I’ve got a pair of centrelock Shimano-hubbed wheels that I’m looking to use to replace some aged 6-bolt Hope-hubbed ones.

I’ve just been eyeing up some adaptors, and I’d never realised that the rotors mount on pins. Why not just have 6 threaded holes that the rotor bolts attach to? What am I missing engineeringly wise?

Weight and faff I would imagine. You need to use the locking ring to hold the adaptor onto the hub anyway, so why not use it to simultaneously hold the disc on. Also less faff just to undo one lockring than 6 indivdual bolts.

because the outer diameter of the lock ring is more the pcd of the 6 bolt standard?

‘cos it’s simple, light and and it works?!