Mission accomplished. 285/40/ZR18 on all four wheels.
The ride is superb. The handling is very improved. The Pirellis were softer, squishier, and liked to slide around my parking lot test oval. The BFGoodrich were ok, but tended to skip around the oval. The Goodyears plant firm and makes no noise nor loss of traction around the oval. Having 285s on the front is a feeling like no other. It almost feels like one continuous wheel from driver to passenger side wheel wells.

I checked the spacing between the Koni Yellow/Sport shock and the tire. There is maybe 3/8" on passenger side, 1/2" on the driver side.

The rest of the story is that I was looking for four 255/45-18 tires for my GT/CS wheels. Yoko Advan Sport or BFGood g-force t/A KDW2 or the Dunlop Direzza Sport Z1 Star Spec. With shipping, they were all around $1100. Discount Tire would match the price and install for $15 each. Plus disposal fee $16, plus valve stems $8, plus tax $80, etc. Well it turned into a $1250+ for four tires. Then I went to Ebay.com and found GT-500 tires for $925+$140 shipping, with scratches. Cheaper, but the winner was getting ALL 285 tires instead of the staggered/no rotation set for about $200 less than that. So I am very happy. Now to the pictures...
Size evidence up front, the car, the wheel gap in front and rear. Enjoy!

 

Those are big Rev. I've got 275's by 4 and I thought they were too much. Anyway, the GT500 rims look great, good luck w/them.

 

Which BFG's Rev? I replaced my GY:F1's with KDWII's and noticed a big difference with sidewall stiffness. The F1's had the softer sidewall.

Anyways looks sweet.

 

The 285's look so much better on those rims then the 255's. I think when mine needs new sneakers up front I will go up one size in the front. I like that 255's have a great response/feel to them and I don't really want to give that up. I would think that the 285's up front would give you a lot of side wall flex.

 

Hey i noticed your suspension setup! Hows is the quality of the ride... i'm going the same way only i'm putting on koni streets... what other suspension mods you went with in addition to what you have in your sig?
I'm thinking with my Koni streets and frpp K's to go with J&M camber plates, x5 steeda ball joint, and adjustable PHB!

 

The stock F1 Supercars.

 

I run the bfgoodrich A/S sport tires. In 275/40 R18 all around. The wider tires are allot of fun in the twisties. The steering is heavier & it tracks with truck groves. But honestly the larger tires are worth the money. My set was 600shipped from tire rack with production date of tires only 3 months before purchase.

Only advice I can give is have the wheels road force balanced and or high speed balanced. As they wear, the size makes regular balancing useless. Ask me how I know.

In any case. Those look killer. I may go for one size larger next time around.