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Chain skipping on large chain ring.
This has me baffled.
I just replaced the chain on my bike. It had approximately 4000 miles on it. I never had any problem with it, except over the last 1000 miles it got slightly more noisy. It shifted perfectly and was a breeze to tune. My Park CC-2 told me it was .5% worn, so I decided to replace it. I don't have any calipers or machine rule to measure wear with, just the CC-2. So I replaced the chain. The cassette on the bike is relatively new. I frequently swap cogs around between cassettes so some cogs are newer than others. I recently switched to an 11-21 setup from a 12-25 so I took 4 links out of the chain when I installed it. It now is 104 links long instead of 108 links. It it sized to allow me to shift into the big/big combo without putting the rear derailleur into the wheel. I never use the big/big or small/small combo. After putting on the new chain, everything works perfectly, except the big ring. The small ring is smooth whether pedalling forwards or backwards. The cassette is smooth and does not skip. The big ring, however, has a bit of hooking action going on when pedalling forwards, and if I pedal backwards the chain rides up the teeth every once in a while and then plops back down where it is supposed to be. Here is a pictu http://www.teamendorphin.com/jpg/skip.jpg I doubt the chain will suck up because of the tension on the chain from the derailleur spring. I rarely pedal backwards so I would not normally notice this skipping, except I do pedal the crank backwards when I clean the chain, which is how I noticed this. The chain, BTW, is joined with the Campy pin, not a quick link, in case this matters. I compared the length of the old chain to the new chain and the old chain was a little longer, but not a whole lot. My CC-2 won't even fit into the new chain at all! Either my CC-2 is not calibrated properly or the new chain is ultra tight. I ride 99% of the time in the small ring. I can only think of 3 or 4 times, since I bought the bike, where I have used the big ring. I would expect the small ring to wear out long before the large ring. I would also expect the cassette to show significant wear before the chain rings, and I definitely wouldn't expect to see wear in just a few months. I have seen chain rings that are worn to nubs that still worked fine. I use ProLink to lube the chain and my chain is usually clean enough to eat off of. I believe the chain only needs lubrication on the inside. Any lube on the outside just collects dirt. I doubt lack of preventive maintenance caused this. In fact, when I replaced the chain, I was able to set the old chain down on my white carpet (Why do women like white carpet?) without marking the floor, and this was after a 100 mile ride. I've even read that a totally dry chain is just as efficient as one that is oiled a bunch. I cannot rotate or flip the large chain ring because it is pinned and ramped and because it has an indexing mark/chain catcher thing that tells you where to install it. I had heard that chain rings can develop hooks where the area of greatest power is applied, but like I mentioned I have maybe 20 miles on this ring and I'm certainly not known for generating a lot of power. What I think will happen is I will ride the bike for a few hundred miles and the chain will stretch slightly and fit the large ring properly. Since I rarely use the large ring this really isn't an issue anyways. I'm just curious what is going on here. Any ideas are appreciated! I really don't want to have to replace the whole drivetrain so if this is going to cause abnormal wear I need to know. I typically ride 200-400 miles a week. Thanks! -- Mike (Xyzzy) |
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