Chain skipping in top gear only

[Gixxerman]

Ah I think a have found the issue. The top gear sprocket is very badly worn (Gear 9.jpg). I hadn't really appreciated just how bad it was until a got it off and had a good look at it. Shame as the rest of the cassette isn't too bad (Gear 7, Gear 8). I suppose I could just get a new top gear sprocket. Or maybe I will just treat the whole bike to a new cassette, chainwheels and chain. It would mean throwing away the fairly new chain it has on it now though. The lose cassette nut incident has caused a little bit a damage to the free hub; but it doesn't look too bad (Free Hub.jpg).

 

[avsd]

I have the same problem but have fitted a new chain and cassette last week so were and tear is unlikely to be the issue. I have also checked the chain for stiff links and all of them are moving freely.

Indexing in the lower gears are fine. The cassette is a 105 11/28 with the following gears - 11-28T: 11-12-13-14-15-17-19-21-24-28, The indexing is fine from 11, 12 13, 14, 15, 17, 19i It then skips on 21 & 24 and settles back down on 28!

On closer inspection the skipping is happening around the jockey wheels not the actual chain and cassette. I have new jockey wheels ordered as they have done some 10k miles. Could worn jockey wheels cause skipping.]

@Gixxerman hope you don't mind me joining your thread.

 

[Dragonwight]

Id say cassette movement not sprocket wear, id put a 1mm spacer in and tighten the lock ring good & tight and try it before paying out for a new cassette.

 

[Yellow Saddle]

Ah I think a have found the issue. The top gear sprocket is very badly worn (Gear 9.jpg). I hadn't really appreciated just how bad it was until a got it off and had a good look at it. Shame as the rest of the cassette isn't too bad (Gear 7, Gear 8). I suppose I could just get a new top gear sprocket. Or maybe I will just treat the whole bike to a new cassette, chainwheels and chain. It would mean throwing away the fairly new chain it has on it now though. The lose cassette nut incident has caused a little bit a damage to the free hub; but it doesn't look too bad (Free Hub.jpg).

No need to replace the chain if it is still within spec. A used, but within-spec chain on a new drivetrain will do no damage to the new components.

 

[Yellow Saddle]

I have the same problem but have fitted a new chain and cassette last week so were and tear is unlikely to be the issue. I have also checked the chain for stiff links and all of them are moving freely.

Indexing in the lower gears are fine. The cassette is a 105 11/28 with the following gears - 11-28T: 11-12-13-14-15-17-19-21-24-28, The indexing is fine from 11, 12 13, 14, 15, 17, 19i It then skips on 21 & 24 and settles back down on 28!

On closer inspection the skipping is happening around the jockey wheels not the actual chain and cassette. I have new jockey wheels ordered as they have done some 10k miles. Could worn jockey wheels cause skipping.]

@Gixxerman hope you don't mind me joining your thread.

Worn jockey wheels could cause skipping if the wear is in one particular mode. If the teeth are simply worn down from top to bottom, they will not cause skip. By this I mean that the teeth have worn to a point where the tips are sharp rather than flat on top. However, if you cross-chain a lot and wear the jockey wheel down from the side i.e. make them thinner, then they tend to derail and cause the jockey to stick, giving it the appearance of a sprocket skip. However, this is only a similar appearance, nor a rear sprocket skate.

 

[TheJDog]

Not all that relevant since OP seems to have found the cause of his skipping, but on my new bike, it turned out to be a chain side plate dent. When this dent hit the adjacent sprocket, which only happened on the small gears, it skipped a few teeth. I flipped the chain over and that solved all my problems. Brand new SRAM red chain, so was slightly miffed. Must remember to keep an eye on that link..

 

[avsd]

My issue was not the jockey wheel but a lack of skill in indexing gears. LBS fixed it in less than five minutes.