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My bike's stock componentry was Ultegra Di2 6800 (compact 11-32 / 50-34)

Last month installed new semi-compact R8000. Chain left as was. Smooth shifting as per usual.  Very happy. All good.

Two days ago, I ditch the Ultegra cassette/chain and add a shiny new Dura Ace C9000 11-25 cassette and a KMC X11EL (nothing out of the ordinary) - but ever since, the shifting is all out...ESPECIALLY from 11 to 10

It actually shifts kind of OK between 9 - 1 but no where near as crisp as it was before. No amount of micro shifting does the trick. Basically, if you get it perfect in one area (near enough impossible) it goes out in another.

For the KMC chain, I have kept the same chain length again - though it was slightly shorter due to old one having 1cm stretch - and visually it looks OK....but I can't be 100%

Also, mech hanger looks OK and is unlikely to have been damaged during work being carried out....but again can't be 100%

So, I'm confused: too long a rear mech cage... chain compatibility/length... alignment issues...bent hanger or bent cage.....or what?!

Any ideas?

Thanks

31 comments

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CXR94Di2 [2151 posts] 3 weeks ago
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Did you adjust the b screw when fitting a smaller cass?  It should be adjusted, so rear derailluer just clears the largest cog.  The next thing to consider chain length. 

 

I had a similar problem shifting down onto the 13t,12t,11t and decided my chain was too short, so bought a longer one (one link) and this cured the poor shifting, because the derailleur was now further forward and had more wrap around the cogs and jockey wheel

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Plasterer's Radio [416 posts] 3 weeks ago
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Turn the chain around to run the other way.it may be designed to run in one direction.

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shmooster [28 posts] 3 weeks ago
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If you've gone from 11-32 you must be on a GS derailleur, that has a minimum low sprocket of a 28, you're running a 25 so really need an SS derailleur. You can try tweaking the B screw but you're operating the derailleur out of spec.

https://bike.shimano.com/en-EU/product/component/ultegra-6870-di2/RD-687...

KMC chains are not directional (that I've seen anyway).

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fukawitribe [2500 posts] 3 weeks ago
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Anecdotal evidence from the 'tubes suggest that GS derailleurs shift 25T cassettes just fine, even though not officially recommended.

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kevvjj [403 posts] 3 weeks ago
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shmooster wrote:

If you've gone from 11-32 you must be on a GS derailleur, that has a minimum low sprocket of a 28, you're running a 25 so really need an SS derailleur. You can try tweaking the B screw but you're operating the derailleur out of spec.

Surely if it shifts perfectly well on a 11-32 it should have no issue shifting to a 25 tooth cog? Surely somewhere on the 11-32 cassette there exists a 24/26/26 tooth cog?

The issue is more than likely (as already mentioned) chain length. Given you have gone up two teeth in the small chainring and down 7 teeth in the laregest cog it would make sense that the chain lenght needs to be shorter than you had previously.

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shmooster [28 posts] 3 weeks ago
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fukawitribe wrote:

Anecdotal evidence from the 'tubes suggest that GS derailleurs shift 25T cassettes just fine, even though not officially recommended.

Anecdotal evidence from the tubes suggests lots of things  1

It might work, so worth tweaking the B screw to bring it closer, but more likely to be sensitive to anything slightly off (chain length, bent hanger, dirty cassette or chain etc). Shimano wouldn't go to the bother of having two different derailleurs without a reason.

New derailleur not cheap, if the OP has an 11-28 lying around maybe worth a bash as a compromise?

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shmooster [28 posts] 3 weeks ago
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kevvjj wrote:

Surely if it shifts perfectly well on a 11-32 it should have no issue shifting to a 25 tooth cog? Surely somewhere on the 11-32 cassette there exists a 24/26/26 tooth cog?

By that logic you could have a 32-11 instead of an 11-32

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VeloUSA [264 posts] 3 weeks ago
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Two issues you are faced with.

1. If you're running a GS cage, Shimano states low sprocket minimum is 28t. Yeah, didling aound with the b-screw might get it to work but the spring tension will be off causing the 10-11 shift issues to occur. Ideally an SS cage for 11-25 is the better match.

2. Shorten your chain. Here's an how to video..skip to 3:34 for mathmatical formula.

https://www.youtube.com/watch?v=Vg2SoOOrpE8

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jterrier [209 posts] 3 weeks ago
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As above, your chain is too long,so is your mech,and your b screw is way out. Fix all 3.

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madcarew [748 posts] 3 weeks ago
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Your mech is no issue as it is designed to shift on any sprocket down to a 10. The shimano recommendation is that if going above a 28 for largest sprocket you will need a gs derailleur. The issue is simply chain length. You have about 6 extra links in it. Fix this and the B screw and you will be fine.

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kevvjj [403 posts] 3 weeks ago
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shmooster wrote:
kevvjj wrote:

Surely if it shifts perfectly well on a 11-32 it should have no issue shifting to a 25 tooth cog? Surely somewhere on the 11-32 cassette there exists a 24/26/26 tooth cog?

By that logic you could have a 32-11 instead of an 11-32

If the GS derailleur shifts from 11 -12 then 25 can't be too small can it. Have a think about it...

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rambino [11 posts] 3 weeks ago
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Thanks guys.

Tonight I tried out my old Ultegra 11-32 - just to be sure about there being no hanger/cage damage - and the shifting was buttery smooth between all shifts.

So, I guess that means it must be to do with the chain length and b-screw then

I'll have a fiddle around tomorrow and if I cant sort it out myself then it'll have to be a LBS job.

Oh and just one more thing... if I accidentally remove too many links on the chain, will it be OK to reinstall one of the links with the regular pin or would I need to use another quick link?

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CXR94Di2 [2151 posts] 3 weeks ago
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Before you start removing links from chains, take two side on photos of the bike showing the chain ring and derailleur in the whole photo.  One photo with the chain on the inner ring and on 11t cog and the other photo with the chain on the outer ring on the 11t cog.

just by looking at the derailleur positon, it should be clear whether you need to remove or even get a longer chain, see my derailleur in big chain ring and 11 cog

 

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madcarew [748 posts] 3 weeks ago
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rambino wrote:

Thanks guys.

Tonight I tried out my old Ultegra 11-32 - just to be sure about there being no hanger/cage damage - and the shifting was buttery smooth between all shifts.

So, I guess that means it must be to do with the chain length and b-screw then

I'll have a fiddle around tomorrow and if I cant sort it out myself then it'll have to be a LBS job.

Oh and just one more thing... if I accidentally remove too many links on the chain, will it be OK to reinstall one of the links with the regular pin or would I need to use another quick link?

If it is a shimano chain you will need to use a specific shimano replacement pin, but really it's easier to just use one or more quick links.

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madcarew [748 posts] 3 weeks ago
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Better diagnostic photos are big-big and small - small.

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rambino [11 posts] 3 weeks ago
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Can't upload 2 at the same time for some reason, but here goes....

Looking at the bib-big picture I'd say it almost looks like I've already taken out 1 too many links, right? Though, it's not as if I'm ever going to be riding in this gear so perhaps it's fine as is?

 

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rambino [11 posts] 3 weeks ago
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Small-Small

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CXR94Di2 [2151 posts] 3 weeks ago
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the small small photo, the chain looks slack as though the derailleur has no more spring tension. Take one more photo with it big chainring and 11t cog please. I would say chain is too short by one link(2pairs)

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rambino [11 posts] 3 weeks ago
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Here you go...

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CXR94Di2 [2151 posts] 3 weeks ago
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The final photo, there looks to be plenty of wrap around the 11t cog and the jockey wheel.

A quick check, you fitted a 11 speed chain not a 10speed? There is a small difference in external width, a chain can sometimes be reluctant to drop down a cog because it's sits on the edge of the larger cog.

Did you fit the Cass yourself? Check the cogs are all facing the correct way, eg all numbers face outward

finally it could be just a compatible issue and kmc doesn't like the Dura ace cassette

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rambino [11 posts] 3 weeks ago
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Yes, I did the cassette myself. 

Chain definitely 11 spd

Really can't see why KMC would make a chain that wasn't compatible with Shimano 11spd drivechains. I've checked online and can't find any mention of compatiblity issues.

I bought the cassette, 2 new Corsa G+ clinchers, lates tubes and the KMC X11el chain to breathe new life into my bike's recently redundant stock DT Swiss RR21 wheels, which had been shod with GP4000 clinchers. The sidewalls had worn through on the Contis so I'd been cycling around on the massively practical Bora 50 tubulars. But get this, after fitting the new tyres, tubes, chain and cassette, I took the bike for a ten minute spin to a mini Sainbury's. And in that time, all of ten minutes, I somehow managed to destroy both brand new tyres. First the front brake shoe spun around, destroying the tyre wall and buckling the wheel, then, when i got home to inspect the damage, I realised that my rear tyre had a massive gash in it, just above the side wall. Talk about bad luck, right? That or somebody sabotaged my bike whilst I was in Sainsbury's. Both tyres now complete write-offs. Anyway, this is why I've gone back to the really annoying Bora tubulars which you see in the photos. Though, weirdly...the 11-25 shifts slightly better attatched the Campy free hub body than the DT Swiss. Very odd, very confusing and very annoying. I can still ride my bike but the shifts are just very clunky. Forget about shifting out of the saddle whilst attacking a climb! Because hey, that's always been my strong suite!! Not...

Now I'm waffling...

Thanks for the help and advice

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Podc [105 posts] 3 weeks ago
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Sorry if this is insulting but is the wheel seated in the drop-outs properly?

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rambino [11 posts] 3 weeks ago
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Podc wrote:

Sorry if this is insulting but is the wheel seated in the drop-outs properly?

No, not insulting...

Just a moment ago I removed the wheel, checked the cassette and inspected the dropouts and all looks good.

Everything should work together fine - compatibility should not be an issue.

Current and last generation Dura Ace and Ultegra are cross compatible. And the 11spd KMC chain has been specifically designed with these groupsets in mind. It should work!

I'm almost back to thinking the mech hanger is slightly bent, but ...the drivetrain returns to normal if I go back to the ultegra cassette, so it's unlikely.

I'd temporarily go back to the 11-32 had I not shortened the chain so damn much!

I'm totally at a loss. 

Looking like a LBS trip.

 

 

 

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kevvjj [403 posts] 3 weeks ago
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That chain looks too short by a couple of links at least. That shouldn't really affect the shifting as much as you state though. Have you played around with the limit screws? From experience I have found that there is often a subtle difference in overall width between some cassettes and getting the limit screws adjusted makes some difference, especially when shifitng from the biggest cog.

I really would also check the B screw adjustment too.

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kevvjj [403 posts] 3 weeks ago
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Oh, and if your new chain shifts perfectly on your old cassette then I would also check (as previously advised) the cog orientations on the new cassette.

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mc [7 posts] 3 weeks ago
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Looking at the photos, the B-screw needs adjusted to bring the top jockey wheel nearer the cassette while on the biggest sprocket, however that may mean it fouls on the smaller sprockets.

The problem may be the GS is designed to have a higher ramp over the cassette, so with the B-screw adjusted so it clears the small sprockets, the gap is too large on the big sprockets, which can cause imprecise changes/jumping.
Whereas the SS will be designed to have a shallower ramp, and keep closer to the sprockets. (Ignoring the chain growth problem, if you were to fit it to a wide range cassette and adjust it to clear the large sprocket, it would likely be too far away on the small sprockets, giving shifting problems on the smaller sprockets)

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rambino [11 posts] 3 weeks ago
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mc wrote:

Looking at the photos, the B-screw needs adjusted to bring the top jockey wheel nearer the cassette while on the biggest sprocket, however that may mean it fouls on the smaller sprockets.

The b-screw is currently all the way out - so don't think I can get it any nearer the cassette. Besides, it doesn't seem to make a huge amount of difference how the b-screw is set.

 

kevvjj wrote:

That chain looks too short by a couple of links at least. That shouldn't really affect the shifting as much as you state though. Have you played around with the limit screws?

 

Are you absolutely sure about chain length? Look at how stretched it is in the big-big picture. I'd be worried taking any more off.

And no, I haven't fiddled with the limit screws. If memory serves me correct you need to be extra careful with the limit screws on Di2 RD's? Apparently if not set correctly it can greatly reduce battery life? I'll have a go anyway.

 

Thanks

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kevvjj [403 posts] 3 weeks ago
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rambino wrote:
mc wrote:

Looking at the photos, the B-screw needs adjusted to bring the top jockey wheel nearer the cassette while on the biggest sprocket, however that may mean it fouls on the smaller sprockets.

The b-screw is currently all the way out - so don't think I can get it any nearer the cassette. Besides, it doesn't seem to make a huge amount of difference how the b-screw is set.

 

kevvjj wrote:

That chain looks too short by a couple of links at least. That shouldn't really affect the shifting as much as you state though. Have you played around with the limit screws?

 

Are you absolutely sure about chain length? Look at how stretched it is in the big-big picture. I'd be worried taking any more off.

And no, I haven't fiddled with the limit screws. If memory serves me correct you need to be extra careful with the limit screws on Di2 RD's? Apparently if not set correctly it can greatly reduce battery life? I'll have a go anyway.

 

Thanks

I think you misread my quote. Indeed I believe the chain needs lengthening - it is currently too short.

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CXR94Di2 [2151 posts] 3 weeks ago
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Its an odd one, but long cage derailleurs shouldnt spoil the shifting.  chain length and setup are the usual culprits

The obvious clue, taking your comment, is that when you change the cass back to the ultegra 11-32 all works fine again.  So the issue points to the DuraAce cassette.  Do you have another 11-25 cass either ultegra or sram to try? 

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andsaw [36 posts] 3 weeks ago
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Try putting chain over big front ring and big ring on cassette and miss out the rear derailleur altogether and add one full link will be correct length of chain.

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