D52D13

Bought a used Trek 1.5 and had to replace the FD shifter cable. While replacing the cable I found out it has a Triagra STI triple shifter for the front derailleur but only has two chainrings (50/34). Is this the standard setup? Are there any settings to make it work? Or do I need to add another chainring or change to the Triagra STI FD shifter to work with these chainrings? I am new at bike mechanics.

dsbrantjr

The shifter has positions for 3 chainrings, you need to use two of them. Just set the cable/shifter so that you use the outer two; in this way the cable is slack in the un-used (innermost) position. In this way if you try to shift to the non-existent position the cable will slacken farther. If you set it for the inner two, the shifter can try to shift past the outer ring and you can jam the shifter against the outer limit stop.

oldbobcat

Here's a little background to what dsbrantjr said.

Shimano tried using triple shifters for double applications of Tiagra and 105 for a year or two, but started making double shifters after complaints from consumers and its OEM customers.

The OEM recommended way to set up these shifters was to adjust the cable for the two inner positions (the small and middle rings) and lock out the outermost position using the outer limit screw on the derailleur. Properly adjusted, the shifter should work just like a double.

The problem starts when the cable starts stretching, and the rider instinctively double-shifts to raise the chain to the big ring. This pulls the cable tight against the limit screw, making the subsequent downshift extremely difficult. The rider then forces the shift and breaks the ratcheting mechanism in the shifter, makes a disparaging post on a board such as this, and then grudgingly buys a new shifter. Shimano listened, although many would argue it was too little, too late.

dsbrantjr recommends adjusting the shift cable to use the two outer positions. That way you can't "overshift" when the cable loosens. While I haven't tried it this way, it makes sense. The only disadvantage I can think of is the slack cable possibly getting dislodged from the cable stops while using the small ring.

If you find that you've double-shifted into the big ring and can't get back down, don't force the lever. Just loosen the cable (or let out the outer limit screw) until the downshift ratchets easily, and readjust carefully when you get home.

D52D13

Thanks for the response. While messing with the bike I did "shift in to the big ring" and could not get it to down shift so I loosened the cable. Looks like the best way is to set it up for the inner two rings.