I took my 3 out in some snow over the weekend and had something odd happen. I should say first that it did fine in the snow (P3D-). Most 2-wheel drive cars were having issues as we were on a somewhat steep access road, but I never felt any real loss of control. Anyway, what happened was that I had to stop to wait for another car to get out of my way. The road had a small amount of new snow over some heavily compacted earlier snow. It was slippery. I stopped on a slope, I can't estimate but for a regular street it was moderately steep. I would not have chosen to stop there if not for the car having issues ahead of me as momentum was definitely in my favor at that instant. When it became apparent that the car ahead was going to be a while, I put my car in "P" and let off the brakes. Immediately I started to slide backwards. It was a slow slide, and just putting my foot back on the brakes carefully stopped it, but that was a surprise to me. Does P only engage the rear brakes? And is that typical, being so close to sliding that a lack of four locked wheels would allow a slide to start? I'm a lightly experienced snow driver as I live in Southern California but grew up with snow. I have not seen this before but I also would not be likely to put an ICE in Park as readily as I put my Tesla in P.
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Slip on snow in Park
- Thread starter lotusland
- Start date
AlanSubie4Life
Efficiency Obsessed Member
Seems plausible that this could happen with the exact right slope angle and snow conditions. I think the parking brake is only on the rear wheels (you can tell by listening to where the sound comes from when you engage the parking brake...). Why not just push extra hard on the brake to engage hold mode? Certainly more convenient, and I assume that would hold all four wheels, though I have no way to test your scenario of course.
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Did you put it in Park (P) or hold your finger for a second to set the Parking Brake? I believe Park just disengages the motors, at least that is what the tech told me.
EVSteve
110% Solar Powered
Parking brake is only rear wheels and the motors have no physical catch in the gearbox when in park.
In the future press more firmly on the brake until (H) shows up on the dash. The car will hold the brakes for you until you depress the brake again or press the accelerator.
In the future press more firmly on the brake until (H) shows up on the dash. The car will hold the brakes for you until you depress the brake again or press the accelerator.
ibdb
Any excuse for a road trip
I saw a video last night someone shared from their doorbell of their driveway. It showed their pickup, initially parked unattended in their snowy driveway, start to slide down the driveway, into their yard and through a fence. It wasn't even that steep an incline. I can only imagine what that phone call to the insurance company sounded like.
Parking brakes typically only lock rear brakes in modern cars. The hill hold feature in the Tesla will lock all four, and might be a better choice in that situation.
Parking brakes typically only lock rear brakes in modern cars. The hill hold feature in the Tesla will lock all four, and might be a better choice in that situation.
eprosenx
Active Member
FWIW, this is how all RWD ICE vehicles are as well. I once parked my truck in my driveway on snow/ice and went out for a walk. When I got back I found my truck half way in the street.
After that, I always would leave it in 4wd (in gear of course as it was a manual) when conditions were icy. I just had to be careful to pull it out of 4wd before driving the next day if the snow/ice melted overnight.
That is interesting that it happened to your AWD M3. Indeed, sounds like there is no motor locking mechanism in the Tesla’s like there is in an automatic transmission. Good to know! I guess our M3’s rely solely on the parking brake when parked?
After that, I always would leave it in 4wd (in gear of course as it was a manual) when conditions were icy. I just had to be careful to pull it out of 4wd before driving the next day if the snow/ice melted overnight.
That is interesting that it happened to your AWD M3. Indeed, sounds like there is no motor locking mechanism in the Tesla’s like there is in an automatic transmission. Good to know! I guess our M3’s rely solely on the parking brake when parked?
I actually was in Hold when I was on the brakes, in fact I am sure there were periods where I had my foot off of the brakes and had Hold engaged. This process of waiting on the car (s) in front of us took some time. It was only when I went to "P" -- by pressing the stalk button a single time -- that I began to slide. I actually did this because I was going to exit the car and go try to help the motorist ahead. In other words I was going to "park" the car temporarily. Luckily I did not jump out quickly or I would have been in trouble. I have the stock 18" wheels and tires.
The manual seems pretty clear on how "Park" works, with the momentary touch that I used:
"When you finish driving, shift into Park by pressing the button on the end of the gear selector. The parking brake automatically engages and all systems keep operating."
Using "Hold" does not make sense to me. If you are parking the vehicle -- and especially getting out of it -- then you should use "Park". I had a car full of scouts so it is not likely I would have left the car one accelerator-press away from launching. I think the solution here is don't put it in Park on a steep snowy slope without other restraint.
"When you finish driving, shift into Park by pressing the button on the end of the gear selector. The parking brake automatically engages and all systems keep operating."
Using "Hold" does not make sense to me. If you are parking the vehicle -- and especially getting out of it -- then you should use "Park". I had a car full of scouts so it is not likely I would have left the car one accelerator-press away from launching. I think the solution here is don't put it in Park on a steep snowy slope without other restraint.
C141medic
Active Member
eprosenx
Active Member
FWIW, I think if you open the drivers door (or maybe it is keyed on when you get out of the drivers seat?) it will automatically put the car in park if I am not mistaken. I wonder if you are in "hold" mode and it decided to shift to park if that releases the front brakes (which in this situation could cause you to slide down the hill).
The fact that the car goes from four wheels having brakes applied to just two when shifting into park is unfortunate. In most vehicles (that are say front wheel drive and automatic transmission), when you put it in park and put on the parking brake, all four wheels are resisting movement.
Possibly (or likely), but I think the key here is that you are going from all four wheels having brake force applied to only two of them having brake force applied.
AlanSubie4Life
Efficiency Obsessed Member
Yeah, it is a bit different than what would happen in many cars, which is probably why it was surprising to the OP. I wonder how much standby power it would take to just engage hold mode (definitely just the brakes, not using the motors to hold the vehicle, according to owners manual) using the brake system, while parked?
Seems like this is an opportunity for Tesla to use that neural net when your car starts moving, when you're not present. They should be able to detect motion and at least engage the hold mode to try to stop it. Or maybe it can just wake itself up and summon itself back to its original location.
What could go wrong?
davedavedave
Member
C141medic
Active Member
I had this happen to me last week. I had the door ajar and put car in reverse backing out of my garage. After a few feet the car automatically placed itself in park and I got a warning message on screen to the effect that the parking brake was applied to prevent roll away. Scared the hell out of me, thought I hit something. I won’t be doing that again.
Not very typical, but possible, however improbable. Conditions were perfect for the coefficient of sliding friction of two tires locked and two rolling to cross the threshold and stop the car from sliding when you pressed the brakes stopping the front tires. To happen on that snow at the exact angle you were parked with the exact weight of your vehicle and its passengers combined.
That’s some kind of science experiment, Congratulations!
I put the car in P before opening the door, just a matter of habit. I would never exit the car in H even if it was possible. As soon as I pressed P -- and took my foot off the brake, where I -think- it had been sitting -- the car slid. As I said I was on and off the brake pedal but was in H for sure. I don't think there is a mystery as to the mechanism, it's as Eriamjh1138 posits, having two wheels instead of four provided less friction. The car is very heavy so on steeper slopes this is probably not even going to be that rare.
I'm on the stock 18" wheels and tires, whatever comes with the P3D-. Regarding ice under the snow, it's possible but the snow itself was very slippery. Every 2WD was having issues as the road got steeper. I did not see any crashes but I saw a lot of sliding cars. Below is a photo of the parking space I was headed towards. That's my buddy's car on the left, we took a space that had one truck in it when we arrived.
I'm on the stock 18" wheels and tires, whatever comes with the P3D-. Regarding ice under the snow, it's possible but the snow itself was very slippery. Every 2WD was having issues as the road got steeper. I did not see any crashes but I saw a lot of sliding cars. Below is a photo of the parking space I was headed towards. That's my buddy's car on the left, we took a space that had one truck in it when we arrived.
C141medic
Active Member
chibi_kurochan
Member
another way to Engage the Parking brake, Press and Hold the Park button for a few seconds to manually apply the parking brake.
Tho the manual also warns about the traction in snow while on park, especially without winter tires.
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