Would there be any problems with using discs with the wrong size hole for the hub?
i.e. using discs with a 70mm hole on a civic which has (iirc) 64mm hub

I know the disc wouldn't be able to move much due to the wheel studs/nuts, but I think there would be a little movement in there, which at high speed might cause wheels and/or brakes to be unbalanced.
Would it be possible to fabricate some sort of spacer ring? would this need to bear any sort of load?

Thanks in advance for any input

 

Yes, spacer/hub rings to keep the rotor hub-centric will do the trick. This is a common thing for some of the more exotic oem big brake upgrades. You may want to contact Brian @ www.fastbrakes.com .

They won't be load bearing. Just needs to be something that can take a little heat.

I would be concerned with using the rotor without having it centered on the hub for the exact reasons you mentioned. considering the fact that the rotor is probably anywhere from 11-15lbs and rpms from the wheels and that is a lot of potentially unbalanced weight...

 

i wouldn't even attempt this...even if u use a centering hub spacer u are still going to run into other problems like distance from mounting bracket to caliper also under hard braking without the correct size stud holes the rotors are still gonna try and shift away putting stress on the hub spacers and eventually breaking them and u'll keep have to replace them....i say just get the right size rotors to avoid other problems u might get from this