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Slipping on inclines while in park

Spaceosaurus

Member
Aug 26, 2020
67
95
Bellevue, WA
On two occasions now I've put my Model Y in park on an incline and it begins rolling. It seems the back tires lock up but the front two keep rolling. This has only happened on slippery surfaces when the car is in park, and even with very good traction tires (X-ICE Snow). If I keep my foot on the brake pedal the wheels don't roll and it doesn't slide.

Does anyone know what's going on? This isn't something I've seen on my other cars, when it's in park the tires won't roll (even without engaging the parking brake).
 

brkaus

Well-Known Member
Jul 8, 2014
8,058
6,557
Austin, TX
The electric brakes are on the rear tires. All 4 wheels do not get locked except when you are holding down the hydraulic brakes (pedal).

An automatic transmission car will only lock the drive wheels when in park.

Emergency brakes are typically on the rear.

Your car is sliding, not rolling.
 
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Spaceosaurus

Member
Aug 26, 2020
67
95
Bellevue, WA
The electric brakes are on the rear tires. All 4 wheels do not get locked except when you are holding down the hydraulic brakes (pedal).

An automatic transmission car will only lock the drive wheels when in park.

Emergency brakes are typically on the rear.

Your car is sliding, not rolling.

Interesting! Would manually engaging the parking brake (e-brake) solve this? I'll admit I don't know what the e-brake does on these cars given your description.
 

frankvb

Supporting Member
Supporting Member
Feb 29, 2020
920
559
San Diego, CA
Would a long hold of the 'park' button make a difference? Not sure to be honest what's the difference between just putting the gear selector in park as opposed to that. Just selecting park seems to put on the brakes on the rear wheels (judging by the sound).
 
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E_R_N

Member
Jun 16, 2020
155
137
Vancouver
Interesting! Would manually engaging the parking brake (e-brake) solve this? I'll admit I don't know what the e-brake does on these cars given your description.
I am going to assume the tires are sliding and not turning. You are probably used to having a front wheel drive car where you put it in park and the front lock then you engage the park break so you have front and rear tires holding you back. My diesel Dodge Ram will slide out of my driveway if I park it wrong. Park so the front is pointing uphill and clean the parking area so it isnt covered in wet leaves. That’s the fact of life for most rear wheel drive vehicles. Pushing the park brake button is no different then getting out of the car.
 

brkaus

Well-Known Member
Jul 8, 2014
8,058
6,557
Austin, TX
I believe the manual states that P automatically applies the e-brake. So functionally it’s the same.

Not sure why this would be different in regard to sliding from other cars. Perhaps you had a front wheel drive - in park would lock the front and the parking brake would lock the back.

I don’t think I've ever had a car that would lock the front via parking brake. Just based on experience jacking cars up and changing tires. Trucks, BMWs, mustangs.

The weight distribution might be different?

Place sand (kitty litter) under the rear tires?
 

Daks

Member
Oct 21, 2020
135
93
Anchorage, AK USA
My pickups would do this. Press the brake, no sliding, release and down the driveway we go... I had a work around, which was leave it locked into 4WD. One time I had to get tie straps and tie it to a tree as ALL 4 wheels locked up were sliding down the driveway. I salted my driveway and put a good amount under the tires and problem solved.

Obvioulsy if you are out parking in a public lot, you'd want to look for a flat spot of the parking lot... I only seem to have this issue in residential driveways (including my own).
 

jcanoe

Active Member
Oct 2, 2020
3,275
3,261
Maryland
This is a known limitation of Tesla vehicles when parking on even a slight incline covered in snow or ice. There is no transmission parking gear to lock up the drive wheels, the electric parking brake only engages on the rear wheels. The front wheels are always free to roll. If you park on a snow covered incline the weight of the vehicle will compress the snow into ice and the rear wheels can start sliding almost immediately after you park.

Here is a video of a Model 3 sliding down a driveway in this exact scenario.

There is supposedly a fix that the Service Center can apply that will cause the front brakes to also engage when the eBrake activates. Not sure if this fix can be applied to all model Tesla vehicles. It will help but the issue remains. Don't park on a snow or ice covered incline. When parking on the street on a hill you must turn your front wheels towards the curb when pointed down hill or turn the front wheels out away from the curb if the vehicle is pointed up hill. This is standard street parking procedure in cities such as SF.
 
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brkaus

Well-Known Member
Jul 8, 2014
8,058
6,557
Austin, TX
This is a known limitation of Tesla vehicles when parking on even a slight incline covered in snow or ice. There is no transmission parking gear to lock up the drive wheels, the electric parking brake only engages on the rear wheels. The front wheels are always free to roll. If you park on a snow covered incline the weight of the vehicle will compress the snow into ice and the rear wheels can start sliding almost immediately after you park.

like most rear wheel drive cars?
 

jcanoe

Active Member
Oct 2, 2020
3,275
3,261
Maryland
like most rear wheel drive cars?
True that. Somehow in over 40 years of driving front wheel drive and rear wheel drive vehicles (Detroit iron) I never once recall any caution against parking on an incline. In Driver's Education they taught the students to always turn the steering wheel when parked on a hill.
 
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LevelHeaded

Member
Dec 31, 2019
530
391
Salt Lake City, UT, USA
True that. Somehow in over 40 years of driving front wheel drive and rear wheel drive vehicles (Detroit iron) I never once recall any caution against parking on an incline. In Driver's Education they taught the students to always turn the steering wheel when parked on a hill.
Maybe a dumb question as a new-to-snowy-residence person, but if the tires are indeed all sliding due to lack of traction rather than rolling, why would aiming them in a direction prevent it?
 

DaveORD

Member
Mar 12, 2020
733
641
Chicagoland
Maybe a dumb question as a new-to-snowy-residence person, but if the tires are indeed all sliding due to lack of traction rather than rolling, why would aiming them in a direction prevent it?

Ever go skiing? Angling the front tires may not stop the car from sliding but it should make it turn to only slide so much and not go all the way down the driveway into the street. The turned tires should be like leaning on skis to turn, at least in theory it should but it may not turn that quick.
 

jcanoe

Active Member
Oct 2, 2020
3,275
3,261
Maryland
Maybe a dumb question as a new-to-snowy-residence person, but if the tires are indeed all sliding due to lack of traction rather than rolling, why would aiming them in a direction prevent it?
Not a dumb question at all. When you park any vehicle on a hill you should turn your front wheels in the direction of the curb or shoulder if you are facing down hill, otherwise point the front wheels away from the curb if you are facing up hill. That way if the automatic transmission's parking gear (this is just a small pawl that prevents the wheels from turning) or the vehicle's parking brake should fail, or in the case of parking a manual transmission RWD vehicle (for example a Ford Mustang) or any Tesla vehicle on ice should the rear wheels break free, the worst that will probably happen is the vehicle will roll or slide a few feet until the innermost front tire contacts the curb. This is the correct way to park on a hill as taught in Driver's Education classes everywhere. In cities with many hills such as SF you will get a ticket if you do not properly set your innermost front wheel/tire against the curb when parked so the vehicle cannot roll. Of course your vehicle could also slide into the vehicle parked directly behind your vehicle but your vehicle will not roll down the hill.

On a sloped driveway covered in snow or ice, should the tires break free, there is nothing to prevent the vehicle from sliding down the driveway.
 
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noshadow

Member
Mar 18, 2020
444
292
Berkeley, CA
I used to put my AWD into first gear along with a parking brake when I was on a steep hill (obv. a manual car). It was awesome, especially on steep driveways without a curb to brace the front wheels on. Still not 100% better, but at least I got 2 more wheels holding still.
 

jcanoe

Active Member
Oct 2, 2020
3,275
3,261
Maryland
I used to put my AWD into first gear along with a parking brake when I was on a steep hill (obv. a manual car). It was awesome, especially on steep driveways without a curb to brace the front wheels on. Still not 100% better, but at least I got 2 more wheels holding still.
If pointed down hill I was taught to place a manual transmission vehicle in reverse gear, always set the parking brake. At one time I drove a manual transmission VW Rabbit, I got in the (bad) habit of leaving the Rabbit in gear when parked without setting the parking brake. I was living in an apartment; one morning as I was getting ready a neighbor knocked and asked me to move my car so he could leave. During the night the Rabbit somehow slipped out of gear and slowly rolled backwards across the parking lot until my Rabbit came to rest against the rear bumper of another vehicle. There was no visible damage to either vehicle but I was quite embarrassed. After that little incident I always set my parking brake.
 
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ZippyDC

Member
Dec 2, 2019
37
21
Nevada
As someone who took Driver's Ed in Florida, where there are neither hills nor snow, I can say it's not taught everywhere :D. Wish it was! This is good to know (and makes good sense).
Page 36 of FL driver handbook.
 

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Spaceosaurus

Member
Aug 26, 2020
67
95
Bellevue, WA
Page 36 of FL driver handbook.

Welp, guess you're going to have to reach out to Mr. Brooks from my 2004 high school driver's ed class! He clearly missed a page. Should've focused less on alligator dodging, seems like that module took a whole week!

All that said, since it seems like we're in the mood to be zealous internet comment crusaders, my situation was on a driveway, not a street, and thus all the talk of curbs is moot. That situation doesn't apply here, and isn't pertinent to the main question in the post.

But hey, who am I to spoil your fun!
 

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