The string method will only tell you if something is askew with the alignment. It won't tell you what is out of alignment. The string method is only effective if one can confirm that the head and seat tubes are in the proper plane. Then measuring the string's gap from the seat tube will accurately define the stays symmetry or lack thereof. A rear end can be spread any old way you want but the best results come from using an alignment table and a competant frame builder.
Curt Goodrich
Minneapolis, MN
>
> Dale said:
>
> You do have to be very careful to set it correctly so the frame remains
> symmetric. That is the same amount of change on each side.
>
> A Campy straight edge tool is very useful here. ...
>
> ______________________
>
> A string can also be used, tied to each rear fork end and looped around
the
> head tube. Make sure the string leave the fork ends symetrically. Then
> measure the gap between the string and seat tube on each side. I use a
> caliper to measure. It is surprisingly accurate. It is also shocking how
> poor the alignment is on many frames.
>
> These two methods have slightly different datums for alignment. The
straight
> edge method aligns to the BB shell and should optimize the chainline. The
> string method aligns to the head and set tube and is an estimate(about
three
> steps removed) of alignment to the plane formed by the centers of those
> tubes. If both methods don't agree you've got some bigger problems. Some
of
> the most cronically baffling shifting problems turn out to be BB shells
that
> are askew.
>
> Joe Bender-Zanoni
> Great Notch, NJ
>
>
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