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Having spent hours fiddling with my rear derailleur I have to admit defeat and ask for help....
The bike is an MTB, 2x10 set-up, and has just had a full refresh of the drivetrain as everything was worn-out after a wet summer followed by a wetter winter. I spent the money on good kit (except for the rear derailleur itself, which I suspect is the culprit), bought over time in various sales. I have double-checked that the new kit is all compatible, here is the spec:
- FSA afterburner crankset, 38/24
- SRAM XX10 front derailleur (2x10 compatibility confirmed)
- SRAM X9 rear derailleur (2x10 compatibility confirmed, max range 37T, medium sized cage
- SRAM XG1080 10S cassette, 11-36T
So, front derailleur seems to be perfectly adjusted - no rubbing on high or low, or when other problems occur. Rear derailleur is well adjusted on the high and low ends, the problem occurs in the middle and that's what's got me stumped. In cogs 4-5 it skips and jumps. It resolves itself it I adjust the tension, a lot, but then it will no longer go down into the small ring. When I adjust the tension back the problem recurs.
The bike is also prone to chain suck, which I assumed was down to my worn out kit but it is still happening even with a brand new crankset (it didn't used to happen, when the bike was new).
Since I changed the kit, I have done only a few rides and it broke a brand new (albeit hollow-link) chain.
Could it be a bent mech hanger? I've eyeballed it and it looks straight, and I would have expected a bent mech hanger to affect one of the extremes rather than the middle. Could it be a crap derailleur? Any ideas?
Do you have a spare mech hanger you could swap over and try? if you haven't it's worthwhile getting one anyway because you will likely need to replace it at some point. If that's not it it might be a bent mech cage.
I do, and was thinking of trying that but it didn't seem the likely cause. Maybe worth a try though.
Chain suck.
If every thing is new, then it gets a bit difficult to track down. It's normally when the chain rings, especially the granny, is worn or has a bent tooth. But I've seen it caused by a bent rear mech cage, worn jockey wheels, putting side on pressure on the chain enough to make it suck.
Skipping.
Most likely bent mech hanger. You could fit a new one but there is no guarantee that the new one will sit straight in the frame. Alignment tool needed or LBS to check. It could also be the cage on the rear mech.
Where are you. If you're Hereford area you're welcome to come and use my
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Thanks for the reply, and the ideas. I'll definitely start by chaining the mech hanger and go from there. I'd take you up on your offer too, only I'm just outside of Paris 🙂 Thanks again!
Just nip over in your lunch hour tomorrow. 🙂
So, I changed the mech hanger and re-adjusted the derailleur - no change.
Am now wondering if it could be the cassette given that the chain seems to struggle to line up with the teeth, but I've just double checked again that both are 10 speed and they are.
Any ideas?
What shifters are you using? Do they match the derailleur?
The shifter lets out the cable and that controls how the Derailleur moves. This is the most likely culprit 🙂
Did you change the bottom bracket when you changed the chainset? If so, did you replace any spacers that were on or did you put any on that weren't there? Could alter the chain line..
Sounds exactly like cable wear/contamination, try replacing it.
If a gear hanger looks straight, it is straight.
All cables are new. Shifters and derailleurs are both SRAM and all compatible for 2x10. Crankset FSA afterburner, as was the old one - spacers are identical to the old version. However, there were two changes:
- new crankset is 4 bolt so that I can change just the rings next time
- I changed from a 39/27 to a 38/24 (easier on the uphill)
A random thought - could chain length be the culprit? How would I check if it is the right length?
Really appreciate the contributions 🙂
This is handy for getting your chain length right, especially if it's a full suspension bike:
http://www.pinkbike.com/news/Tech-Tuesday-Chain-Length-Basics-2012.html
doubt it - chain length would create problems at one extreme of the cassette, I thinkA random thought - could chain length be the culprit? How would I check if it is the right length?
CHeck by putting in big front/big rear and seeing how much spare there is - there shouldn't be much at all* (there are posher ways but they're all fallible, esp if you have a suspension rear)
*If you suspension movement causes the chain to "pull" make sure you test at both extremes of suspension movement or else you may damage something when the suspension compresses and you're in big/big
Just a thought, but is it a new chain? I had problems with a new chain on a worn cassette. Would a worn chain on a new cassette also cause a problem?