Well to put is short and sweet, 275/40/20 (Toyo Proxes 4-Plus) do not safely clear the front suspension on the 2nd Gen 300's even with a 3mm BT spacer up front.
For those that don't know I have a set of 1st Gen 3SRT wheels installed on my 2011 300C and planned on going with 275/40/20 all the way around as so many others have done, but I'm now realizing after the fact that all those that have posted this size all have SRT's. I guess I'm going to be somewhat staggered now as the 275/40/20 Toyo's cleared the rear and a set of 245/45/20's are on their way for the front.
Sorry no pics yet. There was literally only a hair width of clearance between the tire and upper control arm, which was way too close for my liking. I tested for clearance both up on the rack and on the ground with a load on the tire just to see if the suspension geometry would change just enough with the car on the ground, and that was a no go. Maybe a different tire make would of fit but not the Toyo Proxes 4-Plus. I'm just glad that I didn't commit to the 275's up front and 315's out back like I originally planned.
Also keep in mind that this was with a set of OEM 3SRT wheels and not a aftermarket set.
I was checking out my new stance a little more closely this afternoon and the subtle stagger is looking quite nice. I think I will stick to this set-up. Now on to the next order of business lowering it a bit.
One other little fact...the offset on the SRT wheels is different to clear the Brembo brake calipers so a wider tire on the front is easier to fit with more clearance to that upper suspension bit.