Snow Driving And Regen Braking

[JohnK]

First time out in snow today...it was terrifying. On stock 21" tires, AP mode with standard regen. Everything seemed fine in a couple inches of soft snow on flat city streets, and uphill stop and go presented no surprises. But downhill on hard packed snow was another story. No amount of feathering the throttle would prevent lockup at low speeds, such as typically encountered approaching intersections on a downhill. The wheels lockup and the truck starts to slide sideways.

I've been driving Teslas for nearly 10 years, so one pedal driving is second nature. While none of that was in the snow before this winter (4WD F150 w/ snow tires was my snow vehicle for the past 15 years), I was still not prepared for the abrupt effect of the rather strong standard regen on snow in the Rivian.

Traction on hard packed snow in 30 degree weather with the 21" all seasons was about what you would expect - not great, especially abrupt braking. No doubt winter/snow tires would make a huge difference, if only they could be had to fit the 21s. However, I doubt even studded snow tires could compensate for the regen lockup. Hopefully, Rivian is really working on a "snow mode". Until then, this truck stays in the garage when the roads are icy. The really sad thing is that I want this to be my ski vehicle. I guess that ain't happening this winter!

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[SteveInBend]

First time out in snow today...it was terrifying. On stock 21" tires, AP mode with standard regen. Everything seemed fine in a couple inches of soft snow on flat city streets, and uphill stop and go presented no surprises. But downhill on hard packed snow was another story. No amount of feathering the throttle would prevent lockup at low speeds, such as typically encountered approaching intersections on a downhill. The wheels lockup and the truck starts to slide sideways.

I've been driving Teslas for nearly 10 years, so one pedal driving is second nature. While none of that was in the snow before this winter (4WD F150 w/ snow tires was my snow vehicle for the past 15 years), I was still not prepared for the abrupt effect of the rather strong standard regen on snow in the Rivian.

Traction on hard packed snow in 30 degree weather with the 21" all seasons was about what you would expect - not great, especially abrupt braking. No doubt winter/snow tires would make a huge difference, if only they could be had to fit the 21s. However, I doubt even studded snow tires could compensate for the regen lockup. Hopefully, Rivian is really working on a "snow mode". Until then, this truck stays in the garage when the roads are icy. The really sad thing is that I want this to be my ski vehicle. I guess that ain't happening this winter!

I took my R1T out today, too. The roads were slick with a thin layer of wet snow and traction wasn't great with the 20" A/T tires, either. Went up to one of the school parking lots and tested a few driving modes; none of them inspiring a lot of confidence. I'm hopeful that colder temps up on the mountain (i.e., Mt. Bachelor) and deeper & drier snow will improve the handling. Heading up should be good, but I'm going to be cautious when coming back down after a day of skiing. Glad they do a good job plowing the Cascade Lakes Hwy.

P.S. The R1T is my only vehicle!

 

[evergreenmachine]

Hey all, I sent a note to my guide on how sketchy the regen mode seems to be on downhill descents, and got the attached reply. Sound like an issue for a number of folks, and seems that they are working on a fix???

 

[johstacy]

Hey all, I sent a note to my guide on how sketchy the regen mode seems to be on downhill descents, and got the attached reply. Sound like an issue for a number of folks, and seems that they are working on a fix???

I hope they get something very soon I am about to take delivery of my R1T and it's starting to make me nervous as I live in the snow like really snowy conditions. Last year I got 24 feet in December alone.... seriously praying for a snow mode by the time I take delivery!

 

[MountainBikeDude]

Hey all, I sent a note to my guide on how sketchy the regen mode seems to be on downhill descents, and got the attached reply. Sound like an issue for a number of folks, and seems that they are working on a fix???

My brief chat with Rivians VP of software development in October

 

[atebit]

I wonder where “very s00n” lies on the “s00n” spectrum? Is it like “ infinity minus one”?

 

[aw113sgte]

Your foot controls the level of regen, just don't use as much and you'll be fine. This truck tires so much confidence on dry roads I think people have unrealistic traction expectations

 

[cbrcanuck]

Your foot controls the level of regen, just don't use as much and you'll be fine. This truck tires so much confidence on dry roads I think people have unrealistic traction expectations

Have you driven downhill in snow? You can’t keep your foot on the accelerator down a steep hill, you have to coast and/or brake gently. If the vehicle doesn’t let you do this and locks up the wheels itself, you’re SOL. Based on all the feedback, I’m glad some way of turning off the hard regen before I take delivery will happen as this will be our ski-tripper!

(edited for grammar)

 

[Aag12]

Your foot controls the level of regen, just don't use as much and you'll be fine. This truck tires so much confidence on dry roads I think people have unrealistic traction expectations

May work on flat roads, but when you driving uo/down mountains with quick changes in elevation I'll guarantee that your technique won't work 100%

 

[RivianNE]

Regen has been one of my worries with snow. Don’t get me wrong, I love the strong regen, but only on dry surfaces. I have been driving a Tesla for many years. It’s all fine on “normal” snowy road conditions. But when stuck in a heavy snow storm or driving down/up hill, no matter what I do, I always lock the tires at least once. And yes, I have snow tires. A snow mode will be welcome! I was hopping the 20s will be enough with the snow, it seems like I may need to revisit that plan.

 

[bjcleaver]

My experience in snow has been pretty good overall on the 20" ATs. We've had a few decent storms so far and I live in the mountains and we have some steep hills. No issues going uphill during a pretty good storm with heavy, wet snow where some other cars' wheels were spinning. Downhill was what you'd expect given the regen - it can lock up if you come off the pedal too fast. But each time I drive I get better with the "feathering" and keeping at it a consistent slow speed to avoid the regen. There is no way to coast so you have to be on the accelerator pedal pretty much all the time. As long as there is some feedback on the pedal the regen will back off. But a winter driving mode with lower regen would be welcome.

I'm hoping the AT tires will get me through the winter but I'll get snows if it starts to feel sketchy.

 

[R1Tom]

My experience in snow has been pretty good overall on the 20" ATs. We've had a few decent storms so far and I live in the mountains and we have some steep hills. No issues going uphill during a pretty good storm with heavy, wet snow where some other cars' wheels were spinning. Downhill was what you'd expect given the regen - it can lock up if you come off the pedal too fast. But each time I drive I get better with the "feathering" and keeping at it a consistent slow speed to avoid the regen. There is no way to coast so you have to be on the accelerator pedal pretty much all the time. As long as there is some feedback on the pedal the regen will back off. But a winter driving mode with lower regen would be welcome.

I'm hoping the AT tires will get me through the winter but I'll get snows if it starts to feel sketchy.

In a panic stop, what would happen? I mean like I want to mash the brake pedal and let the ABS do the best it possibly can to save my bacon. I assume in that case, the brakes take over. I am also thinking that if the regen starts to cause a pitching action, the stability logic would kick in and hit brakes too?

We aren't going to end up like I am in my first car, '79 Camaro, sideways going down road, right?

 

[bjcleaver]

In a panic stop, what would happen? I mean like I want to mash the brake pedal and let the ABS do the best it possibly can to save my bacon. I assume in that case, the brakes take over. I am also thinking that if the regen starts to cause a pitching action, the stability logic would kick in and hit brakes too?

We aren't going to end up like I am in my first car, '79 Camaro, sideways going down road, right?

Maybe not sideways but yeah, I don't know. I would assume the same, that if you hit the brakes then the brakes do the work. But if it's just regen doing the braking, I don't know how it controls things from that point but you'd think like you said the traction controls and everything would take over.

Any Rivian engineers on the forum?

 

[bdavis171]

I put on 20" Blizzaks last week here in Minnesota. We've had snow all week, with Monday being quite slippery for other vehicles. I slid slightly when under 6mph or really hammering the throttle. I would advise feathering the throttle as stated above.

 

[EBEG]

Engineering Explained goes over a bunch of the issues related to traction in the following video:

The issue in snow may be related to the analysis at about the 6 minute mark. Basically, the R1T thinks that locking up when traction is limited will shorten the stopping distance, which may actually be true, but in very slick conditions, it can also cause a loss of control.

It's also worth noting that torque vectoring still works under regen (at about the 9 minute mark). It's not clear how the torque vectoring would work, if at all, under a lock up situation with one or more wheels.

Hopefully software updates improve the situation going forward.

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