So I just built up my first road frame, and everything went smoothly until I tried adjusting the rear derailleur. Even with the derailleur cable disconnected and the high stop screw loosened all the way, I cannot get the derailleur to move the chain into the highest gear. Attaching the cable didn't help.
Looking into the problem, I found that clamping the rear wheel skewer (with moderate clamping force) makes the hanger flex such that the bottom of the derailleur cage moves inward by 4-5 mm. I *think* this is probably why the derailleur can't reach the highest gear.
(Even if it could reach the highest gear and I got it adjusted perfectly, since the amount of flex is dependent on clamping pressure it could mess up my shifting if I changed a tire and put the wheel back on with different clamping pressure.)
The replaceable hanger is molded (not machined) and has rounded sides, which creates a gap between the hanger and the frame near the axle. I think clamping down on the skewer closes that gap, which rotates the hanger.
I've contacted the frame manufacturer, but has anyone else run into this problem? Or am I barking up the wrong tree? Any suggestions would be appreciated. (Frame is a 2010 Lynskey R230).
There's a web site specializing in aftermarket hangers that are CNC machined, but it doesn't look like they have an exact match.