Thanks for the input. The reason I wanted to change out the tire is that my friend hasn't ridden a road frame before and is feeling a little shaky with the body position, drop bars and down tube shifters. I left the original 25's on and he's going to try it out and see how he likes it.

The trails are hard-packed dirt covered with crushed limestone. Right now, they're hardpan but later in the season, especially after they've been repaired, they tend to accumulate loose material in curves and at the bottom of hills and they can suck the wheel out from under you if you're not careful.

His SR400 is probably mid-90's. It's a blue fade paint job with RX100 comps. I couldn't find any specs on maximum tire size but the brakes don't seem to be long-reach.

I'm trying to encourage him to ride that bike on the road where it belongs.