Our tandem is equipped with a Shimano GRX 600/810. That works fine, I'm happy with it, however, I'd like to change to 12 speed to get a broader range of gears, which is important for a tandem. To safe money I'd like to keep the front front derailleur and just add an DI2 827 rear derailleur, together with a new right break lever of course. So the left side would stay mechanic, the right side electronic. Would this work?

If not, would it be possible to change the GRX 600/810 mechanic components for the rear derailleur with mechanic 610/820 components?

“brake” not “break”

I’d have thought just swapping the mechanical lever and cassette (for a 2x 12speed) would work. I don’t know if mixing Di2 and mechanical is possible (the front mech has autotrim based on the rear selection for example, not to mention the auto and semi auto shifting) but I don’t think it’s wise.

I don’t see what difference it would make whether you trim the FD manually or the system does it automatically, as long as the front has trim capability. If the chain rubs the FD, you trim - what does the rear shifting care how it’s done?
unless the DI2 system baulks at the absence of an FD - they’re connected, after all 🤔

Not very likely for DI2 to be scared of a missing FD: There is a 1x12 version out there.

Indeed it would probably work, I was just saying it’s designed with an integrated system in mind and spending all that money on half a groupset (which doubtless costs more than half the full thing as you need the pricey rear mech and battery anyhow) seems an odd approach, and you’d miss out on some of the features of the integrated system (and no left hood button for the Garmin either ) and you said you wanted to save money.

I would be more bothered by riding two different hood shapes, regardless of the mechanics working fine.

good point. Didn’t even think of that.

My 11 speed Di2 has fast, reliable front shifting. So much easier than the full throw of mechanical front shifting. And it does an auto trim in three steps as the rear is shifted through it's range. It's really the key improvement over mechanical shifting. (along with using any finger to shift the rear!)


I suppose that's not as important on tandem, where both riders have to be ready for a front shift. On my single bike, I might shift the front at the last minute for a 25 foot hill, since it's so easy.