When I go to the music store, I notice nylon strings are grouped by tension
instead of gauge like steel strings. The nylon strings are labeled from
"extra low" tension to "extra high" tension. According
to the guitar guru there, you can put any of these on most nylon string guitars
with out fear of damage, the main difference here is playability, sound, and
personal taste.
The higher tension strings will make a guitar sound louder but it will be harder
to fret for example. Heavy handed strummers would probably like the high
tension strings.
Low tension strings would sound better on a lighter braced guitar perhaps and
they would offer easier playability.
Gman ( o )==#