You can tour on anything and I do. My bikes range from full rack drop bar touring bikes to a vintage Raleigh Twenty folder 3 speed.
As long as it fits, is comfortable and in decent mechanical condition you can tour on it. Will you do 100 miles days? Doubt it, but even with my "tour" bike I seldom exceed 60 miles a day, and I have done that on my Raleigh Twenty more than a couple of times. My usual daily average is 40-50 miles regardless of the bike I am riding.
Here is a
link to a guy that has/is touring around the midwest on a Trek Bellvue 3 speed! And having a great time doing it.
Aaron
