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Keith Tanner
Keith Tanner MegaDork
11/20/19 4:16 p.m.

Volvo just introduced an EV station wagon show car. First, yay station wagon! But what got my attention was the fact that it's RWD. The single motor Mach-E? RWD. Single motor Model 3? RWD. Single motor Model S? RWD. Chevy Bolt? FWD. Damnit, there goes my thesis. But you get my point.

Most of these ground-up EVs are going RWD if they're only going to power two wheels. It makes sense, FWD is a much bigger pain in the butt to engineer and package. The only reason that ICE cars are FWD is because it's easiest to have the engine at the same end of the car as the drive wheels, and ICEs are hard to package and cool in the rear of the car. Also, they have weird handling characteristics that apparently take several decades to sort out.

EVs have different packaging constraints, so it's easier to put the motor in the rear and all that complex steering and cooling stuff up front. Better for weight distribution and tire wear too.

The end result is that we're seeing the return of RWD. Could this mean a return to better driving dynamics and steering that is not affected by power delivery? 

Does anyone have experience with both the RWD and AWD variants of some of these cars? I guess that really means the Tesla S and 3 as nobody's driven the Ford yet.

_
_ Dork
11/20/19 5:16 p.m.

I know Tesla's awd system is crazy good for the snow. There's a YouTube video where they dance on ice in awd trim. Essentially, the host says all you have to do is put it in a certain mood, and then press the Excelerator and steer the direction you want to go

rslifkin
rslifkin UltraDork
11/20/19 7:26 p.m.

RWD has been slowly creeping back in for a while, although the trend with electric cars seems to be pushing it a little faster.  Think about recent ICE cars.  Lots of people buying RWD Euro sedans (although more are going AWD).  I see more newer Mustangs being DD-ed than I used to.  Plenty of people go for the Charger and Challenger. 

For the most part, the "RWD is dangerous" stigma seems to have faded off a bit.  Although I do still get plenty of people thinking I'm insane for DD-ing something RWD in the winter...

Knurled.
Knurled. MegaDork
11/20/19 7:29 p.m.
Keith Tanner said:Could this mean a return to better driving dynamics and steering that is not affected by power delivery?

 

I'm going to have to say "no", because powr delivery is a drop in the bucket of steering destruction compared to the things manufacturers have to do in order to make giant wheels with rubberband tires tolerable on the street.

 

Want a shining example?  Find a General Motors vehicle with EPS.  Put it on a lift, grab one of the front wheels, rotate the steering side to side.  Now, start the engine.  You will not be able to BUDGE the steering.  The EPS will actively fight you.  We have gone from "poor steering feel" to "actively killing all steering feel" with some of these EPS implementations.  And it is all due to Design's fetish for huge wheels and zero-sidewall tires, which have no self-aligning torque, so they will happily wander and tramline unless you design the suspension and nowadays the EPS to fight it.  Which means, no steering feel.

 

Want a RWD with good steering feel?  Insist on manual steering, and tires with canoe-shaped contact patches. (That means 70-series hoops, max)

MrJoshua
MrJoshua UltimaDork
11/20/19 7:48 p.m.

I would assume regen cannot be as potent on a RWD car. Maybe comfortable decceleration is within normal rear wheel regen capability so it doesn't matter much?

Streetwiseguy
Streetwiseguy MegaDork
11/20/19 7:53 p.m.

Well, after contemplating the whole story, it seems likely that it has to do with packaging and simplicity as much as anything.  Fire a couple of electric motors at the back wheels, eliminate the issues with getting power to a steering tire.  Small motors, so there is still trunk room.  Lotsa battery room available both front and rear.  

Keith Tanner
Keith Tanner MegaDork
11/20/19 8:16 p.m.

Sure, it’s packaging that’s making it more viable. Heck,it may actually be preferable because now the halfshafts don’t have to deal with as much craziness and will last longer.

  But it also means RWD doesn’t carry a packaging penalty, so it’s a more viable option for companies that prioritize handling. 

mtn
mtn MegaDork
11/20/19 8:48 p.m.

“Conspiracy theory” version: back when moms Roadmaster wagon was totaled around 2000, I distinctly remember the Ford salesman telling dad — who was complaining about the lack of RWD options — that he wouldn’t sell even half of the explorers that he did if the average buyer knew that power was going to the rear wheels when it was in 2wd. He said that the overarching feeling among his customers was FWD was much safer. 

 

So, the “conspiracy” theory that I have  is that they could pretty easily put the drive wheels wherever they want, but they’ll get more upgrades to AWD if RWD is standard than they would if FWD was standard. 

(And I don’t put any weight in this, I believe Mr Tanners packaging idea more than mine - just a fun idea I had when thinking about it)

ebonyandivory
ebonyandivory PowerDork
11/20/19 9:31 p.m.

If I know most car companies, if there's a return to RWD, it IS NOT because we enthusiasts are clamoring for it. It's a financial/packaging decision pure and simple.

mad_machine
mad_machine MegaDork
11/20/19 11:37 p.m.

doesn't tesla put the motors in the hubs? I can see where not having those heavy things in the front wheels would be a good thing for steering

Aspen
Aspen HalfDork
11/21/19 8:28 a.m.

Up here in the north everything is going AWD.  I bet they will sell very few RWD EVs, likely special order.

People generally think I am crazy to drive my RWD 2 series in the winter.  So far it is excellent with winter tires and manual trans.  Sometimes getting going from a stop takes a while and the stability control is over active when in comfort mode.  Sport mode is more gratifying.

I think most people will get along fine with a nicely balanced RWD car with winter tires and modern stability control.  Of course the marketing departments with convince them that they NEED AWD or they are irresponsible.

ebonyandivory
ebonyandivory PowerDork
11/21/19 8:37 a.m.

In reply to Aspen :

Funny how up until the 70's, FWD wasn't a thing. But my mom and dad never missed a day of work in New England (well, a few in the Blizzard Of '78). They owned a Mercury Montego and a Falcon.

 

AngryCorvair
AngryCorvair MegaDork
11/21/19 8:37 a.m.

chassis controls and powertrain controls are so advanced and so well-integrated these days, IMO an empty pickup truck is probably the only edge case in which RWD plus winter tires might not be enough for most people.  and that's only because the "people for whom RWD plus winter tires isn't enough" are E36 M3ty drivers year-round. i see plenty of RWD vehicles being driven year-round here in SE MI. challengers chargers mustangs camaros and yes, even pickups.

STM317
STM317 UltraDork
11/21/19 8:45 a.m.

I think a RWD layout, even with an EV, typically allows for a longer wheelbase and improved ride quality/comfort vs the same vehicle in a FWD configuration. Interior room is a big deal too.

I'd guess that's a big reason why the new Explorer/Aviator returned to a RWD based platform.

FuzzWuzzy
FuzzWuzzy HalfDork
11/21/19 8:51 a.m.

I never got the appeal for AWD, especially in places that never snows or snows only a couple of months out of the year. The rest of the year you now have a heavier car, giving you E36 M3tier MPG. Congrats.

I for one am happy to see RWD making a comeback, albeit in a technology I still can't afford. Maybe once the market is saturated w/ EVs, it'll be more financially feasible to start EV swaps.

mtn
mtn MegaDork
11/21/19 9:41 a.m.
FuzzWuzzy said:

I never got the appeal for AWD, especially in places that never snows or snows only a couple of months out of the year. The rest of the year you now have a heavier car, giving you E36 M3tier MPG. Congrats.

 

 

I agree. Not even getting into the whole "Harumph, learn to drive in the snow get snow tires garbleblarblelasdfjasdf" stuff, I drove a lowered Miata through 4 winters. Yes I had snow tires. But If I can drive a lowered Miata through 4 Central Illinois/Chicago winters, there are really very few use cases for AWD/4WD that are legitimate. There was 1 single time I was stuck. Guess what? Every business, including Caterpillar and State Farm was closed that day.  

That isn't to say that it isn't the right answer for some - Colorado for instance. Or, my parents try to have at least 1 AWD vehicle since they live 1/2 the year in the Upper Peninsula, and when they're in Chicago the driveway is very steep and they're older and may not be able to get the driveway cleaned in time. Or those who live in rural areas where it may legitimately take a few days to clear the snow. But for MOST people living in urban and suburban areas, it just is paying more for piece of mind because they don't realize how little they'd actually use it. For my wife and I, it makes little to no sense whatsoever - we did have AWD for about a year, since my wife was an "essential employee" at a hospital that was far enough away and going through 4 towns and 2 counties to get to it, so there may have been issues with snow removal, but even that wasn't really necessary.

 

 

 

With the EV's, (and I could look this up, but... lazy), what is the performance breakdown between the 2? Like, is there a difference in the 0-60 for each? Range? Charge times?

Nate90LX
Nate90LX Reader
11/21/19 9:46 a.m.

This has be driven by overall cost. It must be cheaper to package the drive components in the rear than the front. Most of the recent higher end EV's have a AWD option, so the manufacturers could choose either FWD or RWD as the default. I wonder if RWD is cost-neutral, but it causes more of the general public to choose the AWD option. 
I hope this RWD trend continues as the low end EV's start coming out for the sub $30k market. 

Kreb
Kreb UberDork
11/21/19 9:55 a.m.

I flogged one of the dual-motor Tesla 3s pretty hard. The power we all know about - massive and seemingly endless. As far as handling, it wanted to understeer, but if you got your braking done before the turn and powered through, it would take a nice neutral set. The performance potential was obvious, but I still wasn't that impressed. No matter how good the engineers may be, you just can't escape the fact that it weighs about the same as a base F-150.    

z31maniac
z31maniac MegaDork
11/21/19 10:02 a.m.
Knurled. said:
  And it is all due to Design's fetish for huge wheels and zero-sidewall tires, which have no self-aligning torque, so they will happily wander and tramline unless you design the suspension and nowadays the EPS to fight it.  Which means, no steering feel.

Huge wheels come from larger, heavier cars, which need larger brakes, which need larger wheels to fit them. But even if that wasn't needed, the size of modern cars on 15" wheels with 70 series would look dumb, at least to me. 

Then again, I'm a huge fan of the "Touring Car" look.

TopNoodles
TopNoodles Reader
11/21/19 10:06 a.m.

I might be an outlier but my preference for RWD is mostly because of serviceability. With the drivetrain distributed over a bigger area I find access easier for most components. Even better if it's a solid axle and there's no CV axles to worry about. On the track RWD is still king for its balance and lower weight than AWD, but today there is a huge selection of FWD cars that are well balanced and very pleasant to drive on the street. New EVs so far are not made to be easily serviceable by the owner nor are they meant to please anyone who cares about driving dynamics, so while a return to RWD sounds exciting initially, I don't see any correlation with cars that are actually fun to drive or own.

Keith Tanner
Keith Tanner MegaDork
11/21/19 10:07 a.m.

Tesla does not use hub motors. Nobody does at the moment as far as I know. But all else being equal, packaging halfshafts and dealing with torque delivery through the steering wheels does not help with steering feel. Heck, just looking at the front strut design for RWD vs AWD Teslas makes it clear what a hassle the halfshafts are.

The AWD EVs have greater performance, as the way you do AWD on an EV is by adding motors and thus power. That's a big difference over an ICE, which simply adds more transmission parts to move the power around.

For example, the single motor (RWD) Model 3 Long Range has a single 283 hp motor and weighs 3800 lbs. The AWD has a 252 hp rear motor and a 197 hp front and weighs 4072 lbs. The Performance has the 283 hp rear motor from the RWD and the 197 hp front motor and is rated for the same weight. All of those have the same battery pack. The RWD is a little more efficient, 26 kWh/100 miles vs 29 kWh/100 miles.

0-60 is quoted as 5.0, 4.4 and 3.2 for the three variants. Some of that is the extra power, some of it is the extra traction. Like it or not, AWD will provide more forward thrust when traction is marginal for the needs, whether it's due to a low coefficient of friction on the road or a high torque delivery at the wheel.

Keith Tanner
Keith Tanner MegaDork
11/21/19 10:08 a.m.
TopNoodles said:

. New EVs so far are not made to be easily serviceable by the owner nor are they meant to please anyone who cares about driving dynamics, so while a return to RWD sounds exciting initially, I don't see any correlation with cars that are actually fun to drive or own.

Porsche might like to have a word.

ebonyandivory
ebonyandivory PowerDork
11/21/19 1:11 p.m.

I like my burnouts to sound like "WAAAAAAAAAAAAAAAAAHHHHHHHH!!!" not "ssssssssssssssssssssssssssssssqueeeeek".

Knurled.
Knurled. MegaDork
11/21/19 1:19 p.m.
FuzzWuzzy said:

I never got the appeal for AWD, especially in places that never snows or snows only a couple of months out of the year. The rest of the year you now have a heavier car, giving you E36 M3tier MPG. Congrats.

I for one am happy to see RWD making a comeback, albeit in a technology I still can't afford. Maybe once the market is saturated w/ EVs, it'll be more financially feasible to start EV swaps.

Due to the way tire losses are nonlinear, all wheel drive is actually more efficient over a certain speed.

 

This is why Haldex equipped Volvos always engage the rear diff to some degree, not just when the front tires are slipping.

rslifkin
rslifkin UltraDork
11/21/19 1:22 p.m.
Knurled. said:

Due to the way tire losses are nonlinear, all wheel drive is actually more efficient over a certain speed.

This is why Haldex equipped Volvos always engage the rear diff to some degree, not just when the front tires are slipping.

I'd be absolutely shocked if this is the case in the real world.  It's almost guaranteed that the higher losses in the extra spinny bits and losses due to extra weight (both rotating and non-rotating) out-weigh the gains in tire efficiency with AWD.  

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