I have a small amount of play in the disk on a 2006 YZ450F. If I lock the front brake the front tire will shift back and forth slightly. It seems that the play is coming from where the disK that hits the pad is riveted to the part that is secured to the bike. Do these typically loosen like this? Is this at all normal? I can't believe I would have to replace the disk after only 6 months of riding. Thanks for any input.