FBinNY 

How's that possible? it keeps coming up when folks talk about pressure gauges, calipers, and lately wheel tension meters, and even chain wear gauges. Many years ago (when Wang Labs was a startup) my college buddies called me "an analog man in a digital age" and I guess it stuck. I still tend to prefer analog readouts for many applications - can't stand the digital speedometers in some cars - but I've no technical objection to digital stuff except for the assumption that digital means accurate.

I referred to a bubble level because most people are familiar with it and know what I'm talking about, but a level is a level so folks should use what they have.




I knew that's what you meant. I eyeball lots of stuff, and often spot badly aligned frames this way. But I don't know how sensitive eyeballing is. You can only use the top half of the rim, since there isn't a reference for the lower half, and the distance rim to seat tube varies on the arc which can introduce parallax error. Not saying it can't be done, just not sure. I also wear glasses and often curvature of field makes eyeballing this sort of stuff hard.

The key in making a decent diagnosis of anything subtle like frame alignment is to avoid snap judgments and/or tunnel vision. There are many factors involved, and it's important to keep an open mind and get a good overview before jumping in and possibly making things worse.