With the types of gravel I encounter (very loose and sometimes sandy) I would not go below 45. I did a gravel race on 40s two years ago and a few sections were unnerving with 40s.
If a gravel bike doesn't accept 45-50 tires I will not buy it.
Pick the right tire and you lose nothing going from 40 to 45-47. But you do gain traction and a more comfy ride.
I'm running the Tufo Gravel Thundero 700 x 44 (that actually measure 45) and they are fast on the paved sections and easy gravel or groad/gravement sections. They rank very well on the rolling resistance test.
Last edited by prj71; 04-24-24 at 09:42 AM.