Compatibility - ST-R9100 shifter and FD-6800 front derailleur

[NHAero]

This looks like it is compatible according to Shimano, but their graphic confuses me as it has separate boxes for the older series. I think the graphic shows that both boxes of FDs will shift the older cranksets but only the new FD series will shift the new cranksets (which is why the FDs are in two boxes).

[prototoast]

Those 6800 FDs barely worked with 6800 shifters. If it were me, I'd spend the $25 for a newer one, but you can probably get it to work as is with enough cursing the 5 inline barrel adjusters.