Is this chainring toast?
#1
Senior Member
Thread Starter
Is this chainring toast?
Just changed chains and the new one keeps falling off the big ring up front. At first it seemed to have been cut too short, so I lengthened it. Situation has improved, but still there, chain falls off the outside edge off the front chainring when under load. Doesn't happen while shifting, just normal pedalling.
Can't think what's going on other than maybe it's time for this ring to retire.
Thanks
Can't think what's going on other than maybe it's time for this ring to retire.
Thanks
#3
Junior Member
As stated, move the FD down until it just clears the teeth when moving the chain to the big ring. It makes a huge difference in both shifting response as well as keeping the chain on that ring.
#4
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^This^ x 2.
But...if it's not while shifting and just happens when you're riding along you've got something else going on. The derailleur being too high won't make the chain shift itself off the ring.
But...if it's not while shifting and just happens when you're riding along you've got something else going on. The derailleur being too high won't make the chain shift itself off the ring.
#6
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Thread Starter
Yeah I agree. The cassette is being a bit of a nightmare too, hard to index. I'm wondering if it's worn and the root cause of all this.
#7
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Might need to re-visit chain length if after correcting the DR height you still have the chain fall off occasionally. I usually would expect too long a chain having slack in some gear combo's to be more prone to falling off the front.
Chain length will be low on my list of other things to check normally for dropped chains. I only bring it up because you said you lengthened it.
Shimano rear DR? They tell you how to size the chain in their DM's for that model DR.
https://si.shimano.com/
Chain length will be low on my list of other things to check normally for dropped chains. I only bring it up because you said you lengthened it.
Shimano rear DR? They tell you how to size the chain in their DM's for that model DR.
https://si.shimano.com/
#8
Senior Member
Thread Starter
Might need to re-visit chain length if after correcting the DR height you still have the chain fall off occasionally. I usually would expect too long a chain having slack in some gear combo's to be more prone to falling off the front.
Chain length will be low on my list of other things to check normally for dropped chains. I only bring it up because you said you lengthened it.
Shimano rear DR? They tell you how to size the chain in their DM's for that model DR.
https://si.shimano.com/
Chain length will be low on my list of other things to check normally for dropped chains. I only bring it up because you said you lengthened it.
Shimano rear DR? They tell you how to size the chain in their DM's for that model DR.
https://si.shimano.com/
#9
Really Old Senior Member
It's an 11 speed crank.
How many speed chain & cassette?
This is how I make a quick in situ chain length measurement.
Put the chain on BIG:BIG.
You should have between 1 to 2" slack.
How many speed chain & cassette?
This is how I make a quick in situ chain length measurement.
Put the chain on BIG:BIG.
You should have between 1 to 2" slack.
Last edited by Bill Kapaun; 05-14-22 at 10:04 AM.
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Agreed on the FD height, but regarding the chainring teeth, if they aren't worn yet, they might be on their way. A closeup photo would help, but new chains and new teeth always play better together.
#11
don't try this at home.
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Since you are moving the front derailleur, you should start from scratch and readjust it.
This Park Tool repair guide is always the first place I go to. They have easy step-by-step instructions.
Front derailleur adjustment
Not just the height, but the limit screws and cage angle, and cable adjustment too.
This Park Tool repair guide is always the first place I go to. They have easy step-by-step instructions.
Front derailleur adjustment
Not just the height, but the limit screws and cage angle, and cable adjustment too.
Last edited by rm -rf; 05-14-22 at 10:17 AM.
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#12
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But one thing that can wear out cassettes and chainrings is keeping a very "stretched", worn out chain for too long. It puts high force on just a few teeth at a time.
My Ultegra chainring has almost 30,000 miles on it, from 2014. It's still good: no shifting problems or unusual chain wear. (And the Di2 system still works perfectly.) It's so hard to tell just by looking.
Last edited by rm -rf; 05-14-22 at 10:37 AM.
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Big chainrings take a very long time to wear out, tens of thousands of kilometers. They take much longer to wear out than small chainrings. The one in the OP's photo is pretty dirty, but doesn't look all that worn
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Whenever I replace a chain, I take the opportunity to evaluate the cog and chainring teeth, especially if I experience any skipping, dropping, or missed shifts with the new chain.
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Is there any more to the story than just a changing of the chain?
Changed crank or chainrings? Swapping out components with another bike? Just bought the bike from someone?
Changed crank or chainrings? Swapping out components with another bike? Just bought the bike from someone?
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I wouldn't be surprised if a new chain skipped on that big chainring, but I'd at least expect it to stay in place. Perhaps if you're in a high enough gear (small cog), the chainline is crooked enough that the chain will also derail when it skips.
#17
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Thread Starter
The other day I noticed the shifting wasn't great and checked the chain - it was worn, so I swapped it out. I cut the chain to the same length again, but this time got a kmc x11 rather than a Shimano. Immediately noticed terrible chain issues when in the big ring, tried to shift to big and big but couldn't. It's a mystery to me why the Shimano didn't behave this way and the kmc did, but it seems I've been running a short chain for a while without realising.
Added a bit of length to the chain, can shift into big big now, but other problems persist.
#18
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I should mention the previous owner had to replace the inner ring due to wear. No idea how many miles the big ring has done before I got it.
#19
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Since the front and rear DR aren't from the same group, then a previous owner has been changing stuff out. Was the original group on the bike 105 or Ultegra? Possibly the limits on the front DR are not set correctly if the front DR was changed along with the crank. That will let your chain fall off too, but get the DR height over the ring correct first.
The exact model and version numbers will be on all of your Shimano components somewhere. Usually the backside and sometimes you won't see it without removing the component. But with those numbers, you can find all the tech documents for them at the link I gave in an earlier reply. The DM's will give you the best information to check if they are installed and adjusted properly.
The exact model and version numbers will be on all of your Shimano components somewhere. Usually the backside and sometimes you won't see it without removing the component. But with those numbers, you can find all the tech documents for them at the link I gave in an earlier reply. The DM's will give you the best information to check if they are installed and adjusted properly.
Last edited by Iride01; 05-14-22 at 01:02 PM.
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Might need to re-visit chain length if after correcting the DR height you still have the chain fall off occasionally. I usually would expect too long a chain having slack in some gear combo's to be more prone to falling off the front.
Chain length will be low on my list of other things to check normally for dropped chains. I only bring it up because you said you lengthened it.
Shimano rear DR? They tell you how to size the chain in their DM's for that model DR.
https://si.shimano.com/
Chain length will be low on my list of other things to check normally for dropped chains. I only bring it up because you said you lengthened it.
Shimano rear DR? They tell you how to size the chain in their DM's for that model DR.
https://si.shimano.com/
#21
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Originally Posted by Iride01 View Post
Might need to re-visit chain length if after correcting the DR height you still have the chain fall off occasionally. I usually would expect too long a chain having slack in some gear combo's to be more prone to falling off the front.
Chain length will be low on my list of other things to check normally for dropped chains. I only bring it up because you said you lengthened it.
Shimano rear DR? They tell you how to size the chain in their DM's for that model DR.
https://si.shimano.com/
Might need to re-visit chain length if after correcting the DR height you still have the chain fall off occasionally. I usually would expect too long a chain having slack in some gear combo's to be more prone to falling off the front.
Chain length will be low on my list of other things to check normally for dropped chains. I only bring it up because you said you lengthened it.
Shimano rear DR? They tell you how to size the chain in their DM's for that model DR.
https://si.shimano.com/
How would this happen? If you're pedaling the bike the 'tension' on the chain is what it is depending on how hard you're pedaling. The chain has no more or less 'slack' because the top run of chain will have tension on it. The bottom run has tension from the pulley cage of the derailleur. The only place you could have slack is on the bottom run in the smallest cog or 2 when in the small ring if it was actually too long. As long as there is tension on the bottom run of chain in small/small it'll be the same everywhere else.
#22
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When I'm getting a chain dropping off a ring, I put the bike up on the stand to see exactly what's causing it. Sometimes it will always happen on the same section of ring. In that case I'm looking for a damaged tooth or pin on the ring, or the ring has a wave to it Sometimes it happens on the same section of chain. Then I look for a stiff link or a bent plate. To check for a worn out ring, put the new chain on the big ring, pedal gently, and look for daylight between the front of the tooth and back of the chain link.
#23
Senior Member
Thread Starter
seems like way too much. What's between the two master links in the photo below is what I added:
I just took the additional length out, this is where we're at now:
however the derailleurs can't get the chain in big big. I put it there manually, but the minute I start pedalling it shifts down.
This is the derailleur in big big with the smaller chain:
I haven't yet lowered the FD, will do that after work today.
#24
Really Old Senior Member
Put it on the BIG ring and 5th smallest cog. (assuming it's an 11 speed)
Stand behind the bike and sight down the chain.
Note how much of an angle the chain is at vs "straight ahead".
Repeat with chain on the SMALL ring and 5th largest cog.
The angle should be extremely similar, but to the other side.
This should give you a rough idea if the chain line is correct.
Stand behind the bike and sight down the chain.
Note how much of an angle the chain is at vs "straight ahead".
Repeat with chain on the SMALL ring and 5th largest cog.
The angle should be extremely similar, but to the other side.
This should give you a rough idea if the chain line is correct.
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Modern Shimano 4-arm chainrings wear significantly quicker than you would expect. Likely due to the heavy shaping they get to aid shifting, and 11/12spd needing narrower chainrings so there is already less material to work with.