Front derailleur indexing fail

Equipment
1

My front derailleur will only shift from small to big ring if I am in the 11 or 12 tooth cassette, and the derailleur then rubs on the outside of the chain. In the larger sprockets the front derailleur doesn’t move outward enough to allow the shift from small to big ring. I have installed new cables, happy with the derailleur alignment and height, L screw limit and there is plenty of cable tension (although have to fully unwind barrel adjuster for it to make the shift). I have tried to unscrew the H limit screw to move the derailleur outwards and give the chain more room, but this has no affect and does not move the derailleur (even fully unscrewed).

Anyone know what the issue might be or how to fix this?

edit: it is a Shimano ultegra FD-R8000, mechical.

2

Not really! We can start with, what model of front mech is it?

3

Shimano ultegra FD-R8000, mechical.

4

I know you said you were happy with alignment, but that is where I would look first from what you describe.

Mike

5

Can’t recall this from memory, but this dealer’s manual:

https://si.shimano.com/pdfs/dm/DM-RAFD001-04-ENG.pdf

Says to turn H limit screw clockwise in order to get more movement to the right (into the direction of the big ring). Normally screwing the limit screw in gives less movement, this appears to be the opposite.

Edit: page 19

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6
7

Sounds like not enough cable tension to me.
Also, can the derailleur cage rotate? It might be pointing too much inwards.

8

Thanks for all the advice, I have fixed the problem thanks to @alexgold123.

It wasn’t the limit screws, but the user manual was the answer. It recommends adjusting the cable tension in the middle ‘trim’ position, instead of the little chainring like every other resource on the internet suggests. When I moved the chain to the trim position and pressed on the FD spring to move it across to the big chain ring manually, it revealed some loose cable tension, which I was then able to tighten. Now I have perfect shifting!

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9

They made the new front derailleurs way too complicated these days. I found that this video bellow to work best for the new Shimano Front Derailleurs. They should have left them alone with the prior model ones but we had to get clever with the new ones. Shimano Ultegra R8000 Front Derailleur Fitting Guide - YouTube

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10

Well, the long arm design was decent in use, but quite limiting for the expansion of tires. Perhaps they could have tried to keep more of that than the current whiz-bang model, but this was driven from desire to fit wider tires on road, all-road, and gravel bikes.

And that old one wasn’t without it’s own quirks. I still use the Allen wrench trick that worked to make them easier to set up, with the latest gen versions. Seems the the pretension is something I fight with in all the later models.

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