Brake slipping on wet road

[hedgehog99]

*My apology if this has been well discussed on here, but I'm not a car guy and not familiar with the proper terminology.*

I noticed on wet roads in the morning, or in rain, when I break for a complete stop (stop signs, red lights, etc), the car jerks. The car almost stops, then it feels like something slips, and it is jerked (or pushed) forward just a little bit before coming to a full stop. I use 1PD, and it's a 2023 Select RWD with 10K. This happens even if the car was parked inside out of the rain before the drive. I've had a Tesla before, and don't recall anything similar. None of my ICEs before did this. So I don't know if this is an EV thing, a Ford thing, a MME thing or just my brakes.

I've found this thread: https://www.macheforum.com/site/threads/rain-pads-stuck-to-rotors.27471/ Not sure if this is the same issue.

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[kens]

Your feeling it switch from the regen braking over to the brake pads at the very end. The car will use the brake pads at the end of a stop, and will keep the pads engaged while stopped. Nothing wrong with the car, just the way it works.

Some people are more sensitive to it, or some cars more noticable. It's never bothered me and I don't feel it even when looking for it with rare exceptions, but I've heard others bring it up. There's a popular reviewer that likes to bring it up. Wet roads will exasperate it, since the pads aren't being used much, wet brakes don't work very well and slip.

The other thread you referenced is a result of locking in the brake pads while parked when they're wet. They can stick to the rotors and grab when you first start up after getting back to the car. That would be more of a thunk after you've been parked for a while and start moving the first time.

 

[andycunn]

With one pedal driving both my wife and I rarely use the brake but for an unexpected urgency in traffic. I do notice a rough growled feel on the brake after or during rainy weather. My guess is that a "patina" of surface rust builds on the rotors in that kind of weather and the patina is heavier on the Mach-E as compared to ICE cars because the brakes are so much less frequently applied. After a few rolling brake applications the rotors should shine back up and smooth out.

 

[OH2AZ2OH]

Regenerative braking only works above a certain speed, below which the car needs to transition to friction braking. That transition can be tricky, and some cars handle some situations better than others. My experience has been the Mach E does it quite well, but there are definitely situations that can catch it out. I have one braking zone that is bumpy with wheels getting weighted and unweighted and that one will do a little of what you are describing. That spot would sometimes trigger ABS in my previous car though, which also wasn't great.

The crunchy rotors are definitely a thing. That also happens in ICE vehicles, but it clears up faster with them since ICEs use 100% friction brakes. Mine will oxidize even in the garage if it is raining. I ride the brakes easing out of the garage, and that clears up the fronts decently, but the rears sometimes don't completely clear even after my 10 mile commute. The oxidized rotors are definitely more grabby, and that may be confusing the 1PD algorithm. I don't use 1PD, so maybe that's why I don't notice this?

Unlike a Tesla, there is no efficiency gain using 1PD in the MachE. The braking is always hybrid, with the computer deciding how much regen and friction braking to use.

 

[Maquis]

It’s the ABS kicking in. The first time I experienced it, I thought I lost braking for a split second.

 

[MachhE-CT]

The only time I have I actually use the brakes to stop the car is when someone in front of me stops more suddenly than I anticipated or when the stop sign or traffic light is at the bottom of a hill. I usually need to briefly touch the brake pedal for a second or two to come to a full stop. Otherwise the regenerative braking does all the work for me and I have driven for days in one-pedal mode and have never touched the brake pedal. Which probably means the brake rotors get a little dirt or corrosion. So they can be a little touchy when I do use them. Wet or dry. If the car does use the brakes in one pedal drive I have never noticed. And brake coach always says 100 percent energy recoverage which it doesn’t do if I manually use the brakes . Every car I have ever owned builds up oxidation on the brake rotors when parked in humid or rainy weather garages or not. Perhaps on a noisy ICE vehicle you might not notice but I sure did on all my ICE vehicles.

 

[Teslaeata]

Other weird thing is that when coming to a stop downhill on OPD car reversed back up hill a brief moment!

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