I'll try and keep this brief. Got a problem that's driving me mad. Could hear a bit of a humming noise I think from passenger rear wheel. Changed the rear discs (as they needed doing) and therefore the bearings along with them. So it now has new rear bearings. Thing is, now I can hear the humming a bit louder. I noticed this the same day I fitted the new discs. At first I had lightly greased the shaft the bearing slips onto. I then thought maybe the whole bearing was rotating rather than the inner part staying still while the outer part rotated around that. So I took the disc back off and cleaned it of grease, put it back together and the noise is still there. One thing that confused me during the procedure was a ring thing at the back of the bearing. The new disc and bearing did not have this ring thing. The ring thing was separate from the old bearing so I put it back on the shaft and put the new bearing on top. Without this ring thing, the disc slides (in my opinion) a little too far onto the shaft and the abs ring then does not sit right underneath the sensor. I'm wondering if this ring this is causing the humming. Here are some pictures of said ring thing... This is it at the back on the old bearing (top arrow): and this is it in my hands after taking back apart to degrease the shaft: I'm putting it on the shaft with the bevelled inner circle on, facing the car (other way round than in the pic above). Please some one tell me if I do need this ring thing. The humming noise is doing my nut in. I did the drivers side the exact same way but I can't hear any noise from that side. Could be the front that's possibly causing it but it just seems a coincidence that the day I do the rear discs, the noise is worse. I have checked all the wheels for a bit of give by shaking them and they all seem fine. The brakes aren't sticking, the wheels aren't rubbing. Help greatly appreciated. Cheers.