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Chain skipping

Old 07-15-22, 02:16 PM
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XxHaimBondxX
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Chain skipping

Trying to figure out why chain skips under load on 24 speed road bike. Bought a new ig51 chain 116 links, for 8 speeds, made it even worse. Thinking it's the cassette. Can anyone visually tell?

https://youtu.be/m7dNhDgwBK0
https://youtu.be/Sd0QETB8MqQ
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Old 07-15-22, 03:27 PM
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Depending on how badly the old chain was worn and how many miles is on the cassette you might have a worn cassette or at least the cogs on the cassette you use the most might be worn.

Are you certain it's on the rear that it's skipping? Mine was a worn out front chain ring when I had a similar issue after getting a new chain.

I'm not certain what you think we are supposed to see in the videos. Chain skip is something you'll experience when you are on the bike and start to put some power into the crank and then it feels as if it suddenly lets go and slips for a most of a pedal stroke.

Just spinning the crank with the wheel unloaded might be showing us any number of issues, most being adjustment or bent hanger.

If your skipping is more like a bad shift, then did you put the correct speed chain on the bike?

Last edited by Iride01; 07-15-22 at 03:34 PM.
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Old 07-15-22, 03:51 PM
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I'm not sure what information experts would require so i though shooting some videos would help. Chain skipping whenever I'm spinning by hand or on the bike. When I'm on the bike, it doesn't grip at low cogs at all. It looks like original is SRAM PG-830 8 speed 11-32, can I replace it with 11-28?
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Old 07-15-22, 04:10 PM
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The cassette looks suspect to me. As long as it is shifting correctly and only skipping under load I would swap it for a new one. The jockey wheels on the derailleur look worn. A video from the rear showing going through gear shifting would be helpful.

Last edited by ARider2; 07-15-22 at 04:26 PM.
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Old 07-15-22, 04:20 PM
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Before spending more cash have you checked the rear derailleur hanger alignment?
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Old 07-15-22, 04:26 PM
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Cassette does look pretty bad to me, all the cogs uneven. Derailleur looks straight to my untrained eye. Still question remains, can I replace it with 11-28, which is $14 vs $30-40 for 11-32?




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Old 07-15-22, 04:29 PM
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Yes you can swap to 11-28 without problem it will make going up hills a little more challenging.
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Old 07-15-22, 04:40 PM
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I suggest that the cogs would need to be far more worn than that for it to skip when turning by hand.
5 seconds with a hanger alignment tool might, just might save you some cash.
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Old 07-15-22, 04:54 PM
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Comparing to someone's same cassette for sale, my teeth are a lot thinner and sharper. 11-32 is $5 more expensive, so I might just splurge for that.

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Old 07-15-22, 06:54 PM
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If you run a used cassette with a new chain you are likely to get skipping depending on how worn the cassette is.
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Old 07-15-22, 07:06 PM
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I purchased a new 11-28 cassette, black. Spent too much time and money on this bike already.
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Old 07-16-22, 05:50 AM
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Your sixth gear looks like it's worn to points. Check your chain rings too. Even if they don't skip, they may be rough and noisy.
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Old 07-16-22, 07:56 AM
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Originally Posted by XxHaimBondxX View Post
I purchased a new 11-28 cassette, black. Spent too much time and money on this bike already.
Report back to let us know if the new cassette solved the skipping.
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Old 07-21-22, 03:02 PM
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Originally Posted by Crankycrank View Post
Report back to let us know if the new cassette solved the skipping.
New cassette totally worked, it was riding well even with loose chain you see in the pic, since then I removed two links. It was a little surprising how much smaller 11-28 cassette looks vs 11-32, if I keep this bike, I'll totally kick myself for not spending extra few bucks.
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Old 07-21-22, 03:50 PM
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You have a third chainring up front—you won’t miss the 32.
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Old 07-24-22, 08:44 PM
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If you have your old chain, you can measure the rivet spacing on 12 links. Ideally, it should measure 12" (brand new). As wear occurs, this spacing will increase. If the same length measures 12-1/16" the chain probably did not damage the cassette. If the spacing measures 12-1/8", then chances are the cassette was damaged by chain. I tend to measure my chain as a habit, just to avoid damaging the cassette.

Basically, a worn chain physically damages the cassette by forcing the cassette to match the chain dimensions. Then when you install the new chain, it doesn't match the worn cassette and hence chain skip.
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Old 07-25-22, 05:13 AM
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Originally Posted by MudPie View Post
Basically, a worn chain physically damages the cassette by forcing the cassette to match the chain dimensions. Then when you install the new chain, it doesn't match the worn cassette and hence chain skip.
I know the chain use also ‘wears’ on the cassette teeth, but I’ve always wondered if the main reason for a cassette ‘wearing out’ (stretching out really) was using a stretched chain—sounds like that’s what you are saying and it makes sense. Similar to your chain test explanation, is there a relatively straightforward way to test/measure cogs in a cassette to see which might be worn (other than a visual)? Using a chain wrap?
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Old 07-25-22, 05:23 AM
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Originally Posted by Sonofamechanic View Post
I know the chain use also ‘wears’ on the cassette teeth, but I’ve always wondered if the main reason for a cassette ‘wearing out’ (stretching out really) was using a stretched chain—sounds like that’s what you are saying and it makes sense. Similar to your chain test explanation, is there a relatively straightforward way to test/measure cogs in a cassette to see which might be worn (other than a visual)? Using a chain wrap?
I put a new chain and test if it skips under load.
All the other methods are not very accurate.
Visual inspection especially.
Visual inspection works OK for the fornt chainrings, but not for the (smaller) rear ones.
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Old 07-25-22, 09:48 AM
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Originally Posted by Sonofamechanic View Post
I know the chain use also ‘wears’ on the cassette teeth, but I’ve always wondered if the main reason for a cassette ‘wearing out’ (stretching out really) was using a stretched chain—sounds like that’s what you are saying and it makes sense. Similar to your chain test explanation, is there a relatively straightforward way to test/measure cogs in a cassette to see which might be worn (other than a visual)? Using a chain wrap?
The worn, elongated chain forces the cassette to wear to the chain's dimension, so the cassette becomes matched to the chain. Then when a new chain is installed, the cassette no longer matches the chain and the incompatibility causes skip. Also, I like to compare the lengths of an old and new chain by hanging them vertically from the same nail. Over the length of the chain, the difference is very obvious.

Unfortunately, as others stated, there are no reliable ways to gauge cassette wear with typical shop instruments and inspection tools. There have been times I put on a new chain, thinking the cassette was fine, but only to have it skip with a new chain. Then I'd reinstall the old chain, ride around until I can get a new cassette..
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Old 07-25-22, 10:53 AM
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Mostly good advice above, as this problem is common - if replacing a worn chain results in skipping under load, the problem is the cassette was also worn to match the worn chain.
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Old 07-25-22, 11:54 AM
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Originally Posted by MudPie View Post
There have been times I put on a new chain, thinking the cassette was fine, but only to have it skip with a new chain. Then I'd reinstall the old chain, ride around until I can get a new cassette..
2 follow ups on this: (1)…wouldn’t the front chainrings be equivalently worn/stretched and also need replacement, or does the shorter radius of the rear cogs somehow cause greater wear or create lower tolerances before skipping? (2) on measuring/checking rear cogs for stretch…couldn’t you cut a short section of tubing/pipe that fits tightly into the ‘trough’ between the ‘teeth’ of a brand new rear cog and then use hat as a measure? When you can wobble it back and forth more than a mm then that cog is worn?
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Old 07-25-22, 01:25 PM
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Seems to me on cheaper bikes it worth just replacing both and skip the guesswork, although on this bike someone already replaced the chain, but being it from fb marketplace, I chose not believe that.
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Old 07-25-22, 07:58 PM
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Originally Posted by Sonofamechanic View Post
2 follow ups on this: (1)…wouldn’t the front chainrings be equivalently worn/stretched and also need replacement, or does the shorter radius of the rear cogs somehow cause greater wear or create lower tolerances before skipping? (2) on measuring/checking rear cogs for stretch…couldn’t you cut a short section of tubing/pipe that fits tightly into the ‘trough’ between the ‘teeth’ of a brand new rear cog and then use hat as a measure? When you can wobble it back and forth more than a mm then that cog is worn?
1) Chainrings are generally larger and rotate less, and they're thicker material.
2) KMC makes a sprocket check tool, but the lead mechanic in a shop where I got some training didn't trust it. Others may have a different take on it.
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Old 07-25-22, 09:35 PM
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Originally Posted by Sonofamechanic View Post
2 follow ups on this: (1)…wouldn’t the front chainrings be equivalently worn/stretched and also need replacement, or does the shorter radius of the rear cogs somehow cause greater wear or create lower tolerances before skipping? (2) on measuring/checking rear cogs for stretch…couldn’t you cut a short section of tubing/pipe that fits tightly into the ‘trough’ between the ‘teeth’ of a brand new rear cog and then use hat as a measure? When you can wobble it back and forth more than a mm then that cog is worn?
You're asking some good questions!
1. Like you, I would expect the front chainrings to wear because they're usually made of aluminum (softer material than the steel chain and steel rear cogs). As mentioned previously, the larger diameter should favor the chainring but even factoring larger diameter my chainrings seem to last longer than I'd expect . And they do wear, as the teeth on my chainrings do no have a symmetric shape, but yet they chainrings don't skip. I have over 30,000 miles on Ultegra chainrings.

Sheldon Brown discusses chain wear and how a chain should properly engage into the cogs and chainrings. He also discusses the worn cog / new chain problem: https://www.sheldonbrown.com/chain-wear.html

2. I assume you could make some sort of gauge that measures the width of the trough (or wear of the teeth), but slipping might also have to do with tooth profile shape, too. I'm also guessing different cassette brands have different teeth profiles, although imperceptible to the eye. I really don't know, but it's fun to think about
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