Coil Vs. Air, consider AWD too
the scales tipped when I took the coil springs into a curve and accelerated and for the first time in any S I've driven I felt body roll. call me spoiled but one of the things I've been awed by with the S (with SAS) from day one is how it defies gravity with it's fantastic cornering.
Teslas don't roll, in general. Let's be relative. The amount of give a coil car has is something I bet you can feel, but it can't be much given the roll-center of a GT40. I see a speed where what you describe is better, with SAS, but then a higher one where many of the coil buyers are going to keep their nerve. I still think SAS hunts for where to put the air, throughout a turn. It's flat, where I might build confidence, but I don't have it as I'm trying to figure out just how much load I'm putting onto the tires, as I want to lift, point, and then step on it. Since the OP is concerned about bias, I had a SAS '15 P85 loaner, on 19's, on the exact same roads our S85 Coil 19 Primacy car, and to me it was smoother, and more quiet. I get this impression consistently. I haven't tried, but don't think a more compliant 19" tire, or letting some of those 50lbs out, is going to match SAS. I bet having softer springs might do it, at minimal expense to roll. There are places that will wind them, but is it worth this kind of small change?
Hard Driving: A tangent for the thread, but it can come down to how hard you plan to drive the car, and what you want to drive through with SAS trying to keep things level. Practically speaking, few drive hard enough, or regularly enough, for me to think they would be better off with coils. There is also
a difference between Tesla's AWD and RWD, when it comes to Air. The RWD SAS P85s had rear outboard squat, and front inboard lift, to excess when accelerating out of turns. I think a lot of sport drivers were selecting coils, or the P85+ SAS version, to fix this. With AWD, it's a different story. You don't get these dynamics, as at least 85D/70D have equal rated kw motors, front and back. This produces less squat, and probably enables more enjoyment of the Air suspension. P85D may go the other way, putting more power (and fun) in the back, again, with perhaps a greater argument for coils to deal with it.
Cost: Beyond the $2,500 option, elsewhere it is posted the SAS assemblies are $3,500 each corner (X4). One part number, for damper, spring, air spring, together. It's better "around town", but only you can decide if the increment/risk is worth it. If Air develops problems, owners of Air cars could have a harder time trading away from Tesla's CPO program. That said, there are so many Air cars, that I doubt they will allow chronically high bills without some rebuild/re-manufacture. I'll never buy a used car, with "iffy" shocks that could set me back $14k.
