Brad from St Louis on 7/2/2009 10:21:58 AM:
"Road bike" can mean a lot of things.
I've put a lot of miles on the Katy using a Trek 520 touring bike. That's a road bike, but it can take tires up to maybe 700x40.
I've also been on the trail for day-trips using a sport bike with 700x25 tires. I was OK.
On some trips I've encountered areas of loose gravel.
Wider tires feel more stable on loose surfaces. Also the trail can get soft after a heavy rain, and the wider tires would help with that.
I'd recommend at least 700x28s if they fit. But no matter what you ride, you do have to pay attention on the Katy. Loose gravel, rocks, holes, branches, turtles, etc.