I know that 105 5800 shifters need to be mated to 5800 series derailleurs only. This is due to the cable pull the 5800 uses compared to 5700.

Its news to me though that 5700 10sp 105 front derailleurs will only work with 105 cranksets. Thats...odd.

Couldnt you just get a 105 triple and swap the chainrings as needed to get the gearing you want? The granny ring is a 74bcd on the older 5 arm 105 10speed cranks. Youold get a 26t ring for it instead of the stock 30t.


Back to 105 derailleurs only working with 105 cranks...that cant poasibly be correct as i know of 4 bikes off the top of my head from riding buddies which use FSA cranks.