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Chain skips on 12t cog

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Chain skips on 12t cog

Old 03-15-15, 09:35 PM
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Chain skips on 12t cog

Okay this is driving me nuts.

On a fairly new bike (less than 20 miles, it's an MTB), my chain has begun skipping in the 12t cog. It's a Sram X4 3x8 setup. Today I did tweak the derailer hanger a bit, but I took it off and straightened it (new one on the way) and re adjusted the derailer.

My shifting is great. I've gone both ways on my tension adjustment, and both ways on my high limit with no success. It skips no matter what ring I'm on in the front. I did find one stiff link, but I can get it to skip if I pedal hard enough no matter what part of the chain I'm in (I did loosen the link). I've also tried lubing the entire chain. Chain line seems like it should be fine since I don't remember having an issue before, but maybe I wasn't pedaling hard enough at the time.

I'm at a total loss. My only other thought would be that I'm just pedaling to hard for the small amount of engagement the chain has on that cog, but I'm not anywhere near a pro and it seems like they'd be able to stomp harder than me.

Thanks!
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Old 03-15-15, 10:27 PM
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Are you sure it's not an 11t cog with 12t locking?
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Old 03-15-15, 10:32 PM
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Originally Posted by Al1943
Are you sure it's not an 11t cog with 12t locking?
Yes. I read about that issue and have seen the pictures where the lock ring causes the chain to sit up out of the cog. The cog is stamped 12 so I'm assuming it's a true 12t.

It's weird cause everything I'm reading points to either that, or a worn chain or worn cassette, and it shouldn't be any of those.

That's why I'm just dumb founded.
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Old 03-16-15, 04:51 AM
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Originally Posted by Shinkers
. The cog is stamped 12 so I'm assuming it's a true 12t.
You could try counting the teeth.
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Old 03-16-15, 05:19 AM
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When a chain gets older, stretches, it can begin to skip on smaller.chain rings. If it's at this point, the chain has likely caused some weAr on the cog pattern. If all components are new, this should be a non issue. If you have a new chain, pull it off & compare the length. maybe there is something off.
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Old 03-16-15, 06:25 AM
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Hey it's a new bike and under warranty. Take it to the LBS where you bought it.
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Old 03-16-15, 08:40 AM
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Originally Posted by JerrySTL
Hey it's a new bike and under warranty. Take it to the LBS where you bought it.
I'd like to try and figure this out on my own if I can.

the cog is definitely a 12t. The lock ring is not extending up into the grooves of the teeth.
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Old 03-16-15, 08:44 AM
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"I'd like to try and figure this out on my own if I can".

^^ So Why are you asking for help on BF?
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Old 03-16-15, 09:01 AM
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I know from experience that a installing a Wipperman Connex link upside down will cause this to happen. What brand is your chain/master link?
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Old 03-16-15, 09:29 AM
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Originally Posted by 10 Wheels
"I'd like to try and figure this out on my own if I can".

^^ So Why are you asking for help on BF?
Good question. I don't know why I ask anything on here.
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Old 03-16-15, 09:50 AM
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Internet age, "on your own" has been re defined.. to just not paying some one to take care of it.

.. back to the Guess-fest..
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Old 03-16-15, 11:33 AM
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back to the Guess-fest..[/QUOTE]

Nope. Don't bother.
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Old 03-16-15, 11:44 AM
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Originally Posted by fietsbob
Internet age, "on your own" has been re defined.. to just not paying some one to take care of it.

.. back to the Guess-fest..
It's the modern equivalent of researching in the library with less vetting of information, heck we can all play expert. Millenials are being taught to use the internet as a reference tool all of my high school child's texts are online along with many video lectures and assignments. My college age child has a choice between online texts and hard copy but classes are heavily supplemented with online material and coursework. I for one can't stand trying to scroll around an IPad when helping with math homework but the younger generation doesn't appear to have an issue with it and I used to access usenet from sparcstation to collaborate on homework in college. What really frightens me about the internet is how much privacy we have forfeited for the convenience of using it so we are paying for the information we receive but in a different way.
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Old 03-16-15, 12:01 PM
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I thought the point of this subforum was to ask questions and help others. I thought someone might have an idea or suggestion that I could use to fix my problem without having to take it some where else, and I would know how to fix it in the future. My bad.

You guys have been extremely helpful in the past, so I thought it was worth a shot.

Is it a guess fest? Yep. All I've done is told you what it's doing and what I've already looked into and tried. I'm down to guessing myself and thought maybe somebody has experienced this problem before.

So when I'm using my Zinn book as reference, does that count as doing it on my own?
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Old 03-16-15, 12:15 PM
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Originally Posted by Shinkers
I thought the point of this subforum was to ask questions and help others. I thought someone might have an idea or suggestion that I could use to fix my problem without having to take it some where else, and I would know how to fix it in the future. My bad.

You guys have been extremely helpful in the past, so I thought it was worth a shot.

Is it a guess fest? Yep. All I've done is told you what it's doing and what I've already looked into and tried. I'm down to guessing myself and thought maybe somebody has experienced this problem before.

So when I'm using my Zinn book as reference, does that count as doing it on my own?
I had the same problem with my Wipperman Connex master link. It was upside down and I pulled my hair out for two days before I found the problem, removed it, flipped it over and have been problem free since. Another shift problem was due to a weird cassette body, Novatec SLS, Super Light Steel, but being you didn't remove your cassette I won't offer that solution.

Did you check the brand of master link on your bike? Sometimes guessing is an important part of troubleshooting. Eliminate enough guesses and you'll find the answer.
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Old 03-16-15, 12:16 PM
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Since we're having a guess-fest, mine is that the high limit screw is set too far inboard, so that the chain will generally run on the smallest cog but is on the hairy edge of riding up on it under power. Under that scenario, shifting to and from the other cogs might still be fine.

There's no shame in taking a bike in under warranty and having them figure it out and explain it, though. Wear and bent parts shouldn't be issues for a bike so new.
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Old 03-16-15, 12:19 PM
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It doesn't look like the chain has a master link unfortunately.
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Old 03-16-15, 12:32 PM
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I was assuming, wrongly, that you removed the chain to remove and adjust your derailleur hanger. How exactly did you straighten the hanger?

In that case, I'm withThermionicScott, check the high limit screw or your hanger is quite as straight as you think it is. Now I'm all out of guesses but do follow up as I'm curious what the problem actually is.
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Old 03-16-15, 12:43 PM
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I took the derailer and hanger off and straightened the hanger using a vice. Listening to everyone's suggestions, I'm thinking you may be right that my hanger still isn't straight enough.

I've got a new one on the way, I'll see what that does.
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Old 03-16-15, 12:53 PM
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It doesn't matter if the hanger is straight when it's off the bike. The important thing is that it's aligned with the plane of the wheel and cogs, which needs to be tested and adjusted with the hanger installed.

ThermionicScott already voiced my first guess: high limit screw juuuust a hair too far inboard.
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Old 03-16-15, 12:58 PM
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Originally Posted by Shinkers
I took the derailer and hanger off and straightened the hanger using a vice. Listening to everyone's suggestions, I'm thinking you may be right that my hanger still isn't straight enough.

I've got a new one on the way, I'll see what that does.
I would still check or have the alignment checked even with a new hanger...

Park Tool Co. ParkTool Blog Rear Derailleur Hanger Alignment
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Old 03-16-15, 08:47 PM
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Okay, spent 4 hours on this tonight and still haven't figured anything out.

I've backed the high limit all the way off, and it still skips. I've gone up and down with tension, it still skips. I went up and down with the B screw, it still skips. I got that one link as loose as all of the rest, it still skips.

So it's time to admit defeat and go get my hanger aligned I guess. Every single angle that I look at it from looks straight to me but...

I hate taking my stuff into the bike shop.

Thanks for the help.
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Old 03-16-15, 11:54 PM
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Might have too high cable tension then. If you have barrel adjusters on derailleur or shifter try turning one or the other in a bit. I like to do derailleur one in the shop, shifter one on the road.
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Old 03-17-15, 06:19 PM
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Just checked and even with the tension backed all the way off, it's doing it. There doesn't seem to be a specific pattern to the slipping either.
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Old 03-17-15, 07:14 PM
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Originally Posted by Shinkers
Okay, spent 4 hours on this tonight and still haven't figured anything out.

I've backed the high limit all the way off, and it still skips. I've gone up and down with tension, it still skips. I went up and down with the B screw, it still skips. I got that one link as loose as all of the rest, it still skips.

So it's time to admit defeat and go get my hanger aligned I guess. Every single angle that I look at it from looks straight to me but...

I hate taking my stuff into the bike shop.

Thanks for the help.
if i had backed the high limit screw all the way off a rear derailleur and it DIDN'T create havoc i would be suspicious. i would think i had a derailleur that was having trouble collapsing completely, or an out of date one that didin't have the amount of lateral adjust-ability necessary for the width of the cassette i had, or possibly a slightly bent IN hanger or cage. i've even had a small pebble get in the parallelogram and muck up things.

i would remove the chain, and possibly the wheel, and see if in fact the derailleur, with absolutely no cable on it, was capable of positioning the jockey wheel at least half a cog's width outside the smallest cog. it should be able to do this, otherwise "high" limit screws serve no purpose and designer's wouldn't require them. if that's the problem, one solution, maybe not the best, would be to shim the DR at the mounting point.

of course, before doing anything, i would spin up the wheel with the crank, then slowly screw the "high" limit screw in until it shifted to the second smallest cog, then slowly back out to the smallest cog, and then slowly continue until the chain either derailed or hit the dropout. continuing to crank the entire time.

Last edited by hueyhoolihan; 03-17-15 at 07:36 PM.
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