Opinion: The truck needs to switch to front wheel drive automatically on the highway.

[jjswan33]

Conserve eats up the front tires in stop and go. Definitely will cost more in the long run than the energy savings you get. If you are in a situation where you absolutely do need the energy savings, use conserve instead.

Don't get me wrong. I wasn't advocating using conserve unless you need it. Just questioning how much you would save since most of the energy loss on the highway is due to aero.

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[CommodoreAmiga]

I'd be curious to know why. There is no driving feel difference when highway cruising and your efficiency goes up a good bit.

There absolutely IS a difference in the driving "feel". Torque vectoring is a real benefit, both for performance and safety. If I'm in perfect weather, on a straight highway, and babying the throttle so I can hypermile to a distant DCFC on a long trip then I will engage Conserve. But outside of those narrow conditions I want AWD with torque vectoring active.

The way Rivian implemented Conserve includes a physical disconnect of the rear motors. It isn't as simple as "not powering" them. Re-engaging the motors requires a little time and the input/output of a mechanical coupling must be aligned. This is why you sometimes hear a "clunk" when moving from Conserve to another drive mode. You shouldn't rely on this transition in adverse conditions, such as a loss of traction. Just stay in AP in those cases.

 

[loudog3114]

There absolutely IS a difference in the driving "feel". Torque vectoring is a real benefit, both for performance and safety. If I'm in perfect weather, on a straight highway, and babying the throttle so I can hypermile to a distant DCFC on a long trip then I will engage Conserve. But outside of those narrow conditions I want AWD with torque vectoring active.

The way Rivian implemented Conserve includes a physical disconnect of the rear motors. It isn't as simple as "not powering" them. Re-engaging the motors requires a little time and the input/output of a mechanical coupling must be aligned. This is why you sometimes hear a "clunk" when moving from Conserve to another drive mode. You shouldn't rely on this transition in adverse conditions, such as a loss of traction. Just stay in AP in those cases.

Are you suggesting every front and rear wheel drive car is just sitting at the limit while cruising along on the highway? I can guarantee you you've never even approached the limit of longitudinal grip with two wheels driving on the highway if there isn't snow on the ground, let alone four.

 

[Diddy123]

 

[Inkedsphynx]

Are you suggesting every front and rear wheel drive car is just sitting at the limit while cruising along on the highway? I can guarantee you you've never even approached the limit of longitudinal grip with two wheels driving on the highway if there isn't snow on the ground, let alone four.

Southbound I-5 to I-90 interchange 2 nights ago in the rain. 65mph. I power slid around the entire corner on the highway.

Wet roads have a lot less traction, especially during one of the first rains of the season.

Yea, I've approached, reached, and exceeded that limit, on a highway, without snow.

You don't know nearly as much as you seem to think you do.

 

[loudog3114]

Conserve eats up the front tires in stop and go. Definitely will cost more in the long run than the energy savings you get. If you are in a situation where you absolutely do need the energy savings, use conserve instead.

I would want it to kick back to awd below 70ish mph anyway. But the wear on the front tires is just going to be evenly spread to the rears in awd anyway. Tire wear shouldn't be an issue in front wheel engaging only on highway cruising, or we would hear about the front tires constantly needing attention on Tesla's (and every other car with a front wheel drive bias)

 

[loudog3114]

Southbound I-5 to I-90 interchange 2 nights ago in the rain. 65mph. I power slid around the entire corner on the highway.

Wet roads have a lot less traction, especially during one of the first rains of the season.

Yea, I've approached, reached, and exceeded that limit, on a highway, without snow.

You don't know nearly as much as you seem to think you do.

That's lateral grip which awd will do nothing for but help try and correct when you make a big mistake in going too fast under too much throttle (by sending power to your wheels with grip, which were the fronts anyway if you kicked the rear end out). If it was at 65 I'd have the truck be in awd anyway as that's not highway cruising speed in my book.

 

[Inkedsphynx]

That's lateral grip which awd will do nothing for but help try and correct when you make a big mistake in going too fast under too much throttle (by sending power to your wheels with grip, which were the fronts anyway if you kicked the rear end out). If it was at 65 I'd have the truck be in awd anyway as that's not highway cruising speed in my book.

So your argument is my rear wheels were doing no torque vectoring and just spun tractionless the entire time? Um, no. That's not at all how a powerslide works, and that's not at all how it feels or behaves when you're doing it.

As far as 'longitudinal' grip, I guess you mean forward/backwards, in which case I have no idea why you'd even raise that point, since it seems entirely irrelevant to the discussion being had here. I don't recall anyone saying they needed more grip from AWD going straight forward, but as I'm sure you know - not every highway is a straight line start to finish...

 

[Dark-Fx]

I would want it to kick back to awd below 70ish mph anyway. But the wear on the front tires is just going to be evenly spread to the rears in awd anyway. Tire wear shouldn't be an issue in front wheel engaging only on highway cruising, or we would hear about the front tires constantly needing attention on Tesla's (and every other car with a front wheel drive bias)

I think the issue is going to be that the system Rivian is using to engage and disengage doesn't allow for any discrepancy in RPM when it's being engaged. If you do it under acceleration, it tends to bang because it wasn't well synchronized.(I stopped doing that after the first two times). I'm not sure what's being used in other EVs or if they do the same thing. My Polestar 2 is AWD all the time.

 

[astonius]

Damn, lots of piling on the OP here...

I think it's a great idea as an option. My Velar had a "dynamic" mode which would intelligently switch drive modes automatically based on how you're driving in the moment. Something similar would be nice -- as an option, not forced.

 

[diz]

Conserve mode saves a ton of juice. I mean I have seen upwards of 25%. Dual motor Model S' automatically switch to front wheel drive above 70mph or something like that. Rivian needs to program this truck to do the same for highway travel.

Edited for clarity.

If you are cruising down the highway thinking to yourself that you really wish you had 25% more range then you probably should have been in conserve mode to begin with. This is poor planning, rather than, a manufacturer oversight.

 

[loudog3114]

I think the issue is going to be that the system Rivian is using to engage and disengage doesn't allow for any discrepancy in RPM when it's being engaged. If you do it under acceleration, it tends to bang because it wasn't well synchronized.(I stopped doing that after the first two times). I'm not sure what's being used in other EVs or if they do the same thing.

I can only speak for the teslas moving power front and back based on throttle but there is no noticeable change at all. I'd be curious what is disengaging those motors as there is no driveshaft, transfer case, etc connecting the front and rear. The 'bang' (I find it more subtle then a bang, but a noticeable bump) might just be those rear motors being briefly underpowered compared to the front. In a world of turbo lag, transmission downshifts, etc still being a thing... I'd take that subtle bump if I were to stomp it and it transitioned from front to all wheel.

 

[SolartoEV]

I tried to get my tires rotated at 7,000 miles. By the time Rivian could get me in i was closer to 12,000. I live 70 miles one way from our closet city so i used to use conserve for the trips to maximize my 70% charge so i wasn't dropping below 10% before i got home. Words from the wise my former front tires ( now rear tires ) are toast. Maybe ill get another 1000 out of them.

I would say to only use conserve when you absolutely have too. The weight of that truck seems to burn through fast

 

[loudog3114]

If you are cruising down the highway thinking to yourself that you really wish you had 25% more range then you probably should have been in conserve mode to begin with. This is poor planning, rather than, a manufacturer oversight.

Woof, everyone here just loves pissing away money and time I guess.

 

[Dark-Fx]

I'd take that subtle bump if I were to stomp it and it transitioned from front to all wheel.

Yeah, not a subtle bump. Definitely a noise that says "keep doing that and I'm going to break"

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