This bike originally came with 26x2.125" tires and as a 24.3" frame (Trek's official sizing) it looks really odd with the small tires and giant head tube. Since coming into my possession, I've ran 26x2.3" , 700x38 , and now 650x50. The 26" are sure footed on the trails, but feel sluggish on the pavement needed to connect in-town trails. 700c is fast! I still think it's a great combo for a long gravel ride on a dry day. 700x38 has very little clearance with the fork crown. Also it raises the bottom bracket a lot. 650b is really hitting the sweet spot for me. A good compromise for a bike marketed as "all-terrain". I feel confident with this tire on any of the in-town singletrack although I may need to use more finesse going through root-y or technical sections than with the 26x2.3", but the trade off for when I'm on the pavement is worth it.
