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Very disappointing snow experience

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Glad you're okay Rob! To add to the excitement on the drive back from Mt. Bachelor to Bend it's difficult to know if you're going to have regen or not. A message pops up and disappears every once in a while "Acceleration and regen braking reduced until battery warms up" leaving a tiny little indicator on the dash but without looking it's a surprise, am I going to have regen or not when I let off the accelerator? I really wish there was an option to turn regen completely off.

Screenshot 2023-01-16 at 10.51.16 AM.png
Yes, I see this a couple of times on every return trip.
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MountainBikeDude

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Hi all,
I think that Snow tires (studs) are a must have. My wife and I got caught in an ice storm and the rivian went off road twice. The second time was on a flat section of road. I have the all terrain tires and was in snow mode going about 15mph. I let off the accelerator lightly and the truck slide sideways into a ditch. I think that if there were better tires this might not have happened, but I agree that the programming on the 4 motor was the main cause- regen tried to kick in and that was the end.
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Shitty, any damage to the passenger side?
 

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Yes, I see this a couple of times on every return trip.
This happens to me, as well. It pops up just as I start heading downhill after Meissner Nordic. I'm pretty sure that I hear a chime when the notification appears. I'll try to remember to listen for it when I'm on my way back from skiing tomorrow.
 

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Better tires help, yes. For exactly the reason you indicate, it increases traction. However, as discussed adnausiem, the lack of mechanical advantage in the Quad-motor design remains a handicap for the vehicle, so studs are almost a must for ice, whereas just good winter tires on the Model Y keep in quite manerly in the same situation.
Please explain how the quad-motor design creates problems where a mechanical differential creates the solution. From these descriptions it sounds like the regen is creating the problem. Our natural reaction to loss of control is to remove our foot from the throttle, but this creates a locked wheel on slippery surfaces and thus loss of control. The fix would seem to be detecting slippage and allowing more freedom for wheels to spin as needed to gain control of the vehicle, right?

I am not saying the current setup is good and these low traction issues definitely sound scary. It just seems to be more of a programming issue than a purely mechanical one. Why couldn't the software use the quad setup to mimic either an open OR locked differential anytime it was warranted?
 

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This happens to me, as well. It pops up just as I start heading downhill after Meissner Nordic. I'm pretty sure that I hear a chime when the notification appears. I'll try to remember to listen for it when I'm on my way back from skiing tomorrow.
Yes, I think there is a chime. But it doesn't let you know when regen returns other than maybe that tiny little snowflake above the range disappears. For me it happens several times on the drive back to Bend.
 

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This happens to me, as well. It pops up just as I start heading downhill after Meissner Nordic. I'm pretty sure that I hear a chime when the notification appears. I'll try to remember to listen for it when I'm on my way back from skiing tomorrow.
Mine chimes
 

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Please explain how the quad-motor design creates problems where a mechanical differential creates the solution. From these descriptions it sounds like the regen is creating the problem. Our natural reaction to loss of control is to remove our foot from the throttle, but this creates a locked wheel on slippery surfaces and thus loss of control. The fix would seem to be detecting slippage and allowing more freedom for wheels to spin as needed to gain control of the vehicle, right?

I am not saying the current setup is good and these low traction issues definitely sound scary. It just seems to be more of a programming issue than a purely mechanical one. Why couldn't the software use the quad setup to mimic either an open OR locked differential anytime it was warranted?
The mechanics of why this happens has been explained in exquisite detail in prior posts. Not sure what else to tell you. Without a physical connection along the axle, it is programming that is trying to overcome physics. An open differential will always allow the wheel with the lease traction to slip, allowing the wheel with the most traction to remain static on the ground. That static wheel is all that is holding the vehicle from going sideways. There is nothing special about a live axle that makes this happen, it is basic physics. That static wheel on each axle provides for the greatest side to side stability possible under the slippery of conditions. This is precisely why you do not want to use differential lockers or even limited slip if possible when you encounter this type of condition.

Again, as many people have described time and again, a quad motor design has no physical connection along the axle. With no physical connection, and lacking the natural physics of a live axle, the software has to compensate when the wheel slips. Since it has no way to know the surface traction dynamics in advance, the wheel must actually slip for the software to compensate. The millisecond that happens, the vehicle starts moving sideways and in extreme situations you're going to be in the ditch.
 

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The same would apply to engine braking/regen with an open diff? Like the wheel with the least traction would skid first?
No, it would not skid "first", it would skid "period". The wheel with the most traction never slips due to torque. When engine braking with an open diff, the differential will allow the side with lease traction to slide, but because it is a natural, mechanical torque vectoring device it will always allow the tire with the most traction to continue rolling and not slide; maintaining the vehicle's lateral stability until such time as there are no wheels that have enough traction to overcome inertia/weight (like going too fast around a corner).

Let me see if this helps people understand. It is well known that with an open differential there is always a "dead wheel," right? This "dead wheel" rolls along the road, never slipping, because torque is vectored to the other side: whether accelerating, or engine braking. Do you want an example of why the quad motor is so tough in these situations? Hit the brakes. When the the brakes are engaged, all your wheels have stopping torque, they all slip, and you go out of control. We have been taught our whole lives to let up the brakes when this happens, then the dead wheel on the differential will spin freely again and you are usually able to regain lateral control.

This never happens in the quad motor design. There is never truly a dead wheel, because of the very design of the powertrain. In very slippery situations there is some torque present on all four wheels, and it acts very much like an old school truck with the brakes locked and away you go.
 
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TAZ

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In conserve mode the rear wheels are "dead". Since this is possible than it seems to be a programming issue and not a quad motor design. Regardless, in ice that bad only snow with studded tires will help. I'm having snows installed tomorrow after driving in a few storms this year on AT's.

There needs to be an option to turn regen completely off would fix a lot of this.
 

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In conserve mode the rear wheels are "dead". Since this is possible than it seems to be a programming issue and not a quad motor design. Regardless, in ice that bad only snow with studded tires will help. I'm having snows installed tomorrow after driving in a few storms this year on AT's.

There needs to be an option to turn regen completely off would fix a lot of this.
Well, no lol.

Conserve Mode unhooks the rear axles from the motors. Since this is a physical action, it really has no bearing at all with what is "possible" with programing, but lets follow your thought process a step farther.

In Conserve mode the vehicle would indeed have "dead" wheels in the back, and would indeed retain enhanced lateral control in the rear in this circumstance; the rears are free-wheeling. The vehicle is essentially a front-drive Honda now, _except_ with no physical torque vectoring in the front you are likely to lose grip on both front wheels.

YIKES!!!!!!!!!!!! I sure would hate to be at the wheel of that vehicle...

But, continuing to follow your train of thought, if you physically disconnected one front and one rear axle (no, not a reasonable solution), you would have an almost equal standing with an open diff... except you would not.

A live axle will let the dead wheel roll (maintaining lateral stability) until it suddenly becomes the wheel with less traction and then it switches. Instantly. There is no sensor, no computer algorithm, no calculation. It is physics. Let me see if this helps:

With a live axle Both wheels on the axle are never slipping at the same time unless F/r=0.

Period.

This is impossible to replicate without that physical connection between the wheels.

Period!


The more testing we do, the more convinced I am that this will be my last quad-motor vehicle for this reason. It is a handicap that will never be completely overcome. Good, studded tires masks the problem, but it does not eliminate it.

Finally, lets examine why attempts to turn off regen completely did not fix this. With regen set to zero, lateral stability while under power is not affected; it is still the same problem we started with. But now, with no regen, we have a different problem; STOPPING!!! With no regen or compression braking, all you are left with is your 4-wheel disc brakes to scrub off speed.

What happens when you apply brakes to all your wheels on ice? Yes, you lose control. How do you regain control? Let off the brakes and let your live axles find you any traction possible to get a wheel or two turning again, so you can restore lateral stability (get going straight).

If you have no regen/compression breaking connected to such a device, you have no way of restoring lateral control.

It really really is that simple.
 

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sgec

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No, it would not skid "first", it would skid "period". The wheel with the most traction never slips due to torque. When engine braking with an open diff, the differential will allow the side with lease traction to slide, but because it is a natural, mechanical torque vectoring device it will always allow the tire with the most traction to continue rolling and not slide; maintaining the vehicle's lateral stability until such time as there are no wheels that have enough traction to overcome inertia/weight (like going too fast around a corner).

Let me see if this helps people understand. It is well known that with an open differential there is always a "dead wheel," right? This "dead wheel" rolls along the road, never slipping, because torque is vectored to the other side: whether accelerating, or engine braking. Do you want an example of why the quad motor is so tough in these situations? Hit the brakes. When the the brakes are engaged, all your wheels have stopping torque, they all slip, and you go out of control. We have been taught our whole lives to let up the brakes when this happens, then the dead wheel on the differential will spin freely again and you are usually able to regain lateral control.

This never happens in the quad motor design. There is never truly a dead wheel, because of the very design of the powertrain. In very slippery situations there is some torque present on all four wheels, and it acts very much like an old school truck with the brakes locked and away you go.
I have learned a lot from your explanations, thank you! I've done some experimenting with the Rivian driving on extremely slippery surfaces and it's disconcerting to say the least to have the whole vehicle slide due to even mild regen and the the camber of the road. At low speeds I've found shifting into neutral and feathering the brakes helps in some situations. I wish there was a way to turn regen off completely.
 

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R1T on 22" all-season tires: I live in the Utah mountains and we have 3+ feet of snow on the ground, so I have driven up and down the mountain passes to the ski resort 12 mins away many times, with little issue. However, today we headed up to Snowbird as the snow was falling hard. It had turned from rain to slush to snow and was admittedly slicker than normal, but as we progressed up a steeper incline, I couldn't keep the truck from sliding sideways as the tires slipped. The truck slowed to 8 to 9 mph and wouldn't go faster. I couldn't even make the tires spin if I wanted to. It was like it went into a turtle mode but had no indicators. I decided to put it in Sand mode as none of the other modes seemed to help, as I hadn't updated the software to have access to a Snow mode yet. I barely made it to snowbird. Yes, i don't have dedicated snow tires and I am sure I will get a lot of "duh" comments saying they aren't meant for snow and they are also 22" but it is disappointing performance regardless. Unlike a traditional 4x4 (5 Jeep Grand Cherokees in our family over the years), there wasn't that clear sense of the 4x4 doing some extra work despite poor tire grip.

Time to bite the bullet for snow tires.
I had the exact opposite experience. I drove the truck up to SnowBowl after a night of 12 inches of snow and actively snowing and 30 degrees and never lost traction for even 1 second on the trip up and down. Granted I had snow mode on but I had street tires and it performed flawlessly. The mountain was under 4x4 or chain advisory at the time.
It was powerful peace of mind with our family of 4 on our way to the slopes.
 

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I have learned a lot from your explanations, thank you! I've done some experimenting with the Rivian driving on extremely slippery surfaces and it's disconcerting to say the least to have the whole vehicle slide due to even mild regen and the the camber of the road. At low speeds I've found shifting into neutral and feathering the brakes helps in some situations. I wish there was a way to turn regen off completely.
Glad to help, we continue to test and provide feedback to the manufacturer.
 

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I had the exact opposite experience. I drove the truck up to SnowBowl after a night of 12 inches of snow and actively snowing and 30 degrees and never lost traction for even 1 second on the trip up and down. Granted I had snow mode on but I had street tires and it performed flawlessly. The mountain was under 4x4 or chain advisory at the time.
It was powerful peace of mind with our family of 4 on our way to the slopes.
Before you get overconfident and get yourself in trouble, understand the dynamics. Problems start the minute the vehicle does start to lose traction. If you're not losing traction, you're obviously not having any problems.
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