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Adjusting front mech for double chainring

stealthbikestealthbike Posts: 84
edited July 2007 in Workshop
I need some advice about adjusting my front mech on my road bike. I have a double chainring but my front mech has a three click motion - i suppose to allow it to work with a triple chainring. Do how do i set it up correctly to work on a double? It currently is fine in the smallest ring but the next click takes it to the big ring but ir catches ateeny bit when on certain rings at the rear, if I then click up it if fine again on some of the rear ring but catches on the front mech on others. My question really is can i just set it to do two clicks? or can i adjust my second click to sit spot on for my large front chainring - then make sure that if i do happen to click it agin it won't fly off the front chainring. what's the best method for cracking this double chainring/front mech issue?

Posts

  • gkerr4gkerr4 Posts: 3,408
    no - the three clicks give you a 'trim' position when using the small chainring and small cassette cog - the triple lever actually has four positions for the same reason!

    I recently setup my triple chainset and it was a complete pain - however, I found that the best setup guide was from shimano themselves. (assuming you have shimano gear!)

    try here:
    http://techdocs.shimano.com/techdocs/index.jsp

    andscroll over 'road' to select your groupset, then look for the front derailleurs and the document which starts "si - " (for service instruction)

    so the tiagra one I used is here:
    http://techdocs.shimano.com/media/techd ... 606943.pdf

    Hope this helps!

    Graham
  • BronzieBronzie Posts: 4,927
    Depends on the groupset you have, but most front mech shifters have a "trim" facility - this allows you to move the front mech by just a small amount to stop the chain rubbing the cage as you move the chain across the rear sprockets. In other words, it's probably a double front shifter anyway and this is normal.

    The correct setup is to have the chain just touch the inner face of the cage with the chain on inner chainring and large rear sprocket - the shifter should be fully released (ie no more clicks down) and the gear cable should be just tight so there is no slack. You may need to adjust the screws on the top of the front mech to get this position right. If the gear cable is slack, adjust it by pulling a little more cable thro the clamp on the front mech.

    Then set the upper limit (again using the small screws on the top of the front shifter) so that on the outer chainring and small rear sprocket, the chain is just rubbing the outer face of the cage again. This should give you the correct full range of movement in the front mech.
  • Thanks, I understand how it all works now - phew no need to fettle ot purchase replacement kit!
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