Please god someone help - Skipping Chain !!

Hi all,

I've got a Colnago Dream with Ultegra 6700 (pic attached) and have been having SERIOUS issues with it. I thought it might have been a bent rear mech hanger but i've just had this changed at Brixton Cycles and everything dialed in and whilst it seemed like it had sorted it after 2 fairly short rides the skipping is back.... and it's driving me insane - and making the bike pretty much unrideable.

On the flat whilst in gear it feels like the rear mech is trying to pull up a gear then flicking back down, and sometimes struggles to shift up, only doing so when i skip up 2 gears (and even then it struggles to change up). It started on the smaller cogs and has very quickly manifested its way pretty much all the way through the gears (small or large front ring making very little difference).

The only thing that i can think it might be is that i changed some time ago from 10 speed 105 to 11 speed Ultegra, and kept the same wheels (Reynolds Attack). When i first made the change i had no issues for months. Could it be an issue with the rear hub/cassette ?

Please please i'm open to any suggestions to try and get this fixed as at the moment i may as well hang the bike from the wall as a piece of art, riding it is just out of the question.

Hopefully someone on here can give me some ideas to at least take back in to BC for them to try if i can't do myself. BC haven't really managed to diagnose anything as it only seems to happen when there is load going through the pedals.

Look forward to people's suggestions.

AJ

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Nice bike. There seems to be an 11 speed freehub body on the market for these wheels. Whatever that means.

Loose guide under the bb.
Back wheel not true/spindle cracked .

something wrong with the chain, probably a side plate coming loose, or a tight link

well the photo shows it cross chained big time which wont help ;) ive known chains to get damaged by that. were too many links taken out the chain?

Thanks guys, i'll check out the spindle, BC didn't mention anything about the wheel not being true and it's been in there 4 times now. I can ask again though.

I did go through a stage of running the big ring more but since moved back to the smaller ring to spin up more, is it worth me just changing the chain in case ? No idea if too many links were taken out. A bike shop fitted the Ulteg for me so i wouldn't have thought so ?

It seems to be that it goes into the shop, is sorted for a couple of rides, then goes back to skipping again, which is what i don't understand. If i take it in somewhere tomorrow what should i be asking them to check ?

Chain wear, BB guide, Wheel Truing, Spindle. Anything else ?

Thanks so far guys !

sounds like a worn cassette to me.

Friend had something similar on her Bianchi with Ultegra, needed almost constant tuning that never seemed to last.
Eventually tracked down to a weak return spring on the new Ultegra rear derailleur.
Changed the derailleur.

I feel like it might be the deraileur as it seems to be fine once it's tuned, then just slip back out really quickly.

No excessive movement on the cassette and chain is still really tight on the front ring. The Cassette and new groupset will have done less than 1k so i'd be surprised if it's them, chain seems fine as well.

Perhaps i'll try a new derailleur first ..

chain / cassette worn ? new chain on old cassette ?

Just watched something on youtube and i think it's the chain. Peddling backwards one particular link is getting stuck and pulls the derraileur. Chain change tomorrow and will report back if it's not that.

Cheers guys !!

Similar to the loose BB guide theory, if the cables are unlubed or routed a little poorly it can be possible to squeeze enough extra movement out of them, usually when pedalling hard, to trigger a phantom semi-shift.

I had a flexy frame (also with 6700 funnily enough) and it would often do this if I let the BB guide (or the cable housing) get gunked up. Cleaning and relubing them usually solved the issue...

Thanks guys, i'll check out the spindle, BC didn't mention anything about the wheel not being true and it's been in there 4 times now. I can ask again though.

Take it to a different bike shop for another look if BC couldn't find anything.

Very hard to find cause without looking at the drivetrain in person.

Peddling backwards one particular link is getting stuck and pulls the derailleur.

What chain is it? Shimano one doesn't have a quick link and need to be rivet in, if using incompatible chain tools, could damage the link and cause it to be stiff.

Best solution really is to removed the offending link and put a 11 speed quick link on (SRAM).

.

Sorted, it was the chain. Had a sticky link. Changed and now back to normal - at last !!!! Cheers chaps !

just wiggle the link to and fro ( sideways ) and it should loosen up

sexy bike...