New chainring and chain at 1100 miles - seriously?

[luvmyguys]

First, I'll say that I love my lbs - it's warranty work.

I've been having problems with my front derailleur for a while, and it never seemed that they could be adjusted out. I'd shift down to the small chainring, and once I was at the top of a hill and when I knew the rear derailleur was in the middle of the cassette, and I'd try to move to the big chainring and the FD would just sit there and go "ka-thunk, ka-thunk, ka-thunk". Turns out the pins on the big chainring had worn out early? I live in a very flat area and seeing that I've actually had problems with the FD for a while, I've actually suffered up a few hills (outside of town) that should have used the small chainring because I was afraid I wouldn't get it back at the top of the hill.

Can anyone think of what might cause the pins to wear down that fast? I have a SRAM Apex and they changed the chain out with the chainring - turns out that I didn't have a SRAM chain, but some other brand. They put a SRAM chain on. At first, they said "Well, if you change gears a lot . . ." Thing is, I've only been doing more heavy duty hills in the past 200-300 miles, and it was acting finicky before that. In any event, the owner of the shop said it shouldn't have gone out that fast, and he's calling it warranty work.

Was this a fluke, or is there something I can do to make sure this one lasts longer? I'm hesitant to say whether or not I could have done something better, since I was a newbie and unsure (even though I usually didn't tough my FD too much).

[Hi Ho Silver]

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).

[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!