A month or two ago I bought a new 2011 Rockhopper. After some ongoing chainsuck issues the LBS replaced the bike.
I've had the new one for about a month. I've been careful with the shifting and had some minor gliches with the shifting but nothing too bad.
Yesterday, the new bike started sucking the chain when downshifting from the middle to the smallest chainring.
So. I'm pedaling up a very slight rise and I downshift from the middle to the small chainring and the chain, while in the process of shifting from the middle to smallest ring, starts to stick and wrap itself around the smallest chainring. I immediately stop pedalling and I stop the bike to have a look at what's going on.
What I found was the section of chain that was bridging between the chainrings was firmly stuck. This segment was about 3 inches long. One end of the segment was stuck to a tooth on the middle ring, and the other end of the segment was firmly stuck to a tooth on the small ring. This segment was under noticable tension. It took some prying to get it unstuck.
I was not pedalling hard when this happened. In fact, I have never really put a lot of torque on the pedals of this bike. It's nearly new and it hasn't seen much off-road use. It's been ridden rather mildly.
Has anyone ever seen this kind of condition, or know why it could be doing this?
I'm guessing that one or both chainrings could be out-of-spec, with excessively deep valleys between the teeth, or the teeth could be too tall. I don't see how else the chain could get trapped while straddling the two rings.
This is the second identical Rockhopper that has done this to me. I talked to a customer rep when the first bike acted this way and he said he knew of no ongoing problems with 2011 Rockhoppers.
The LBS was closed today and it is about an hour's drive away. Looks like I have no choice but to return this bike also.