235 vs 245 on 8.5" wheel
Fender rubbing:
The 235/40 Michelin PSS just barely contacts the fender (mounted on 8.5" wheel) leaving a faint ring of scuffing where the lettering is. This isn't the audible, problematic rubbing that most people consider "rubbing". I consider it acceptable but it is a good indication that 235 is approximately the limit. This wear is not shown in the picture below.
Other wear considerations:
After 2 days on track my 235s looked like this. What you're seeing is not fender rubbing but rather wear from the tire rolling over. 235 is slightly stretched on the 8.5" wheel and I think this contributes to the degree to which the wear goes beyond the tread blocks.
I'm still using this set up as-is but thing the issue could be improved by using camber plates and a 245. The 245 will have more square sidewalls and the camber plates will both allow clearance and help out with the rolling through added negative camber. Ground control has a design for the mk6 that allows adjustment without removing the strut but they haven't released a plate for the mk7 yet. I've been pestering them via email and they suggest it is close.
TLDR: 235 is the best fit without altering camber but 245 might be ideal with enough camber to clear.
