Originally Posted by
Happy Feet
Touring means different things to different people which is why your question doesn't have a quick answer.
^this.
For example, I tour fully unsupported on surfaces from gravel to pavement on a cross bike with 30c tires and carrying less than 25lbs (and closer to 20lbs) of stuff including tent and sleeping bag. I've done lighter touring on my road bike. I can't imagine riding around with 4 panniers on two racks like some. They can't imagine going without all the stuff I don't want. Different needs = different bikes.