This happened to me about a year ago, but I wanted to get some input in case something like this ever happens again.

I bought a new $1200 mountain bike from an LBS. On my very first ride, as I was climbing a steep hill, something went very wrong and the pedals jammed. Fortunately, I recovered without crashing. I looked at the drivetrain and saw that the chain had broken and had gone into the rear derailleur and bent it.

I took the bike back to the shop and they were very apologetic, replaced the chain, and fixed the derailleur. They said the chain was "defective." I later spoke to an expert bike mechanic about this and she said, "No, the chain was installed incorrectly." My question is, should I have demanded they replace the damaged derailleur with a new one? Should they have done this anyway? At the time, I had to trust their word that the chain was defective, but I had my doubts...

It was most likely installed improperly, which is what caused everything. There is one or two links in the chain that are removable to access the chain, and someone must not have put it on properly. It was their fault, but you're lucky you weren't hurt.

If the damage was slight, I think a fix would be ok, but if it were severe damage, since it was their fault, I would expect them to get you a new one.

If the fixed derailleur is shifting smoothly for you, keep it. But if it's clunkin' around, take it back up immediately and demand a new one.

Well, the derailluer has been working fine since then, so I guess there was no permanent damage. I was just wondering if it should have been replaced as a matter of principle. I guess it really hurts the shop in the long run. Although they were very nice, I lost trust in them and I have not been back there since.

They fixed the mistake, so they deserve another chance. If they had told you it wasn't their fault, and charged you for the repair, they would have done something wrong. Owning up to a mistake shows that they actually give a rat's a$$ about their customers- a rare thing in this modern world. I'm not perfect- state of the art, but not perfect, so why should I hold anyone else to a higher standard than I hold myself to?

Well, putting a chain on incorrectly is kind of hard for me to let go. It's a life-endangering mistake on what should be a simple procedure. I've never worked in a shop, but I still know how to put a chain on right. And telling me the chain was "defective" means they didn't own up to their mistake.

Chains come installed by the factory like 99.9% of the time. There was no way for them to know the chain was put together poorly and they probaly didn't test ride it under the load that it was under when going uphill. It sucks that it broke and it is good you were not hurt but you can't fault them. I have yet to see a bike come out of a box that does not already have the chain installed and through the derailluers, heck most even come with the rear wheel already on.

I didn't know that. I guess it probably wasn't their fault then. If that's the case, I'm glad I didn't raise a big stink about it in the shop.