I had lowered the back end over the winter and added heavier springs, and the wheel rim to control arm clearance was fairly close,so I assumed the springs must have settled in and the wheel had rubbed the control arm just a bit, as there were some rub marks on the edge. I added a 5mm wheel spacer and took the car back to the track yesterday. I went out slowly, and sure enough the noise was still there. Brought it in and decided it must be a wheel bearing. A few others even looked at the problem and decided that the very subtle wheel movement must be bearing related.
I just removed the wheel bearing from the upright and could find no signs of wear or damage. I then decided to take a real close look at the wheel.
It didn't take much to see the real problem:


Two broken spokes..out of 4.
How can something so basic, and easy to see, be overlooked! I wasn't looking for a cracked wheel. I feel so stupid...

These are 3 piece Keizer wheels..and the center is magnesium. I just got off the phone with Keizer...they were surprised to hear that a hub had cracked..however,it does happen..and they do make a billet aluminum replacement, which is MUCH stronger. I ordered replacements for all my rear wheels.
The thought of that center breaking is not something I want on my mind..

Moral of the story..do not assume anything is unbreakable.When looking for a problem,look at every possibility, including something you think is unbreakable…and check your wheels,closely every chance you get..

