OK bought some new ashima rotors from bike discount, when i fitted them on the cross bike both were out of true so that they caught on the pads, i wonder if this has something to do with the 6 bolt mounts not being perfectly flat and in line with each other, but then the old rotor on there does not have the same issues and runs freely no catching. Any advice??

The only reason to change the rotors is after a winter of commuting the old ones have surface rust on the spiders any top tips for getting it off?

many thanks

Did you use new bolts when fitting? Did the bolts have threadlock on them? If yes to both, remove bolts, clean away excess threadlock from behind the rotor and refit. Its a common problem with some manufacturers bolts.

I’d just use a bit of fine grain wet & dry to get the surface rust off the old rotors if they are in otherwise good nick