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? |
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. |
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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Originally Posted by Wilfred Laurier
(Post 20932462)
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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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. |
Originally Posted by Retro Grouch
(Post 20932470)
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. |
Originally Posted by Wilfred Laurier
(Post 20932462)
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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Originally Posted by HillRider
(Post 20932479)
+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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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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Sun Race cassettes are a good value, ~$30 on Ebay.
https://www.ebay.com/itm/Sunrace-CSR...ss!93230!US!-1 |
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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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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Originally Posted by dja1
(Post 20932473)
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.
Get a new cassette and check your chain more frequently. |
Originally Posted by Wilfred Laurier
(Post 20932459)
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. |
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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Originally Posted by ramzilla
(Post 20933398)
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.
Still I shall replace the casette... it's probably due it anyway in all honesty since I left the chain for so long. |
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- |
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. |
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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Originally Posted by Lemond1985
(Post 20937096)
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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Please post a pic of your drivetrain if possible.
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Originally Posted by Lemond1985
(Post 20937168)
Please post a pic of your drivetrain if possible.
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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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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. |
Originally Posted by Lemond1985
(Post 20937239)
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.
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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