periodic "spongy" brakes. that don't stop. if i die please have my family sue Porsche

[JimBob]

Im confused by this. When regen is ‘off’, that just means you don’t get it when you lift off the gas. When you hit the brakes, you still get regen braking first before you get into the actual brakes. At least that’s my understanding of how braking works in the Taycan.

There are two kinds of regen.
Lift off when you take your foot off the accelerator. This is weak regen and you can turn it on and off.
Brake regen when you hit the brakes. This is strong and accounts for most of the braking in a Taycan.

There is some general descriptive material out there. Porsche calls it PRM. Search under Porsche Recuperative Management

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[Jrkennedy37]

Im confused by this. When regen is ‘off’, that just means you don’t get it when you lift off the gas. When you hit the brakes, you still get regen braking first before you get into the actual brakes. At least that’s my understanding of how braking works in the Taycan.

When the car starts cold, it defaults to zero regen so it will use the actual brakes to clean them and warm them a bit. Braking feels different at this stage, pedal travel is longer before you get any bite.

I imagine rain/moisture on top of this warm up period could make the braking feel and pedal travel even worse.

 

[JimBob]

When the car starts cold, it defaults to zero regen so it will use the actual brakes to clean them and warm them a bit. Braking feels different at this stage, pedal travel is longer before you get any bite.

I imagine rain/moisture on top of this warm up period could make the braking feel and pedal travel even worse.

I just tested this, this morning as there was an earlier question/answer on this which I disagreed with. It is not what I am seeing. The temperature was -14.2C/6.4F this morning. There was neither liftoff or braking regen when the car speed was below 8 kph/5 mph. Either within seconds of departure or minutes. As soon as I was above those speeds I had both kinds of regen and there was no difference in brake feel between the two cases. I have had the "spongy" brake feel after a car wash so I know what it feels like.

 

[IBZman]

i've had a few odd electronics/pcm 'quirks' - but nothing that scares me. Even when the PCM reboots - my car is safe and drivable

however - i'm scared to death of my car. in the rain.

before posting this - i've been reading the boards and google - and i haven't seen anything similar reported or experienced. One person DID mention: SPONGY BRAKES AFTER GETTING A CAR WASH - AFTER ONE GOOD (AND LOUD/SQUEAKY) STOP AFTER THE CAR WASH - THEY WERE FINE AFTERWARDS. This person used the best term - 'spongy brakes' - that discussion kind of ended with - BAH - IT'S A PORSCHE "FEATURE" WITH THE HIGH-END BRAKES. ONE GOOD STOP AND YOU'RE FINE, NO WORRIES

"Gogs" in this post https://www.taycanforum.com/forum/threads/strange-braking-issue.4818/
said : When braking the brake seems to work then it sinks a further few inches without any braking torque. If you push further then it seem to slow down. But not as fast as normal.

His post kind of went nowhere- i don't think the others were experiencing the same thing.

so i was hesitant to say anything. I thought - maybe this is normal.

i'm driving a 2021 4s with PSCB. i notice this ALMOST EVERY TIME I'M DRIVING IN MODERATE OR HEAVY RAIN. Not not every stop in heavy/moderate rain. If i'm running errands in that weather- i imagine i'll use brake pedal 6-8 times each way of a trip - this will happen maybe 1 of 7 brake applications

my brakes don't work. well, that is. My brakes don't work well in the heavy or moderate rain. For some stops

i get a weird/odd pressure from the brake pedal. I've driven this enough to know what the feedback pressure from that left pedal should be - and it's like it goes limp. Best analogy i have- imagine in an older car - if the bake line were cut, you'd have no pressure when you push in the brake pedal (i imagine??). I won't say my brakes aren't gripping (and yes, yes, yes, i know, blah blah blah majority of stopping is regenerative blah blah blah) - sorry- i won't say my brakes aren't gripping - it's more like my pedal goes bad and isn't telling them to

I HAVE TO LAY ON MY BRAKES SO HARD, THAT MANY TIMES, THE GREEN HOLD IS LIT ON MY DASH AFTER ATTEMPTING TO STOP. (if you didn't know - if you're stopped, and then press the brake pedal even harder, a green HOLD lights on the dash, you can take your foot off the pedal, and your car will sit there and not slowly inch forward)

And i'm not a 16 year old boy jamming the pedals all the way when i drive - i'm driving the same stop/start speeds as the other cars around me. normally - i apply 10-20% brake pedal - no one should EVER press the brake pedal hard enough to have the HOLD light come on after a stop

It was so bad once - my car wouldn't stop coming up to a light. i was going to hit the car in front of me, thank goodness, the turn lane was empty so i got into it and the car DID stop before the light. My kid asked where we were going (knowing it wasn't the way home) and i made up some excuse that sounded better than "daddy almost killed you in this death trap"
Two reasons i'm hesitant to take it in:

1) i'm 90 minutes from the dealer
2) it's so un-reproducable that i'm SURE they won't experience exactly what i am when this happens. then they'll think i'm exaggerating and not take it seriously.

ok, that and my kid is away on active duty, and i can drive her car in the rain. Says something abut this car when i'd rather drive a '18 Nissan Kicks on wet days....

This happened to me three times on a dual carriageway at 70 MPH and could have been fatal. Had my little one in the car too when it happened the second and third times (sane trip).

Take your car in now. Your description is identical to what I had experienced.

They said it was an ‘ABS fluid leak’ or ‘ABS air leak’.

For anyone saying ‘regen’, this is no ‘feature’, this is nothing other than failure of her breaks!

 

[Jrkennedy37]

I just tested this, this morning as there was an earlier question/answer on this which I disagreed with. It is not what I am seeing. The temperature was -14.2C/6.4F this morning. There was neither liftoff or braking regen when the car speed was below 8 kph/5 mph. Either within seconds of departure or minutes. As soon as I was above those speeds I had both kinds of regen and there was no difference in brake feel between the two cases. I have had the "spongy" brake feel after a car wash so I know what it feels like.

Good to know. If I flip to sport mode right away I haven’t noticed it. In normal mode it’s very apparent for the first 1-3 minutes in the morning. It coincides with the dash showing zero regen while braking.

When picking the car up at the dealership, I drove the car down a parking garage to the ground level lot and overshot the parking spot by about 4 feet. Fortunately there was no cement parking block otherwise I would have smacked it.

I’m not a fan of the coasting in normal mode since I prefer the engine braking feeling (I’ve only owned one torque converter in the last 16 years, specifically seeking out three pedal manuals or DCTs) but after the first few minutes the braking is predictable and the regen starts as soon as I touch the brake.

 

[Jrkennedy37]

Recorded the no regen when braking moment this morning. Brake feel is vastly different without regen kicking in. I exceeded 40mph without regen kicking in while braking. Within 2-3 min braking regen starts up.

 

[DerekS]

Yeah the first couple of stops each day for me have no regen.

It's to keep the brakes clean (and probably to make sure they get wear on them for service cost reasons!)

 

[McgR]

Its not funny and dangerous when this happens Sia even mentions this in her song Unstoppable.

 

[atebit]

can you link to something?

The repair invoice cites “SY 90/21”.

 

[Taycan_friend]

Recorded the no regen when braking moment this morning. Brake feel is vastly different without regen kicking in. I exceeded 40mph without regen kicking in while braking. Within 2-3 min braking regen starts up.

This is the morning routine. Brake refresh function to have the brakes in perfect condition.

 

[Jrkennedy37]

This is the morning routine. Brake refresh function to have the brakes in perfect condition.

Correct. Someone above said the no brake regen phase only happened under 5mph and for a few seconds which is not true and why I posted the video. I did not record braking from 40+ mph with no regen kicking in for obvious reasons.

My original comment and question was that the lack of regen plus water on brakes can potentially combine to create an especially spongy brake response and long pedal travel. Even without water on the brakes, I was caught off guard the first few times I drove the vehicle from a cold start in normal mode. I now know what to expect in normal mode and typically switch to sport right away which immediately uses regen.

Just trying to help troubleshoot the circumstances leading to the OP’s issue for him to reproduce the issue at the dealership. I’ve gotten the run around a few times when dealers (Porsche and other brands) can’t identify the issue and find I need to provide very detailed instructions how to reproduce it and/or record a video to prove the issue exists.

 

[bootsie]

I've had something similar the first drive after washing the car - sometimes the next day. It's the first 5 minutes of driving when regen isn't enabled. I've pushed the brakes and nothing happened, STAMPED on them and then they worked fine. I've also had horrible grinding noises at this point on occasion.
It's always at the same junction so I'm aware of it now. It's only ever been the first drive of the day, usually after washing the car. I have PSCB brakes (maybe that makes a difference somewhere?).

 

[sean711]

I live on the west coast (extremely dry climate) and have been experiencing this since I took delivery of my car. It's a MY 21 Taycan Turbo with standard PSCB's. I immediately took it back to the dealer and told them something was wrong. They told me there was nothing wrong. I made my sales advisor bring up a 2021 Taycan 4s with regular brakes and 2020 4s with PSCB's and both did not have the issue. I also noticed that the PSCB calipers on the 2020 4s were significantly larger than mine, something my sales advisor had no explanation for. I don't know what to do at this point, this is a really bad safety issue that Porsche doesn't seem to want to rectify.

 

[R Benny Waered]

The brakes do have different feel at different times - had to explain to the wife! Yours sounds like a fault though OP.

When mechanical brakes are in use to clean them up/dry them up for the first few minutes (more often if the wipers are on?) then you have to press harder - esp if they are rusty/wet.

I notice regen brakes are not used at v low speed as they would not be effective or hold the car once stopped so its mech brakes below say 10 mph. V clever how they blend the mech in as the regen tails off.

Love the tip: " to ensure the disks are clean is to put the car in to Neutral while rolling and apply the brakes which prevents regen from activating so I know they are cleaning the disk for certain". Sometimes human does know better - especially if you just washed it and want to dry the brakes...!

 

[TaycanTurboUK]

From a previous post of mine;

Thanks for the replies, I have noticed this a few times at different speeds, but as W1NGE says mostly at lower speeds.

I have had it on a couple of occasions where I have been approaching traffic lights and it is one of those where the lights turn and you are almost committed but not quite, so you firmly apply brakes and not much happens so you have to go that much harder quick to stop before the line and have ended up skidding, looking like a bit of a plank as their are inevitably lots of people about.

Am sure this is a combination of the weight and also the second that you lose when the thing doesn't slow down as you expect initially. When I drive the wife's Range Rover I almost put her through the windscreen the first couple of times I brake.

Is definitely one that keeps you on your toes.

I have mostly has this in the dry, spongy is defiantly the right terms for it, and it catches you out as there doesn't seem to be any consistency with it.

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