POLL: What will my 60-0 stopping distance be with Pilot Sport 4S 265/40R18s be?

[dfwatt]

So my only question is here in regard to the Pilot 4S, is that its been mentioned that the edges of the tire are optimized for cornering grip with a different compound, while the center of the tire utilize a harder compound for LRR that Tesla has specced in our tires that way you get the best of both worlds (this is also the same in all Pilot 4S, but Tesla's center patch may be harder than normal PS4S tires). Proper inflation pressure still seems to be my thoughts and following Tesla's 42 PSI number would make logical sense.

Yes, I would not probably not second guess Tesla's TP recommendations for street driving. Unclear if 42 lbs though is optimal for track work/autocross/best skidpad times. It might be, but I have no idea, and I haven't really played around with TP much on our cars to see if going higher means better grip or not. Also unclear if the Telsa version of the 4S is any different other than just the addition of acoustic foam. We run 42-44 in our cars, but I don't have enough miles on either one to confirm if that results in the expected even wear pattern. Lots of things about this car are just too new for anyone to have detailed understanding of these things.

 

[dfwatt]

So what are the implications of this for chalking tires? Do you actually want to see a bit more chalk left on the outside, or does that all go out because hard cornering should move that back towards wanting to see even chalk removal across the tire because you're pushing it hard enough to deform anyway so you want it to deform to "normal"?

Not sure what you are asking exactly, but here you can find some very interesting images of tires under various load conditions and inflation states.

One of the most interesting of those is the one showing how suboptimal suspension geometry moves all the contact load out to the edge, while more optimal geometry keeps the contact patch more evenly loaded (almost pristine and perfectly even in this image!). I suspect that image is frankly a bit idealized - there is almost always deformation of the contact patch under heavy cornering load, where the outside edge broadens due to the extra weight it is carrying, and the inside edge constricts at least a bit as load moves away from that side. But this collection of images does give some information about tire patch shape under varying loading and various inflation states - it's normally somewhere between an oval and a rectangle.

The forces on the outside edge of the tire are truly violent as cars approach 1G lateral acceleration. In the case of the Tesla, that means four contact patches totaling a few dozen square inches are carrying ~ two tons of lateral load. That's a lot of weight per square inch, and creating a shitload of heat coming directly from the rapidly alternating (left-right-left-right) shearing forces - not a surprise when track work destroys the outside of the tire. It's a testimony to the progress made over many decades in relationship to tire compounding chemistry and technology that tires can tolerate this at all.

 

[dfwatt]

Presumably it's something along these lines that results in wider tires being necessary for more straight-line acceleration? Traction is not currently an issue for the P3D, but I was wondering about this the other day. The contact patch is wider and shorter for a wider tire for a given PSI with the same vehicle weight, but not any larger area. Somehow that must be more "stable" for high acceleration g forces? I guess it's the same as contact patch stability, but perhaps the pavement stability also fares better if the heat & acceleration is spread across a wide patch? I've seen melted pavement in the past...though probably that was from burnouts; wouldn't be enough heat generated for a proper acceleration run.

Again, one of these days I'll get around to testing the 60-0 with my stock 235s and see how they compare to @Daniel in SD . Hopefully we can do side-by-side comparisons to eliminate a bunch of variables. For now, I've been saddled with a variety of boring 0-60 experiments.

Good questions Alan - not sure myself, but your description of wider contact patches with no more surface area is correct from my understanding. As for 0-60 runs, it would seem that the stock PS4S have more vertical grip (over 1 G) than the car has torque (accel G has consistently been measured as maxed at about .85 G), hence, no wheelspin under max 'throttle' (that term seems inappropriate here!), but perhaps the traction control system is modulating torque - don't know on that one.

 

[Feathermerchan]

Just a few data points from me. I have launched my 3P on WET concrete several times and seemingly accelerates as fast as dry. Trying that over crosswalk stripes I do feel some slippage but it stops as soon as I cross them. Even others in the car have said it seems as fast (accelerating straight) in the wet as in the dry. Actually scary.

 

[dfwatt]

Just a few data points from me. I have launched my 3P on WET concrete several times and seemingly accelerates as fast as dry. Trying that over crosswalk stripes I do feel some slippage but it stops as soon as I cross them. Even others in the car have said it seems as fast (accelerating straight) in the wet as in the dry. Actually scary.

Same here! The traction in the wet of the 4S is REALLY impressive. Would love to drag race an exotic with RWD - even if it might beat the 3P+ on a dry track catching and passing it at the end of the quarter, the launch gap on a wet dragway might be too much for a McLaren or Ferrari to overcome.

Tire Rack's track results here validate our subjective impressions as it even beats the RE71, arguably the most popular track tire, around the track in the wet. And it's only two tenths of a second behind in the dry. It's the best street tire by a mile. Interesting that in an area of mature technology that there is such a screaming best - unusual in established tech, given how the margins tend to shrink to minimal ones. Not here. Don't leave home with them