If you are meassuring off of the inside flats of the rear dropouts, the method is fine - there is no offset of the right dropout/stay - that is why wheels have to be dished.
Now, if a frame is entirely straight, than this rear triangle meassurement will check out fine. But, as a rule, I don't advise ever aligning a rear triangle unless the main triangle is aligned first. If the front changes, the rear may need to be moved yet again.
You will see photos of the Rene Herse shop where the string check is being done. But I assume the main triangle has been built and aligned, and therefore this check for the rear is fine to do.
Mike Kone in Boulder CO
> I read somewhere that one way of checking a frame's alignment is to string a
\r?\n> string from one rear dropout, around the headtube, then back to other rear
\r?\n> dropout. Then measure distances from string to seat tube...they should be the
\r?\n> same on each side.
\r?\n>
\r?\n> Isn't this method as I described incorrect because it doesn't take into
\r?\n> account an offset of the right chainstay that provides freewheel space? If you
\r?\n> took offset into account, would this method then be OK? How would one calculate
\r?\n> the offset based upon dropout spacing?
\r?\n>
\r?\n> Jack Romans
\r?\n> Sacramento, California