The aero is only checking for one point's height above the ground while colliders check for an entire object's intersection of the track's 3d mesh (of course both do calculations after that, but for a computer they're much quicker than the ones mentioned), so it's nowhere near as bad as adding collision.ini entries. I'm sure there's an effect on performance, but I haven't noticed it - and my CPU's nothing special so I wouldn't worry about it (I can check actual loading in the performance app at some point). Anyway to do this car anywhere near accurately, this is actually the minimum (maybe 9 could work if you condensed the front splitter and its diveplane/louver combinations) that it needs in AC...thats plenty of surfaces does this influence performance in a way multiple entries in the collision.ini would?