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Front derailleur can't reach middle cog...

aaronhaskinsaaronhaskins Posts: 6
edited May 2013 in The workshop
Hi,

I've seen posts where the front derailleur can't get go to the largest cog but my bike won't currently go to the middle (there are three). If I change gear again, it goes to the largest one. I can then go to the middle by going down a gear.

Looking at it, it tries to reach the middle gear but doesn't quite go high enough and falls back to the smallest before trying again. Is this down to my higher / lower limits?

Thanks in advance!

Posts

  • shadow4532shadow4532 Posts: 133
    by chance is this an ultegra 6700 groupset?
    GIANT PROPEL SL1 for racing and posing
    TREK 2.5 training and commuting
    GIANT REVEL 1 LTD for when it gets all snowy
  • Ah sorry, I'm not sure and don't have my bike with me at the moment. It's a Carrera Subway 2, bought it in 2009 if that helps?
  • Haha, googled it... definitely not :)

    My knowledge of bikes is... limited.
  • shadow4532shadow4532 Posts: 133
    thats ok just wondered because i know someone else that had this problem.
    have you checked the cable tension (it may be that the cables have streched just far enough to stop it getting on the middle chainring)
    GIANT PROPEL SL1 for racing and posing
    TREK 2.5 training and commuting
    GIANT REVEL 1 LTD for when it gets all snowy
  • shadow4532shadow4532 Posts: 133
    GIANT PROPEL SL1 for racing and posing
    TREK 2.5 training and commuting
    GIANT REVEL 1 LTD for when it gets all snowy
  • What a great website - I'll use this later and let you know how I get on with it. As for cable tension, is that just releasing the cable and re-attaching? How tight should it be pulled? Also, I keep hearing about barrel adjustment - where would I find this?
  • owenlarsowenlars Posts: 719
    Try pulling the cable with your hands from underneath the downtube (or alongside the seat tube if it goes by that route). If you can get the front mech to move the chain across by doing that it is cable tension. If the front mech stops whilst you are pulling the cable it is probably the limit screw or possibly the front mech is out of alignment. It is more likely the former though.

    If you have a very slack cable disconnect from the front mech and reconnect with the chain in the smallest cog and the front mech lined up with the smallest cog.

    The barrel adjusters are for making micro adjustments whilst indexing. In effect if you turn the adjuster anti clockwise you will see it appear to move away from the bracket which holds it to the bike. This effectively shortens the cable thus effectively tightening it slightly. If you screw it clockwise the opposite happens.

    Remember the rule you loosen the cable to get to a smaller cog. Tighten it to get to a bigger cog.
  • shadow4532shadow4532 Posts: 133
    the barrel adjuster on yours i think would be on the side of the gear shifter ( depending on what gears you have) or on the down tube. thwe other questions are answered better than i could in my last link.
    all the best and good luck
    GIANT PROPEL SL1 for racing and posing
    TREK 2.5 training and commuting
    GIANT REVEL 1 LTD for when it gets all snowy
  • It was the cable tension! I've adjusted that and it now changes through the gears. My new problem is that when on the largest ring at the front, it sounds like it is rubbing - does this mean I need to raise the derailleur slightly?
  • shadow4532shadow4532 Posts: 133
    so looking at it, is it rubbing on the chain or the crank?
    GIANT PROPEL SL1 for racing and posing
    TREK 2.5 training and commuting
    GIANT REVEL 1 LTD for when it gets all snowy
  • supersonicsupersonic Posts: 82,708 Lives Here
    The derailer cage should clear the largest ring by 1-2mm.

    Slight rubbing in some gear combos is not uncommon.
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