I have been running fn2 disc and calipers on my bb4 and have just up graded to 5stud hubs and found the fn2 disc will not fit over the new hubs, it's quite a difference in size!!
I have wondered if aftermarket disc or maybe even ep3 disc will clear the new hubs? Or will atr disc be the same offset and thickness as the fn2's
Please help, my head hurts from trying to find out
EP3 and FN2 use the same disc with same centre bore.
ATR disc is same diameter and offset but has the larger 70mm centre bore you need. However it is thicker so you would need to machine the inside faces of the carrier for clearance
Ah right, I see what you're saying now.
Yes the ATR disc "bell" is bigger itself so will fit over your hub "flange" no problem.
As I said though, the ATR disc itself is thicker 28mm vs 25mm (EP3 and FN2) so you will need to either machine out the inside faces of the carrier to go over the disc and give adequate clearance (it's only 1mm a side and plenty of material left so this is not a problem) or swap to ATR calipers and carriers which would actually be a better brake set up anyway - this is what I would do tbh.