Campagnolo Chorus rear mech setup

I've just rebuilt one of my bikes with Chorus.

When i set the rear mech up, it shifts fine initially at the bottom of the cassette, but seems to get out of sync as it moves up the block towards 1st gear.

The rear mech will be in 1st and the shifter still click as if it's got another gear to go, but it doesn't appear to move and doesn't over shift (limit screws are set correctly at both ends)

it's like the shifter clicks 10 times for the 11 positions, but the rear mech is skipping up a gear somewhere along its travels.

I suspect it's a bent mech hanger? the rear mech was working fine when i removed it from the previous bike it was on.

Any help appreciated!

I suspect it's a bent mech hanger?

My first thought; check that first.

Yep, i've ordered an alignment tool, so i'll do it when it arrives.

Earlier in the week, I ordered the only spare hanger i can find on the entire internet and royal mail seem to have lost it.

Have you got all of the spacers in the right place? Campagnolo cassettes tend to have different spacings as you move up the block. Also sometimes the cable isnt as tight as you think, the shifter starts slipping that first gear as you try to locate the cable. I tend to back off the adjuster screws, set the barrel adjuster somewhere central ie start again. You can try and trick the mech ie push it in a bit as you tighten down the cable, then slack it back off with the adjuster to sit on the 1st sprocket. Sometimes they just never seem to set up right in which case id rather do an extra little half shift to move up the block than have it refuse to go back down again so i set the bias that way.

11 speed spacers are all the same width. A method I have read and helped me a bit is to shift up to about the 5th sprocket, then fine tune the chain / jockey wheel alignment using the barrel adjuster.

My first thought, too.
I had the exact same issue with the same mech and, with a bit of 'tweaking' of the hanger, it was sorted.

Great, this gives me some confidence at least that it’s the hanger and hopefully not the mech being trashed

OK so quick update, i bought a half price mech alignment tool and tweaked the mech hanger quickly this afternoon.

It's lots better, it now shifts well upto the extremities of the block with the right number of clicks.

it seems quite sensitive to cable tension and i can get it to shift well up the block but not down or vice versa if i adjust the cable tension, maybe i'll reset the limit screws and set everything up from scratch tomorrow.

maybe i'll reset the limit screws and set everything up from scratch tomorrow.

I'm sure you know, but the limit screws only determine how far the derailleur can move outward maximally at both ends of the cassette; it doesn't have any effect on shifting up and down the cassette. So I won't get my hopes up that resetting them will improve anything.

What about the cables? Are they used? Consider getting new ones. My bike shifted like crap, and I was worried the shifter was toast. Turned out the cables were totally corroded.

Yeah of course, the limits do actually look ok currently.

The shifters and cable set are all brand new, maybe i'll ride it round the block a bit and see if i can get the tension right

If it will shift correctly one way and not the other, and all other factors around alignment are catered for, that suggests a spacing issue, a derailleur set up error (in some circumstances), friction in the cable system or incorrect cables.

Check:
Cassette spacers are correct - Krankers is not strictly correct, they are only "all the same" on the Potenza and Centaur cassette - Chorus (which is used on many occasions with the Centaur group), Record and Super Record all have a 2.3 mm spacer between sprockets 6 and 5 (counting the smallest sprocket as number 1), all the other spacers are 2.2 mm.
Cassette properly tight (40nm tightening torque).
Cassette body properly tight on the axle (the fixing nut is LH threaded, 16nm torque).
"H" screw correctly set on the biggest sprocket / small chainring combo - especially if you are running a wide cassette like 11-29 or 12-29.
Campagnolo cables (not "compatibles") and new outers, also Campagnolo, metal (not plastic) ferrules. You'll read all over the place this makes no difference - it does.
Don't "California Cross" (unless the frame / cable guide system is designed specifically for it).
Internal cables - make sure the cables are not interfering with each other.
Under-bracket tunnel - make sure it's clean, that it's tight to the frame and that it's not worn - cables can wear a groove that eventually traps the inner, adding friction.
You generally have approx 1/2 turn of the cable adjuster lattitude each way from the perfect "sweet spot" (same as Shimano) so dialling in should not be super-hard.
Last - limit screws can affect cable tension but maybe not in quite the way you might expect - so, disconnect the RD cable, set the high limit screw without the cable attached, then attach the cable and tension. If you adjust the high limit screw with the cable attached, it may be the cable that is limiting how far towards top gear the RD can travel, so preloading the cable more than it would be pre-loaded by correct use of the limit screw & barrel adjuster.

Excellent, thanks for all this info.

I have re-done everything this morning, it seems to be working ok so far, i would say the only thing is it's a bit lazy going from the smallest 11t sprocket up to the next gear, but it's fine up and down the rest of the cassette. I think it might need a retune after a few rides