bovien

So... I've nailed it down to being related to center bolt, lubrication/greasing of that or cleanliness/deterioration of the contact face of the hub carrier, possibly hub carrier itself. Or a combination of all.
I realize this is a bit vague but here is what I have experienced:

I swapped center hub nut from rear to front. That reduces the sound some. I then replaced the front left nut (most noisy) with a new one, which again reduced the sound. But it was still there, but vague.
Then I had the car past the OPC again, who told me that Porsche had released a tech bulletin on GT2 RS (991), saying this issue in those cars are down to cleaning out the contact between brake disc and hub carrier. The GT techie told me he had seen the issue on track with several GT2 RS's and it had helped somewhat following this, although they still have the sound. Also they had a very pronounced issue with a 918 where the guy was even scared to drive on the street as the sound was that noticeable even low speeds.

So after following this in my car the noise was reduced yet again, it's still there, but getting towards me accepting it, as the fact that these things reduce it, tells me it's not a danger or accident waiting to happen,
I've tried an even more thorough cleaning myself, but that did not change anything.

I'll go in track tomorrow to testify out. I'll bring a jack, the old center bolt nut and optimoly, so I can test out if I can nail it down to a specific part. Next step would be to replace the hub I think. Sounds expensive...

- by he way; I noticed the new center nut had 'sills' in it on the contact towards the wheel in stead of one, ant that the part of that which is in contact with the wheel when mounted is less than the original nut (optimoly paste remains on the area not in contact with wheel mounting face). Have any of you noticed this? I think it's strange, as it's only applicable the the new nut. Maybe Porsche changed design a bit?

sixtyfiver

If it’s a clicking noise, I had the same problem. To troubleshoot, simply go to parking lot start turning in circles until noise starts, press on brake with left foot while keeping same speed and if noise goes away it’s most likely the following. Springs holding the rotors together that are clicking, typically caused by too much lube in centerlock. I had the same problem, dealer switched out carbon rotors, noise went away and then came back after 150 miles, then dealer changed out centerlocks, noise went away and never came back as they come pre-greased from factory. After 3,000 miles noise came back, had dealer Re-torque wheels and noise is gone. It’s a torque issue with centerlocks coming a bit loose after time, if too much grease is there, the small amount of space caused by the grease allows the brakes to separate while turning and the springs go click- click - click.

bovien

Thanks

But the noise is not affected by braking.

Also, when switching to the new center but, which came with more grease than my old one, the noise was actually less.

However, I do think the optimoly paste had something to do with this issue, but the exact place I haven't determined yet