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

[bluegrassvroom]

Porsche N.A. is working on this issue, testing it at their Atlanta facility on their wet track (water pad, whatever it's called). I've sent detailed notes, some videos, etc. Other people have reported it across the country (world?) at various Porsche dealers, so it's on their radar and they're looking into it.

Hopefully more of an update/fix is forthcoming...

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[Dslev]

I know this is anecdotal as my driving time is 15 miles vs five figures for actual owners, but...

Curiously I have only ever driven a Taycan 4S CT once for a test drive. It wasn't raining but roads were wet. High single digit Celsius air temperature.

Came up to some traffic lights on a 70mph road. I obviously applied brakes in good time as is normal, but I was taken by surprise where the brakes felt mushy and I must have travelled about 1.5m farther than expected. This did not happen anywhere else on the test drive.

Thankfully the car ahead of me had enough space, but it could have been embarrassing not least with the test drive plates on show in the front window ?

I got back to the dealer thinking: why does my Mercedes EQA AMG Line, which makes no claims to its driving performance, have superior stopping power?

It weighs almost the same as the Taycan as well, and bounces around the road like an obese elephant.

Initially I thought maybe I wasn't applying the brakes with enough force, but on reading this article and others on the Taycan forum*, I wonder if there is a bigger issue for some cars, which is why other owners are not reporting these problems.

It could be very dangerous as the OP explains - and have Porsche acknowledged there might be a problem?

*The other thread on this forum about this issue explained for some Taycan's, the brakes need bleeding. It is difficult to diagnose, but "air" is trapped and that needs to be bled, which then provides razor sharp braking once again ?‍

Have complained of the issue, as well as the rain issue. I was provided this memo. As I have said in other posts, the Memo says owners should be notified of the issue, but shouldn't we have been notified prior to purchase?

 

[TaycanHero]

Have complained of the issue, as well as the rain issue. I was provided this memo. As I have said in other posts, the Memo says owners should be notified of the issue, but shouldn't we have been notified prior to purchase?

Very useful, thank you for this. What is described does sound very similar to my experience test driving a 4S CT for 30 mins in damp conditions.

What's even more interesting is Porsche's admission that its upgraded brakes, which are not cheap, provide worse stopping power in some conditions.

That's an easy option to... swerve.

 

[rpd]

Anyone hear back on this? Rainy day here, and am adjusting to the more liberal stopping power ...

 

[wurzitup]

**UPDATE AFTER GOING TO PORSCHE SERVICE**

SO - update - went to the dealer earlier this week. Was predicted to POUR all day. They wanted to ride with me and see what they could observe when the brake issue reared up

while i was waiting for the right person to ride along with me - it was monsoon-ing outside. Of course once we got ready to hop in the car - it was 'just' lightly raining. Normally the brakes ONLY act up in medium to heavy rain.

we drove around a good 30 minutes - it kinda sorta did it once or twice - then the rain started letting up and i KNEW i was doomed - i'd have wasted a trip there and not be able to reproduce the brake issue

a block before returning to the dealer - we took a swing through a parking lot. it had some standing water - so i drove through it, and afterwards - NO BRAKES!!!!! Ok, ok, not quite 'no brakes' but at least the brake issue happened.

it was also a pretty serious puddle/pond - i'd imagine up to 3" deep, about the length of the car, so i could stop in it and let the car marinate in the water...

it was VERY reproducible - sometimes if i went through the water at 5-7 mph, the brakes wouldn't work correctly just 10 feet past the water. Sometimes it would brake fine then, we'd do a U-Turn, head back to the water, slow down to do another U-Turn and BRAKES ACTED UP AT THAT STOP (say 50-60 feet after the puddle). Sometimes the brakes did work at the puddle and also for the U-turn stop.

We must have done it a dozen or so times myself, and the Service Rep (manager?) did it several times as well. - HERE ARE THE OBSERVATIONS MADE when we knew it was coming. when road driving, even in heavy rain - it didn't happen all the time - normally once per trip in the heavy rain (in say, 10-12 slow downs) - so it was difficult to observe what was happening (when you're worried about staying alive and not wrecking) but when there's two peopel and you knwo it's about to happen, you can notice:

-THE REGENERATIVE BRAKING IS NOT TRIGGERING, it is solely mechanical braking

-IT IS NOT MECHANICAL BRAKING like the first 1, 2, 3 times when you drive your car (when you first hop int he car, your first brake or two or three is 100% mechanical, but the brake pedal feels the same as when regen is on, AND you know, the car actually stops)

-The sound is like the sound of your brakes TRYING to brake you after a car wash but slipping and not gripping properly

My new description of the issue: imagine if the first 30% of a NORMAL brake pedal push is FULLY regen braking, then the next 30-40% is a combination of some regen, some mechanical braking. And the last 30% of the brake pedal gives you 100% mechanical braking. Imagine there are servos or something that give you that brake pedal resistance feel - the device actually making the brake pedal push back against your foot. imagine there's one for the regen braking, and another for the mechanical braking. They normally work in a synchronized way where you feel a constant pressure when applying the brakes and engaging the brake pedal. OK, now imagine, something told the REGEN braking system - to 1) do not apply regen braking and 2) do not apply resistance to the brake pedal for that travel distance that is normally 'regen braking' brake pedal usage. so the brake pedal has no resistance the first 30-50% of it's travel distance. that's what the feeling is when this issue is happening: there is no regen braking AND there is no 'brake pedal feel' during that portion of the brake pedal travel

~ ~ ~ ~ ~ ~

As repeatable as it was that day - the service advisor wanted to take ANOTHER Taycan out (4S, like mine, PSCB, like mine, and same wheels even) - THE OTHER TAYCAN PERFORMED THE SAME IN THE SAME SITUATION. YES, A DIFFERENT TAYCAN ON THEIR LOT DID THE SAME THING AND HAD THE SAME BRAKING ISSUES IN THAT PUDDLE

I felt vindicated - A) I wasn't crazy [at least in 'imaging' this happening] and B) it's NOT JUST ON MY CAR

~ ~ ~ ~ ~ ~

I was told there are sensors in the wheel wells for different reasons -for suspension, braking, etc -

one could HYPOTHOSIZE that something somewhere was telling the Taycan NOT TO USE REGEN BRAKING. but for whatever reason, it wasn't telling the mechanical brakes "Hey, do what you normally do when the car is first turned on"

who knows why, who knows what -and nothing beyond these observations is known. I could conjecture, i could imagine, but i don't know, the service advisor didn't, no telling if anyone at Porsche does at this point.

I'm ok with the car deciding, based on telematics and sensor readings and reading tea leaves to NOT engage the regen brakes. BUT - the car needs to engage the mechanical braking like it does when first turned on and give the driver the same feel and the same stopping ability when using 100% mechanical braking. But as-is, it's dangerous. It's dangerous when going through a puddle at 5mph (it was IMMEDIATELY before a main road, and more than once the car stopped past the intended stopping target (sidewalk distance) and went right up to or into the street - and we knew it was going to happen)

Take that same issue - brakes giving the car and driver only a fraction of the stopping power - apply it randomly during wet street driving, and in 1 out of 12 wet stops, you get zero regen braking and your car only gives you a fraction of the physical mechanical braking. It might be when you're trying to stop at a light. It might be when you're trying to park in a spot (imaging overshooting your parking spot 1 of 12 times - by 5-10 feet). It might be when you have to brake in an emergency.

SO far they've taken this seriously and responded appropriately. Hopefully they can come up with a fix, because right now i don't feel safe in this car in the rain, and i wouldn't recommend other people driving it in the rain either

Your description is both detailed and credible enough that I think its a great service to both other owners here, and probably to Porsche themselves.
You know by the time they let something out of the factory, dozens of engineers have poured over this car for years, so I'm sure it must be pretty embarrassing for them to concede that something this serious got past them on the development of this car.
I've been watching WEC for years..... when I was at Le Mans in 2017 and saw the 919 first hand... one of the things that engineers admitted was the most complex issues was the regenerative braking system and the blending of these 2 systems to make them feel like a normal ICE system.
In some ways its no wonder there are still bugs to be worked out.... albeit hopefully not ones that put you into the back of another car, or worse yet.

 

[MartyMeatball]

**UPDATE AFTER GOING TO PORSCHE SERVICE**

SO - update - went to the dealer earlier this week. Was predicted to POUR all day. They wanted to ride with me and see what they could observe when the brake issue reared up

while i was waiting for the right person to ride along with me - it was monsoon-ing outside. Of course once we got ready to hop in the car - it was 'just' lightly raining. Normally the brakes ONLY act up in medium to heavy rain.

we drove around a good 30 minutes - it kinda sorta did it once or twice - then the rain started letting up and i KNEW i was doomed - i'd have wasted a trip there and not be able to reproduce the brake issue

a block before returning to the dealer - we took a swing through a parking lot. it had some standing water - so i drove through it, and afterwards - NO BRAKES!!!!! Ok, ok, not quite 'no brakes' but at least the brake issue happened.

it was also a pretty serious puddle/pond - i'd imagine up to 3" deep, about the length of the car, so i could stop in it and let the car marinate in the water...

it was VERY reproducible - sometimes if i went through the water at 5-7 mph, the brakes wouldn't work correctly just 10 feet past the water. Sometimes it would brake fine then, we'd do a U-Turn, head back to the water, slow down to do another U-Turn and BRAKES ACTED UP AT THAT STOP (say 50-60 feet after the puddle). Sometimes the brakes did work at the puddle and also for the U-turn stop.

We must have done it a dozen or so times myself, and the Service Rep (manager?) did it several times as well. - HERE ARE THE OBSERVATIONS MADE when we knew it was coming. when road driving, even in heavy rain - it didn't happen all the time - normally once per trip in the heavy rain (in say, 10-12 slow downs) - so it was difficult to observe what was happening (when you're worried about staying alive and not wrecking) but when there's two peopel and you knwo it's about to happen, you can notice:

-THE REGENERATIVE BRAKING IS NOT TRIGGERING, it is solely mechanical braking

-IT IS NOT MECHANICAL BRAKING like the first 1, 2, 3 times when you drive your car (when you first hop int he car, your first brake or two or three is 100% mechanical, but the brake pedal feels the same as when regen is on, AND you know, the car actually stops)

-The sound is like the sound of your brakes TRYING to brake you after a car wash but slipping and not gripping properly

My new description of the issue: imagine if the first 30% of a NORMAL brake pedal push is FULLY regen braking, then the next 30-40% is a combination of some regen, some mechanical braking. And the last 30% of the brake pedal gives you 100% mechanical braking. Imagine there are servos or something that give you that brake pedal resistance feel - the device actually making the brake pedal push back against your foot. imagine there's one for the regen braking, and another for the mechanical braking. They normally work in a synchronized way where you feel a constant pressure when applying the brakes and engaging the brake pedal. OK, now imagine, something told the REGEN braking system - to 1) do not apply regen braking and 2) do not apply resistance to the brake pedal for that travel distance that is normally 'regen braking' brake pedal usage. so the brake pedal has no resistance the first 30-50% of it's travel distance. that's what the feeling is when this issue is happening: there is no regen braking AND there is no 'brake pedal feel' during that portion of the brake pedal travel

~ ~ ~ ~ ~ ~

As repeatable as it was that day - the service advisor wanted to take ANOTHER Taycan out (4S, like mine, PSCB, like mine, and same wheels even) - THE OTHER TAYCAN PERFORMED THE SAME IN THE SAME SITUATION. YES, A DIFFERENT TAYCAN ON THEIR LOT DID THE SAME THING AND HAD THE SAME BRAKING ISSUES IN THAT PUDDLE

I felt vindicated - A) I wasn't crazy [at least in 'imaging' this happening] and B) it's NOT JUST ON MY CAR

~ ~ ~ ~ ~ ~

I was told there are sensors in the wheel wells for different reasons -for suspension, braking, etc -

one could HYPOTHOSIZE that something somewhere was telling the Taycan NOT TO USE REGEN BRAKING. but for whatever reason, it wasn't telling the mechanical brakes "Hey, do what you normally do when the car is first turned on"

who knows why, who knows what -and nothing beyond these observations is known. I could conjecture, i could imagine, but i don't know, the service advisor didn't, no telling if anyone at Porsche does at this point.

I'm ok with the car deciding, based on telematics and sensor readings and reading tea leaves to NOT engage the regen brakes. BUT - the car needs to engage the mechanical braking like it does when first turned on and give the driver the same feel and the same stopping ability when using 100% mechanical braking. But as-is, it's dangerous. It's dangerous when going through a puddle at 5mph (it was IMMEDIATELY before a main road, and more than once the car stopped past the intended stopping target (sidewalk distance) and went right up to or into the street - and we knew it was going to happen)

Take that same issue - brakes giving the car and driver only a fraction of the stopping power - apply it randomly during wet street driving, and in 1 out of 12 wet stops, you get zero regen braking and your car only gives you a fraction of the physical mechanical braking. It might be when you're trying to stop at a light. It might be when you're trying to park in a spot (imaging overshooting your parking spot 1 of 12 times - by 5-10 feet). It might be when you have to brake in an emergency.

SO far they've taken this seriously and responded appropriately. Hopefully they can come up with a fix, because right now i don't feel safe in this car in the rain, and i wouldn't recommend other people driving it in the rain either

My guess is that there are sensors that detect when the brakes get wet and deactivate regeneration temporarily so that when you brake the mechanical brakes will be used and dry the brakes.

So now the regen is deactivated and you're relying on wet, mechanical brakes which don't work well, especially in a car as heavy as the Taycan.

My Cayenne's brakes are scary bad when they get wet. When I drive in the rain I periodically apply them with my left foot while keeping accelerator depressed to keep them dry. Perhaps the same technique can be used with the Taycan.

 

[bluegrassvroom]

My guess is that there are sensors that detect when the brakes get wet and deactivate regeneration temporarily so that when you brake the mechanical brakes will be used and dry the brakes.

So now the regen is deactivated and you're relying on wet, mechanical brakes which don't work well, especially in a car as heavy as the Taycan.

My Cayenne's brakes are scary bad when they get wet. When I drive in the rain I periodically apply them with my left foot while keeping accelerator depressed to keep them dry. Perhaps the same technique can be used with the Taycan.

I think you're mostly right- but I think whatever is switching between

Normal braking- regen at first then mechanical if enough force is applied

And

only use mechanical braking

Isn't fully "flipping the switch"

When you first start a Taycan- the first few brakes are 100% mechanical, and it's ok

But once the Regen kicks in, there's something in the circuitry telling the first say 60% of brake pedal movement activates the Regen brakes. And mechanical don't activate until the brake pedal goes past that 60% mark

And when this sensor activates (and deactivates the Regen)- it's like it forgot to tell the mechanical brakes- BTW- kick in at 0%.
So you get no braking from 0-60% of brake pedal travel distance and then the mechanical kicks in at 60%, but not at full strength

---
Would driving around essentially double pedaling work and keep the mechanical brakes drier add ready? Possibly- but if they're not being told to engage until the pedal is pushed really far in, you're still not getting good braking

 

[IBZman]

Porsche N.A. is working on this issue, testing it at their Atlanta facility on their wet track (water pad, whatever it's called). I've sent detailed notes, some videos, etc. Other people have reported it across the country (world?) at various Porsche dealers, so it's on their radar and they're looking into it.

Hopefully more of an update/fix is forthcoming...

What happened in the end with this?

My car is currently in the dealership (for the second time) with this very issue.

 

[bluegrassvroom]

What happened in the end with this?

My car is currently in the dealership (for the second time) with this very issue.

I don't live horribly close to a dealer - that said - they can't do anything until Porsche releases a fix. I'm a former programmer - THIS IS PROGRAMMING, IT IS ELECTRONIC. i'm 99.458% sure. something in the programming is telling the regen NOT TO WORK and it's NOT telling the mechanical brakes to pick up the slack

I HAVE A "FIX" THAT MAKES IT A LITTLE BETTER: don't drive in the rain

I HAVE A "FIX" THAT MAKES IT A LITTLE BETTER: for real though - i used to NOT have auto-regen on. now i turn it on and i haven't experienced any HORRIBLE cases of this (horrible = OH ______ I'M GOING TO DIE AND TAKE OUT THREE CARS WITH ME).

for anyone who hasn't experienced it - PLEASE trust us - it's not slight. it's not minor. imagine having ONE TENTH OR LESS of your normal braking ability. It's serious issue. i can't believe it's not fixed yet. I'm seriously thinking of sending all this in a certified letter to NHTSA so Porsche will take this more seriously and/or at least update us.

this is NOT a 'oh, we'll fix this in a few months and bring us your car when you can" issue - it's a DO NOT DRIVE YOUR CAR IN WET CONDITIONS BECAUES YOU COULD DIE-issue. it's not minor. and now that it's documented Porsche knows about it - if there's accidents because of it they could have some very serious liability

 

[IBZman]

Thanks for the reply. Even more concerning that they still haven’t fixed this. This should be a category 1 issue - i.e. drop everything else and fix this.

I HAVE A "FIX" THAT MAKES IT A LITTLE BETTER: don't drive in the rain

I’m in the UK! ?? ? ?

for anyone who hasn't experienced it - PLEASE trust us - it's not slight. it's not minor. imagine having ONE TENTH OR LESS of your normal braking ability. It's serious issue.

100%. This is SCARY ASF!

 

[DerekS]

I don't live horribly close to a dealer - that said - they can't do anything until Porsche releases a fix. I'm a former programmer - THIS IS PROGRAMMING, IT IS ELECTRONIC. i'm 99.458% sure. something in the programming is telling the regen NOT TO WORK and it's NOT telling the mechanical brakes to pick up the slack

I HAVE A "FIX" THAT MAKES IT A LITTLE BETTER: don't drive in the rain

I HAVE A "FIX" THAT MAKES IT A LITTLE BETTER: for real though - i used to NOT have auto-regen on. now i turn it on and i haven't experienced any HORRIBLE cases of this (horrible = OH ______ I'M GOING TO DIE AND TAKE OUT THREE CARS WITH ME).

for anyone who hasn't experienced it - PLEASE trust us - it's not slight. it's not minor. imagine having ONE TENTH OR LESS of your normal braking ability. It's serious issue. i can't believe it's not fixed yet. I'm seriously thinking of sending all this in a certified letter to NHTSA so Porsche will take this more seriously and/or at least update us.

this is NOT a 'oh, we'll fix this in a few months and bring us your car when you can" issue - it's a DO NOT DRIVE YOUR CAR IN WET CONDITIONS BECAUES YOU COULD DIE-issue. it's not minor. and now that it's documented Porsche knows about it - if there's accidents because of it they could have some very serious liability

Seems to me something is very wrong with your car.

I've never experienced that in 28K miles.

 

[Windpower]

THIS IS PROGRAMMING, IT IS ELECTRONIC. i'm 99.458% sure. something in the programming is telling the regen NOT TO WORK and it's NOT telling the mechanical brakes to pick up the slack

... imagine having ONE TENTH OR LESS of your normal braking ability.

... DO NOT DRIVE YOUR CAR IN WET CONDITIONS BECAUES YOU COULD DIE-issue.

The effect you describe, "the programming is telling the regen NOT TO WORK and it's NOT telling the mechanical brakes to pick up the slack", does this only happen in the rain? Or does this happen under dry conditions too?

 

[bluegrassvroom]

The effect you describe, "the programming is telling the regen NOT TO WORK and it's NOT telling the mechanical brakes to pick up the slack", does this only happen in the rain? Or does this happen under dry conditions too?

in my analytical mind, there's a sensor somewhere, sensing something. Porsche tech seemed to think it was one of the ones in the wheel well, and for some reason, when it gets wet/blinded/obstructed/etc, it seems to tell the regen brakes NTO TO WORK and it doesn't trigger the mechanical brakes to pick up the slack (like they do for the first several stops when you start up the Taycan)

so -NO, not in dry conditions, just in wet. and PRETTY DARN WET at that. not necessarily pouring, it can be not raining with REALLY wet roads.

Best way i've reproduced it: found a puddle, deeper the better, gone through it slow or semi-slow, and either taken a SHARP turn in the puddle/through the puddle or IMMEDIATELY after it , like a U-turn (kind of like the tires at that sharp angle kick up the water to block the sensor?) and then normally the NEXT stop won't, um, stop. sometimes the next several won't

it HAS happened on wet days going 100% straight. Porsche HAS reproduced it on different model years, different trim levels, etc

i normally drive with AUTO BRAKE REGEN OFF. i haven't tried to reproduce it (through puddles purposefully) with brake regen on - but i think i might. rain coming this weekend. lately i've turned the brake regen on just because i feel like i haven't experienced this as often with the auto brake regen on.

 

[Windpower]

in my analytical mind, there's a sensor somewhere, sensing something.

Best way i've reproduced it: found a puddle, deeper the better, gone through it slow or semi-slow, and either taken a SHARP turn in the puddle/through the puddle or IMMEDIATELY after it , like a U-turn (kind of like the tires at that sharp angle kick up the water to block the sensor?) and then normally the NEXT stop won't, um, stop. sometimes the next several won't

Honestly, to me this does sound like a sensor problem. Some sensor is getting hit by water when you have "taken a SHARP turn in the puddle". Its possible you have a broken sensor or a broken wire which is getting hit by water.

I'm not the one who knows how the braking system works, but from your description, someone at Porsche should have a idea what's causing this.

That said, I've been in the computer biz long enough to know that some issues are not that easy to track down. I think you are doing the right thing: getting information to Porsche and pushing them to look at your data. Hopefully the issue gets elevated to someone who can figure out whats going on.

I used to have a BMW i3. While the car was great, one thing which completely annoyed me was that, if you were slowing down using regenerative braking (removing your foot from the accelerator pedal) and you hit a curve, the regen braking would stop and all of a sudden you'd lurch forward. This used to happen to me daily on my way home from work when I exited the freeway onto the exit ramp. While on the freeway doing maybe 75mph, I'd remove my foot from the accelerator pedal, the car would slow down nicely, and they as I exited onto the ramp curve, the regen braking would stop and the car would speed up. I was told that that wasn't a bug, it was a feature.

 

[800v]

Darn, I experienced this today for the first time (2020 turbo, no update). Quite scary!

I was at a car wash and used pressure wash especially on the wheels. After turning out of the spot the brakes did nothing until i pressed much further on the brake pedal. Was going very slow but almost hit the car in front of me.

After this, braking worked fine again. Still love my car but wanted to add my experience here in case Porsche can figure out how this happens

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