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Nasty chain slip. What may be causing it?

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Nasty chain slip. What may be causing it?

Old 05-16-19, 07:00 AM
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dja1
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Nasty chain slip. What may be causing it?

I recently fitted a new chain to my bicycle, it's got <500 miles on it, probably between 300-400. The old one was worn, and I mean to a fairly large degree, it gave zero resistance to the 1% marker on the gauge. The bike seemed ok for a while, had to index slightly, but I'm now starting to notice chain slip, especially when I'm moving off, bashed my knee because of it today and almost came off trying to pedal hard to get out of the path on an ambulance, along with multiple other occurances at traffic lights and I need to sort it before I end up hurting either myself or someone at the club. Shifting feels ok from what I can tell, changes are instant under normal riding conditions and seem to give no resistance and I haven't noticed an mis shifts.

Casette is still the default one and probably has around 5-6000 miles on it, obviously with most of them being with the old chain, I've not a clue how long I'd been riding with a worn chain before I replaced it. It doesn't look battered or chewed up, but it certainly doesn't look pristine any more. I've just cleaned it after getting back from todays ride, gotten rid of the factory lube which was becoming a little gunky, but I'm guessing it not's going to be that causing it?

The link below contains high resolution photographs of the casette and chianrings showing condition. Do either look excessively worn?
https://www.flickr.com/photos/167294...57707116639541

Is a worn casette going to be the most likely culprit here?

Last edited by dja1; 05-16-19 at 07:05 AM.
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Old 05-16-19, 07:04 AM
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New chain on worn cassette = violent skipping under load.

Cassette is worn if chain being used on it is worn - the teeth wear very quickly to match the new pitch of the stretched chain.
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Old 05-16-19, 07:06 AM
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Also - it is very difficult or impossible to 'see' wear on a cassette. The proof is not in the pictures, but in the performance - if a new chain slips on the cassette, the cassette is worn.
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Old 05-16-19, 07:09 AM
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Originally Posted by Wilfred Laurier View Post
Also - it is very difficult or impossible to 'see' wear on a cassette. The proof is not in the pictures, but in the performance - if a new chain slips on the cassette, the cassette is worn.
Thanks Wilfred, I suspected I might encounter issues with the casette when I replaced the chain and it seems the most likely thing. I'll get a new one ordered to fit tomorrow.
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Old 05-16-19, 07:09 AM
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How did you check your old chain for wear? 500 miles is peanuts for chain wear so I'm thinking either a measuring error or something else goofy is going on. You say shifting is good so I doubt it's an adjustment issue.

If it was my bike I think I'd replace both my chain and cassette and see what that does. If you're using a chain checker of some kind, I'd calibrate it by measuring a brand new chain with it to see what it says.
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Old 05-16-19, 07:11 AM
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Originally Posted by Retro Grouch View Post
How did you check your old chain for wear? 500 miles is peanuts for chain wear so I'm thinking either a measuring error or something else goofy is going on. You say shifting is good so I doubt it's an adjustment issue.

If it was my bike I think I'd replace both my chain and cassette and see what that does. If you're using a chain checker of some kind, I'd calibrate it by measuring a brand new chain with it to see what it says.
I used a wear gauge, just the simple stamped metal type, measuring at 0.75 and 1.00 increments. The 1% marker fell right in there with no resistance, and I suspect it may have been like that some some time. The old chain easily had 5000 miles on it, possibly more.
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Old 05-16-19, 07:14 AM
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Originally Posted by Wilfred Laurier View Post
Also - it is very difficult or impossible to 'see' wear on a cassette. The proof is not in the pictures, but in the performance - if a new chain slips on the cassette, the cassette is worn.
+1 Visual inspection is useless unless the wear is extreme. Also, many riders, particularly in relatively flat areas, use only a couple of cogs for the majority of their riding. Even at low total mileage these cogs can be worn enough to skip with a new chain although the rest of the cogs are like new.
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Old 05-16-19, 07:15 AM
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Originally Posted by HillRider View Post
+1 Visual inspection is useless unless the wear is extreme. Also, many riders, particularly in relatively flat areas, use only a couple of cogs for the majority of their riding. Even at low total mileage these cogs can be worn enough to skip with a new chain although the rest of the cogs are like new.
This did cross my mind, I ride hills, but most of my riding is on relatively flat ground/light rolling hills, and it does seem to be happening in the gears that I tend to move off and ride steady in.
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Old 05-16-19, 07:15 AM
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Oops. Your original post said 500 miles. I retract everything that I said. You tried a new chain on your worn cassette and found it lacking. That's common. Time for a new cassette.
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Old 05-16-19, 07:19 AM
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Sun Race cassettes are a good value, ~$30 on Ebay.

https://www.ebay.com/itm/Sunrace-CSR...ss!93230!US!-1
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Old 05-16-19, 07:21 AM
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Your cassette and, possibly, changring are shot. Start by replacing the cassette. I was lazy this winter and left a chain on too long. I knew it was worn and knew I’d have to replace the cassette also. What I didn’t plan on was having to replace the Ultegra chainring. I’ve had worn chains in the past on campy setups where just changing the cassette was sufficient. In this case I ruined a new ultegra chainring in one wet season of riding.
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Old 05-16-19, 07:26 AM
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A chain that's not lubricated will wear quite quickly - and that can happen if the chain gets washed out on a very wet ride. Mileage can be less of a factor in that case - just something to consider if you ride consistently in wet weather.
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Old 05-16-19, 08:26 AM
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Originally Posted by dja1 View Post
I used a wear gauge, just the simple stamped metal type, measuring at 0.75 and 1.00 increments. The 1% marker fell right in there with no resistance, and I suspect it may have been like that some some time. The old chain easily had 5000 miles on it, possibly more.
It's not the 500 miles on the new chain but the 5000 miles on the old chain that caused the problem. Replacing the chain at 0.75% for a 9 speed and less and 0.5% for a 10 speed and more goes a long way towards cassette longevity. Chains generally last about 3000 to 3500 miles before they reach those wear levels. A cassette should be able to outlast at least 3 chains and probably more.

Get a new cassette and check your chain more frequently.
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Old 05-16-19, 09:03 AM
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Originally Posted by Wilfred Laurier View Post
New chain on worn cassette = violent skipping under load.

Cassette is worn if chain being used on it is worn - the teeth wear very quickly to match the new pitch of the stretched chain.
To add. A couple of years ago, I was experiencing chain hop. I swapped out the cassette and chain and it was still there. It ended up being the chain rings.
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Old 05-16-19, 03:14 PM
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I had a real bad chain skip that turned out to be my freehub. The pawls were shot. So, I installed new chain, new cassette and new free hub. No more problems.
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Old 05-16-19, 04:02 PM
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Originally Posted by ramzilla View Post
I had a real bad chain skip that turned out to be my freehub. The pawls were shot. So, I installed new chain, new cassette and new free hub. No more problems.
hmmm I wonder. The freehub on these fulcrum racing sports has given me grief before.. crap had gotten into it need cleaning/resealing. I might take the wheel into my lbs and ask them to have a quick look over it.
Still I shall replace the casette... it's probably due it anyway in all honesty since I left the chain for so long.
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Old 05-16-19, 04:58 PM
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I've had a bad freehub bearing cause nasty skipping under load.

It was a new American Classic wheel bad from the factory about three years ago.

It never shifted quite right from the day the bike was built and eventually got worse to the point where movement in the freehub could be felt by hand and the chain would skip while standing to climb.


-Tim-
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Old 05-19-19, 10:07 AM
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Replaced the casette and the issue is still there. I might just take it into my local bike shop tomorrow and have them take a closer look at it as I'm not sure what to try next and don't just want to go sticking new chainrings on there if it's not required.

Was riding home from work today and it happened worse than ever before, dropped the chain off the crank end of the chainrings and it ended up dropping from one end of the casette to the other.

Last edited by dja1; 05-19-19 at 10:11 AM.
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Old 05-19-19, 10:36 AM
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How's your chain tension? If it's too loose in certain gear combos, that could be the cause. I have never had chainrings get so worn out that they slipped, but I suppose it's possible.
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Old 05-19-19, 11:13 AM
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Originally Posted by Lemond1985 View Post
How's your chain tension? If it's too loose in certain gear combos, that could be the cause. I have never had chainrings get so worn out that they slipped, but I suppose it's possible.
I guess that this would come in hand with chain length? I cut the new chain to the exact same number of links to the old one, which wasn't giving me any issues during any point in it's lifetime, other than the chain dropping occasionally whic is also what happened today. I would have to read up on how to ensure chain length is correct.
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Old 05-19-19, 11:16 AM
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Please post a pic of your drivetrain if possible.
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Old 05-19-19, 11:42 AM
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Originally Posted by Lemond1985 View Post
Please post a pic of your drivetrain if possible.
I can do. Anything in particular? Just the entire drivetrain showing the chain, in certain gears, or individual components?
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Old 05-19-19, 12:01 PM
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Any picture is better than nothing. Maybe a look at how the cassette teeth are engaging with the chain in the back. There's a screw to adjust chain wrap, but that's grasping for straws without pics.
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Old 05-19-19, 12:07 PM
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Replacing the cassette often means that the either or both derailleurs will need to be readjusted, since the new cassette may be positioned slightly inboard or outboard of where the original cassette was positioned. Your description of the chain dropping off the crankset and the chain failing to index correctly on the cassette sprockets suggests that you should check both derailleurs.

Also, for best cassette life, try to get in the habit of using the big chainring in combination with the middle cassette sprockets rather than the smaller chainring(s) in combination with the smallest cassette sprockets for riding on level ground at speed.
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Old 05-19-19, 12:21 PM
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dja1
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Originally Posted by Lemond1985 View Post
Any picture is better than nothing. Maybe a look at how the cassette teeth are engaging with the chain in the back. There's a screw to adjust chain wrap, but that's grasping for straws without pics.
Hopefully these are something to go off, there is one picture either side of the RD and one of entire drivetrain. (3 most recent in the album linked at the bottom of this post) plus some from the other day showing chainring condition.

Just to throw it out there I crashed about a year ago, skidded on gravel and landed derailleur side down. Other than losing the b axle cap in the process everything seems to be ok, hanger does not appear visibly bent and I've never had issues with shifting and indexing.

going to tackle the high limit on the FD in a moment, I'm able to pull the chain off the ring with a bit of effort and back pedaling which I am certain shouldn't happen.
https://www.flickr.com/photos/167294574@N05/?
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