yannisg

Shimano FD-8000.
Upper and lower limits adjusted.
Cage parallel to large sprocket.
FD height within spec
Cranks FSA compact.
Middle adjustment aligned.
The problem is the following:
From lowest position to middle FD does not move even though the shifter "clicks" and the wire tightens imperceptably to the "touch".
In this position the FD cage will not rub unless I go below the 3rd smallest sprocket, and the chain will not rub while in the large chain ring, and the 2nd largest sprocket.
If I tighten the barrel adjuster on the cable the FD will move slightly to the middle position.
However, then when in the large ring, and the 3rd largest sprocket in the cassette the chain will rub on the left side of the cage even with the FD adjusted to the step down mid position.
I can live with the 1st condition since I would rarely go into the 2nd smallest sprocket while in the small ring which would enable me to go to the 2nd large sprocket in the cassette while in the large chain ring occasionally.

I don't remember having this problem with the FD-6800 ST 6800 shifters.

Any advise appreciated.

Iride01 

Is this a 3x crank? The FD-R8000 is only for 2x, IIRC.

yannisg

2x crank

Iride01 

Then I'm not understanding what you mean by this...

If you are talking about shifting on the rear, then the FD is not ever going to move when you shift the rear.

What model of front shifter are you using? And have you followed the installation steps in here and paid attention to all the side notes and pictograms in it?
https://si.shimano.com/en/pdfs/dm/RA...001-05-ENG.pdf

The cable really shouldn't tighten noticeably at all when you shift. It should have about the same amount of tension on it when in either ring. If you have it too slack when in the small ring then it will be wasting pull that should be being used to move to the bigger ring.

yannisg

I am not talking about shifting in the rear.
The FD has a middle position so it is better aligned when you are in the smallest sprockets.
The cable is not too slack when in the small ring, and as I said, the shifter clicks into this middle position, but the FD does not respond.
If I tighten the cable slightly the FD will respond into this middle position, but the other aforementioned problems arise.
This middle position is an alignment, and not to be considered as a shift. In the same way there is an alignment move from the large ring towards the small on when you are using the large rear sprockets.

SoSmellyAir

While hardly clear, I think by "middle" yannisg means FD in Top Trim position?

DM-RAFD001-05-ENG.pdf (shimano.com)

Please review page 18 above and confirm whether you are talking about "(x) T-trim"?

I also do not know what you mean by from lowest position to middle. Assuming that you are talking about T-trim, it is much hard to shift into T-trim from either Low or L-trim than from Top.

well biked

I know what he's saying, and I think the answer is a second look at both limit screw settings. That derailleur is designed for extremely close tolerances regarding the limit screws. Getting that set up right, along with correct cable tension, derailleur mounting position, should take care of the trim function not working well.

Le Mechanic

This style front derailleur is a very different set up wise than all previous Shimano front derailleurs. It sounds like the cable tension is not tight enough. Are you tightening the cable with the outer cage in the came plane as the big chainring by temporarily tightening the low limit screw? I made a set up video a few years ago that might be helpful -

Kontact 

What the OP is experiencing is the normal result of using aftermarket cranks with Shimano shifting. Shimano cranks have the chainrings spaced wider than the FSA cranks, so the range of 4 positions covers that distance. The FSA chainrings aren't four clicks apart, they only use the distance of the top three clicks. There is no good way to correct the cranks.

If you have the low position synonymous with the low trim - that's about all you can do. Every Specialized I assembled with Shimano shifters and aftermarket cranks went home the same way.

SoSmellyAir

You are good! I get what you are saying, but I am still not sure what the OP meant or whether the OP meant to distinguish the "middle position" from the "step down mid position".

My Cannondale Synapse came with Si cranks, a 110 BCD Hollowgram spider, and FSA chain rings, which I replaced with Shimano 105 (5750) chain rings.

(a) I can get the FD to move through all 4 positions, but L-trim is not really necessary.
(b) In the T-trim position, there is obvious chain rub with the largest cog and slight chain rub with the second largest cog.
(c) In the Low position, there is progressively worse chain rub starting with the fourth smallest cog.

In view of what you said about the distance between the chain rings, should I try thin spacers between the spider and the small chain ring? Does that improve both (c) and (b), or just (b)? Does having a more inward L-trim position also result in a more inward T-trim position?

Kontact 

Re-read what I said about correcting the cranks.

SoSmellyAir

I did the first time. Do you mind explaining why what I had suggested with adding chain ring spacers to slightly increase the distance between the two chain rings would not work?

Kontact 

Because the chain will catch between them. Shimano rings are sloped inside.

SoSmellyAir

Even with only 0.6 mm thick spacers? How about installing the small chain ring inside out? Like you said, the chain rings are dished, so doing so should move the teeth of the small chain ring very slightly inward.

Kontact 

Let us know how that works out of you.

yannisg

Let me try to clarify the situation based on Shimano's technical instruction.
I have followed the TI and this is the 2nd FD-8000 that I have installed.
On another bike with a FD-8000 this situation does not occur.
So, FD is in position "V". Cable has no slack.
Down shift (towards large chain ring) shifter clicks, but FD does not move. Cable tension increases slightly.
Down shift a 2nd time and FD goes to position "Y".
Trim Shift (towards small chain ring) and FD goes to position "X".
Up shift and FD goes to position "W"
Up shift once more FD goes to position "V".
In other words, on the down shift the FD goes not go through position "W".
In this situation, when I am in the small chain ring, and down shift to the 3rd smallest cog the chain rubs on the right side on the FD cage. I would like to be able to move the FD to position "W" to eliminate the rub.
If on the other hand, I tension the cable slightly so the FD moves to position "W" on the down shift the following problem arises.
When the FD is in trim position "X" and I am in the 3rd largest cog the chain rubs on the left side of the FD cage;
I can use the 1st situation, but I find the 2nd situation limiting.
I hope I've clarified the situation better.
Thanks for responding

Iride01 

If you add trim when you get to the larger rear cogs, then are you removing the trim when you come out of those larger rear cogs? Use the big lever to remove the trim.

Did you ever say what shifter you are using?

yannisg

Shifter is ST-8000.
I checked with my other bike (Same shifter and FD) I can go from position "V" to "W". The FD moves when downshifting from "V" to "W". Cable tension at position V similar.
The only difference except for the cranks is that the cable routing is internal on discussed bike.

Iride01 

Perhaps a video of what you are trying to explain might help.

If the two bikes have differing chain stay lengths then the one with the shorter chain stays might put the chain at angles that you'll have a hard time keeping off the FD cage even when trimmed.

I'm not able to follow your explanation of what is happening when or what is not happening.

yannisg

Kontact's point that FSA cranks and Shimano shifting are not compatible is the most valid.
My other bike has Rotor cranks, and on this bike with same shifters and FR I don't have this problem

Kontact 

This is not an adjustment problem the chainrings are too close together for the shifter. This is just likr tryong to shift 9 speed with an 8 speed shifter.

The best solution. Is to have both high trim positions and make the two lows the same.

yannisg

At some point, out of curiosity, I'll measure the chainring distances.
The two low positions are the same.
Thanks