Ahh, very sorry to hear this
@plongley .
The issue of diminished braking performance in specific wet/humid conditions with certain cars is real. I've experienced it myself, reported it to my service center, and they acknowledged it as an issue and Tesla had updated parts to address it. I discussed my experience in the
Braking in rain thread, where others discussed theirs as well.
That having been said, a couple things perhaps useful:
1) My belief, after talking to service folks, noting the replaced parts, inspecting the brakes under specific conditions, and talking to others, is that the braking issue has to do with dust/scale buildup on the rotors that can quickly oxidize in wet/humid conditions. Given the amount of regen braking often done, the friction brakes may not have sufficient opportunity to scour the disk surfaces. The reformulated brake pads Tesla now supplies seems to reduce that. They also installed splash guards behind the rotors to help prevent road-spray from getting at them from the back side.
2) While I've experienced the issue in wet conditions such as rain or after a car wash, I can't say that I've ever had it in a cold/snow/slush environment. On slick roads I've always had enough braking that the tire traction was the limiting factor. This was evident by the antilock brakes and/or the skid control systems activating. I'm almost of the opinion that very cold weather would likely
lessen the chance of this being an issue... as it's not likely there's as much free liquid water to oxidize things as quickly (very cold conditions are often very dry conditions).
3) My car is an early '13. I had this work done within the first year. I've rarely, if ever, had the issue happen since. I'd suspect that if your car is much newer than that, you would already have the updated parts.
Now I suppose it's possible that you had ice buildup on the rotors. I've personally not ever experienced that on the disk-brake vehicles I've owned, at least that I know of. I don't know how likely that is, or how that would manifest itself.
Did you feel the ABS kicking in while you were braking?