Funny, i took a closer lock and i found out, that the toyo proxes r888 315/30r18 isnt approved for a 12" rim.
I could throw it on my 11" rim.

 

I wouldnt mix Trofeos with R888s if I were you, no real benefit to do that, better do some cheap tires in front like Federal RSR595 if still want to do it.

I can tell you R888 run wider than 11", maybe they specify 10.5-11-11.5 rim, but imo 12" should be ok even didnt try that combo, for sure better than 11" at least

 

I will see if my car still tends to understeer with my new setup and the toyos in gt2 size.
My setup now is:
Front: left -2'05 right -2'08; track 5 min
rear: left -2'04 right - 2'01; track 22 min

Castor i do have no clue. But i did flip the LCA so the offcenter hole does point to the front.

 

The 8,5 with the 6Gt2 offset getting really close to the upper fender edge. Seems like the 6gt2/3 LCAs + shims do there job. Even with -2 ' camber its damn close. Hopefully no rubbing while racing...

 

8.5s should be a breeze. You should not have any rubbing issues whatsoever. You can always remove some LCA shims and push in the upper mounts for more clearance. It's all about the set up set up set up. I'm on 18x10 ET37 at 20mm below GT2 height. Tires tuck under the fender with no clearance issues.

 

I make some pics later. From the upper mounts too. They are pushed in.
I did not check yet, how many shims are used. I will check that too.

 

After putting 8,5x18 Offset 40 in the front plus 235/40, adjustable lca with about 1,3cm of shims and 2" of camber, the wheel does rub the upper fender and the front fender liner. a bit. Its too close to be save on the racetrack.
I did use the off center adjustment point from the LCA, which points to the front, so the wheel gets further back. Still not enough.
I guess the Offset 40 is too much also. 50 would be better. But what to do about the rubbing at the front fender liner? I do use GT2 Fenderliners.

 

Something is not right. You should not need 13mm of shims per side to get a just 2 degrees of camber. You should be able to do that without any shims when mildly lowered. Bottom line, you have too many shims for your wheel offset. 13mm of shims effectively makes your wheels ET 27 offset. Reduce the shims and use camber plate upper mounts instead to get your desired camber. As I said before, it's all about a correct set up set up set up. If you are trying to achieve desired camber via shims than a wheel closer to ET50 is best. If getting to your goal via the upper mounts, then a wheel around ET40 works best.

Post up a pic of your upper mount bolts on both sides..

 

Hadnt time to make some pics. Will do it tomorrow. But both side are fully pushed to the inside. Anyways i cannot help it so i will use my 8" wheel with offset 50 and put the 235/40 Toyos on these wheels. Still ist tight to the front fenderliner but its no problem. The fender itself will be safe then even at the track.