Taycan 4s parked on snow rolling forward - how why and wtf??

Vim Schrotnock

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Did you not feel the ABS kicking in? What kind of tires do you have?
If you are in snow, I'm going to guess you can't brake hard enough to use the ceramics - all the braking will be done by the motor.





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I was doing no more than a max of 10mph and brakes in plenty of time (with only a slight pressure on the brake)
If you only had a slight pressure on the brakes maybe the regen did not kick in at all. Did you press harder on the brake pedal to get the ABS to kick in? And the discs actually doing the breaking?
 

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evanevery

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Did you not feel the ABS kicking in? What kind of tires do you have?
You might not feel the ABS "Kicking in" in a really well implemented system. The less it upsets the car (and you feel it) the better.

I'm seriously betting the brakes were working perfectly and that this was an icy surface on which the driver "wished" they could have stopped sooner...

I've run M2's and M4's in Northern Sweden with studded tires on a frozen lake for a couple seasons now (NOT including this one unfortunately) and we've never had any stopping issues with Carbon Ceramic Brakes. I've also specifically had the Taycan out last week to drift around my office building in fresh unplowed snow (on P-Zero winter tires). Although, it wasn't as much fun as the pure RWD M2's or M4's, I also did not have any issues with the CCB's.
 

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If you are in snow, I'm going to guess you can't brake hard enough to use the ceramics - all the braking will be done by the motor.
Some time way back when, there was an article about the Model S in snow and how much faster the motor control system could react compared to ABS, which gave the Model S better braking in snow at higher speeds. The same is probably true with Porsche's motor control system. And it definitely seems Taycan regen can generate more stopping force than could be applied to the contact patch on snow.

However, regen ability declines with RPM, and below some minimum motor RPM, regen stops working completely. I don't know what that min RPM might be but at some low enough speed on snow, the hydraulic brakes would be in use, and ABS can and would modulate the brake pressure to prevent lock-up. It's possible on a hill, given the weight of the car and relatively small contact patch, that there may not be sufficient braking force to stop the car. I would have expected this to be a safety concern addressed early in development though.
 

evanevery

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Some time way back when, there was an article about the Model S in snow and how much faster the motor control system could react compared to ABS, which gave the Model S better braking in snow at higher speeds. The same is probably true with Porsche's motor control system. And it definitely seems Taycan regen can generate more stopping force than could be applied to the contact patch on snow.

However, regen ability declines with RPM, and below some minimum motor RPM, regen stops working completely. I don't know what that min RPM might be but at some low enough speed on snow, the hydraulic brakes would be in use, and ABS can and would modulate the brake pressure to prevent lock-up. It's possible on a hill, given the weight of the car and relatively small contact patch, that there may not be sufficient braking force to stop the car. I would have expected this to be a safety concern addressed early in development though.
Its an interesting discussion, but none of this really matters (regen braking vs hydraulic braking) if there isn't enough friction available to stop the car in a "comfortable" distance. ABS is going to modulate whatever braking is available or in use to keep the wheels rolling vs skidding so the operator can maintain some control of the vehicle.

The OP clearly said hail was involved. I'm betting on ABS vs Ice rather than a failure of the Ceramic Brakes to stop the car. That would be pretty unheard of...
 

Vim Schrotnock

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Some time way back when, there was an article about the Model S in snow and how much faster the motor control system could react compared to ABS, which gave the Model S better braking in snow at higher speeds. The same is probably true with Porsche's motor control system. And it definitely seems Taycan regen can generate more stopping force than could be applied to the contact patch on snow.

However, regen ability declines with RPM, and below some minimum motor RPM, regen stops working completely. I don't know what that min RPM might be but at some low enough speed on snow, the hydraulic brakes would be in use, and ABS can and would modulate the brake pressure to prevent lock-up. It's possible on a hill, given the weight of the car and relatively small contact patch, that there may not be sufficient braking force to stop the car. I would have expected this to be a safety concern addressed early in development though.
Yes, it's an interesting question - but I'm probably incorrect in assuming regen in snow if ABS is applied. ABS can individually brake each wheel, which, unless Porsche has some magic up their sleeve, cannot be done with regen. I do agree the brakes were likely working perfectly.
 

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Yes, it's an interesting question - but I'm probably incorrect in assuming regen in snow if ABS is applied. ABS can individually brake each wheel, which, unless Porsche has some magic up their sleeve, cannot be done with regen. I do agree the brakes were likely working perfectly.
Many people, unfortunately, are quite unaware of what ABS feels like when in full use on ice and/or snow.

Folks should go and make a few panic stops in a SAFE icy snowy parking lot to see what it feels like. Your car is not likely going to stop as soon as you would like, but its is going to stop as soon as possible and you will be able to maintain some control/steering during the process. You will be "along for the ride" to some degree...

Physics always wins.
 

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I was doing no more than a max of 10mph and brakes in plenty of time (with only a slight pressure on the brake)
On ice, snow, rain, or almost any surface, the shortest stopping distance is with very heavy pressure on the brake pedal to kick on the ABS. Especially important on slick surfaces so you have steering control (no comments from drifters - I am teaching grandchildren).
 
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I think the issue raised by Fawad is not the same or anything close to the thread subject.

If a parked 2 ton vehicle wont stay still on a very slight incline on 2-3 cm of fresh snow, Porsche have a problem.

If it never happens again to any other driver (please God it doesnt) then I have a problem. I should get a pedal bike probably.
 

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Mine puts the parking brake on when I open the door. I assumed all modern cars did this. All mine do. Would be strange if this could be turned off. It's actually a pain on one car as you have to select Neutral to allow me to put it a few inches into the garage so it doesn't hit a cabinet.


Hi All

Just had a rather scary near miss and felt the need to warn people. Im a UK 4s owner, loving the car which Ive had for 6 weeks (pre cool issues aside).

We have had a classic UK snow fall overnight around a few cm's which is enough to decimate the town!! Drove my Taycan to the office and parked on a very slight incline, handbrake engaged. One foot out of the car and on the ground and the rolling starts!! A 2 ton car rolling on 3-4 cm of snow. Managed to get back in and pulled up a few feet away from a wall.

How the hell has this happened? Imagine this occurring on a sharp incline in a town centre?

Is there no anti-roll safety feature? My wheels were turning so I was told by a witness, meaning they werent locked or fixed by the handbrake.

I would definitely avoid parking this car on an incline in snow. Of more concern is the question as to how the car would behave in traffic facing downhill when stationary in these conditions?

Any thoughts welcome particularly from any UK dealers who may be aware of this issue.
 

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I had the same very bad experience today. I already replied in another similar post here:

https://www.taycanforum.com/forum/t...-day-at-the-office-pt2.3394/page-3#post-49419

It was really scary. There were other cars parked on each side on the same incline and mine was the only one rolling backwards, so no question of slipping !

My 4S equipped with brand new winter tires (brakes are PSCB).

”P” was engaged before shutting off the car and the red brake warning was well illuminated.

I already sent an mail to my dealer, as the occurrence needs to be reported to Porsche asap.

Krgds
 
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I had the same very bad experience today. I already replied in another similar post here:

https://www.taycanforum.com/forum/t...-day-at-the-office-pt2.3394/page-3#post-49419

It was really scary. There were other cars parked on each side on the same incline and mine was the only one rolling backwards, so no question of slipping !

My 4S equipped with brand new winter tires (brakes are PSCB).

”P” was engaged before shutting off the car and the red brake warning was well illuminated.

I already sent an mail to my dealer, as the occurrence needs to be reported to Porsche asap.

Krgds
Hi Werner
Thanks for sharing.

There is definitely a serious problem here that is not being addressed. Ive been told my issue was down to the car not having winter tyres yet yours had brand new Porsche supplied winter tyres.

The gradient clearly makes a difference but what are we to do - take chocks with us when we leave the house or instead look for a flat road to park on?!! This is a £100k car!!!
 

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