Hill-hold releases *after* you get out of the car?

[whitex]

Just a quick warning to MS (and possibly MX owners) when parking on possibly slippery surfaces. Hill-hold will keep all wheels stopped, while parking brake will only lock the rear wheels (even in an AWD S). The issue is that it seems hill hold doesn't release until the car turns off. I say "it seems" because this is my theory of what happened to me. I got home, backed onto a slightly sloped driveway with some snow and ice on it. I put the car in park, everyone got out of the vehicle, as I was already in the car I noticed my car is moving down my driveway! It stopped a couple of feet down, but it was not something I would expect. At first I thought maybe somehow summon got enabled (I keep it disabled) but after looking at the security camera footage I realized that only the front wheels were moving, while back wheels were locked.

Anyhow, I think I will send in a report to Tesla, in the meantime, since temperatures are low in a lot of places, friendly warning to be careful out there if parking on a slippery slope.

 

[Ande]

Yes, for some cars it's normal to have parking break on only two wheels.
For example Citroen Xantia and others have FWD and parking break on front wheels only. (As rear wheels have extra pistons in their calipers.)

Model S os one of those cars that need extra attention when parking on slippery sloping places.

 

[whitex]

Yes, for some cars it's normal to have parking break on only two wheels.
For example Citroen Xantia and others have FWD and parking break on front wheels only. (As rear wheels have extra pistons in their calipers.)

Model S os one of those cars that need extra attention when parking on slippery sloping places.

I understand. The dangerous thing is that the hill-hold keeps the car in place until a minute or so AFTER you get out of the car, so the car moves without anyone in the driver's seat. What it should be doing instead is disengaging the hill-hold as soon as the car is put in "Park" (with driver's foot still on brake pedal) so that as soon as the driver let's off the pedal the car starts moving and the driver has a chance to intervene.

 

[cantanko]

I understand. The dangerous thing is that the hill-hold keeps the car in place until a minute or so AFTER you get out of the car, so the car moves without anyone in the driver's seat.

Not sure that's true, as whenever I've been on an incline with hill-hold enabled and feet off the pedals, if you then engage Park, the car rolls for an inch or so as the service brakes release and the parking brake engages (and the (H)old indicator disappears from the dash). Also, if you have your foot on the brake and shift to Park, on newer cars you can feel the pedal move slightly as the parking and service brakes are handled by the same callipers. If I then lift my foot, I hear a slight creak from the front as those callipers release the front discs.
I'd suggest it's more likely that the car just lost traction after a few moments - unloading and disembarking changes the conditions quite a bit. Incidentally, spare a thought for older Land Rover drivers: the parking brake on those, whilst very powerful, operates on the back of the transmission on the rear prop shaft, NOT the wheels. If the diff locks are out, the front wheels spin freely anyway and if either of the rears break traction, there goes your vehicle! It's an interesting sight to see your car making its way down a hill with one of the rear wheels spinning opposite to the direction of travel!

 

[croman]

What does holding down the park button do? I know mine shows a red P but what is that vs. standard parking brake?

 

[BerTX]

What does holding down the park button do? I know mine shows a red P but what is that vs. standard parking brake?

Manually sets the parking brake, same as setting it from the touch screen.

 

[cantanko]

What does holding down the park button do? I know mine shows a red P but what is that vs. standard parking brake?

Might I point you at this thread...

 

[whitex]

Not sure that's true, as whenever I've been on an incline with hill-hold enabled and feet off the pedals, if you then engage Park, the car rolls for an inch or so as the service brakes release and the parking brake engages (and the (H)old indicator disappears from the dash). Also, if you have your foot on the brake and shift to Park, on newer cars you can feel the pedal move slightly as the parking and service brakes are handled by the same callipers. If I then lift my foot, I hear a slight creak from the front as those callipers release the front discs.

Well, not sure what to tell you other than the car did not slide when getting out of the car, or when I closing the car door - both of which I assume would have higher physical impact on the car than the force of folding mirrors and door handles. Tesla doesn't give us access to logs to be able to go back and check what the car did exactly. Is it possible that the folding mirrors and door handles jarred the car just right? Sure. It is also possible that the passing moon gravitation pull happen to pull my car at just the right time. All I know is what happened, see the video below. The car locks 30 seconds after getting out of the car and starts moving just as it locks.

 

[arnis]

Just saying that on BMW's, parking brake is engaged in every scenario (even if in Drive or Reverse, even if vehicle in motion) as soon
as driver's door is opened and seatbelt unbuckled.

I agree, hill hold should be released as soon as parking brake is engaged.

 

[whitex]

Thinking about it a little more, it is also somewhat possible that the SAS performed self leveling as the car was shutting off, possibly jarring the car just enough. Maybe a good safety would be to monitor if the car starts moving when leveling the suspension while in Park, and if so apply brakes and notify owner?

 

[Chaserr]

You're not the only person this has affected! I remember a recent post in which someone mentioned the same thing happened to them (they did not mention hill hold releasing but it makes sense) and the car slid down their driveway while plugged in, tearing the HPWC cable off of the unit.

 

[arnis]

Well, incorrect tires for those specific conditions. This is actually the main cause of a problem.
Tires with snowflake/mountain symbol are the only ones that are good for any icy conditions.
Doesn't even matter, is it Tesla or any random ICE. Parking brake usually engages on 2 wheels.
FWD vehicles have a small advantage here.

 

[whitex]

Doesn't even matter, is it Tesla or any random ICE. Parking brake usually engages on 2 wheels.
FWD vehicles have a small advantage here.

The problem I am pointing out here is NOT that Tesla parking brake only engages on 2 wheels, but the fact that something changes after the driver gets out of the car and the car locks and shuts down, causing the car to slide without a driver in the car. My theory is that all 4 wheels have brakes engaged until the car shuts down, leaving only the 2 rear tires with parking brake engaged. Instead, the car should have only had only the 2 rear tire brakes engaged BEFORE the driver exits the vehicle - preferably as soon as the driver let's his foot off the brake pedal, so that he has a chance to press the brake back as the car starts sliding.

Well, incorrect tires for those specific conditions. This is actually the main cause of a problem.
Tires with snowflake/mountain symbol are the only ones that are good for any icy conditions.

While tangential to this topic, having grown up with winters, I absolutely get the value of winter tires. However it is practically impossible to use them where I live now, because temperatures are usually in the 50's (F) during the day and only drop to freezing on few days a year. Winter tires are not meant for warm weather, and changing them for a day or two at a time is completely impractical (I don't even think Tesla Service could handle such short notice and often tire change appointments).

 

[arnis]

50F is still fine for winter tires. They do wear slightly faster.
There are now All-Weather tires available for these rare occasion when winter and warm weather change within a day.
All-Weather tires have snowflake/mountain "certificate".

I agree, that hill hold should release with parking brake engagement. If it doesn't right now.

 

[TexLaw]

It could be as simple as that it took a minute or two for the slide to occur. Things don't have to happen instantly.

 

[Saimaannorppa]

Today I noticed the same behaviour in safe, level garage condition, so I support the theory.

I drove car in, used breaks so it was on hill-hold, and spent some time setting up new Wi-Fi. It was on park and key fob in car, but when the car shut down came, there was a clear release noise from front and even very subtle movement. I could hear it as music and A/C was off, and discs were probably a bit sticky due to recent wash.

 

[whitex]

It could be as simple as that it took a minute or two for the slide to occur. Things don't have to happen instantly.

Absolutely it is possible, the question is how likely is it that it will happen at the exact moment the car is shutting down (watch the video, the car starts moving as the mirrors & door handles retract). IMHO the likelihood is very low for it to happen to coincide.

 

[timvracer]

What's all that white stuff on the driveway?
- timvracer from California

 

[whitex]

What's all that white stuff on the driveway?
- timvracer from California

I see we have one of the car's designers on the thread. "Who knew there were other climates our there."

 

[SucreTease]

It could be as simple as that it took a minute or two for the slide to occur. Things don't have to happen instantly.

It could be as simple as warm tires melting the surface snow in contact with them after a few moments, making the water/ice combination more slippery than the snow/ice combination.