Motorazr

Posting this here because it's a gravel-specific question: Has anyone tried upgrading a Tiagra 4700 front derailleur (braze-on) for a GRX 400 version? The Tiagra 4700 FD has a long lever arm which just barely clears a 38mm width tire on my Specialized Diverge.

The most obvious compatibility issue is that the chain line for the GRX FD is 46mm whereas Tiagra is only 43.5mm. I'm not sure if I can overcome that difference using the Hi/Low screws. Also the Tiagra FD has a long lever arm absent on the GRX (for greater tire clearance) so I'm wondering if the two brifters have different leverage. I'd like to upgrade both front and rear Tiagra derailleurs to GRX and thus gain a clutch mechanism in back and more tire-clearance up front. Does anyone know if the front derailleur swap is possible?

https://bike.shimano.com/en-EU/produ...FD-4700-F.html

https://bike.shimano.com/en-EU/produ.../FD-RX400.html

tdilf

https://www.bikeforums.net/cyclocros...-question.html
might answer some of your question

Motorazr

Thanks for the link! Perhaps no one here has made this front derailleur change - maybe because it's too problematic. I'm still looking for a definitive answer. Thanks again.

RocThrower

According to Shimano's compatibility chart, your 4700 shifters will work with the GRX-400 front derailleur:


I think the bigger issue is going to be the chainline difference that you already mentioned. If I was going to a GRX front derailleur, then I would also change my crankset to GRX.

jonathanf2

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This particular bike is running GRX 400 front and rear derailleurs, a GRX 600 10 speed crankset, with Tiagra 4700 brakes/shifters. A good option if you want to run mechanical brakes as opposed to GRX hydraulic brakes for ease of maintenance.