When to replace a rear derailleur hanger?
 

Today I was right hooked while on a road ride and couldn't quite fully stop before hitting the driver's passenger side door. Thankfully, I'm fine, and my frame/fork/wheels are fine (as I hit it pretty slow) but when I was dumped to the right my rear derailleur was hit. When I later tried to ride away, my derailleur cage snapped off the bike entirely (the bolt was sheered off). Aside from a very slightly scraped elbow, I'm entirely fine. Was a very, very great ride otherwise, though!

Sadly, while the driver was very sorry and cooperative, they are apparently jobless and living out of their truck, and claim to have had literally no money on them. At least they gave me and my friend a ride home (which was about 15 miles from the accident). I decided to not press the issue further.

The derailleur is toast (which is sad, as Ultegra 6600 was fairly fancy for my bike) and the hanger rather severely bent in towards the spokes. I've bent the hanger slightly a few times before and brought it back with the alignment tool at the bicycle cooperative near me. I'm pretty good at this now.

I'm wondering if I should finally toss the hanger and replace it--its fairly severely bent this time, and has been bent before, and I'm worried that the metal is beginning to fatigue and become even softer.

Attached is a picture of the hanger. Sorry it's not very good; the lighting in my room is bad and I'm using a cameraphone.

http://img256.imageshack.us/img256/8...1203205012.jpg

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As a rule, I wouldn't replace a hanger until it broke, or I had very good reason to suspect it was near ready to break.

In your shoes, I say the second condition was met and would now replace it.

Given the relatively low cost of the hanger compared to the cost of the derailleur and possible wheel repair/replacement if it fails, if it were me I'd spring for the new hanger.

I'm surprised that the hangar actually bent. Most of the replacable hangers I've seen are made to be "sacrificial", that is they snap off cleanly to protect the rest of the frame and dropout.

most i have seen bend a lot before breaking. evidenced by the many bent hangers that i see and the poor shifting that result.

Assuming the hanger is aluminum, be very careful unitll you replace it and check for crcks every ride. Whnd aluminum is bent it loses a;great deal of strength and can fail catastrophically

No question that bent hangers cause shifting problems but aren't most bent hangers integral with the dropouts, not the replacable type? Replacable hangers are meant to be a bit fragile and act like a "shear pin" to protect the rest of the frame.

they all bend. the replaceable ones do snap but they can take quite a bit of bending and straitening. if the replaceable type is bent pretty good i will take my pliers wrench(parallel jaw pliers) and eyeball it first then align it.

I ended up buying two new hangers at the local Trek dealer. It turns out that the old hanger was so bent that the threading was no longer parallel. Thanks for the advice everyone.