Tiagra ST-4720 on Trek 920 Disc (2016): front derailleur problems I've upgraded my Trek 920 Disc (2016) bike with Shimano Tiagra ST-4720 Dual Control Levers. 

At the same time I've also replaced the disc brake calipers (Shimano BR-MT420) and the rear (Shimano Tiagra RD-4700-GS) and front derailleurs (Shimano Tiagra FD-4700-B).

Everything works well, except for the front derailleur which does not seem to move enough. Meaning that the chain either remains in the lower or higher gear and changing gear is - if possible at all - very rare.

In other words, I have the impression that the spacing between the two front chainrings (of the SRAM S1000, 42/28T crankset) is too big for what the front derailleur is capable of doing.

I suspect a compatibility issue between my front derailleur and the chainrings/crankset. I have tried to look up some specifications about the chainring spacing and the maximal movement of the front derailleur but without success.

Any suggestion on how to make this last piece of the puzzle working would be highly appreciated!
The derailleur is designed for a FC4700 chainset, which from the specs below (x3-x2) is about 7.8mm. If the SRAM chainset is not wildly different from that then I don't suspect the spacing, and SRAM and Shimano chains and cogs are usually sympathetic.

The range of the front chainrings (42-28) is 14 teeth, within the 16 teeth gap the FD4700 can manage, but the 42 tooth is lower than most road derailleurs are specced for. The old road Tiagra (4600) was specced for 50 tooth minimum, but I can't find spec for 4700. 42 does seem like a bit of a stretch outside the minimum value.

So I don't suspect the gap between the two rings, but I do think the low tooth counts are a potential issue.

Beyond that, the newer Shimano front mechs are more involved in how you set them up, you need to eliminate user error in how you set it up. Particularly the limit screws.


Is the derailleur at the correct height and angle?
Did you set up the support plate?
Did you set up the converter correctly? https://si.shimano.com/pdfs/dm/DM-FD0002-05-ENG.pdf
Did you route the cable correctly?
Cable tension and limit screws? I would back off the limit screws to see if that helps, before setting them up again.