Disc brake conversion wheel hub sizing

I don’t think you’ll have any luck finding a disk hub to fit a 2 3/8” wheel hub bore.

The stock 73+ disks have a hub that’s about 2.6” to 2.7” in diameter, that does depend a little on who manufactures the disk. The DoctorDiff aluminum hubs have a base diameter of 2.7”. The current Wilwood kit for 10” drum spindles have a gigantic hub, it’s 3.24” at the base (!!!).

I don’t know about the scarebird kits. The PirateJack kits are just 73+ disks, but the small bolt pattern kits do have the hub diameter machined down to work with earlier rims. I doubt they’re turned down to 2 3/8” though. The wall thickness of the rotor hub at the outer bearing is ~.3175, and the disk I have measures ~2.6” out there. Cutting that down to 2 3/8” would mean a wall thickness of .205” at the outer bearing, that’s like a 35% reduction.

When I spoke with DoctorDiff about the hub diameter on his kit he seemed to think turning them down to 2.5” would be ok, although I didn’t want to cut that much. I ended up having my wheels machined instead, but they’re aluminum and don’t have the rolled shoulder that steel rims have. That’s not an option for you.