I have a 2014 norcom straight and new boyd rims (don't remember dimensions, but they are wide). 25mm conti gp 4000s ii would not work. I could get them in, but they would rub something. It was really minor, but I noticed because it was starting to wear the tire on the sides. It might just be wheel flex on my specific wheelset, but I would stick with 23mm's if I was you.

Thanks! I'm looking at Boyd's also!
Nice wheels?

I had mine built up differently from prowheelbuilder . com using hope pro disc hubs, but I think they are great!

I've got a HED Jet + disc on mine, and it's fine (although I've got a 23mm tire on it). I've had a Flo 30 on the front (again with a 23mm tire).

The dropouts in the rear give a good amount of adjustment and might help you with a larger tire.

I run Hed Jet 5's with 25mm tires. Plenty of room for clearance.

I think I remember reading somewhere that you could run all the way up to 28mm

Cool ok

I have a Norcom Straight and I'm running a Super 9 Clincher with a 25mm tired on the back.

Idk much about measurements but would these work? Roval CLX64s. . External rim width is 29.9