Rivian off-road struggling?

[Zybane]

Hummer's front diff is locking because it's only a single motor and absolutely will just spin one loose tire if it doesn't use the brakes to lock the spinning wheel up. Rivian should make enough torque at each wheel independently to not need anything which will transfer power from one wheel to another.

I expect the issue is the person driving the truck just wasn't giving it enough pedal. You'd fail with the beefiest off-road vehicle if you weren't giving it enough throttle under certain conditions. The hard part with the Rivian is the lack of audible feedback that an ICE has.



The Hummer EV requires 45 psi in those giant tires because of its heft.

You sure you had the front differential locked up? It's a mechanical locking diff, it's impossible for the two front wheels to spin at different speeds when it's locked in the tri-motor Hummer EV. Brakes aren't needed at all.

https://www.aam.com/media/story/aam-s-tracrite-differentials-help-new-gmc-hummer-ev-conquer-the-road#:~:text=The GMC HUMMER EV features,turn at the same speed.

Speed/throttle is the nemesis to a lot of rock crawling. So much in fact that a good driver in an ICE vehicle two-foots over rocks, presses down on the brake pedal with their left foot to create drag and slow throttle modulation to overcome the brake friction and slowly roll over rocks as to not jerk the truck and driveline.

This is possible with something like a Jeep Rubicon that has way, way more mechanical advantage than say the Rivian. In my calculations, a Jeep Rubicon has over 31K of effective ft/lb of torque that can be applies to all four wheels simultaneous in the Diesel.

Richard Farquhar - Vice President of Propulsion - Rivian:

"
Charged: You said that there are symmetrical drive units, so you have four identical sets of motors and drives?


Richard Farquhar: That’s correct – we have four identical motors, left and right, front and rear. Every wheel has the exact same amount of torque and power available to it to maximize performance. We achieve over 14,000 Newton-meters of grounded torque at the wheels combined and 125 miles per hour maximum speed. With the fixed-ratio single-speed gearbox there is no need to change gears, no need for twin speeds. This maximizes efficiency in terms of losses from gear meshing while achieving all of our performance targets. "

14,000 nM is 10,325 ft/lb. That's 2,581 per wheel. Compared to a Jeep Rubicon which can do over 31,000 per wheel.

The mechanical advantage of something like a Diesel Rubicon that has its Engine Torque multiplied by the fluid Torque Converter multiplied by transmissions 1st gear, multiplied by the transfer case, multiplied by the differentials, gives insane torque figures at the wheels. Far far higher than Rivians small motors can accomplish.

But Rivian is more worried about efficiency than climbing over rocks. Rivian motors are actually quite small and aren't geared to put down a ton of TQ at low speed per wheel. Hence why this Rivian having a hard time with this moderate obstacle was readily apparent. This was also readily evident shown by on a cool mountain trail, the Rivian cooling fans kicked into overdrive on this obstacle as the wheels with traction touching the ground were being fed incredible amounts of power.

The Rivian motors could have been getting so hot from the near zero high current torque requests that they were being de-rated too. Rivian is also a quite heavy vehicle, it's no small matter to lift 7K lb up an incline with no momentum. Weight is the enemy of off-roading.

I believe what I am showing above will bare itself out more as the Rivian is off-roaded more and more. Inclines with rocks are going to be its nemesis.

The Rivian will most likely be limited to 3, maybe 3+ difficulty trail on the top end:

https://www.of4wd.com/education/trail-ratings/

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[Dark-Fx]

You sure you had the front differential locked up? It's a mechanical locking diff, it's impossible for the two front wheels to spin at different speeds when it's locked in the tri-motor Hummer EV. Brakes aren't needed at all.

Not speaking of experience- that's why they put a locker in it. The rear of the hummer has an e-locker where it attempts to spin both rear wheels in lock-step. I didn't take the hummer anywhere I needed either. Standard open diff vehicles will use the brake of the spinning wheel to send power to the non-spinning wheel. I'm not sure the Hummer will even do that, and Rivian can't do that because there isn't a mechanical connection. Hummer doesn't have a mechanical connection in the rear, so in that way, it's the same as the Rivian. With ~340 hp per rear wheel, GM probably didn't think it was necessary to have a mechanical connection, even in the worst offroading situations. All I was saying.

 

[Zybane]

Yes virtual or "e-lockers" aren't nearly as good as actual mechanical lockers. You effectively waste the torque of the wheel's motor that is up in the air.

 

[kurtlikevonnegut]

You sure you had the front differential locked up? It's a mechanical locking diff, it's impossible for the two front wheels to spin at different speeds when it's locked in the tri-motor Hummer EV. Brakes aren't needed at all.

https://www.aam.com/media/story/aam-s-tracrite-differentials-help-new-gmc-hummer-ev-conquer-the-road#:~:text=The GMC HUMMER EV features,turn at the same speed.

Speed/throttle is the nemesis to a lot of rock crawling. So much in fact that a good driver in an ICE vehicle two-foots over rocks, presses down on the brake pedal with their left foot to create drag and slow throttle modulation to overcome the brake friction and slowly roll over rocks as to not jerk the truck and driveline.

This is possible with something like a Jeep Rubicon that has way, way more mechanical advantage than say the Rivian. In my calculations, a Jeep Rubicon has over 31K of effective ft/lb of torque that can be applies to all four wheels simultaneous in the Diesel.

Richard Farquhar - Vice President of Propulsion - Rivian:

"
Charged: You said that there are symmetrical drive units, so you have four identical sets of motors and drives?


Richard Farquhar: That’s correct – we have four identical motors, left and right, front and rear. Every wheel has the exact same amount of torque and power available to it to maximize performance. We achieve over 14,000 Newton-meters of grounded torque at the wheels combined and 125 miles per hour maximum speed. With the fixed-ratio single-speed gearbox there is no need to change gears, no need for twin speeds. This maximizes efficiency in terms of losses from gear meshing while achieving all of our performance targets. "

14,000 nM is 10,325 ft/lb. That's 2,581 per wheel. Compared to a Jeep Rubicon which can do over 31,000 per wheel.

The mechanical advantage of something like a Diesel Rubicon that has its Engine Torque multiplied by the fluid Torque Converter multiplied by transmissions 1st gear, multiplied by the transfer case, multiplied by the differentials, gives insane torque figures at the wheels. Far far higher than Rivians small motors can accomplish.

But Rivian is more worried about efficiency than climbing over rocks. Rivian motors are actually quite small and aren't geared to put down a ton of TQ at low speed per wheel. Hence why this Rivian having a hard time with this moderate obstacle was readily apparent. This was also readily evident shown by on a cool mountain trail, the Rivian cooling fans kicked into overdrive on this obstacle as the wheels with traction touching the ground were being fed incredible amounts of power.

The Rivian motors could have been getting so hot from the near zero high current torque requests that they were being de-rated too. Rivian is also a quite heavy vehicle, it's no small matter to lift 7K lb up an incline with no momentum. Weight is the enemy of off-roading.

I believe what I am showing above will bare itself out more as the Rivian is off-roaded more and more. Inclines with rocks are going to be its nemesis.

The Rivian will most likely be limited to 3, maybe 3+ difficulty trail on the top end:

https://www.of4wd.com/education/trail-ratings/

You claim the Rivian was being fed "incredible amounts of power" but ...how do you know with no engine noise? To me, it looked like he was babying the throttle and once he finally gave it enough juice he rolled right over. That's user error.

Other people driving the Rivian have commented that there is a ton of pedal travel in Rock Crawl because it's speed limited. I think he probably felt like he was giving a lot of throttle but in fact he was barely giving it any.

Doug D. specifically mentioned this in his off-road test of the Rivian where he went through similar traction limited terrain and it never even really struggled, but Doug is an experienced driver who does a lot of off-road driving.

 

[Zybane]

You claim the Rivian was being fed "incredible amounts of power" but ...how do you know with no engine noise? To me, it looked like he was babying the throttle and once he finally gave it enough juice he rolled right over. That's user error.

Other people driving the Rivian have commented that there is a ton of pedal travel in Rock Crawl because it's speed limited. I think he probably felt like he was giving a lot of throttle but in fact he was barely giving it any.

The Rivian cooling fans kicked into high on that obstacle. A day with everyone in multi layers of jackets with some snow still on the ground.

 

[ajdelange]

You claim the Rivian was being fed "incredible amounts of power" but ...how do you know with no engine noise?

The evidence that little power is being drawn is visual. No wheel is spinning fast against substantial load. You all are confusing torque and power. Low speed + low load = low power.

 

[cohall]

I can state with confidence that every video I've seen, including the one linked to by the OP, make it clear that the R1 platform is more than capable enough for my plans with it.

I'd also argue that it's impossible to take away any real assessment of capabilities based on a single video, with an unknown driver, and unknown inputs to the driving controls.

We've seen many other videos where the R1T performed admirably on very extreme off-roading situations.

I have no concerns.

 

[Zoidz]

The Rivian cooling fans kicked into high on that obstacle. A day with everyone in multi layers of jackets with some snow still on the ground.

I would not jump to conclusions about how much power was going into the motors because the fan came on. We really don't know enough about Rivian's thermal management plan yet to draw that conclusion, and we don't know how much driving was done prior to that clip of video. For all we know, the fan could have been on 3 minutes before that clip, turned off while they were sitting still, and came back on when the started driving again.

 

[koersontap]

The evidence that little power is being drawn is visual. Now wheel is spinning fast against substantial load. You all are confusing torque and power. Low speed + low load = low power.

Listen to this man, he knows his shit.

Seriously though, trying to equate the torque curve of an ICE to similar torque curve on an EV, for a singular use case like this, is bonkers. Sure, you can quote 31k ft-lbs of torque. But that's at peak RPM. Which is....? Certainly not the 2000 RPM you'll be working at most times. What's it putting out there? And what's it matter anyway? If you only need 1400 to lift over an obstacle, you're just measuring dicks with Chad anyway.

Key conclusion here is give some people some time to give the Rivian it's paces, and we'll get a more full picture how it handles.

 

[Dark-Fx]

The Rivian cooling fans kicked into high on that obstacle. A day with everyone in multi layers of jackets with some snow still on the ground.

I've had mine do this while it was sitting still, parked. I think Rivian just needs to do more tuning on it. Seems to be too reactive and not proactive enough.

 

[Zybane]

I'm just saying being an avid off-roader, expectations have to be managed. The Rivian capabilities aren't going to be as good as I had originally envisioned. I'm still buying the R1S though.

 

[Inkedsphynx]

I'm just saying being an avid off-roader, expectations have to be managed. The Rivian capabilities aren't going to be as good as I had originally envisioned. I'm still buying the R1S though.

Also an experienced overlander and I've watched every bit of R1T video relating to offroading or overlanding.

I think plenty of others have made every point I'd make here, but I concur with everyone else - the R1T struggled because the driver doesn't know what he's doing and isn't familiar with the vehicle.

It is likely that a mechanical locker would have some additional benefit in certain situations. I won't argue that. But I've yet to see an obstacle the R1T couldn't handle, if driven properly. I have no concerns about its prowess, and rock crawling is literally the first thing I'm going to do with mine (Well, second if you count launching repeatedly until my passengers vomit).

I also fully expect software to improve these behaviors over time, though how much difference that will make we will have to see.

 

[Zybane]

I guess it depends on what one means by rock crawling. Small 34" tires with large 20" wheels right off the bat is going to greatly restrict the amount of rocks you can go over.

 

[AllInev]

Definitely agree that there should be enough power to move the truck with 2 tires touching, so probably some further tweaking of the drive mode programming can improve this.

Nothing I saw in this video makes me believe the R1T software needed tweaking to perform well on this trail. The driver simply didn’t have the experience to know what to do. Most likely, the R1T “struggled” due to pilot error.

200+ HP and 200+ lb ft torque at each wheel and competent driving should have been enough.

I’m reserving judgment until I see an actual and legit review of the R1T’s off-roading strengths and weaknesses.

 

[Inkedsphynx]

I guess it depends on what one means by rock crawling. Small 34" tires with large 20" wheels right off the bat is going to greatly restrict the amount of rocks you can go over.

Show me the rocks you're talking about that will get cleared by 37"s on 18"s that the R1T won't clear on 34"s on 20"s. I don't believe there are any. I've yet to run into a rock that I couldn't get my Defender over, and it's not on steelies, so basically the tire combo equivalent of the R1T.

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