GRX 48/31 with 105 front derailleur

Volsung wrote:The GRX crank sits out a bit farther than a road crank.  It might still work but it'd be less than ideal.

Yes, according to Shimano it's incompatible... The GRX chainline is farther from the frame. Even using chainrings with the same chainline, the 105 derailleur maybe won't be able to be adjusted low enough, I remember a YouTube video where the guy had this problem, causing the chain to fall.

You can try, but I think the best option is a GRX front derailleur, they aren't so expensive, and are 100% compatible with your STIs.

Volsung wrote:Maybe different chainrings for your existing crank?

I am running a Dura Ace front derailleur with 48/31 GRX crankset and 4iiii left power meter one one bike, and a GRX 600 front derailleur with a 4iiii 105 50/34 dual sided PM crankset on another bike. Sounds crazy right?  

Bikes were built 3 years apart, and was just based on what was available at the time. There is enough adjustment to work with the different chainline. 

widerisfaster wrote:

I am running a Dura Ace front derailleur with 48/31 GRX crankset and 4iiii left power meter one one bike, and a GRX 600 front derailleur with a 4iiii 105 50/34 dual sided PM crankset on another bike. Sounds crazy right?  

Bikes were built 3 years apart, and was just based on what was available at the time. There is enough adjustment to work with the different chainline.