New chainring and chain at 1100 miles - seriously?

[luvmyguys]

If your front derailleur is the type that fastens via a band around the seatpost, maybe it is misaligned and that is causing excessive wear on the pins when you shift. If the front derailleur is not the band type, all I can suggest is that maybe that the chainring batch was defective (poor mixture of metals).

It is that type - how would I know if it's misaligned?

[lph]

Did the FD shift to the large chainring and then make thumping sounds? Or did it not want to shift?

Once you've shifted the chain should run smoothly with no grinding or thumping sounds. Any sounds after shifting mean that the FD (or something else!) is rubbing against the chain, and needs to be adjusted. The FD should only touch the chain when shifting.

It can make some noise during shifting, but the shifting should be quick and smooth. Very noisy or sloppy shifting may mean that the FD is misaligned so that it pushes against the chain at an angle. If you have a way of suspending your bike, at least the rear wheel while you pedal and shift, you might be able to see if the der hits the chain at an angle or not.

[OakLeaf]

Do you really mean the pins? Or the teeth? I've never heard of the pins wearing out, ever.

Honestly, I've never heard a "ka-thunk" sound, either. Normally when a FD doesn't want to shift but moves over part way, you'll hear a grinding noise as the chain rubs against the derailleur cage. I can't even think what the thunking might be. Does the chain drop off the chainring and hit the pins???

Wearing out a chain at 1100 miles would be "hard usage," within the realm of possibility, but not completely unheard of. Wearing out a cassette that quickly, MAYBE. Wearing out a chainring that quickly ... either pins or teeth ... something is going on, and it's strange that your LBS can't explain it. Hopefully it was just a bad ring.

[luvmyguys]

Did the FD shift to the large chainring and then make thumping sounds? Or did it not want to shift?

Once you've shifted the chain should run smoothly with no grinding or thumping sounds. Any sounds after shifting mean that the FD (or something else!) is rubbing against the chain, and needs to be adjusted. The FD should only touch the chain when shifting.

It can make some noise during shifting, but the shifting should be quick and smooth. Very noisy or sloppy shifting may mean that the FD is misaligned so that it pushes against the chain at an angle. If you have a way of suspending your bike, at least the rear wheel while you pedal and shift, you might be able to see if the der hits the chain at an angle or not.

Didn't like to shift. Once it did, it was a happy drivetrain. Didn't happen frequently enough, but there wasn't a problem after shifting.

I'll look at it tonight.

One thing he said - and I'll put this out there for all of the wise and knowledgeable folks here to confirm or debunk - he said that smaller frames (or, really, any frame that is an outlier size-wise - either really small or really big) sometimes get finicky in terms of getting them tuned well?? Truth or fiction?

[lph]

One thing he said - and I'll put this out there for all of the wise and knowledgeable folks here to confirm or debunk - he said that smaller frames (or, really, any frame that is an outlier size-wise - either really small or really big) sometimes get finicky in terms of getting them tuned well?? Truth or fiction?

Hmm. I'm not that knowledgeable but I'm curious. I guess it's possible that smaller frames could make it harder to get the chain-line right, since the parts are standardized and may be a bit large for very small frames. (Or are they ever custommade?) But I wouldn't expect that to be a problem until you're working on childrens bikes, and then mostly crosschaining would be difficult. Interested to hear if anyone has feedback on this one!