1st phantom brake

[ayavner]

Sorry to revive the necro-thread; I had my first PB the other day after about a month of ownership. I reacted immediately and it was a non-issue, but definitely surprised me. Felt like it had deployed a giant drag chute - definitely not a graceful "slowing down". Believe in this case it was an area where I was coming to an intersection and the lane widened to include the turn lane. I went straight, and the car in front of me moved into the turn lane but nevertheless as I continued and got close to where his bumper would be had he stayed in my lane the hammer came down.

I could see on the front screen the visualization of the other car, and it still saw it as an obstruction even though it was in the other lane.

Just another data point. 2015 MS with MCU1.

 

[haroldo]

There are many reasons, some valid, others not so much, for braking, or slowing,
I witnessed one recently that I hadn't noticed before.
Since getting FSD, I changed the speed limit offset from +10% to +0%. I was driving on a 65 MPH road and used the scroll wheel to adjust to 70 then 75 MPH. The speed limit on the road dropped from 65 to 55.. Since I didn't have an offset, it decelerated from 75 to 55 as soon as I passed the speed limit sign. A quick 20 MPH drop can be misperceived as a vehicle error, but in this case, it was behaving properly
It's possible drivers, startled by the rapid deceleration, might not realize (nor remember), that they passed a speed limit sign