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Shifting from 2nd to 3rd rear cog only works 30-40% of the time ...

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Shifting from 2nd to 3rd rear cog only works 30-40% of the time ...

Old 05-04-16, 06:24 PM
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lineinthewater
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Shifting from 2nd to 3rd rear cog only works 30-40% of the time ...

Sorry about the wall of text, but here goes ....

The symptom: I shift from 2nd to 3rd cog on my 3x10 drivetrain, the derailleur moves to the expected position, but the chain does not shift. The ramping 3rd cog tooth continues to try to bring the chain up to cog 3. Usually, no success - not on the stand, or while riding. Every other gear shifts like butter. Increasing tension on the RD cable by even one barrel notch will simply throw every other gear out of whack, since I've already tried to compensate for this anomaly.

I've spent ENDLESS hours on this issue. In this long process of trying to diagnose, I've swapped out or bypassed, I think, every part in the rear drivetrain. Multiple cassettes, multiple wheels (like-new), multiple shifters (one like-new, one new), multiple chains (all sram, 2 like-new, 1 new), multiple RDs (two like-new, one new), verified pulley orientation, new housing/cabling/ferrules, cleaned the cable guide, checked the chain length, verified cassette spacer size, verified cassette torque, bypassed the regular housing with a single piece of housing from shifter to RD. I've tried everything (I think).

I've checked RD hanger alignment, several times. Although I've noticed that the hanger has been slightly out-of-spec, simply from use (I posted a separate thread about this), it does not appear directly related to this issue. I've aligned it, to within 1mm deflection on the DAG, and it does not solve this issue. I'm sure with most of you this raises a red flag - that was my thought many many hours ago. But, I've gone over this 100 times. I just now re-re-checked it with the DAG-2.2 alignment tool, and it is dead-on. And yet, the shifting continues to mostly fail ONLY in the shift from the 2nd to 3rd cog. Unless the hanger is actually deflecting during shifts, I've eliminated this variable.

My normal set up, before I started swapping in new identical parts, is a 5603 triple crankset (excellent condition, with minimal tooth wear), sram 1051 cassette (500 miles on it), shimano 6600/6603 shifters (1000 miles on them), sram 1050 chain (500 miles).

Today, as another completely desperate attempt to try anything different, I tried (for the first time) a Shimano chain - an old, over-stretched directional Shimano chain that my LBS had lying around (probably a 5700/6700 series since it had holes in the side plates). The setup didn't miss a shift, not on the stand and not on a 4 mile test ride. I don't know if this is a clue to the core problem, or a possible solution. When I got back, I read up on chains for 10 speed systems, specifically TRIPLE drive trains, and it seems that the 6600/5600 series chains are the last chains produced that are recommended. But, it seems this is more related to the crankset ramps than the rear shifting. I have no idea what Sram recommends with their chains on triple 10 speed drive trains. And, I have no idea if my triple setup has anything whatsoever to do with the rear shifting issue.

I'm completely out of ideas, and I've consulted with the LBS on the issue - they are stumped too. Ever have a bike issue that you can't solve? I'm about at that point. Any ideas, however remote, would be most appreciated! Thank you.
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Old 05-04-16, 08:05 PM
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Crankycrank
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Since you mentioned that a different chain, albeit a supposedly worn Shimano chain, worked and all your other chains were SRAM I would look at getting a different brand of chain such as another Shimano or KMC. I'm aware of Shimano advising against using any of their directional chains for triples and they have never explained why but I suspect it has to do with some of their early directional chains were supposedly prone to cracking and the greater chainline angles of a triple put even more stress on the links but who knows for sure. My neighbor who has a 6700 triple, which came with one of the early directional 6700 chains, rode it until it was worn out and never had a problem but switched to a KMC 10.93 after his shop insisted that he use a $Dura-Ace$ chain. The KMC has been flawless. I usually use KMC's myself and have never been able to tell the difference in shifting compared to any Shimano chain. I wouldn't hesitate to try any of the directional Shimano chains either but would keep an eye out for cracks just in case but I suspect it won't be a problem. Chains aren't too expensive so worth a try.

Last edited by Crankycrank; 05-04-16 at 08:09 PM.
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Old 05-04-16, 08:18 PM
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lineinthewater
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Originally Posted by Crankycrank View Post
Since you mentioned that a different chain, albeit a supposedly worn Shimano chain, worked and all your other chains were SRAM I would look at getting a different brand of chain such as another Shimano or KMC. I'm aware of Shimano advising against using any of their directional chains for triples and they have never explained why but I suspect it has to do with some of their early directional chains were supposedly prone to cracking and the greater chainline angles of a triple put even more stress on the links but who knows for sure. My neighbor who has a 6700 triple, which came with one of the early directional 6700 chains, rode it until it was worn out and never had a problem but switched to a KMC 10.93 after his shop insisted that he use a $Dura-Ace$ chain. The KMC has been flawless. I usually use KMC's myself and have never been able to tell the difference in shifting compared to any Shimano chain. I wouldn't hesitate to try any of the directional Shimano chains either but would keep an eye out for cracks just in case but I suspect it won't be a problem. Chains aren't too expensive so worth a try.
It's my understanding that, based on some threads I read here on BF, the primary reason they don't recommend using the 6700 chains on the triple is because of the ramps on the front chainrings, and their interaction with the unidirectional chain. This is apparently straight from the horse's mouth (Shimano), but the real reason may have been lost in translation. Like you say, most threads about the topic say it's not recommended, but only because "the engineers said not to".

I picked up a 6701 chain today at the LBS, before I knew about the compatibility issue, and that didn't have any missed shifts either. However, it didn't feel as smooth at the Sram, and that might be because of the minor incompatibilities. I think testing the 6600 chain is on top of my troubleshooting list.

Thanks for the KMC suggestion. I use one on my hybrid, and I like their master links, but I've never used one on the road bike.
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Old 05-04-16, 08:25 PM
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Did you adjust the screw that keeps the derailleur pulley close to the cogs? B axis screw, I think is the right name.
Is the pulley close on those two cogs? Get it as close as possible.
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Old 05-04-16, 08:31 PM
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andr0id
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Originally Posted by lineinthewater View Post

Thanks for the KMC suggestion. I use one on my hybrid, and I like their master links, but I've never used one on the road bike.
I'm really big on using Shimano groups all together. The one exception I make is that I run KMC chains after the initial replacement of whatever came with the group. The break off pin on Shimano chains is just stupid and I think KMC chains are quieter and last longer. I've run 9, 10 and 11 speed KMCs all with great success.
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Old 05-04-16, 08:33 PM
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Originally Posted by 2manybikes View Post
Did you adjust the screw that keeps the derailleur pulley close to the cogs? B axis screw, I think is the right name.
Is the pulley close on those two cogs? Get it as close as possible.
I've tried every B screw position known to man. I'm running an 11/26 cassette, and I think the best behavior is all the way out, but I notice very little difference overall.
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Old 05-04-16, 08:34 PM
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Originally Posted by andr0id View Post
I'm really big on using Shimano groups all together. The one exception I make is that I run KMC chains after the initial replacement of whatever came with the group. The break off pin on Shimano chains is just stupid and I think KMC chains are quieter and last longer. I've run 9, 10 and 11 speed KMCs all with great success.
Thanks for the 2nd vote of confidence on KMC.
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