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 picture:
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)