105 double front mech misbehaving

mkitson
mkitson Posts: 7
edited March 2009 in Workshop
I have a Focus cayo and have done about 3,000 miles on it. At the end of a 50mile ride the front mech suddenly would not shift to the lower chainring (compact crankset). No falls or knockes of any kind on the ride.

The position of the front mech has not changed-it's attached to a braze on. The lower limit screw is at it's lowerst setting and the cable is slack in this position. The shifters appear to be working though I have noticed it makes a slightly louder 'clack' when shifting down.

I have cleaned an lubed the mech and it does not appear to be broken in any way. I have removed the crankset and replaced it to be sure it had not moved or come loose. I have fiddled with the limit screws-all to no avail. It is almost like the whole draileur has moved 6mm or so away from the bike as the H limit screw (before I fiddled with it) no longer keeps the chain from falling off the big crank when shifting up.

It is driving me nuts! Any ideas anyone?

Martin

Comments

  • John.T
    John.T Posts: 3,698
    If the cable goes slack when operating the shifter the problem is unlikely to be there. It could still be but far more likely at the mech. If the cable is slack then the mech should be on the lower limit stop. If it is not then something is jamming it. . Very difficult to guess without seeing the bike.
  • markos1963
    markos1963 Posts: 3,724
    Have you looked at the cable routing? Most go under the bottom bracket and get covered in crud. This can often lead to the cable jamming up.
  • mkitson
    mkitson Posts: 7
    Thanks for the suggestions. Cable routing is fine-cleaned and lubed. What is baffling me with the cable slack and the lower limit screw at the lowest setting it is just not far enough to the left to shift down from the big chainring.

    The mech is up to the lower limit stop as when I tighten the screw it moves to the right straight away.
  • John.T
    John.T Posts: 3,698
    If it is on the lower limit stop and moves when you turn the stop then there are not many possibilities. Either something has broken in the mech and put the cage in a different position or someone has moved the screw. Are all the pivot pins in place. Can you readjust it and make it work. Just start from scratch and see if this sorts it.
  • GavH
    GavH Posts: 933
    I'm having the EXACT same problem with my brand new, arrived last week Bianchi 928 which has a 105 front mech. It wasn't setup at all when it arrived so I took it to my LBS who got it right, but on my first ride out, I discovered it woudln't shift down onto the lower chainring. I shifted the levers to place it in the lowest gear then undid the cable and pulled it tighter. I tweaked teh H and L screws to ensure it wasn't rubbing but twice now on rides I've had it all of a sudden fail to shift down. On one ride it woudl shift down fine, but shifting back up caused it to throw the chain off. I finally thought I'd cracked it after Saturday and did over 40 miles on Sunday with no problems. Bikes not been touched since then but after only 5 miles at lunchtiem today, guess what, couldn't select the bottom chainring. The really strange thing is that it amost appears as if teh mech is creeping out the way as the gap between teh chain and the outer plate of the mech is MUCH wider than when I had it correctly setup on Saturday. Then it was 1-2mm MAX. Now it is closer to 5 mm maybe?

    REALLY frustrating. Is it possible that the cable may slip ever so slightly out of the clamp? I'm at a loss to explain why I can seemingkly set it up but then a couple of days later its not working again. Like I said, it's brand new. :?
  • ride_whenever
    ride_whenever Posts: 13,279
    have you tried completely removing the cable and the lower limit screw? Is it the mech hitting the braze-on/seattube?

    If the mech is as far over as possible then check the height of the mech and check there is no play in the crankset/bb
  • GavH
    GavH Posts: 933
    I've given up trying now, its going into the LBS asap. I've taken the front mech off, given it a squirt of WD40 and a good wipe then re-attached it, allowing for 2-3mm clearance of the outer teeth and parallel to the chainline. Adjusted the L screw to give about 2mm clearance of the chain. Re-attached cable to clamp having already flicked shifter to 'lowest' position (ie cable at its slackest) and with chain on inner chainring and biggest sprocket at the back (lowest gear).

    Now when I operate the shifter it doesn't move the mech at all. When I operate the inner lever to slacken the cable again I get that loud 'clack' that the OP mentions. Front Mech broken already?
  • John.T
    John.T Posts: 3,698
    There have been several reports of faulty 105 LH shifters on here. It sounds more like that.
  • synchronicity
    synchronicity Posts: 1,415
    I have another faulty shimano LH 105 shifter (double). Happened on Sunday. Felt very stiff, then would not shift down, even if you pressed the lever 10 times as hard as normal. To the point it was obvious that something was not right. We even looked at the BB cable guide as the culprit... but between me and the local bike mechanic guru, we just couldn't figure it out... I ended up shelling out for a new shifter + FD. The old unit has gone to Madrid for servicing...

    After this mishap, I finally got this bloke to admit that campy levers are superior to shimano! :twisted:
  • nferrar
    nferrar Posts: 2,511
    Yeah my 105 LH shifter was always a bit dodgy, about 50% of the time it would shift down fine, 45% of the time it would take two sweeps for it to shift down and 5% of the time it would take a lot of sweeps of the lever and a lot of cursing before it would shift (never completely stopped working though). Managed to crash a few weeks ago and replaced them with Ultegra shifters, now it seems more like 90% shifts fine, 10% takes a double shift to sort (although also had the inner and outer cables replaced at the same time so can't say for sure the levers are the improvement).
  • Fifer
    Fifer Posts: 60
    I just had my LH lever replaced also at my LBS. When I picked my bike back up, the LBS said that Shimano had received a lot of complaints about faulty levers. :(

    When I was out on Sunday with the club, the new shifter seemed to work better but was still not 100% perfect. Might aslo look at upgrading to Ultegras.
    Winter Bike: Specialized Allez Elite
    Summer Bike: Specialized Tarmac Pro SL
  • GavH
    GavH Posts: 933
    Just took the bike into the LBS. Mechanic reckons its a faulty LH shifter. I've left it with them as they're going to send the levers away to Shimano for replacement. He reckoned the problem isn't widespread, but about 20% of LH shifters seem to have an issue. Didn't ask who does such statistical analysis as I couldn't care less, in my case its 100% of LH 105 shifters are faulty!
  • Fifer
    Fifer Posts: 60
    GavH wrote:
    Just took the bike into the LBS. Mechanic reckons its a faulty LH shifter. He reckoned the problem isn't widespread, but about 20% of LH shifters seem to have an issue.

    I would say that was pretty widespread. 1 in every 5 LH shifters is broken or has the potential to break is shocking. :shock:
    Winter Bike: Specialized Allez Elite
    Summer Bike: Specialized Tarmac Pro SL
  • mkitson
    mkitson Posts: 7
    Thanks for the interest, at least I am not alone! :)

    Well I have taken the mech off again and reset everything from scratch-same result.

    Began to loose my temper and ragged it about pushing the cage to it's extremes of movement with my hand, guess what? -it works (of a fashion) again.

    Seems as though something in the internal mechanism was limiting it, pushing it about has given it back a bit more range of motion. The thing was clean and well lubed but obviously some more violence required!

    On the road it shifts only about 60% of the times so there are still issues. At least I am sure it's the mech and not the shifters, so I have just ordered an ultegra front mech and hope I have better luck with that.
  • markos1963
    markos1963 Posts: 3,724
    If it gets too frustrating do a Lance and use a downtube shifter for the front mech. :)
  • mkitson
    mkitson Posts: 7
    New ultegra front mech on the bike now and working perfectly. Still can't really say what the malfuntion was with the 105 front mech but at £32 for the new one I won't loose a lot of sleep over it.

    By the way, ordered from chain reaction cycles. The new mech arrived less than 24hrs after ordering online, postage free. Pretty impressive service. :D