How much X chaining should I expect the bike to cope with ?

[Andrew Br]

I've just had fitted Ultegra 8000 series hydro shifters, FD and RD to my Dirty Disco by the LBS. It was an upgrade from 10 speed. I didn't change the chain set which is a venerable Campag Centaur 10 speed compact.
I'm running 50/34 chain rings with an Ultegra 11-34 cassette and a Shimano 11 speed chain. Rear hub is also aged: it's a Hope Evo which can't take 11 speed cassettes with an inner ring smaller than 34.

After the intial "running in" it became difficult to get onto the big front ring so I took it back for adjustment. It now shifts there in an instant but, unless I'm in gears 8-11 (with "1" being the inside, 34 teeth cog and "11" the outside, 11 teeth cog) the chain chatters on the inside of the FD. "Trimming" the FD doesn't help much.

Which gear combos should I reasonably expect to be able to use ?
I'd imagined 1-9 on the small front ring and 3-11 on the big.
Mechanic at the LBS expressed doubt that the Centaur chainset would work. I thought it would (and should), I'm just expecting him to want to replace it as the easiest and most profitable solution.

[Brucey]

FD rubbing depends on setup, obviously (and it can't be quite right if the trimming makes no difference) but it also depends on how stiff the frame, BB spinde and chainset are.  And how hard you push on the pedals, obviously. 

I'd expect you to be able to use more gears than that once the FD is set up and trimmed correctly, but if anything is flexy and/or you push very hard on the pedals, this will result in fewer gears being rub-free.

http://ritzelrechner.de/?GR=DERS&KB=34,50&RZ=11,13,15,17,19,21,23,25,27,30,34&UF=2215&TF=90&SL=2.6&UN=MPH&DV=gearInches

suggests that sprockets 2-7 on the big ring produce gears that duplicate those with sprockets 6-10 on the small chainring. This being the case you could just use sprockets 1-7 on the the small chainring, 4-11 on the big ring, and you would have every gear ratio you would need.

cheers

[rafletcher]

You could try judicious alterations (1/8 of a turn at a time) to the FD stop to limit the outward movement slightly, checking that your shifting is still acceptable. It may also be that a small rotation of the FD clockwise (looking from above) might improve matters too.

As to the chainset, the rings of a 10sp are a greater distance apart (about 0.4mm ISTR) than those of an equivalent 11sp version, and it's possible the (ever so slightly) greater range of movement required by the FD to compensate for this could be exacerbating your issue.

[Andrew Br]

Thanks for the input.
A further trip to the LBS (and a different mechanic) has resulted in a vast improvement; it's now shifting as well as I'd hoped it would.
The solution was to rotate the FD slightly and tweak the cable tension.

Now all I have to do is ride the bike in some rain and/or mud to stop the new brake pads howling .....