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I can't figure out why I am getting chain skip, what next?

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I can't figure out why I am getting chain skip, what next?

Old 04-10-20, 02:50 PM
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dja1
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I can't figure out why I am getting chain skip, what next?

I'm getting really severe chain skip whenever I ride my bike; more often than not when I move off in the big ring, standing & putting torque on the drivetrain, my cranks slip, almost resulting in an accident. I need to fix this, but I can't figure out why it is happening.


I first noticed this last summer and assumed straight away that it was the chain as I'd never replaced it after lots of miles, possibly as much as 12-15,000. I got a new chain, along with some tools and a checker, so I could keep on top of it in future, fitted the chain and tested the bike. It seemed ok at first, but the skipping soon returned. 140 miles after changing the chain, I went out and got hold of a new 105 cassette and installed it, but again, it wasn't a solution, and I haven't rode since.


I've also tried;
  • Stripping the chain of its factory grease, wiping down the drivetrain with a solvent, and relubricating the chain.
  • Tried a clubmates rear wheel & (different ratio) cassette on my bike, and encountered the same issue. I thought maybe the pawls are not returning (sticky), I want to say this rules this out but maybe I could revisit this one?
  • Inspected the chain length, which seems o.k., in big-big combo, I cannot quite turn 2 links over on each other, forming a Z.
  • Indexed the gears earlier today; they seem ok, going from 25 to 28 took a fair bit of adjustment but every shift seems smooth, that said, something about the 25 to 28 change still feels the tiniest bit off even though it works, but this isn't usually a jump I would make in the big ring.
  • asked a LBS to get into the freehub and check it out, but they couldn't. It's an OEM hub designed not to be disassembled, meaning replacing is the only option.

Photo of my chainring (click for hi-res). Do they look like they are badly worn? https://imgur.com/a/JeDcWVr

Stock image of a 50 tooth FC-9000 for reference: bit.ly/2VgsVmd


I'm a bit stuck, maybe someone will have a better idea here

Last edited by dja1; 04-10-20 at 03:07 PM.
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Old 04-10-20, 03:27 PM
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What kind of frame is this? Steel, carbon? What comes to mind, from someone who rides steel, is the derailleur hanger alignment.
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Old 04-10-20, 03:29 PM
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Originally Posted by noobinsf
What kind of frame is this? Steel, carbon? What comes to mind, from someone who rides steel, is the derailleur hanger alignment.
​​​​​​
It's a carbon frame. The hanger looks straight, but I know it's one of those things that sometimes isn't visible to the naked eye, and I understand this may be a poss. culprit.
£25 for a new one from Planet X.
I did crash this thing a while back, but if this was a cause then it's took a while to come to light. I skidded on some gravel, and hit the deck; not too hard mind, but the derailleur 100% did take a whack, as I lost the b-axle cover cap. This happened around 400-500 miles before I noticed the skipping.

Last edited by dja1; 04-10-20 at 03:34 PM.
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Old 04-10-20, 03:32 PM
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Chainring worn completely out? I'm no expert but looking at the profile of the stock chainring photo and your chainring it looks completely different. Looks like lots of wear, even on the flanks of the teeth.
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Old 04-10-20, 03:46 PM
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dja1
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Originally Posted by noobinsf
What kind of frame is this? Steel, carbon? What comes to mind, from someone who rides steel, is the derailleur hanger alignment.
Originally Posted by August West
Chainring worn completely out? I'm no expert but looking at the profile of the stock chainring photo and your chainring it looks completely different. Looks like lots of wear, even on the flanks of the teeth.
I find this hard to gauge myself, but I agree that the teeth do look a lot different from when they were new, but I wouldn't say they look hooked or like shark fins much, the telltale signs they are excessively worn. I do find that hard to visualise though.
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Old 04-10-20, 03:48 PM
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Originally Posted by August West
Chainring worn completely out? I'm no expert but looking at the profile of the stock chainring photo and your chainring it looks completely different. Looks like lots of wear, even on the flanks of the teeth.
You know, I didn't look at the pics initially, but I agree with this -- your chainring looks a bit shark-toothy. Maybe time for a new one? Does it skip in the small ring?
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Old 04-10-20, 04:02 PM
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Originally Posted by noobinsf
You know, I didn't look at the pics initially, but I agree with this -- your chainring looks a bit shark-toothy. Maybe time for a new one? Does it skip in the small ring?
I don't think it skips in the 34 tooth, but I'd have to check this one. Struggling to find a direct replacement in the UK, so I might go for a replacement from AbsoluteBlack. I suspected this to be the issue last year but couldn't say for certain.

Last edited by dja1; 04-10-20 at 04:27 PM.
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Old 04-11-20, 08:00 AM
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Originally Posted by dja1
I've also tried;
  • Stripping the chain of its factory grease, wiping down the drivetrain with a solvent, and relubricating the chain.
I do not understand why people do this, to my mind it is like digging a hole and then filling it back up again.
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Old 04-11-20, 08:11 AM
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Originally Posted by dsbrantjr
I do not understand why people do this, to my mind it is like digging a hole and then filling it back up again.
In case any links were sticky. I couldn't feel any but cleaned and lubricated it anyway to be sure.

I've ordered a new direct replacement for the chainring. It looks so much different than when it was new as a result of not staying on top of chain changes. Fortunately only 140 miles on this chain and 15 on the casette so they should be fine.

Hopefully I can change the large ring without having to take the cranks off.
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Old 04-11-20, 06:00 PM
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Originally Posted by August West
Chainring worn completely out? I'm no expert but looking at the profile of the stock chainring photo and your chainring it looks completely different. Looks like lots of wear, even on the flanks of the teeth.
I agree. I was blissfully ignorant of chainring wear until the LBS guy said my chainring was like "shark's teeth". "Gotta replace the entire drive train, dude."

Edit: my new drive train is awesome!!!

Last edited by DeadGrandpa; 04-11-20 at 07:19 PM.
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Old 04-11-20, 06:39 PM
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Originally Posted by DeadGrandpa
I agree. I was blissfully ignorant of chainring wear until the LBS guy said my chainring was like "shark's teeth". "Gotta replace the entire drive train, dude."
more detailed pics: https://imgur.com/a/rCUDhVb
and a better image of the stock ring: https://bit.ly/34sx4HM

when I compare the teeth above the 'dura-ace' engraving, it seems that those on mine have become more rounded and some have taken a more ramped profile than on the pristine part. I do hope the new ring changes it.

is it worth installing new jockey wheels and gear cables?

turns out it may have less miles than I thought - possibly 6k. Going to need to stay on top of these chains in future and look at my cleaning regime as I always seem to get a gritty/sandy paste in the chain. Are the chain cleaner tools any good?

Last edited by dja1; 04-11-20 at 06:43 PM.
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Old 04-11-20, 06:51 PM
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Originally Posted by dja1

I first noticed this last summer and assumed straight away that it was the chain as I'd never replaced it after lots of miles, possibly as much as 12-15,000. I got a new chain, along with some tools and a checker, so I could keep on top of it in future, fitted the chain and tested the bike. It seemed ok at first, but the skipping soon returned. 140 miles after changing the chain, I went out and got hold of a new 105 cassette and installed it, but again, it wasn't a solution, and I haven't rode since.
Aye, there's your problem right there. Derailleur chains elongate past usefulness after 1500-3000 miles, depending on hygiene, maintenance, and riding style. Properly replacing chains, you should have to replace the cassette every 2-4 chains. Properly replacing chains and cassettes, chain rings should last a long long long time.
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Old 04-11-20, 09:00 PM
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Originally Posted by dja1
more detailed pics: https://imgur.com/a/rCUDhVb
and a better image of the stock ring: https://bit.ly/34sx4HM

when I compare the teeth above the 'dura-ace' engraving, it seems that those on mine have become more rounded and some have taken a more ramped profile than on the pristine part. I do hope the new ring changes it.

is it worth installing new jockey wheels and gear cables?

turns out it may have less miles than I thought - possibly 6k. Going to need to stay on top of these chains in future and look at my cleaning regime as I always seem to get a gritty/sandy paste in the chain. Are the chain cleaner tools any good?
You have confused me with someone who knows stuff about drive train wear. I would estimate that you could easily need to replace your chain after 5k miles. If you did so, you (theoretically) might be able to put off replacing the chain rings until you have pedaled 10k or more miles. My experience is riding a 38T chainring for most of the time until it just seems janky or funky and you don't know why. And suddenly you have to buy new chainrings and a new cassette as well as the new chain, and you feel better about supporting your LBS.

As for cleaning the chain, I use a cheap pressure sprayer to knock off the crud and grit, spraying into the grooves of the cassette and derailleur while rotating the chain and chainrings. Then use WD-40 to get the water out of the chain links, then the chain lubricant of your choice. I use Fluid Film, a lanolin based industrial product, but anything including 3 in 1 oil is better than nothing. Hundreds of threads about that. Flush the grit out, replace with oil of some kind. Replace when it wears out, apparently.
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Old 04-11-20, 10:33 PM
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When people describe this behavior, I usually assume it is a free hub issue: a sticking pawl, or a damaged one (broken, spring damaged, etc). Though it is possible I don’t understand what you mean by “skipping”. If you put pressure on the pedals and the crank slips forward, chain/chainrings aren’t the first place I’d look.
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Old 04-12-20, 01:03 AM
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The teeth on the big ring are pretty worn from that old chain. Replace the ring and things should work better, I doubt your rear hub has anything to do with the skipping.

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Old 04-12-20, 08:38 AM
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There are those who contend that chainrings will never skip. Worn chain rings will cause chain suck, where the chain comes around the back side and won't release.

Normally, chain skip occurs when a new chain is installed on a worn cassette. Even then, the skipping will only occur on a few of the most worn sprockets. It should only be noticeable when pedaling with a high torque, like might occur when pedaling up a hill, with a low cadence and pushing hard on the pedals. Then the chain skips over the top of some of the teeth and only transmits power intermittently. Chain tension is greatest when using the little ring and more likely to cause chain skip.

While it is possible for chain skip to occur with a very worn chain and cassette, the chain must have some very extreme elongation. If a new chain is installed on that cassette, it will most certainly skip.

A faulty freehub might skip at any time, in any gear combination and may result in the crank dropping quickly to the bottom of the stroke, with no forward motion of the bike.

When the problem occurs, you need to pay attention to what's going on.
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Old 04-12-20, 08:52 AM
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Ya chainring is munted... (That's Aussie for your chainring is worn beyond it's serviceable limits)
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