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@carson
i'm looking at a friend's bike with a front mech shifting problem. there is a lot about on the internet from a few years ago with people having trouble with the 105 double / tripple LH (left hand) shifters - i assumed they would be identical in function to my ultegra shifters and have set up and serviced the bike in the past accordingly - they are not though it seems. if anyone has any knowledge to contribute i would appreciate it.
from what i can gather the shifters were for a period designed to be used on either double or tripple chainring set ups (and so allowed for the lever to move up or down 3 positions). if the front mech was set up on a double chainring but with the gear lever in the first position, the lever would allow you to shift up twice, once onto the big ring, and once, perhaps inadvertantly, again beyond that - limiting the derailleur would stop it pushing the chain off the ring, but the cable tension would be increased enough to fuck up the shifter and sometimes lead to the inside rachet mechanisms failing.
to set them up properly on a double chainring, i'm guessing you need to start fitting and adjusting the front mech with the shifter in the second position. you could then inadvertantly shift down an extra click but without causing any problem as the derailleur limiter screw would stop you chain from being pushed off and the cable would just be a bit slack.
is this right....? am gonna see and play with the bike tomorrow anyway.