One of my guys came in with the usual "it ain't shiftin' right" complaint. Fooled with the rear DR for some time before I noticed it was badly tweaked, looked like a bent hanger. Guy swore he didn't drop it...

Called the shop (I hate paying shop rates) to see what a new hanger would cost, and the guy said "bring it in, we have a tool."

He did, too. Nifty little rig that screws into the DR mounting hole. Has little measuring arms that you run up against the wheel rim and then rotate 180% to check against the other side of the wheel. If there's a difference, you just use the tool body to tweak the hanger. Do this at four points around the wheel, and she's straight! (if it doesn't break...)

I was impressed. Only cost the department 8 bucks. Not worth the price for the casual cyclist, but handy to know about.

Had a minor crash ( my wrists still sore ) and now my chorus rear der shift like crap... I can only dial in either lower cogs or higher cogs but not the whole range plus over all chain runs much noisier than before.... I am thinking it could be bent hanger or also possibly indexing in the shift lever is outta whack or something is wrong with the hub/cassette...changed the cassette with spare one but the same problem... switched the wheel... still same....

When it crashed it went down on the right shift lever ( stem wasn't tightened down and move, the cause of crash -lack of sleep plus doing things in hurry, which I think saved the shift lever and the handle bar from damaged more...scuffed the plastic body above the lever a bit and the rubber cover got slightly ripped) then it landed on left side on side of the saddle (scuffed a tiny bit) and I suppose on the rear wheel/ tire (Ksyrium SL; looks fine and not out of true at all no damage whatsoever.)

I took my Look rear der hanger off and looked at it but looks just fine but might possibly slightly bent... who knows... Now I can check the der hanger with the tool and not wonder about it... got it at something like $35... not bad for piece of mind now and in the future ( many bikes)...by simply eliminating the possible der hanger damage... before start looking for a replacement hanger (which should be a breeze if it is indeed bent....)