Front derailleur - Idiots guide to adjust please

Bokdrol
Bokdrol Posts: 15
edited August 2013 in Workshop
Dear All

The wife's FD (Tiagra) on her bike needs a small adjustment - I hope. All gear shifting is smooth without any problems, but some rubbing on the FD occurs only when she is on the smallest gear at the back and on the small cog at the front.

I am hoping a Samaritan will provide me with an idiots guide, or an easy to follow link, to solve this annoying chain scraping on the derailleur.

Thanks in advance.

Photo attached.

Comments

  • freezing77
    freezing77 Posts: 731
    The general advice would be not to use that combination of chainring and cassette as it will accelerate chain and cassette wear.

    http://www.bicyclechainrings.com/crosschaining.html
  • freezing77
    freezing77 Posts: 731
    edited August 2013
    There is a trim position on the shifter to obviate this occurence.

    It looks like the lower stop may need adjusting and cable tension perhaps increasing, preferably by someone who knows what they are doing. The trim on the shifter can then be used.

    But this is only serving to promote bad practice!
  • rhext
    rhext Posts: 1,639
    freezing77 wrote:
    The general advice would be not to use that combination of chainring and cassette as it will accelerate chain and cassette wear.

    http://www.bicyclechainrings.com/crosschaining.html

    +1. You shouldn't need to use that combination as you should be able to get a similar gear ratio using the big ring and the middle of the cassette.

    If you must try to stop the chain scraping, there should be a barrel adjuster somewhere in the cable run (I think there's actually one on the side of the shifter - where the cable emerges). Twisting that will move the cage in/out depending on which way you turn it. The problem will be that if you eliminate rub for that gear combination you'll introduce it somewhere else. I think that the Tiagra shifters have a trim adjuster (so if the chain rubs on the inside of the cage on the big ring, the first 'downshift' click moves it slightly without changing gear), so that might help if you do try to use the barrel adjuster.....but the best advice is that it's not a good idea to use that combination in the first place, and chain rub is nature's way of reminding your wife to choose a different gear!!

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