Shimano GRX chainset compatibility question

Hi all. Happy New Year.

Probably a stupid question, but can you use a standard Shimano road chainset (e.g. 52/36 Ultegra) with the rest of the gearing being Shimano GRX di2? If I wanted to go for 52/36 up front and an 11-40 cassette at the back, would I need to swap in a standard di2 front derailleur (so ultegra di2 up front and grx di2 at the back)?
The GRX di2 front derailleur is apparently set 2.5mm further out than a standard Shimano derailleur, so I’m not sure if it’s compatible with an Ultegra chainset.

GRX chainset (crankset for US people) and the matching GRX front derailleur are 2.5mm more outboard (for tire clearance). So, it’s best to use matching chainset & FD (Road or GRX) to keep that aligned.

Besides that, I think mixing Road front and GRX rear can work. Just be sure to confirm chain takeup specs between the rear derailleur and the gaps between the chainset chainrings.

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Thanks Chad, that makes sense.

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Here’s a compatibility chart that MAY help.


Im not sure there rear derailer can take up enough slack for that wide of gear range,

I run an 8000 series Ultegra 46/36 up front and GRX 800 in back with 11-34 out back. I have no issues with the 2.5mm offset. I want to try a little larger cassette, but not sure if my RD will handle it.