BobZEQEC300

In Southern CA there has been a lot of rain and a couple of disturbing things have happened to my EQE Sedan when driving in the rain. Both yesterday and today when leaving the driveway (car is parked outside) when I got maybe 500 ft to the first stop sign maybe going 25MPH, I brake and its feels like the brake popped and slipped, immediately the car lunged forward and then i had to re-apply the brake again to stop. Honestly depending if someone was right ahead of me I could have re-ended them. No warning lights on my dash. Car seemed to run fine with my errands in both cases after that "event". I do have dashcam turned on and I tempted to see if there is anything there to at least see the lunge to show to the dealer or even MB themselves.

Anyone else have this issue? And no, the car was not hydroplaning or anything like that, i was not in water or a puddle, just a wet street and going to a stop sign after the car was parked in the rain for 24hrs each time.

bytemaster0

What regen mode were you in? I'm assuming "normal" mode for now. If you reach the point during sudden braking where ABS activates, you may notice that the brake pedal goes down further, as the car is signaling to you (via brake pedal) that ABS braking has started and that regeneration is reduced or stopped. (Actually, I do think that the car applies some regen even during ABS, I've noticed this on the rear axle in the SUV in snow, it seems to have different engagement than the front. This may be to help with directional control, I'm not sure). When this happens, your braking force is actually not reduced - the brake pedal itself is fully brake-by-wire. As long as you keep holding all the way down, you'll stop as fast as you possibly can. Given where you live, you may rarely or even never experience ABS braking, so it may feel different than normal.

If you were in "intelligent recuperation", it's possible that the car decided to stop slowing due to a condition in the road (e.g., no traffic, or it thinks you're ignoring the intersection). While I completely understand why intelligent recuperation does what it does, it is a bit "wrong thing at the wrong time" for me, or at least, it doesn't always mirror what I might do in that situation. For that reason, I use "no recuperation" to maximize coasting, and to use as much regen as possible when I do apply the brake pedal.

If you can give us a bit more background, we may be able to shed some light on it.

BobZEQEC300

yes the car was in Normal mode, what you said makes sense, thank you. But i really cant see how ABS would have kicked in, barely drizzling, wet aspalt yes, but no "Stormageddon". It literally was at the first stop sign each time down the street. There was defintely a pop/thunk and something like the brakes slipping. There was a lunge forward and you are right I do recall the bake pedal going down further. I saw no ABS light come on. The best way I could describe was a pop, mini-bake failure, and fast recovery within 1-2 seconds on a wet residental street going 25mph tops and probably more like 15-20mph.

MBNUT1

I remember on my Audi A4 the rotors would get a slimy coating of oxide in the rain and the first application of braking would be pretty ineffective.

bytemaster0

ABS engagement doesn't cause any dash lights to come on, unlike when ESP activates. If the activation was long enough, you may even see a "slippery sign" on your navigation screen, as the car has V2X technology and will alert other vehicles to a slick spot, either due to ESP or prolonged ABS engagement. A light coating of drizzle on the road is actually the most likely time you'll slip during rain - oil coatings that have been on the road rise up as they are hydrophobic, and create a *very* slick layer. Here in the midwest, we are always apprehensive of the first light rain after a long period of dry or sun during the spring and summer - all those oils from cars and particulate matter is pulled up and you get super slick surfaces. After it's been raining for a while, it washes away, but those first few minutes or hours often see quite a few accidents as a result.

The popping sound could be the brake pads having been a bit stuck while it was sitting in the rain - if you were mostly regenerating before, there probably wasn't much pad application. On our SUV, after dirt and salt buildup, you could hear the pads click and clack back and for just a bit when stopping at a stop sign or reversing. It went away after I washed the car - the brake pads float on the guide pins.

The first time ABS kicked in for me on a brake-by-wire EV (in the EQE sedan during the summer, I went over a pothole and rough surface on dry road, causing ABS activation), I was a bit surprised, but learned quickly that the brake pedal indeed goes down a bit to let you know "hey, you're not stopping normally, you're in ABS braking now". The car feels like it's not stopping as quickly, as during ABS activation it works to prevent spinning out and wheel lockup during activation. This actually very much feels like the lunge you described - you went from strong deceleration to much reduced deceleration during ABS operation. Then, as wheelslip is normalized, the deceleration resumes more strongly again. It'd feel the same on a standard non-brake-by-wire car, but you'd have a different pedal feel. Once you're used to it, it'll feel normal. This also mirrors perfectly what you said - when you let go of the brakes, this allows wheels to resume traction, and then you re-applied brakes and decelerated more strongly again. ABS does this much faster, and in net, you'd have stopped faster if you'd just simply held the brake pedal than letting go and re-applying, once the system figures out the updated split-mu traction situation.

Some people rightly get surprised that during ABS activation, the car slows down much less than during normal brake usage. Thing is, if it didn't, and you have split-mu traction (different friction coefficients at different wheels), the braking force by wheels with strong traction would actually cause your car to yaw violently and you'd spin out. So, ABS application (and ESP, for that matter), is a very carefully balanced dance of stopping you as fast as possible while maintaining control.

I will say that if you had any brake issues whatsoever, the car would immediately throw a code. These brake-by-wire systems are highly sensorized and redundant, I strongly suspect you didn't have a failure, just a different regime of operation.

bytemaster0

If you want some interesting videos that cover these situations (I'm an engineer, so this stuff fascinates me), I highly recommend these videos, one of which is specific to the EQE:

shakoomakoo

You can come up with all the excuses in the world but the reality is beaks on the eqe suck. It is by far the worse braking power and feel on any car I have ever owned.

Crito

It took several hundred miles before my brake pads bedded in and started to bite correctly. I got in the habit of just using the left paddle to switch to strong regen when I want to stop quickly. I then right paddle back to normal regen after turning/stopping. Works just like down shifting in a gas car. Now that the brakes are worn a bit they stop much better though.

bytemaster0

@Crito , I had the same experience, it took over a thousand miles before my brake pads felt like they had enough bite. @shakoomakoo has a point though, brake-by-wire will never feel quite natural. I remember it on my dad's 2005 W211 E-class, which had Sensotronic brakes (which failed under warranty, like most of them did, so all W211s that came equipped with it have a 25-year warranty for the braking system). The pedal feel was decent, but it felt somewhat disconnected. The EQE is better in that regard, at least from what I feel. While it certainly doesn't have the feel of mechanical brakes, I'm quite used to it now and feel like I can modulate it quite well.

BobZEQEC300

Wasnt raining today and same path / same errand and brakes did not act up today. Thanks everyone for their comments and feedback especially @bytemaster0 .

sno

you sir are spot on... I have turned one year with mine and the brakes still suck. They grab and then let go and grab again and in the rain (FL here) they are unpredictable. Funny on our EQS SUV its not bad.

lkfoster

You've never driven a '35 Ford with mechanical drum brakes. I'll never complain about any brakes ever again.

I don't know about the EQEs but I have no issues with the EQS brakes. Even the moving brake pedal that some of the interwebs influencers don't like.

teksurv

I've had instances where slowing down over newly paved pot holes (SoCal, rain, yeah...) using strong regen causes a brief sensation of the brakes letting go and then immediately slowing down again. It's an odd sensation but never was something that I felt was of concern. It feels like, and likely is something like ABS kicking in. In my case, it just feels different in the EQE due to regen vs. a typical gas car.

bytemaster0

Definitely ABS engagement. Because the brake system is brake-by-wire, you won't feel as much response during ABS actuation. You'll definitely notice a deceleration change though as the car tries not to spin out - it has to reduce brake force proportionately on the opposite lateral wheels to prevent yawing. Then it should re-engage as the slipped wheel is back in control. I first noticed the different feel vs. standard brake-boosted cars when we went over a pothole as well. Once you know what to expect, it isn't a surprise, thankfully.