Depends if they are fully floating or semi floating. The cast iron discs on my 748sp were fully floating and you could physically waggle them about. The EBC semi floaring race discs on the race wheels you can rotate the bobbins but that's about it. Andy
Depends on the type but around 1.5mm total movement is normal, if you know who they're made buy you should be able to find specs on their website. If they're outside of spec they need changing rattle or not. If the rattle's because the wavy washers have no spring left in them, then as long as the amount of movement's ok you may be able to change the washers themselves depending on construction. The washer's only there to prevent noise, some race discs don't have them.
As oneball says you probably want to check the manufacturer specs before even listening to us. But just so you know, the standard semi floating type on my 748 had a little movement but were quiet, while the brembo iron full floating race disks i have rattle like crazy and move plenty. They did when new, and it's to stop warping when they get track riding hot.
as all the above, but the full floaters on my rattle like a skeleton having a tug in a biscuit tin....i even had an advisory on an MOT once because the numb nuts had never even heard of floating discs..a quick google made him refine the MOT....mine have a lot of play and rattle when you oush the bike around..also if you hold the brake and compress the forks you can hear them knock..this is perfectly normal according to those in the know..
