Sorry to irritate you and thanks for your prompt response as usual but I have no idea what you are talking about.
  • skyd0gskyd0g Posts: 2,539
    See above.
    http://www.parktool.com/blog/repair-help/front-derailleur-adjustments
    Problem probably caused by either cable too tight, outer adjuster not set properly, the cage isn't set to parallel or cross-chaining.

    Which three rear cogs does the cable rub when the front mech when you're on the big ring? Smallest or largest?
    Cycling weakly
  • Big ring , smallest three rear sprockets - chain rubs outside of front mech. Cable has been pulled 'hand tight'. If I turn the stop screw anti clockwise all the way up the thread nothing happens. If i turn it clockwise the mech moves towards the frame and rubs the chain more. According to park tools and the video the mech should move away from the frame when turning the stop anti clockwise.
  • smidsysmidsy Posts: 5,273
    Shift down to the small chainring and large rear cog. Screw both adjuster screws all the way in. Undo the FM cable.

    Set the inner plate where it needs to be and then re-connect the cable. Cable needs to be tight.

    Shift to the big chainring and smallest rear cog.

    Now you will have the full adjustment available for the outer plate. Adjust the limit screw to move the outer plate away from the chairing.
    Yellow is the new Black.
  • Thanks – that makes sense. Hopefully will get the ride the thing tonight
  • Above advice is sound - but it sound to me like the front cage is not lined up properly - it must be parralel to the centre line of the bike to allow full range. Also are you aware that most system have a trim function to slightly alter the alingment when using these end of range gear combo's? Although that said I never use mine as its easy to shift and avoid extreme chain lines which cause excess wear.
  • skyd0gskyd0g Posts: 2,539
    Hmm, depending on the front mech you have, as mentioned above, there may be a 'trim' function on the gear lever.
    ie. Position 1 - Small chainring. : Position 2 - Shifts up to larger front chainring. Position 3 - Stays on larger front chainring, but moves further out to eliminate rub when you're on the smaller half of the rear cog.
    Cycling weakly
  • nicklousenicklouse Posts: 81,520 Lives Here
    skyd0g wrote:
    Hmm, depending on the front mech you have, as mentioned above, there may be a 'trim' function on the gear lever.
    ie. Position 1 - Small chainring. : Position 2 - Shifts up to larger front chainring. Position 3 - Stays on larger front chainring, but moves further out to eliminate rub when you're on the smaller half of the rear cog.
    the trim function is in the shifter not the mech.

    how many clicks can you get out of it.

    still sounds like cable tension. wind out the top stop and getting working without the top stop.

    then wind the top stop in to stop any over shift.

    but you may have played with it too much so start from the beginnings (see parktools).
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Thanks for the pointers, yet to apply to them, I ended up in the pub last night eating fish and chips and watching football..... Hopefully be burning some calories tonight with the help of a beautifully adjusted mech.
  • The mechs work..... Not entirely sure what I did different for the 10th time but both derailurers now work properly. Feel more angry than satisfaction – what an utterly stupid, temperamental mechanism. Roll on 2020 when they have sealed gearboxes made of rice paper.
    Since having the bike upside down I have noticed a lot of excess grease seeping from the bottom bracket! (chain ring side?) Please tell me this is supposed to happen on a new bike.....? Jesus wept.......
  • smidsysmidsy Posts: 5,273
    Get a workstand - much much easier to do stuff. Trying to set things upside down is not helping.
    Yellow is the new Black.
  • keef66keef66 Posts: 13,286
    The BB grease could be good news or bad.

    Good news if it is simply evidence that the BB threads were greased before installation of the BB cups. Wipe it away and if more appears, see if you can tell exactly where it's coming from.

    Bad news if it is actually grease making it's way out of the bearings.
Sign In or Register to comment.