Okay I did it. I've ridden these trails a lot on my cross bike, so I knew there were some steep bits. Positioning was very important, but still there were some places I just couldn't keep traction. Oh, and walking in road shoes on gravel/dirt is not very fun. My very supple 25s were probably better than most road tires on these surfaces, but it was still pretty terrible.

I mean...if I had just witnessed a mob hitman kill some guy, and now I had to run away from them and they had blocked all the other routes - yea, okay, I could ride my road bike up some steep gravel/dirt trails. I can't imagine too many other situations in which I would do this. I certainly wouldn't do it for fun.

Gravel/dirt roads, however are another matter, and no problem. There's a division there between roads and trails that seems important. If you look at a route and think 'yeah I could drive my car on this' probably your road bike is fine. Otherwise, you can do it, sure - but purely as a novelty.

I took some pics, I'll stick em up later tonight if anyone's interested.