I run 32mm and 40mm tires, Schwalbe Marathon Pro's. I use Schwalbe because I ride my skinny tires on dirt and gravel roads a lot. Marathon tires are incredibly tough and flat resistant. I also have a pair of 700 x 32C Gatorskins that I really like. I use Velocity and Sun rims on all my bikes and have not had tire mounting issues. As us56456712 mentioned all tires need to be easy to dismount for repair while riding. I have had to replace one of my 27" Marathon Pro's with Gatorskin because the Marathons are just not available at the present time. I guess worldwide supply issues. For my style of riding tubeless creates more problems than it solves so I use tubes in all my tires.