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I am having some issues with my drive trainsystem. I have changed my chain after quite a while (shame on me) with a new one, that i sized exactly on the same number of links as the old one. When pedalling however, when putting a high pressure on the pedal the chain skips.

My issue is, whether the chain is not sized properly (since I havent had this issue before) or is there a problem with worn casette cogs or the freewheel.

I get a from-factory setup of Sram casette and probably Shimano hub (not sure). The cogs are quite loose on the freewheel as you can see on the picture. I dont know if this normal, but would expect to hold firmly.

I usually ride on tough gears, so I dont know if the end of the freehub is demaged by this as you can see on the picture, or it is the design of the freehub.

enter image description here

Talking about the cogs, once again I dont know if they seem to be worn, or the edges are not sharp and look like this by design.

enter image description here

I would very much appreciate your advice on whether the cogs, or freehub have to be changed or it is probably just an issue with the chain length. Thanks in advance ! :)

Martin

EDIT: I just made a video to demonstrate how loose the cogs are. Even after tightening the lock, one can still rotate the cogs on the freewheel. Is this normal ?

My loose cogs on freehub (video on Youtube)

EDIT 2: I also post the picture of the fron chainring. Is this worn to much, or you think this is more probably causing the chain skipping, than the rear?

enter image description here

  • Freehub looks fine. Whats the entire drivetrain you're running? That doesn't look like a sram cassette; you normally get all the big cogs on one thing and the little one free. – Batman Feb 12 '17 at 16:23
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    When a new chain skips most likely the cassette has been worn down by the old chain and needs to be replaced. This happens typically when the old chain has been lengthened by more than 2%. You can measure this over 10 chain elements - a new element is exactly 1 inch (2.54mm) long. So 10 elements should not be longer than 25.9cm. – Christian Lindig Feb 12 '17 at 16:29
  • @Batman the casette lock says SRAM,but I dont know the exact model. Before i was using KMC chain and shifted to Shimano. I have a Shimano hollowtech (dont know exactly the model) crankset and a Shimano Deore XT rear derailleur. Is it okay for the clogs to be so loose on the freewheel ? – Martin Melis Feb 12 '17 at 16:41
  • The answers to bicycles.stackexchange.com/q/18408/7309 might help (though the question is as little different) – Chris H Feb 12 '17 at 18:01
  • Both cogs appear to be fairly badly worn, though not to the point that would usually cause a problem. But we can't see the chainrings, and a worn chainring is more likely to cause problems than worn rear cogs. The freehub does appear to have unusual grooves in it, but I can't tell from the pictures whether they are deep enough to allow slippage. – Daniel R Hicks Feb 12 '17 at 19:44
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Are you worried that the cogs skip on the hub? I'd consider this extremely unlikely.

The most likely reason is that the old chain has worn down the teeth of the cassette, especially when you ride on small cogs because the same load is distributed over fewer teeth. If you happen to have the old chain around, measure the length over 10 elements (see my comment above): if 10 elements are longer than 25.9mm (from pin to pin), the old chain damaged the cogs and you need to replace the cassette. The chainring in the front is often still good because it has more teeth and wears down slower.

The image shows the interaction between a new chain and a worn-out cog. It is from technical documentation by Rohloff.

Having watched the video, I do think that the cassette is unusually loose. While it would not cause the chain to skip, it will damage the hub. I found this discussion on this site relevant: make sure to tighten the ring that holds the cassette in place. A mix of road and MTB components could be the root of that problem.

enter image description here

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    Despite being a dedicated proponent of metric, this is one time that inches are a good unit of measure. Great image. – Criggie Feb 12 '17 at 18:54
  • Hi Christian and thank you very much ! I have just edited the question and added a video showing how loose the cogs are. Would you consider that an issue, or is that normal ? – Martin Melis Feb 12 '17 at 22:08
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    @Criggie It would work just as well if the standard length were 25mm. Actually, it doesn't really matter what the standard length is, as long as there's a standard. In fact, I'd argue that it doesn't really work in inches: ten links plus 2% would be 10.2 inches, but nobody does tenths of inches so you end up calling it 10 3/16 inches or 10 7/32 or something. – David Richerby Feb 13 '17 at 0:17
  • Thank for the diagram - that's the best illustration I've seen of this phenomenon. It's one of those things that's hard to describe verbally. – Mike Baranczak Feb 13 '17 at 1:42
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If the chain is skipping after replacing the chain, then it is almost certainly a matter of cassette wear. If you don't replace the cassette immediately, the new chain will also experience accelerated wear.

Most freehubs are made of aluminum, which is light, cheap, and soft. Some seems softer than others. Also, manufacturing with higher tolerances is also cheaper. The result is movement of the cogs, especially when the cogs are all separate pieces. When the cogs dig into the freehub, they can be difficult to remove. Tightening beyond the recommended 50 N/m (say to 70 N/m) can he helpful in controlling the digging, but there may be drawbacks as well .... With a steel freehub, digging will not occur.

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Bear in mind that you're only putting force on the cogs in one direction. So they shouldn't move around too much once everything is assembled, even if they feel loose when you slip them on the cassette.

It's usually a good idea to replace the chain and the cassette at the same time. If they're heavily worn and you only replace one of them, you may get chain skipping. The divots that I see on your freehub are something to be expected - no need to replace the freehub.

  • Hi Mike, thak you for your answer. I just edited the question and put up a video of how loose the cogs are. Do you consider that normal, or should the freehub/casette be definitely replaced ? – Martin Melis Feb 12 '17 at 22:10
  • I watched the video, and no, that's not a problem. A little slop is normal. Like I said, you only put torque on the cogs in one direction (clockwise) - as long as the grooves prevent the cogs from spinning on the freehub, you're OK. – Mike Baranczak Feb 13 '17 at 1:38

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