I have a 2007 Giant OCR 3, came with a triple Sora shifter and Triple FSA crank (model FSACK400SST). I took off the small ring on the crank and set the limits on the derailleur to make it a modified double (just because I did not like the unreliable triple front derailleur and never used the small ring).

I am now looking to upgrade the crank to a Tiagra double to have a stiffer crank with outboard bearings. Will I be able to use this with the tiple Sora shifter if the derailler limits are set for a double? My concern is that the spacing between the rings might be different on a double compared to a triple, causing the indexing in the shifter to be off. Also, I am concerned the chainline might be different, causing the derailleur not to work on this crank. Any ideas? Thanks!

The change in chainline, if any, can be accommodated by readjusting the limit screws. Otherwise the fd and shifters should work as well as they do now.

I would suspect that if you get the right bottom bracket for a double the chainlines would be different. You want the center of the rear cluster lined up with the middle ring on a triple. On a double you want the center of the rear cluster to be lined up between the rings.

So yeah, it's possible the triple shifter won't work right. Maybe you can mess with the cable tension to fudge it or get a bottom bracket with a longer spindle to position the rings farther out as if they were part of a triple. I've had enough trouble getting crisp shifting and no chain rub on the front even with things that are supposed to work that I'd be worried.

What might be best is to sell your current Sora triple on Ebay and pick up something compatible with a double.

The double and triple both use the same BB, its the Tiagra 4500/4503/4550 English Bottom Bracket.

Might wanna bugger off your triple FD for a smaller normal one too.

For the record, the Tiagra crank worked fine with the Sora triple derailleur and triple shifter. Just set the limit screws, readjusted the FD a little higher to accomodate the larger ring, and worked just like before. The upgrade is awesome, it is way stiffer, the 170 crank arms compared to 172.5 fit me better, and the larger chainrings give a better gear ratio. Now I just can't wait for the ice to clear to get out and put some heavy miles in.