mrrabbit- You are correct in that any wheel placed in the drop outs crooked will not agree with the hanger's alignment from a wheel that had been placed properly (given both wheels are true). I guess that the mistake i made in describing my view of hanger alignment was assuming that any one who knew about using a hanger aligning tool also knew enough to install their reference wheel fully. But i still maintain that a true wheel is the only quality that the wheel needs to be used as a aligning reference. The aligning tool does not care or know whether the wheel's rim is wider or narrower. And a well trued wheel, but not dished, is the same as far as the drive side's rim side wall placement WRT the hanger's outer face (where the tool touches the frame). So a wide rim trued to the NDS is potentially the same as a narrow rim trued on center. Will the aligning tool be able to differentiate between the two? I say no. If an off dish but true wheel is properly fitted into the drop outs the tool's extending part will just reach out more or less to touch the rim's side wall. If the rim is true the extending part will still touch the true rim as the tool rotates around the rim. That we need to go to this level of discussion surprises me.

The most common reason to have a rear wheel not properly seated into the drop outs fully IME is having the QR skewer spring back wards. No one has mentioned this yet. Andy.