Off-Road settings experience (for Dual Motor R1)

[R.I.P.]

I have gotten quite a few off-road specific questions today regarding how to use traction control settings. It seemed reasonable to start a discussion thread, so others can chime in with their experiences.

This thread is going to mainly concern the DM machines. It is no secret that I am not a fan of the QM for the type of off-roading that I do, so I will let somebody else do the QM thread. QM's have a number of off-road modes to try to compensate for the lack of a differential. Some situations they do fine, others they do not. I'll leave it at that.

The DM does not need special modes to try to help the computer understand what it is driving on, because it has differentials. The differentials act as mechanical devices that automatically vector torque all by themselves; no computer or outside intervention needed.

For most driving situations, nothing more is ever needed. The differentials will smoothly balance power where it is most useful, while giving the vehicle the best possible lateral stability in slippery situations. The DM has "Snow" and "Sand" modes, but frankly, it does not need them. Snow mode does reduce torque to the wheels, but the driver can do that with his foot. Handy for the very inexperienced I suppose.

For the driver that wants to experiment with more challenging off-road trails, however, understanding how to use the truck's traction control to your best advantage can be helpful. I will address some common obstacles:

Rock Crawling:
This is where lockers would be best, but since they are not available (yet), start with TC "On". You want the least slippage possible. If the vehicle starts stalling because of lack of footing, switch to "Reduced" to get some more wheel speed. Careful, rocks can really do a lot of damage.

Lose inclines:
Use "Reduced" setting to keep wheel speed up.

Lose declines:
Use "On" setting for best all-wheel holding while regening down the decline. Try to use regen, with as little brake as you can. Braking will take away your lateral grip, regening (in a DM) will not.

Mud:
"Reduced". If digging is going to help you (hardpan underneath), use less TC.

Off-camber slippery:
"Off". If you cannot get enough traction with it off, try "Reduced", but you may slip sideways more.

Flat slippery:
"On". Usually. If you need more wheel speed to dig through it, reduce TC. If super slippery and you have to dig all the way to what is underneath, "Off".

Slippery incline:
"Off" for maximum lateral stability. Switch to "Reduced" if you need more traction.

Slippery decline:
"Reduced", to improve lateral stability. Try to use regen, with as little brake as you can. Braking will take away your lateral grip, regening (in a DM) will not.

Water crossings, with boulders:
"On", think of this as a rock crawl.

Water crossings mud/sand:
"Reduced"

Deep snow:
Usually "Reduced" or "Off". but snow can vary a lot. If digging is going to bury you, then "On". If you need to dig to the gravel below, "Off".

I hope this gives DM drivers a better idea of how the machine functions, and makes you more confident playing with your settings next time you are on the trail. Another tip is to keep the vehicle in "Standard" height unless you need the extra clearance. This gives you the best articulation and keeps your center of gravity as low as possible.

Happy trails.

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[Glembi2]

Most interesting point for me is using regen and not brakes in declines.

And thanks for putting this together. I was thinking it would be interesting to identify those situations that differentiate open diffs, locked axles, limited slip diffs, torque vectoring, QMs, and DMs. Well maybe just QMs and DMs. The other four are pretty straightforward.

For instance, a high horsepower sports car with a locked rear diff is made to go straight on dry surfaces, not quickly around corners in the rain.

 

[R1Tom]

This is all nicely detailed for the DM team.

One thing that I think aids the discussion that you don't mention, unless I am missing something on how the DM works(edit...see subsequent post by KELVN...I misstated how the torque is distributed...it is even between the two wheels on same axle which can result in tire with less traction to slip/spin)

I used to experience this in my first car....a Camaro with a 350 and an open rear diff. Hit the gas enough....and the low friction tire would just spin and spin....and Camaro would almost sit still....or even sit still in the right set of conditions. Next car....LX5.0 Mustang.....limited slip....no more of that.....now fishtailing read end(lateral instability)becomes the result.

In lateral stability...this is great. But if forward motion is needed, in some cases, it can result in a tire at each end of vehicle, spinning without any torque being sent to the stationary tire.

This is where a limited slip differential or in the Rivian case....brake induced torque vectoring. Meaning if one tire is in the air on each end of the truck, or one tire on each end of vehicle is on ice, without traction control, one would need to physically push the brakes while pushing the accelerator to transfer some torque to the stationary tire. Or with traction control on. Then the computer can apply that brake and vector that torque to the higher friction tire.

All this can work very well.

Ultimately a locker at each axle would be the ultimate, but brake induced torque vectoring can work very well too.

Is that accurate R.I.P?

 

[Glembi2]

I believe yes with the distinction between a limited slip diff (1:1 and other ratios), a locking diff, and computer-controlled torque vectoring.

Limited slip diffs are generally great but can lead to squirly situations - decelerating around a corner where one wheel is rotating appreciably faster than the other. A standard limited slip will engage too early and turn into oversteering fast.

Asymmetric limited slips address this (reducing engagement of the clutches during deceleration). This: https://www.rrtransmissions.com/blo...y-15-way-and-2-way-limited-slip-differentials

and this: https://itstillruns.com/differential-car-act-like-goes-bad-12197983.html

Computer-based torque vectoring (what we have) takes the sharp slipping/not slipping transition and smooths it to be less disruptive.

This: https://link.springer.com/chapter/10.1007/978-3-642-33744-4_30

 

[Kelvn]

is that an open diff will send the most torque to the wheel with the least traction.

Correction based on my understanding, open diffs do not send more torque to the wheel with less traction. They always equally split torque between the sides (hence lateral stability).

What you are experiencing is a lack of available torque transfer to the ground.

If you have 100% traction 100% of torque goes to the ground split evenly between the two wheels.
If you have 50% traction in one wheel, you get 50% of torque to the ground evenly split.
If you have 0% traction in one wheel, you get 0% torque to the ground evenly split.

Traction control works by engaging the brake on the wheel loosing traction. The act of engaging the brake now builds up potential torque on the spinning wheel.

If you have 0% traction in one wheel, you get 0% traction to the ground evenly split
Add brake pressure to the 0% traction wheel, you start adding torque effect to that wheel, say this torque equates to 100% torque, now you get 100% torque evenly split, wheel with traction gets that torque and transfers to the ground.

 

[R1Tom]

Correction based on my understanding, open diffs do not send more torque to the wheel with less traction. They always equally split torque between the sides (hence lateral stability).

What you are experiencing is a lack of available torque transfer to the ground.

If you have 100% traction 100% of torque goes to the ground split evenly between the two wheels.
If you have 50% traction in one wheel, you get 50% of torque to the ground evenly split.
If you have 0% traction in one wheel, you get 0% torque to the ground evenly split.

Traction control works by engaging the brake on the wheel loosing traction. The act of engaging the brake now builds up potential torque on the spinning wheel.

If you have 0% traction in one wheel, you get 0% traction to the ground evenly split
Add brake pressure to the 0% traction wheel, you start adding torque effect to that wheel, say this torque equates to 100% torque, now you get 100% torque evenly split, wheel with traction gets that torque and transfers to the ground.

You are correct. I was being too lazy in saying torque(and inaccurately) but you explained it better than me for sure!

 

[R.I.P.]

This is all nicely detailed for the DM team.

One thing that I think aids the discussion that you don't mention, unless I am missing something on how the DM works(edit...see subsequent post by KELVN...I misstated how the torque is distributed...it is even between the two wheels on same axle which can result in tire with less traction to slip/spin)

I used to experience this in my first car....a Camaro with a 350 and an open rear diff. Hit the gas enough....and the low friction tire would just spin and spin....and Camaro would almost sit still....or even sit still in the right set of conditions. Next car....LX5.0 Mustang.....limited slip....no more of that.....now fishtailing read end(lateral instability)becomes the result.

In lateral stability...this is great. But if forward motion is needed, in some cases, it can result in a tire at each end of vehicle, spinning without any torque being sent to the stationary tire.

This is where a limited slip differential or in the Rivian case....brake induced torque vectoring. Meaning if one tire is in the air on each end of the truck, or one tire on each end of vehicle is on ice, without traction control, one would need to physically push the brakes while pushing the accelerator to transfer some torque to the stationary tire. Or with traction control on. Then the computer can apply that brake and vector that torque to the higher friction tire.

All this can work very well.

Ultimately a locker at each axle would be the ultimate, but brake induced torque vectoring can work very well too.

Is that accurate R.I.P?

Yes it is.
??

 

[UnsungZero_OldTimeAdMan]

How about som love and advice for QM owners? I feel inadequate.

 

[Nine_One_Six_R1S]

What about suspension? Is that the same setup in DM vs QM?

In my QM, I've found that going to Stiff is better than staying in Soft. This could be common sense to someone experienced but in my newbieness I started in soft and when swithced to stiff it made a big difference in ride quality.

It prevented bouncy behavior that could potentially make you bottom out

 

[R.I.P.]

How about som love and advice for QM owners? I feel inadequate.

My tests and findings with the QM have already been published, and are pretty well known on this list. As far as I'm concerned, is not a machine that you should try to do any serious off-roading with. The picture below is at the top of buckhorn trail. QM's can't even make it up the trail without being tied to trees to prevent them from slipping off and over the cliffs.

Trying to keep a QM on an off camber slippery trail is a terrifying proposition that I don't recommend.
?

 

[R.I.P.]

What about suspension? Is that the same setup in DM vs QM?

In my QM, I've found that going to Stiff is better than staying in Soft. This could be common sense to someone experienced but in my newbieness I started in soft and when swithced to stiff it made a big difference in ride quality.

It prevented bouncy behavior that could potentially make you bottom out

Suspension is the same, and the settings you use are entirely dependent on the surface. Soft setting will get you better articulation, and is usually the setting I leave it in.

On faster sections, are you often need to firm things up for better control.

 

[UnsungZero_OldTimeAdMan]

My tests and findings with the QM have already been published, and are pretty well known on this list. As far as I'm concerned, is not a machine that you should try to do any serious off-roading with. The picture below is at the top of buckhorn trail. QM's can't even make it up the trail without being tied to trees to prevent them from slipping off and over the cliffs.

Trying to keep a QM on an off camber slippery trail is a terrifying proposition that I don't recommend.
?

Which is just fine. Realistically, won't be doing anything that serious.

 

[R.I.P.]

Which is just fine. Realistically, won't be doing anything that serious.

Oh... I should mention. If I spent all of my time in Baja sand, I would absolutely go with a QM.

So at the end of the day, it really is how you intend to use the vehicle.
?

 

[R1 EVY]

Happy trails.

? Wasn't a big enough support for this post. I'm seriously interested in taking Evy out on some trails but honestly don't know what's a smart (or stupid) way to use it for what it was made (other than 0-60 in 3.5 seconds).

Your post totally makes sense and further reinforces the awesomeness of this community. I'm going to go out on a limb and infer R.I.P. is an acronym for Really Into Providing-amazing-information-for-novice-off-roaders or something like that? ??

 

[Glembi2]

Trying to keep a QM on an off camber slippery trail is a terrifying proposition that I don't recommend.
?

Works for me. Knowing the particulars of what will likely fail is encouragement to find a path that, while still being adventurous, does not have the same level of risk.

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