[harshaw]

I experienced a curious event this morning. In the northeast we just had a big snowstorm. This morning I cleaned off my driveway with the snowblower and, as it happens, there is some amount of slush / snow left on the driveway. My driveway slopes up out of garage to the street. I moved my Ioniq5 out of the garage and parked it on the slope of the driveway.

When I moved the car onto the driveway - I put it in a park and the car just sat there. I turned off the car and started to get out - it started sliding down my driveway towards my garage! I quickly got back in the car. Luckily the slope isn't that bad that it was going to hit my garage or house. I tried the experiment again. I drove up the driveway a little bit, put the car in park, and put on the emergency brake. When I turned off the car - again - the car slid down the driveway.

My only thought is that the car was idling every so slightly, and when the car was turned off, the pressure against the wheels went away and the car slid down the driveway.

 

[dundeeyank]

My guess is warm tires melted the remaining snow and the slide began. Darn warm garage.

 

[msandman1943]

I had a similar experience driving a 1961 VW Beetle up an icy slope. At a certain point the car stopped, the wheels spun a bit, and then it started to slide backwards down the hill, with the car still in first gear and the wheels rotating forward. I'm sure your driveway wasn't as steep, but an Ioniq 5 weighs about 2.5 times what that Beetle weighed, and gravity is an immutable force.

 

[KiwiME]

Well, an EV doesn't really "idle" but I would imagine that the parking pawl is on the same axle as the EPB, so the front wheels will be free to turn when you release the foot brake. On my FWD Kona the EPB is on the rear so all wheels are locked.

 

[harshaw]

Not sure if the wheels turned or the car slid.

 

[rbdavis808]

Not sure if the wheels turned or the car slid.

I was wondering about this. Huge difference, of course -- if the car slid with the wheels locked, i.e., not rolling free, then it's really got absolutely nothing to do with any failure on the part of the car. Conversely, if the wheels were rolling free then this is a car and/or operator error that is completely independent of the weather, and you would be at risk parking on a hill under any conditions whatsoever. There was a parking brake recall many months ago, but no car made since mid-22 should be subject to it AFAIK.

Did the slide only begin exactly or shortly after you got out, i.e., removed your own body weight from the equation?

 

[KiwiME]

I confirmed from the docs that both the SBW (parking pawl) and EPB (electronic parking brake) are on the rear axle, leaving the front wheels free to rotate. So the rear wheels had to hold the entire weight of the car, which clearly they couldn't.

... I would imagine that the parking pawl is on the same axle as the EPB, so the front wheels will be free to turn when you release the foot brake. On my FWD Kona the EPB is on the rear so all wheels are locked.

 

[Pixelated]

I confirmed from the docs that both the SBW (parking pawl) and EPB (electronic parking brake) are on the rear axle, leaving the front wheels free to rotate. So the rear wheels had to hold the entire weight of the car, which clearly they couldn't.

Can you link to the source? That is interesting. Since the front and rear motors are not physically connected, and they only installed one parking prawl, then that scenario tracks. Is there a reason why the prawl isn't on the front since the parking brake is on the rear?

 

[rbdavis808]

I confirmed from the docs that both the SBW (parking pawl) and EPB (electronic parking brake) are on the rear axle, leaving the front wheels free to rotate.

Can anyone explain to me what is the difference in physical (or other, e.g., magnetic) mechanism between the 'regular' Park mode on I5, and what happens when you engage the parking brake? Is one stronger than the other, either generally or under specific conditions?

I've never been a motorhead, but I always understood that Park gear on an ICE actually engaged the transmission somehow with mighty toothed cogwheel thingies or some such to hold a car stationary, while the parking brake was a much weaker friction device of some sort that clamped onto the axle or elsewhere but could easily be defeated by putting the car into drive and just driving away. (These notions may be entirely inaccurate.) I assume an EV Park gear must be quite different due to the lack of a transmission.

 

[KiwiME]

OP did not indicate an AWD model but I re-checked the docs and there is no parking pawl on the front drive unit, only a (drive) disconnect actuator, so AWD or not doesn't matter. It's totally obvious to me that with only the rear wheels locked there was not sufficient grip to hold the car on the icy slope. It's quite dangerous really so don't park there in those conditions!

... Is one stronger than the other, either generally or under specific conditions?
I assume an EV Park gear must be quite different due to the lack of a transmission.

They're both supposed to stop the (rear in this case) wheels from turning but the brake could probably be overcome with enough force. The parking pawl works identically to that in an ICE automatic transmission. This is the one in the I5, it engages a toothed wheel similar to the one shown in the next photo (ignore the yellow arrow).

 

[rbdavis808]

Thanks for that, @KiwiME!

Been googling parking pawl for the last hour, just learned that I've been parking wrong for over 50 years! Oops. Will be checking the I5 manual carefully on this point.

So, there is nothing to lock the front wheels from moving on I5, RWD or AWD? And if the Park button on the shifter stalk is engaging a pawl, then any idea what is the actual braking mechanism for the EPB?

 

[rbdavis808]

Been googling parking pawl for the last hour, just learned that I've been parking wrong for over 50 years! Oops. Will be checking the I5 manual carefully on this point.

Hah, the I5 manual says to do the opposite of everything I just read on the google about parking. It says to shift to Park first and then apply the EPB. I have not been parking wrong for 50 years, I've just been practicing for I5 ownership!

 

[Phasetaylor]

gonna take a guess and say the car was running bridgestone blizzak snow tires lol

 

[Neptune]

If only the rear wheels lock, then why does everyone use a flatbed to tow this car when the ICCU fails?

 

[Pontanius Black]

If only the rear wheels lock, then why does everyone use a flatbed to tow this car when the ICCU fails?

Because they don't know if the front motor has disengaged or not, is my guess.

 

[Theblackstig]

I experienced a curious event this morning. In the northeast we just had a big snowstorm. This morning I cleaned off my driveway with the snowblower and, as it happens, there is some amount of slush / snow left on the driveway. My driveway slopes up out of garage to the street. I moved my Ioniq5 out of the garage and parked it on the slope of the driveway.

When I moved the car onto the driveway - I put it in a park and the car just sat there. I turned off the car and started to get out - it started sliding down my driveway towards my garage! I quickly got back in the car. Luckily the slope isn't that bad that it was going to hit my garage or house. I tried the experiment again. I drove up the driveway a little bit, put the car in park, and put on the emergency brake. When I turned off the car - again - the car slid down the driveway.

My only thought is that the car was idling every so slightly, and when the car was turned off, the pressure against the wheels went away and the car slid down the driveway.

Used to have a similar issues except my garage was at the top of the hill. I used this for the rare time's I parked outside. https://a.co/d/7TpFGuw

 

[theSeb]

Can anyone explain to me what is the difference in physical (or other, e.g., magnetic) mechanism between the 'regular' Park mode on I5, and what happens when you engage the parking brake? Is one stronger than the other, either generally or under specific conditions?

I've never been a motorhead, but I always understood that Park gear on an ICE actually engaged the transmission somehow with mighty toothed cogwheel thingies or some such to hold a car stationary, while the parking brake was a much weaker friction device of some sort that clamped onto the axle or elsewhere but could easily be defeated by putting the car into drive and just driving away. (These notions may be entirely inaccurate.) I assume an EV Park gear must be quite different due to the lack of a transmission.

Engaging the parking brake allows one to do cool handbrake turns whether going forwards or backwards.

 

[stomish]

Engaging the parking brake allows one to do cool handbrake turns whether going forwards or backwards.

Not with an EPB though!

 

[KiwiME]

It says to shift to Park first and then apply the EPB.

I doubt they meant that to be a hard and fast rule and I don't see that it matters in most cases because you will generally be holding the car still with the foot brake until both are applied. If you are parking on a steep slope I'd suggest you try applying the EPB first, remove foot from brake pedal then select Park. The idea is avoid having the car move slightly after applying the pawl, loading it and then having it make a loud clunk noise when you next take it out of Park.

If only the rear wheels lock, then why does everyone use a flatbed to tow this car when the ICCU fails?

Not wanting to go down another rabbit hole but that's because you don't want to spin either motor with the car powered off. Being in Neutral does not disconnect the rear motor from the wheels and it can generate high voltages at-speed that may be harmful - at least in theory.

For what it's worth Munro Associates (who tear down EVs for analysis) pointed out that the Audi e-Tron Q4 has fitting points likely intended for installing a front EPB. It already has one at the rear of course.

 

[rbdavis808]

I doubt they meant that to be a hard and fast rule and I don't see that it matters in most cases because you will generally be holding the car still with the foot brake until both are applied. If you are parking on a steep slope I'd suggest you try applying the EPB first, remove foot from brake pedal then select Park. The idea is avoid having the car move slightly after applying the pawl, loading it and then having it make a loud clunk noise when you next take it out of Park.

Your advice here seems to be what pretty much every web source recommends for cars in general. Odd that the I5 manual specifically states the opposite order (i.e., EPB last) -- who knows if there's an actual good reason behind this or if it's just careless writing?

After another two hours googling main brake and EPB videos and writeups, I guess my only remaining curiosity is whether or not the I5 EPB is doing its braking via the very same disc brake pads as the main brake system. Apparently the same pads, disc or drum, are activated by both the main and parking brakes in some but not all cars via different activation mechanisms? If they are, then I can see (exactly as you said) that it really makes no difference whether you hit the EPB before or after entering Park mode assuming that you've got your foot on the main brake pedal throughout the whole procedure.