Please Explain Shimano Front Derailleur Shifting!
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  1. #1
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    Please Explain Shimano Front Derailleur Shifting!

    I just got into road biking, though I've been doing mtn biking for a while. I got a 27 spd road bike with 105 shifters/Tiagra FD/105 RD. I'm trying to figure out how the FD shifting works. It seems like there are some "inbetween" shifts. Definitely not just the 3 shifts, like I'm used to on my 24 spd mtn bike.

    Why are there more than 3 shifts? It seems to me that you use a "big" shift to get the distance needed to get into the next chainring, and then pop it back a "small" shift to get it to ride smoothly in that ring. Am I insane or does this sound right to anyone? In either case, please explain it to me!

    Thanks,

    Chris

  2. #2
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    Quote Originally Posted by Creelove
    I just got into road biking, though I've been doing mtn biking for a while. I got a 27 spd road bike with 105 shifters/Tiagra FD/105 RD. I'm trying to figure out how the FD shifting works. It seems like there are some "inbetween" shifts. Definitely not just the 3 shifts, like I'm used to on my 24 spd mtn bike.

    Why are there more than 3 shifts? It seems to me that you use a "big" shift to get the distance needed to get into the next chainring, and then pop it back a "small" shift to get it to ride smoothly in that ring. Am I insane or does this sound right to anyone? In either case, please explain it to me!

    Thanks,

    Chris
    Sounds right. Downshifting is more or less indexed. That is to say there are only 3 different positions for the FD to be in. However when upshiftinting, there are a lot more "clicks". That is called trimming. Trimming allows you to move the FD by small increments to avoid the chain rubbing on the FD. This feature is espcially useful on a triple setup ( which I have).

  3. #3
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    Detents

    If you have a triple (three chain rings) you should have four main positions, one for the big ring, one for the granny, and two for the middle ring (one on either side of the middle ring). When on the middle ring the two positions on either side allow you to access all cogs on the cassette without chain rub. Shifting from the granny ring to the middle ring normally requires taking the derailleur to the position right of the middle ring (second click) in order to get the chain to climb onto the middle ring. Then if you are riding on the left most two cogs cassette you will need to move the derailleur back to the position just left of the middle ring to avoid chain rub. Through the past 5 years Shimano has added trimming features to the shifters that may be used to move the derailleur 5mm from the extreme left side or from the extreme right side. My wife's 2003 Ultegra shifters have the additional trimming, her 1998 Ultegras did not. The same shifters are used on doubles and triples which I think creates a lot of confusion for double owners.

    ~Al

  4. #4
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    why I like Campy...

    All of the clicks are the same, no partial or soft clicks and the left shifter works equally as well with double or triple cranks. Double cranks use the same clicks for the small and big ring that triples use for the small and middle ring. Doubles don't have access to the extra clicks needed for the triple, since they are beyond the limits imposed by the big ring limit screw on the double derailleur. Double users may not even realize that the extra clicks are there.

  5. #5
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    Trimming?

    Quote Originally Posted by C-40
    All of the clicks are the same, no partial or soft clicks and the left shifter works equally as well with double or triple cranks. Double cranks use the same clicks for the small and big ring that triples use for the small and middle ring. Doubles don't have access to the extra clicks needed for the triple, since they are beyond the limits imposed by the big ring limit screw on the double derailleur. Double users may not even realize that the extra clicks are there.
    I don't necessarily agree or disagree. I ride D-A 9-speed double and Record 10-speed double, may wife rides Ultegra 9-speed triple. I prefer the way the D-A front shifter works because it is double specific. It has two positions, one for each ring plus soft click trimming. After 7 years I have never needed to trim the front derailleur because the chain never rubs. I'm ok with the Record 10 but it needs to be trimmed when I use more than six or seven cogs with the chain on either chainring. With a double I would rather have a slightly wider derailleur and no clickstops at all.

    ~Al

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