i have shimano 105 set up with crank arm...
i have shimano 105 set up with crank arm with 3 chain rings. I plan to change crank with compact dura ace which has 2 chain rings. does this create a problem with the shifting of gears?
Yes, your "triple" front derailleur will most likely not work correctly with a "double" crankset right "out of the box." Your chainline will be messed up (check http://www.sheldonbrown.com/chainline.html for info. on chainline). Your left shifter will also likely give you trouble if you have 10 speed 105 (10 cogs in the rear cassette) as it has different model shifters for double and triple. 9 speed 105 shifters are compatible with both double and triple. It may be possible to get it to work consistently by adjusting your front derailleur limit screws, etc. (I'm not even sure how much you can adjust 105) so that it will shift from the small chainring next to large and then just not ever click shifter to the third level but it will take some tweaking/adjusting on your part. Check here: http://www.bikeforums.net/archive/index.php/t-444962.html