Very disappointing snow experience

[DB-EV]

I just had them swapped at a local tire shop. Had to bring in the pucks for the lift but otherwise it was straightforward. Might consider a second set of wheels when there are more options.

Thank you sir. The pucks are pucks specific to the R1s for jacking?

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[R.I.P.]

Fair point. And essentially you are just turning off the VDC or traction control on your vehicle to stop it from intervening. I would argue that throttle control would be key with the Quad system, which should be better achieved by putting it into rock crawl mode no? It limits the vehicles speed to give you a longer gas pedal for more precise power modulation in those more off road, scaling a wall sideways instances.

As an old man, and one who has many decades of off-roading experience, I am often the one that has to swap seats to get one of the Rivians through tough spots. I can tell you that when it comes to super slippery surfaces, no amount of feathering the throttle helps. The vehicle attempts to provide torque to all Wheels, because it has no way of knowing in advance what the friction coefficient actually is. The result, I can tell you from many many hours of getting them through tough spots, is pure evil.

Again, snow mode has gone a long way toward helping this. And, yet, again, because the vehicle has no way of knowing just how slippery the surface is until it actually senses a slip, there's no way to completely cure it.

It actually puzzles me that some have a hard time grasping this concept, but there are certain situations where the sheer design of the differential gives you an advantage. My pre-order for a Rivian is for the dual motor model for exactly this reason. I am extremely happy with the way my model Y handles very slippery roads, and I want my rivian to do the same, with two motors and a differential, not super complicated algorithms trying to figure out how to manage all four motors.

Four motors blows the doors off the competition in a number of scenarios. But not all scenarios. Mark this thread to review it in a couple of years when there are a number of dual motor Rivians on the road, and I bet that in snowy/icy conditions, the dual motor Rivian owners feel more planted and secure. It is just the physics of how the technology works.

 

[Whyz]

The vehicle... has no way of knowing in advance what the friction coefficient actually is.

...yet, again, because the vehicle has no way of knowing just how slippery the surface is until it actually senses a slip...

How is this different from any other vehicle? What vehicle knows in advance what the coefficient of friction is?

 

[R.I.P.]

A few pieces of additional information to the "slippery surface" discussion.

I am an avid and active off-roader, and have been since the early 1970s. My current group consists of the requisite Yoda's, classic broncos, new broncos, modified pickups, you name it. My personal off-road rig is a highly modified TJ. I of course have full control of both differentials. I can run anything from wide open to fully locked and absolutely anything in between with magnetic clutches.

We have had a Rivian in our group for a number of months, and this past week have had a second one join us. As a senior member in the group and an avid EVr myself, I have become extremely familiar with how the Rivian's systems operate, both in theory and on the ground. More often than not I have assumed control of these trucks on difficult points in the trail when the drivers were afraid they were going to break something. I can tell you that they are an amazing vehicle, and when properly outfitted are about as unstoppable as any of the other rigs out here.

EXCEPT! When it comes to extremely slippery surfaces and any kind of off-camber situation. They just flat go sideways. So many designs out there, and each has its Achilles heel. Snow and ice is the Rivian's Achilles heel.

I can recreate the quad motors difficulty by dialing in some torque on my traction wheel on my Jeep. I too then go sideways instead of being able to hold my line. Not only is it pretty easy to figure out what is going on, but it is absurdly easy to demonstrate it in the real world, on the ground, with real vehicles, on real ice.

Moral of the story? If snow and ice are where you're often driving, get really good tires; maybe even studs.

OR, if yours is not built yet, consider the dual motor option.

 

[MountainBikeDude]

How is this different from any other vehicle? What vehicle knows in advance what the coefficient of friction is?

To his point of an instance of a lets say 30 degree incline, with the rivian traversing it laterally, an ICE non traction controlled setting would be marginally less likely to slide sideways due to the heavier lower side of the vehicle shoehorning the slope while the top side wheels coax the vehicle forward as they claw forward. On the rivian his point is that the wheels, all moving instantly, would immediately cause the truck to not only move forward, but also slip sideways in a low Mu situation before the vehicle can pull power away.

 

[R.I.P.]

How is this different from any other vehicle? What vehicle knows in advance what the coefficient of friction is?

Whew. I am not sure how else to put this to help you.

Okay, let me try this. Let's take my 20-year-old Jeep off-roader. Now, let's put this 20-year-old Jeep off-roader on an off-camber road that is iced over. Let's make sure that this off-camber iced over road is extremely slippery.

Now, let's take a traditional open differential, without any traction control or locking mechanisms in place. It is common knowledge that when you apply power to this type of system, only one wheel will spin. Why? It's an open differential. Torque will move to the side with the least resistance. The vehicle has no knowledge of how slippery the road is, and doesn't even know what "friction coefficient" means. It simply will spin the wheel with least resistance. Because of that, the opposite wheel does not slip, and will maintain its coefficient of friction to keep the vehicle from moving sideways. Once again, the vehicle has no way of knowing that the road is slippery, that is simply how the technology works.

A quad motor system has no connection between the wheels and does not share torque. For this reason, it must depend on sensors in each wheel to monitor torque, wheel speed and use traction control. It has no native torque vectoring the way a differential does. It must simulate torque vectoring based on a computer algorithm. Because of this, there is never really a dead wheel the way the common, old-fashioned differential has always worked.

The result? If torque is applied to both rear wheels, the rear will simply slip out. If you are in an off camber situation, you will move toward the ditch or the trees or whatever is downhill from you.

Does that help?

 

[Whyz]

To his point of an instance of a lets say 30 degree incline, with the rivian traversing it laterally, an ICE non traction controlled setting would be marginally less likely to slide sideways due to the heavier lower side of the vehicle shoehorning the slope while the top side wheels coax the vehicle forward as they claw forward. On the rivian his point is that the wheels, all moving instantly, would immediately cause the truck to not only move forward, but also slip sideways in a low Mu situation before the vehicle can pull power away.

ok thanks. I'm trying to thoroughly understand all of this because often visit family who live at the bottom of a steep and cambered hill. It's often very very icy. I'm not worried about sliding down the hill but rather sliding off to the side. If the Rivian has any issues with lateral movement then I need to be fully ready for that.

 

[Whyz]

Whew. I am not sure how else to put this to help you.

Okay, let me try this. Let's take my 20-year-old Jeep off-roader. Now, let's put this 20-year-old Jeep off-roader on an off-camber road that is iced over. Let's make sure that this off-camber iced over road is extremely slippery.

Now, let's take a traditional open differential, without any traction control or locking mechanisms in place. It is common knowledge that when you apply power to this type of system, only one wheel will spin. Why? It's an open differential. Torque will move to the side with the least resistance. The vehicle has no knowledge of how slippery the road is, and doesn't even know what "friction coefficient" means. It simply will spin the wheel with least resistance. Because of that, the opposite wheel does not slip, and will maintain its coefficient of friction to keep the vehicle from moving sideways. Once again, the vehicle has no way of knowing that the road is slippery, that is simply how the technology works.

A quad motor system has no connection between the wheels and does not share torque. For this reason, it must depend on sensors in each wheel to monitor torque, wheel speed and use traction control. It has no native torque vectoring the way a differential does. It must simulate torque vectoring based on a computer algorithm. Because of this, there is never really a dead wheel the way the common, old-fashioned differential has always worked.

The result? If torque is applied to both rear wheels, the rear will simply slip out. If you are in an off camber situation, you will move toward the ditch or the trees or whatever is downhill from you.

Does that help?

that does help, thank you.

i would assume that the rivian's algorithms make hundreds/thousands of measurements per second and could react quickly enough to this and simulate something like an open diff. But I understand thats not happening with current settings.

 

[R.I.P.]

To his point of an instance of a lets say 30 degree incline, with the rivian traversing it laterally, an ICE non traction controlled setting would be marginally less likely to slide sideways due to the heavier lower side of the vehicle shoehorning the slope while the top side wheels coax the vehicle forward as they claw forward. On the rivian his point is that the wheels, all moving instantly, would immediately cause the truck to not only move forward, but also slip sideways in a low Mu situation before the vehicle can pull power away.

Yes, except it's not an ICE or an EV thing. It is a differential thing. My Tesla has two motors connected to differentials. It is very mannerly in slippery situations where my buddy's Rivian is not; because it has actual living mechanical torque vectoring. Exactly the way it will be in Rivian's dual motor trucks.

Did I mention I'm super excited that Rivian is now offering this system? The dual motor will not be for everybody, but for my particular application, and I would argue for those that frequently encounter snow and ice, it will offer a more stable platform.

 

[R.I.P.]

ok thanks. I'm trying to thoroughly understand all of this because often visit family who live at the bottom of a steep and cambered hill. It's often very very icy. I'm not worried about sliding down the hill but rather sliding off to the side. If the Rivian has any issues with lateral movement then I need to be fully ready for that.

So, it is exactly to your situation that I am speaking to. For your situation, if you do not already have your Rivian, I would argue that a dual motor version of the truck will perform better in that particular situation then the quad motor is able to.

I want to circle back to the fact that the latest snow mode update helps tremendously in very low friction situations. I expect that will get even better still over time. However, due to the physical difference in the way traction is applied, it may never actually reach the point of being on par with a good old differential in that specific situation.

 

[Dark-Fx]

Yes, except it's not an ICE or an EV thing. It is a differential thing. My Tesla has two motors connected to differentials. It is very mannerly in slippery situations where my buddy's Rivian is not; because it has actual living mechanical torque vectoring. Exactly the way it will be in Rivian's dual motor trucks.

Did I mention I'm super excited that Rivian is now offering this system? The dual motor will not be for everybody, but for my particular application, and I would argue for those that frequently encounter snow and ice, it will offer a more stable platform.

You should make friends with someone that has a Hummer EV, I've always thought slippery off-camber stuff is where crab walk could be insanely useful, but we don't have terrain around here at all that would benefit so I never got a chance to test.

 

[R.I.P.]

You should make friends with someone that has a Hummer EV, I've always thought slippery off-camber stuff is where crab walk could be insanely useful, but we don't have terrain around here at all that would benefit so I never got a chance to test.

I am super looking forward to being able to play with one of those! They are kind of large for our Oregon trail systems, but hey, as long as I'm not the one fitting the repair bill lol.

The Hummer should have similar struggles on extremely slippery surfaces, at least in the rear. The front has a differential, so potentially, unlocked, it could anchor the vehicle while the other three wheels spin. Because the rear has a motor on each wheel, it's going to have the same Achilles heel.

I confess I do have a reservation for one, but will most likely not capitalize on it if my Rivian gets here first.

 

[BrentInCO]

As an old man, and one who has many decades of off-roading experience, I am often the one that has to swap seats to get one of the Rivians through tough spots. I can tell you that when it comes to super slippery surfaces, no amount of feathering the throttle helps. The vehicle attempts to provide torque to all Wheels, because it has no way of knowing in advance what the friction coefficient actually is. The result, I can tell you from many many hours of getting them through tough spots, is pure evil.

Again, snow mode has gone a long way toward helping this. And, yet, again, because the vehicle has no way of knowing just how slippery the surface is until it actually senses a slip, there's no way to completely cure it.

It actually puzzles me that some have a hard time grasping this concept, but there are certain situations where the sheer design of the differential gives you an advantage. My pre-order for a Rivian is for the dual motor model for exactly this reason. I am extremely happy with the way my model Y handles very slippery roads, and I want my rivian to do the same, with two motors and a differential, not super complicated algorithms trying to figure out how to manage all four motors.

Four motors blows the doors off the competition in a number of scenarios. But not all scenarios. Mark this thread to review it in a couple of years when there are a number of dual motor Rivians on the road, and I bet that in snowy/icy conditions, the dual motor Rivian owners feel more planted and secure. It is just the physics of how the technology works.

I don’t get why Rivian won’t simply employ a differential lock, but watch the Rivian Stories video on YouTube from a week ago … the Rivian dual motor engineer said there no plan to consider a differential.

Or, have you seen that video, and you’re aware / comfortable there will be no differential, because the dual motor torque vectoring will be better than the quad motor’s?

 

[bjcleaver]

Thank you sir. The pucks are pucks specific to the R1s for jacking?

Yes. I got these:
https://www.rivianforums.com/forum/posts/263624/

 

[R.I.P.]

I don’t get why Rivian won’t simply employ a differential lock, but watch the Rivian Stories video on YouTube from a week ago … the Rivian dual motor engineer said there no plan to consider a differential.

Or, have you seen that video, and you’re aware / comfortable there will be no differential, because the dual motor torque vectoring will be better than the quad motor’s?

You are correct. I am not buying the vehicle to be a rock crawler, so I have no need for diff lock. Dual diffs with traction control has been in refinement since 1935, and is hard to beat for most scenarios. I am glad Rivian is offering it as an option.

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