Tesla in Park suddenly moved forward [air temp 33, snow on ground, parked on incline, OEM tires]

[Occhis]

Just a thought. Maybe the extra weight of the passengers kept the car in place until they exited the car, making the car weigh less, just enough to loose traction. Temp at 33 was at the point that it would be most slippery, tires just warm enough to melt a film of water between tires and snow/ice.

 

[ChrisH]

Craziness!!!
My 3 was a trooper up hills on the stock MxMs on the first day of a major snow storm here last year. I promptly parked it in the garage and didn’t drive it again til the snow was gone but I was super impressed how it did driving around. Will definitely not park on a hill in snow or icy conditions now though.

 

[TSLA Pilot]

There's always somebody on the Internet that feels that they need to respond to a post like this by reciting the manual or basic troubleshooting tips, in order to blame the original poster and make them feel like an idiot. It's common to software forums and car forums alike it seems.

Suffice it to say that in my history of owning and driving several vehicles on this driveway over a series of many many years, and having lived my entire life in northern snowy climates, this is the first time that I have ever encountered such an issue.

I suspect the guidance I provided is also mirrored in the Owner's Manual, and the drivers manual for many states as well . . . so RTFM applies. And I am glad you've had remarkably good luck in not being aware of basic physics for so many, many years.

 

[bradyb23]

So which brand and model tires are we talking about here?

I'm the original poster; mine were the OEM tires with less than 1000 miles.

 

[DiscordianDave]

I'm the original poster; mine were the OEM tires with less than 1000 miles.

Same story here, OEM tires with ~3300km on them

 

[bradyb23]

I suspect the guidance I provided is also mirrored in the Owner's Manual, and the drivers manual for many states as well . . . so RTFM applies. And I am glad you've had remarkably good luck in not being aware of basic physics for so many, many years.

TSLA Pilot, I'm the original poster and while the parking spot was on an incline, after I pulled out and onto a flat spot, I went back to inspect the space and another car pulled right in, the driver got out and gave me a funny look because I was standing alone staring at an empty parking space, and went into the movie theater without incident. Just want to emphasize some of the detail that might have been lost along the way. Note that as one of the other posters on this thread noted, the issue appears to have been replicated. In my case, I did not wait to see if the car stopped moving after two feet; the moment it started rolling I jumped in and jammed on the break and it stopped. It is possible that the car stopped by itself at the moment I hit the break (which would be consistent with about a 1 foot roll, I suspect), but I have no way to test this now. Note also that it is not possible to exit the car with it in drive (which was my first thought, even though my rear seat passenger said she saw that it was in P; I tested this by opening my door the other day (not in snow conditions) and the car alerted me that it was going into P for safety a moment after I opened the door.

 

[SMAlset]

@bradyb23 Just last night I was reading similar posts by some owners over on reddit. We have a sloped driveway but not the wintery conditions as described by people so haven't experienced this behavior when parking my car at home. I've parked my car both forward towards the garage and backed in when charging in the driveway with no issues, but on dry pavement. Closest experience I've had to your situation was when I was once in a friend's Prius and she had pulled into a parking spot at a shopping center, think the spot had a slight dip forward, and we were getting out of the car. I had my door open and I one of my legs on the ground and was about to fully exit when her car suddenly started moving forward, the action jerked my body in an unnatural way and I was actually sore for a few days. She jumped back into the car but not before it hit the car parked in the spot immediately in front of hers. It was a rather frightening experience to have so I can understand everyone's concern even if no damage was caused.

My friend was understandably upset and confused as to what happened. Her BEV Prius was quiet like our Model 3s and she could only think that maybe she pulled into the spot, the car stopped and she never actually put the car in park and turned it off. Being so quiet, she hadn't realized it. To me it didn't feel like it simply rolled forward as the action had a very sudden forcefully forward movement. I'm not familiar with Prius' but have wondered about her parking accident a number of times since, and wondered if she went into a brake hold and it released and with the car still "on" moved forward. Unsettling to say the least and of course you want to know exactly what happened.

Now I have pulled into a parking spot for a period without putting the car in Park (brake hold was on) and spent some time sitting inside the car only to open the door to get out but have on those occasions gotten a loud alert and believe text alert on the screen that the car then put itself into Park. This sounds totally contrary to what people have described happening so based on my experience like this don't think people forgot to put their cars into Park.

 

[illYay1337]

I just had this happen to me in Tahoe. I’ve owned the car for a bit over a year and have never had this happen before. Me and my friends were suspecting it might be a recent software upgrade?

it was terrifying to arrive at the air bnb, park my car, unload a bunch of things, close the trunk, and suddenly watch helplessly as my car rolled into my friend’s car in front. Thankfully there was no visible damage to either of us. I then moved my car up the drive way and turned the wheels to the side. Lo and behold it happened again!!! I wonder if this is a recent software issue. I’ve driven my car to Tahoe and in the snow many times and owned it for over a year and would never expect this to happen. Maybe I need to get some break maintenance at the very least.

I then had trouble reversing out of the driveway as if I was stuck in snow. My friend’s Subaru effortlessly reversed out of the driveway while mine was sliding sideways even with slip start mode on. It was the craziest experience ever. Just weeks ago I was driving in insane conditions in Yosemite during a time when hurricane warnings were in effect in California. It really makes me suspect some recent software update made the car have issues in the snow.

 

[TSLA Pilot]

I assume the issue would also occur with a RWD ICE vehicle. But probably you have not had one of those in that driveway? Definitely this is something that might take many people by surprise, since RWD vehicles do tend to be more rare.



A bit more charitable explanation would be that people in snowy climates probably get it in their mind that their AWD vehicle (which is probably the predominant Model 3 vehicle in these climates) will behave similarly to their previous AWD or FWD vehicles in this situation. But the Tesla Model 3, when turned off, behaves like a RWD vehicle - the front wheels are free to roll when the car is off.

Excellent point.

Also, when a FWD vehicle is placed in "Park" the front wheels are locked, and that is where the majority of the weight is located in a FWD vehicle. Furthermore, with only a few exceptions, using the parking brake on a FWD vehicle will also lock the rear wheels, thus providing the best possible situation to prevent sliding on an icy, sloped, parking spot with all four wheels helping keep the car from sliding. (However, a FWD vehicle would be still be likely to slide if parked facing uphill on a steep slippery slope if just left in "Park." Because Physics.)

A Model 3 is far more evenly weight balanced, and ONLY the rear wheels are locked. Thus there is a slightly increased possibility for it to slide once you release the regular brakes. Then you go from four wheels locked to only two. This is exacerbated when parked facing downhill. (Because Physics.)

I wonder if there might be a software fix for this human error? The car could apply some limited front service brake pressure if:

1. Temps at or below freezing.
2. Vehicle parked facing downhill on a steep incline. (Because Physics.)
3. Temperature has not increased above freezing for more than 12 hours.
4. Front wheel rotation exceeds 2 or 3 degrees.

But keeping all that processing going, and front brake pressure applied for an extended period, would take battery power and possibly cause wear to the ABS Module.

Interesting interaction between Human Factors and Physics resulting in sliding Teslas however . . . .

 

[TSLA Pilot]

If it's not an issue with tire traction, my suspicion is that a small layer of ice is freezing on the pads, so they stop the car when they initially actuate, but after however many seconds the ice melts after absorbing enough heat from the rotors and the car rolls downhill.

I think someone should (safely!) try spraying the brake pads with a bit of water and then parking their car on an incline to see if they can replicate this problem.They may also need to brake enough to warm up the rotors, and will need to continue to spray the pads only until they see them ice up. Checking the rotor/pads with an IR thermometer after a drive should help with finding a good temperature/time range to try the experiment.

Another way to check could be to switch creep on. If you can't replicate the problem at all with creep on that suggests it's associated with one-pedal driving using the brakes a lot less in specific cold/wet environments.

Highly unlikely this is the case. The rear wheels are locked when in "Park" and, while novel, I can see no situation as to what you have suggested being even a remote possibility. The electric motor which drives the brake pads onto the rear discs is very, very powerful.

The issue here is a lack of understanding of that a Model 3 has equal weight distribution, and, unlike a common FWD car, has less slightly weight (i.e. Force Normal) pressing down on the rear wheels.

The anecdotes here are from cars sliding with two locked rear wheels (with the exception of the Prius examples--which exemplifies that it can happen to ANY car).

 

[TSLA Pilot]

Craziness!!!
My 3 was a trooper up hills on the stock MxMs on the first day of a major snow storm here last year. I promptly parked it in the garage and didn’t drive it again til the snow was gone but I was super impressed how it did driving around. Will definitely not park on a hill in snow or icy conditions now though.

Yes, and if you must do so, park it facing UPHILL to help provide more weight on the rear wheels, which are the locked wheels when in "Park."

 

[TSLA Pilot]

Personally, I would not trust the traction of two studded snow tires to keep the car parked on a steep hill in freezing rain or snow near the freezing point.

I saw my dad skate up our driveway in Oregon with tungsten carbide studs, leaving gouges in the concrete all the way up, too many times to trust them as a solution to every condition. If the conditions are bad enough, they have to get through to pavement to work.

FWIW:

This was an especially informative reply which leads to a suggestion for Tesla.

The car knows the outside air temperature.

The car also knows the angle at which it is being parked.

This Owner's Manual info:

Warning: Your Model 3 may display an alert if the road is too steep to safely park on, or if the parking brakes are not properly engaged.

. . . leads to an idea which will help address this Human Factors issue.

The screen alert could be greatly enhanced if it came on in a large, red box, whenever the car was being parked below or near freezing temperatures, particularly when facing DOWNHILL, by suggesting the driver NOT park there. Perhaps:

"WARNING: Unless this parking spot is free of contaminants (snow, ice, etc.), your car may NOT remain stationary. Recommend parking in a more flat location to prevent vehicle from sliding."

 

[TSLA Pilot]

I just had this happen to me in Tahoe. I’ve owned the car for a bit over a year and have never had this happen before. Me and my friends were suspecting it might be a recent software upgrade?

it was terrifying to arrive at the air bnb, park my car, unload a bunch of things, close the trunk, and suddenly watch helplessly as my car rolled into my friend’s car in front. Thankfully there was no visible damage to either of us. I then moved my car up the drive way and turned the wheels to the side. Lo and behold it happened again!!! I wonder if this is a recent software issue. I’ve driven my car to Tahoe and in the snow many times and owned it for over a year and would never expect this to happen. Maybe I need to get some break maintenance at the very least.

I then had trouble reversing out of the driveway as if I was stuck in snow. My friend’s Subaru effortlessly reversed out of the driveway while mine was sliding sideways even with slip start mode on. It was the craziest experience ever. Just weeks ago I was driving in insane conditions in Yosemite during a time when hurricane warnings were in effect in California. It really makes me suspect some recent software update made the car have issues in the snow.

Has nothing do to with software updates.

Has nothing to do with BRAKE maintenance.

Has everything to do with Physics and Human Factors . . . park in places with less of a slope when it's icy and snowy.

(Also, avoid using slip start unless you absolutely must.)

 

[CAAD]

TSLA Pilot, I'm the original poster and while the parking spot was on an incline, after I pulled out and onto a flat spot, I went back to inspect the space and another car pulled right in, the driver got out and gave me a funny look because I was standing alone staring at an empty parking space, and went into the movie theater without incident.

What make and model car pulled in?

 

[timk225]

I have a hard time believing that the state of wisdom and scientific knowledge is such that people are not aware that the parking brake works on only ONE set of the wheels (the rear wheels) while the foot brake works on all four, and that snow and ice have a low coefficient of friction.

But this appears to be the case.

After reading the first few posts in this topic, I was thinking the same thing. I don't expect everyone to have my level of general automotive knowledge, but does the average person really know so little about how 4 wheel hydraulic vs parking brakes on the rear only work? These are the same people you see flying down the road at 80 mph in a winter snowstorm because "I have 4 wheel drive". There's more to it than that!!!

In addition to this, don't forget weight transfer. If someone is backing up a slippery driveway and puts the parking brake on, the tires are effectively, partially, unloaded once the car is sitting only on the parking brake. Now if they turned the car around and parked in that same driveway with the car facing uphill, the rear tires have more weight sitting on them and the car may or may not slide, with only 2 wheels being held still by brakes.

As an additional solution, Tesla gives us that screw-in tow hook in the frunk. Screw it into the front bumper, and have a chain and hook attached to your house somehow. When you pull into the driveaway, simply hook up the car to hold it from sliding down the snow and ice while you're inside the house.

 

[ChrisH]

Has nothing do to with software updates.

Has nothing to do with BRAKE maintenance.

Has everything to do with Physics and Human Factors . . . park in places with less of a slope when it's icy and snowy.

(Also, avoid using slip start unless you absolutely must.)

how does this explain one car sliding (Tesla) and the Subaru not? AWD vs RWD?

 

[DopeGhoti]

how does this explain one car sliding (Tesla) and the Subaru not? AWD vs RWD?

One car (the Tesla) has two wheels that freewheel when parked; one car (the Subaru) has all four wheels locked to the all-wheel transmission.

This is one of the few downsides of not having a transmission.

 

[Occar]

One car (the Tesla) has two wheels that freewheel when parked; one car (the Subaru) has all four wheels locked to the all-wheel transmission.

This is one of the few downsides of not having a transmission.

It's more that the gearbox has no parking pawl. There is nothing inherent with a multi-gear transmission that grants you front wheel locking while parked (on an automatic).

 

[DiscordianDave]

As an additional solution, Tesla gives us that screw-in tow hook in the frunk. Screw it into the front bumper, and have a chain and hook attached to your house somehow. When you pull into the driveaway, simply hook up the car to hold it from sliding down the snow and ice while you're inside the house.

This literally made me laugh out loud. You have very clearly never lived in a northern climate, particularly one where block heaters are in common use, otherwise you would be familiar with extension cords dangling behind cars and left in the middle of the road because people forget to unplug them.

Suggesting that you leash your car to the house like a dog is quite simply insane. For one thing, the tow hook eye would ice over within a few kilometres of snowy driving (unless you are suggesting that you unscrew it every time you leave the house and screw it back in when you return, which is even crazier). For another, the first time you forgot to unhook it you would either rip a piece off your house or pull the bumper off the car, which I'm pretty sure would not be covered under warranty.

For somebody that claims a lot of general automotive knowledge, you've got some pretty big blind spots.

 

[TSLA Pilot]

This literally made me laugh out loud. You have very clearly never lived in a northern climate, particularly one where block heaters are in common use, otherwise you would be familiar with extension cords dangling behind cars and left in the middle of the road because people forget to unplug them.

Suggesting that you leash your car to the house like a dog is quite simply insane. For one thing, the tow hook eye would ice over within a few kilometres of snowy driving (unless you are suggesting that you unscrew it every time you leave the house and screw it back in when you return, which is even crazier). For another, the first time you forgot to unhook it you would either rip a piece off your house or pull the bumper off the car, which I'm pretty sure would not be covered under warranty.

For somebody that claims a lot of general automotive knowledge, you've got some pretty big blind spots.

It's pretty safe to assume he was using sarcasm;-)