The problem here is that C2 is two steps below C3 (C1, C2, CN, C3, C4, C5) and are not really designed for use in shafts where there is likely to be a good temperature rise during operation. The disk/s can transfer a lot of heat through the wheel to the bearings and the outer ring becomes hotter than the inner. At worst they may seize, at best they will become noisy when hot and wear faster. For the sake of €10 each buy new ones if you cannot change them.
There will probably be fellows saying they have allways used C2 without issue, but everyone uses their bikes and brakes differently, different pads/disks/use transfer heat differently, there are too many variables to go into.
I would change them, it is just not worth the risk.
