Hello all I have a Giant OCR 2 not sure wich year it's blue and silver (2003 maybe). The other day while climbing a steeeep hill I shifted down and heard the chain break then a clunk and looked back and the rear derailleur was hanging. On further inspection the rear derailleur had broken off at the mounting holes. WOW, So the components are Shimano Tiagra and I was wondering a few things. What type of derailleur can I replace the tiagra with and still keep all the other components. Can I upgrade to a better rear component, and do I need a long cage?!? (not sure what this means). Also is it common for chains to break because this is my second broken chain!

You can replace the RD with any fairly modern Shimano rear...

I don't know how common chain breakage is, but I haven't broken one on my Giant Sedona in the 2100 miles I have rode it... nor any other bike I have ever ridden.

How many miles have you rode the bike?

Chains breaking on road bikes isn't real common but it isn't unheard of either.

Newer, narrow chains are a little pickier about how they are connected. Shimano chains, for example, have special replacement pins for making the reconnection. I assume that's because reusing the old pins, like we used to do, makes the chain more subject to breaking.

For several years I had been using Sachs chains which have a separate connecter link with good success. The last couple of chains I have bought, however, were Shimano because that's what the LBS had in stock.

You may want to take it to your LBS, and have them look at the frame as well. I had a similar incident earlier this season. The force of the chain twisting on the rear deraileur was enough to bend the hanger, and frame so that they needed an alignment.

Here's a link, just so you can get an idea which one you may need, as well as the cost.

Shimano Tiagra RD

Thank you for the help I really appreciate it!! Well the rear derailleur isn't as expensive as I thought, thats nice. I might price used or new upgraded models also. I'm prety sure it's not my strength that is breaking chains ) I dont know how the chain was assembled because when I broke the first one I had LBS replace it. Well off to get ne parts and chain hope it holds 0