Roland and Julianna reported back, commenting: "700 x 38 for Julianna, 700 x 43 I think for mine. Julianna had tubeless, which was handy for the most part. They were fine the whole way, but would've preferred Schwalbe Marathons which we couldn't get due to supply-chain issues last spring. Met up with a guy on the Katy trail who did the whole thing on slicks, said he had zero problems. I appreciate a little tooth for when you hit the gravel"