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Chain length/smoothness questions

by TonD
Wed, Feb 10, 2016 12:48
10

Yes, I did search the forum and looked a lot on YouTube and Google, but I'm still not sure what (assuming anything) I did wrong, so any quick help after looking at my situation would be greatly appreciated.

So I'm building my first roadbike, after having had quite a bit of experience in BMX (days long gone) and MTB. So fixed gear and 9 speed systems using Deore etc. This is my first attempt at building a Shimano 11 speed (Ultegra/Dura Ace mix).

When replacing chains, I always had the old one at hand for sizing purposes. Now I'm setting up a new bike, I seem to struggle a bit. I followed both the 'Shimano 90 degree jockey wheel' method as well as "big big plus 2". However, I can't seem to get a smoothly running chain. In quite a few chainring/cog combinations the chain seems to be skipping (not sure if correct term). What I see is that the links are a bit hesitant to fall in between the teeth of the cog. Hope this makes sense.

I'll include two pictures, one is with small/small combination, other is big/big. Is my chain too short, too long? 

Everything except the rear derailleur hanger is new (casette, chain, derailleur, hub, cables etc). Things I've already checked:

  • Directional chain right way facing outward
  • B-screw all the way unscrewed, still puley seems to be a bit far from the small cog?

Again, sorry for such a dreary topic, but I'd love to learn from my mistake(s). 

P.s. as a non-native English speaker, I hope the above makes any sense 1 

Pictures:

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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10 comments

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Martyn_K | 8 years ago
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It sounds like you may be trying to fine tune the gears at the extremes of their working tolerance. Remember that the usual rules of cross chaining should be adhered to. So if you are on the big chain ring then you should try to not run in the biggest sprocket. The same applies when in the small chain ring, try not to run in the smallest sprocket.

When doing this the chain is pulling over a pretty angled line and can make quite a noise. As a personal rule i will not go in the biggest two sprockets when in the big chainring or the smallest two when in the small chain ring.

As a reference use the table below which shows that the gear ratio for a 50/25 (two from top) is the same as 34/17. So do not cross chain simply move chain rings and hop down the cassette to get the same cadence.

You will need to adjust the barrel tensioner carefully to make sure shifting all the way through the cassette is smooth in BOTH the big and small ring. Remember that there is no 'perfectly silent' tuning there is a little compromise at some point.

 

Sprocket - 34 / 50 Ratio
28 - 1.21 / 1.79
25 - 1.36 / 2.00
23 - 1.48 / 2.17
21 - 1.62 / 2.38
19 -1.79 / 2.63
17 - 2.00 / 2.94
15 - 2.27 / 3.33
14 - 2.43 / 3.57
13 - 2.62 / 3.85
12 - 2.83 / 4.17
11 - 3.09 / 4.55

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maviczap | 8 years ago
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A mate of mine had a very similar issue.

We suggested most of the above, but the cure was really simple.

Cable tension, he messed about with the cable tension by using upper barrel adjuster and it sorted out this skipping chain business. Your sypthoms sound very simiar.

Not sure if 11 speed is sensitive to cable tension, but I'd give it a try.

My other thought, is the cassette on properly? The first part of an Ultegra cassette is riveted together, but the smaller cogs and spacers aren't. If one spacer isn't sitting right, it'll mess up the smaller cogs, even though the lockring is done up tight. I've done this myself.

I also found that I'd fitted an old lockring to a 10 speed set up, which explained why the chain was jumping in the 12 tooth cog, it was much larger than the proper 10 speed lockring.

 

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TonD | 8 years ago
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Thanks Alfiehound; certainly could've been the case but I did indeed use a Shimano 11 speed chain from the Ultegra 6800 series. 

I just replaced the mech hanger with a brand new one (arrived today in the post). Don't seem to notice any direct difference/improvement. But at least it's good to know the hanger is now actually properly secured to the frame, instead of barely hanging on.

As the weather is slowly improving, I'll soon(ish) take it to the LBS and ask him to do the finetuning. Hopefully there are no brand new parts already defective out of the box, but you never know. Will update as I learn more 1 

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Alfiehound | 8 years ago
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A mistake I have made - so I'm not 'having a go' but are you sure you have the right gauge chain? A nine speed chain won't settle on an 11 speed cassette.

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TonD | 8 years ago
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Tjuice, thanks for your thoughts as well.

About your points:

1) Performance seems to be worst on the smallest cog and gradually improving towards the bigger ones, so still could point to hanger I suppose.

2) In all honesty I haven't ridden a mile or kilometer yet with the bike, as I want to get it sorted first and weather is a bit prohibitive. Using all Ultegra except for the front derailleur which is Dura Ace as I could pick one up for a good price and have been hearing such raving things about it. Whether true or not, it almost does look like a work of art...

3) Not that I can detect, it also doesn't seem to happen on a specific spot on the chain. 

Anyway, thanks again for your input. I'll update how things go when I receive the new hanger(s).

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Tjuice | 8 years ago
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3 thoughts:

1) I agree about the possible bent hanger - I've had issues with that in the past, although typically, I have found that that seems to encourage chain skip or poor gear changes at one or other end of the cassette, not in the middle

2) I once changed chain, chain rings and possibly also cassette (can't quite remember) all at once on a well used bike (so I knew derailleurs, shifters, etc. were all fine).  I had bizarre skipping in the middle of the range that I could not get to the bottom of (only when I was riding - was fine on the workstand).  But after riding a few miles, the issues went away.  It was almost as though all the very new, sharply cut metal surfaces needed to get used to one another.  Having said all that, I would be surprised if it this issue given you are using Ultegra/Dura Ace.

3) Really long shot - the point where you have connected your chain - the link is not a bit sticky there, is it?  If the chain does not flex as smoothly at that point as it should, that could cause skipping.

Hope you get it sorted.

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TonD | 8 years ago
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Quick update. I reinstalled the cassette, just to verify:

Yes, it's an 11 speed hub and no, there is no spacer present that shouldn't be there (the spacer that came with the wheelset is to be used with 10 speed cassettes so stayed in the box).

Adjusted the rear derailleur cable tension and got the 'normal combinations' working almost like I would want them too, but not quite. The extremes are still nasty.

Removed the rear derailleur hanger, although it doesn't seem to be bent, one of the two threads seem to have been cross-threaded in the past and don't provide much/any torque any more on the tiny bolt. 

So I just ordered two (one spare) rear derailleur hangers, once I've replaced the hanger I'll have to see if I can get everything running as I'd want or visit a good LBS to do the fine-tuning for me  (might've already done so if it wasn't for the weather and the fact that I've just moved to another city and don't know a good LBS here yet). 

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TonD | 8 years ago
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Thanks already for the replies!

 

Rod, thanks, seeing as how I can get into all combinations, the chain is short but not neccessarily too short, right?

Not sure I understand what to look for in the derailleur, how should it look hanging 'vertically'? Thanks again.

Looking at it again just now, it does appear to be an alignment issue as (when rotating the cranks counter-clockwise) the chain comes in not at the correct angle for the cog. I guess this is normal under the extremer combinations but not while riding middle cog and either small or big ring?

 

DanTe, thanks to you as well. Indeed worth a check, so I just removed the wheel and cassette. The wheelset I bought are Mavic Aksium Elite '11 speed' according to the shop I got them from. The rear of the packaging of my CS-6800 cassette is a bit confusing, though. Pictures at the link.

First picture is straight from the back of the derailleur/casette. Does look straight to me? Second is confusing pictograms on Shimano packaging. I hope they mean this CS-6800 cassette is not compatible with 11-speed MTB systems? 

 

 

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DanTe | 8 years ago
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Is it an 11 speed freehub? 

It may be that you need a spacer behind the cassette? Worth a check..

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Rod Marton | 8 years ago
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I would prefer the chain to be a little longer, but chain length doesn't have to be exact so, unless your problems only occur in extreme combinations, this shouldn't be the issue.

Two things I would look at first. First check that the derailleur hanger is at the right angle, i.e. the derailleur hangs vertically. Hangers do get bent, back in the days of steel they could be bent back, but this is not advisable with other materials and they need to be replaced. Yours appears to be replaceable. Second, check the cable tension. The index interval is dependent on the tension, if this is wrong it could cause this sort of problem. To do this, put the bike on a stand and run through the gears, checking that they change correctly. If not, adjust the tensioner.

 

 

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