I have just bought a front disc to replace my current one as its below limits. It seems the outer disc has some play where its connected to the inner disc. the circular 'joints' can be moved around, i cant remove them but they spin easily and prob have about .4/.5mm movement up and down left and right. i checked my disc on my bike and they dont do this. is this because its attached to the bike?? or this faulty? im new to discs, never replaced or touched mine before.

Many Thanks.

Aaron

Front discs should float on the bobbins, it allows for thermal expansion of the metal and  misalignment/run-out between the carrier and hub, its totaly normal.......... I would suggest the original has become seized, another reason to replace it.

Yup, they're "floating" rotors, meaning they can move like that. That is totally normal. I also agree with sledge, if your old one doesn't move at all, that is probably part of the reason it failed..

They move, but are pretty hard to move. Front to back is not good, side to side is OK.
Cool.
Buddha.