Dave Stallard said:I was testing riding some bikes built up with Dura-Ace and Chorus yesterday. The Dura-Ace was
9-speed, I think the Chorus was 10-speed. One thing I did notice on both was some chain rub against
the front cage. Is this an inevitable fallout of the move to ever larger number of rear cogs? I
think I've heard of "trim clicks" for the front derailler; are these designed to handle this
problem? And how do you use them?
After monitoring this thread for a few days now (and contributing one article) I got curious. I just
now went down to the garage and checked the trim capability of both Dura Ace ST-7400 and ST-7700-C
shifters. I removed the chain from both bikes and counted the detents (trim positions).
The ST-7400 (Dura Ace 8-Speed STI) has six detents (seven positions). Starting from the left-most
position and gently pushing the big lever, the sixth click is as far as it will go. A gentle push on
the small (inner) lever will then cause the derailleur to shift to the left a small amount. Another
push will cause it to return to the left-most position.
I tried the same experiment on the ST-7700-C (Dura Ace 9-Speed STI) with somewhat confusing results.
Most of the time I could only count five detents (six positions), but a time or two I got the
derailleur to stop in a position for which I could perceive no click. I would have expected the
newer shifter to have at least as many trim positions as the older model.
While I had the 9-speed bike on the stand I also checked out the big-ring trim. Turns out the first
click on the inner lever while in the right-most position moves the derailleur two detents. In other
words, you can get to an intermediate trim position by clicking the inner lever once and then gently
pushing the big lever one click. I didn't go back and check the older bike for the same capability.
Now that I'm back at the computer it occurs to me that perhaps I had difficulty finding detents on
the newer bike because I've been riding lately with a Gatorade solution in my water bottles. Could
be the BB cable guide is slightly gummy. Also I may have adjusted the cable tension and derailleur
stop so that there's not enough free play to allow the shifter to go down to its last position when
downshifting. I'll have to check this out, but not right now. :-)
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