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RivianXpress

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Zoidz

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Interesting. Not what I would have expected especially for Rock mode. It's acting like an old school open diff. It clearly was not applying any significant power to the wheels with traction. 🤔
 

thrill

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Interesting. Not what I would have expected especially for Rock mode. It's acting like an old school open diff. It clearly was not applying any significant power to the wheels with traction. 🤔
We have no idea how much the pedal was pushed.
 

popoga

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The real downside to this is that you can't treat it like a standard offroader. I remember in the old Doug Demuro offroading video he event mentions how weird it is that you just put the petal down and this thing which should be prone to 0-60 in 3s instead starts to slowly climb over anything and everything.

I agree that it's an unsettling thought tho.
 

Dark-Fx

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I drove up a RTI ramp in my truck in the snow. Once you get to the point where there is basically no traction on two of the tires, you have to push the throttle down harder to get the ones with traction to do anything. In rock crawl, the Rivian will limit the amount of wheel spin on the tires that don't have traction but will continue to apply more torque to the ones that do. My entire truck started to slide sideways because it broke all the tires on the ground loose in the snow.

I'll try to get some video of it next time once everything is dried up here. I'll put a flag on all the tires so it's easier to calculate how much wheel spin there actually is. People are afraid to put more throttle down because it feels like the thing would want to flip over if it kept going up, RTI ramps are pretty unnatural. I wouldn't drive up a feature like this in the wild that just kept going higher and higher on one side.
 
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lmr

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SeaGeo

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Interesting. Not what I would have expected especially for Rock mode. It's acting like an old school open diff. It clearly was not applying any significant power to the wheels with traction. 🤔
We have no idea how much the pedal was pushed.
Yeah, it's odd. If people remember back to Kyle's R1S offroad review he had a similar behavior but it was up against a lip that was basically vertical and it seemed like it was power limited. I am struggling to believe that this is a power limitation. It makes me think that Rex wasn't comfortable flooring it on the ramp (I would not blame him) like @Dark-Fx mentioned, or as someone suggested in a totally different thread if Rivian is intentionally limiting power to the wheels when you're up against an obstacle as a safety feature to try and keep someone from accidentally yeeting themselves the moment it clears said obstacle.
 

Dark-Fx

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It looks like we have decent weather middle of the day tomorrow so I'll see about going to play around a bit on the ramp. I suspect what's happening once you start having wheels slipping is you are still commanding the same amount of total power from the truck, but when two wheels are slipping, its now actually only putting ~50% of your request to the ground.

If that's actually what's happening, you have to double what was being requested to keep traveling up the ramp with just the two tires that still have traction (probably even more since you're now physically lifting parts of the vehicle off the ground). Rivian could probably rebalance the power so it's not this weird feeling of needing to give it way more pedal.
 

Rexbo

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In my experience, the rivian does respond well to dragging the brake while using gas in offroad mode, this helps put a little load on the wheels that freely spin, which can help trick the computers into giving a slightly more linear pedal response.

Play around! Either way the truck seems to know not to launch you from 0-60 into a tree, which is nice.
 

AllInev

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Thanks @RivianXpress and @Dark-Fx for investigating this. It’s something that’s been bothering me, but I haven’t had any opportunities to track it down. It’s a really interesting puzzle.
 

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mmiles2012

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Think it's worth keeping in mind the amount of this behavior that is now managed by software rather than hardware and physical connections - we have 100% software-control of spring rate, ride height, roll stiffness, steering angle, as well as brake and drive torque. This means that you can control A LOT of very specific behaviors. Kind of like Bosch did for VW with diesel engines even though they reminded VW not to use that mode for emissions testing or on production vehicles....

All this to say, wouldn't be shocked to see the engineers recognize a set of conditions (articulation, load, body angles, etc.) that cuts off torque to gripping wheels in situations that look like an RTI/articulation test condition, where 2 wheels have become unweighted and the vehicle is losing some stability. Hence why you're able to get out with some momentum.
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