Grease is the word
 

Need a few opinions:
Had a great track day in Laguna Seca today :D
After session 3 I noticed that a lot of grease was coming off the hub in the center of the right rear wheel and then got pushed by the centrifugal forces all over the rim (see attached pic).

It seems to me that the grease came out the hole in the center of the axle. Seems like the axle is hollow and connected to the CV boot.

So I now have two theories:
a) wheel bearing going bad
b) axle going bad

This does not happen in daily driving only when I'm at the track and the brakes get really hot and apparently "cook" the grease

Anyone had this happen to him before?

Trying to think of less expensive theories... :D
Any chance that prior to you putting the wheels back on recently you applied some grease/oil/ anti seize in that area?
Or perhaps it was just an accumulation of of greasy grimy dirt that under the heat and force of the track freed it self.

I think your sealed wheel bearing has given up the ghost, seal has failed and now you have a dry or nearly dry bearing.

If it was your CV failing, it would sling grease at the other end of the halfshaft.

Thanks,

a little bit more history: not sure if it's useful:
I had the same happen to me at my prior track-event (Buttonwillow)
That time I had grease outside on the wheel AND loads of grease inside (all over the suspension).
My (very trusted) mechanic found that one clamp of the CV boot was loose and therefore the grease went flying.
So he fixed the clamp and this time the inside is clean but the "greasing" continues on the outside.
So my "less expensive" hope is that this is still some grease residue which is now "melting of"

It would be easy enough to plug (or cap) the end of the axle shaft with something to test to see if it is coming from inside the axle shaft or not. If it is then no worry, if it is not then order a new wheel bearing.

great minds .....
we exactly did that yesterday ;-)

grease coming out of the shaft vent hole
 

Having this happen now. The axle shaft is hollow and intended to vent . Grease is coming out of the center of the shaft. This first happened in March at the track; as a interim measure to salvage the weekend I tapped the center and put in a bolt. After the event the half shaft assembly was replaced.

Midway through the next event the same thing. Curious how Chris's issue was resolved - was it the wheel bearing or something else. This has my mechanic really puzzled.

thanks!

PS - we tapped both axle shafts as a precaution and this came in handy last weekend. hope this tip helPS others.

I just replied to your PM

The problem was solved by replacing the axle with an original Porsche part

I had a similar problem AFTER my rear axles were rebuilt. The first time out on the track after the inner CV joints were replaced and the outer joints were cleaned and repacked, I had a thick layer of grease everywhere on the inside of the rear wheels. Since then, nothing more so I never investigated.