After my highside at the track a few months ago, I noticed a very small vibration in the front when slow braking. I had my bike checked out and nothing was found. Now the braking vibration is getting worse and is making a groaning sound at a certain place in the wheel revolution. Any ideas what this could be ?Almost seems like one of the discs is warped ? Everything looks OK to me, however I'm not sure what to look for. Should I stop riding until its fixed ?