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Car wash and bigger tires question…

electruck

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Rivian R1T R1S Car wash and bigger tires question… 2022-rivian-r1t-13-
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Trekkie

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So in my 2019 X you pull up, with foot on break push the gear selector down twice from park (Drive then Neutral) or down once from drive and off you go. The gear selector looks like a turn signal on the right side of the wheel.

Not sure how the newer model without the gear stalk will do it, one of the reasons I'm not wanting more Tesla's. I think it's too early to remove all that stuff.

this is for 'neutral' only, not for towing or anything. I'm unaware of a two wheel tow option everything the manuals state for the AWD Tesla's is YOU MUST FLAT BED TOW or dolly tow.
 
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EVnewb

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AFAIK, that isn't how physics work -- even with 2WD. In normal conditions, where both driven wheels have equal traction, power does go through BOTH wheels. If one wheel has significantly less traction (which makes it much easier to spin) then power causes that wheel to spin and not the wheel with all the traction. Torque is a bit like electricity, in that regard -- it takes any and all paths available to it.

Now before someone says "but wait, doesn't electricity take the path of LEAST resistance?" NO! That is a myth. Electricity takes ALL paths. However, the path with higher RESISTANCE will take less current. Now consider the 2WD vehicle. The traction between the tire and road is resistance. Drivetrain "power" is current. The wheel with higher traction (resistance) will transfer (flow) less power (current). The larger the difference in traction (resistance) between the driven wheels, the larger the difference in how much power transmits through each wheel. Make the difference large enough (like one wheel on a patch of ice) and there may not be enough power to spin the wheel with traction and effectively you get the wheel without traction just spinning.

Limited-Slip Differentials (Posi-track is one such trademark) are useful in those situations because they force at least some power (varies depending on implementation) to the wheel with traction. In normal driving, however, an "open" differential is fine and does "turn" both wheels.
But isn’t that what a differential does? It sends almost all power to only one wheel, which is why you don’t tear up your tires when you take sharp corners on a solid surface. It’s true if you lift both wheels off the ground, they should both turn. But that’s just because of the friction inside the drivetrain causing that isn’t it? Your ice scenario was a perfect example of what I was picturing for a conventional drivetrain. Only one wheel should spin…

But what you’re saying does make sense though if both wheels have traction, then they both have power to them. Haha sorry just working it out in my head as I type. Been a few years since I was in auto shop!

There is no physical disconnect for the motors. If the vehicle is off the cooling systems are also off, which will lead to a heat buildup in the motors and eventual failure. Jeeps can be flat towed because they have physical disconnects. If you forget to do those you're going to ruin something.
Thanks! I googled it last night and saw the same explanation. That also makes sense! 60mph behind an RV or towtruck would definitely cause some damage.

How do they put the car into 2WD and not burn up the back motors though? Shouldn’t it have the same effect driving down the highway in 2WD?
 

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kneebuster

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How do they put the car into 2WD and not burn up the back motors though? Shouldn’t it have the same effect driving down the highway in 2WD?
My best guess is that they send just enough power to the rear wheels to overcome the drag, but not enough to produce propulsion.
 

CommodoreAmiga

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But isn’t that what a differential does? It sends almost all power to only one wheel, which is why you don’t tear up your tires when you take sharp corners on a solid surface. It’s true if you lift both wheels off the ground, they should both turn. But that’s just because of the friction inside the drivetrain causing that isn’t it? Your ice scenario was a perfect example of what I was picturing for a conventional drivetrain. Only one wheel should spin…
Not exactly. The differential allows power to flow to both wheels on the axle. You don't tear up tires when taking corners with an open differential because the two sides of the differential are allowed to rotate as different speeds. Even though the outside wheel travels a little bit faster than the inside wheel, power will still go to both wheels if they both have traction.

This video has an excellent visual demonstration.

 
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EVnewb

EVnewb

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Not exactly. The differential allows power to flow to both wheels on the axle. You don't tear up tires when taking corners with an open differential because the two sides of the differential are allowed to rotate as different speeds. Even though the outside wheel travels a little bit faster than the inside wheel, power will still go to both wheels if they both have traction.

This video has an excellent visual demonstration.

Lol! I love those old demonstration movies! Very good video to teach how it all works. I remember my auto shop teacher telling us open diff cars were actually 1WD. Now I know I’ve been spreading wrong information so thank you for the clarification!

Now I’m wondering what else I’ve been misinformed about in that class. ??‍♂
 

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I have a model Y and it will absolutely not go through a car wash in drive, unless I apply some perssure on the pedal which would scare the "P" out of me to do. Tesla announced recently that they enabled a car wash mode. I have not received the update that has this feature, but the Tesla you saw may have received the beta update.
My Tesla has the car wash mode....but I'd never take it into auto wash. After seeing the first Tesla in the 'hood and looking at my neighbor's Tesla paint fade and swirl after ONE car wash, I decided to continue hand washing every car as I've done since parting ways with my college junker.
 

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Lol! I love those old demonstration movies! Very good video to teach how it all works. I remember my auto shop teacher telling us open diff cars were actually 1WD. Now I know I’ve been spreading wrong information so thank you for the clarification!
I'm convinced that old informational videos from the 30's to 50's are better than almost every modern textbook and video. They really did put a lot of effort into them and they're fantastic. There was another video that explained transmissions with "spinning levers" and I strongly suggest that to anyone who likes those types of videos or wants to know the basics of a transmission.
 

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I'm convinced that old informational videos from the 30's to 50's are better than almost every modern textbook and video. They really did put a lot of effort into them and they're fantastic. There was another video that explained transmissions with "spinning levers" and I strongly suggest that to anyone who likes those types of videos or wants to know the basics of a transmission.
Tim Hunkin’s “The Secret Life of Machines” is an excellent series
 

Vern Bybee

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I didn't read all these
So may have been covered
THERE IS A HUGE DIFFERENCE BETWEEN a slow roll through a car wash and flat towing at 65mph
Seriously
At a slow roll you will create a small voltage on the motors
At 65mph those motors are creating enough voltage to power a city block or apartment complex
To divert the small amount of energy created by the slow roll of a car wash is not a big deal (though I heard the 1st Teslas had issues with that)
But when you spin the motors up to any sort of speed they become huge generators and that electricity needs a place to go
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