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Front Wheel Drive? (Why not? - Logic please!)

Discussion in 'Tech Talk' started by 17.088 ^2, Mar 30, 2017.

?

If you had a choice between (only) Front vrs. Rear wheel drive, what would you select?

  1. Front Wheel Drive

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  2. Rear Wheel Drive

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  1. 17.088 ^2

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    I've been trying to understand why Tesla is only offering the drivetrain in a All wheel or Rear wheel configuration, and not also (or instead) in a Front Wheel drive configuration. If anyone can provide me with some reasonable explanation, I'd certainly like to hear it.

    They're obviously able to squeeze the motor in the front along with the steering mechanism, so technology can't be the reason.

    I suppose they may not like the idea of leaving an open cavity in the rear for collision crunch zones, but that should be able to be overcome with some reinforcement pieces.

    OK, Front wheel drive, immediately adjacent to the steering may be a bit more expensive than a rear wheel drive, but I can't imagine it's TOO pricey.

    Given snow and other road hazards, I can't be the only person who would rather have a Front Wheel Drive Tesla over a Rear Wheel Drive Tesla.


    Can anyone provide some better insight?
     
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    • MelindaV

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      because front wheel drive works in an ICE because of the engine weight. Not so much in an EV. It would be pulling all the weight. There was a writeup a while back that did a great job going over the physics of why the car's weight distribution makes a huge difference in how FWD/RWD/AWD react. I'll see if I can find it - unless someone else beats me to it.
       
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      • Michael Russo

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        Plus if you think of it most entry luxury ICE vehicles targeted by T≡SLA with Model ≡ (with the exception of Audi) are also RWD. Much more fun to drive. I had an Audi A6 years ago and found its road handling stiff & lame... IMHO
         
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        • garsh

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          #4 garsh, Mar 31, 2017
          Last edited: Mar 31, 2017
          • AWD is better than FWD, and they offer AWD
          • RWD is better for acceleration than FWD
          • RWD is better for driving dynamics than FWD
          • FWD cars have problems with torque steer. Electric cars have tons of low-end torque
          FWD is preferred for inexpensive combustion vehicles for two main reasons:
          • You don't need a driveshaft tunnel, which means less intrusion into the middle back seat's foot area.
          • It puts most of the weight of the car right over the drive wheels (most of an electric car's weight is batteries, not motor).
          Neither of these reasons really applies to electric cars. I'm often spinning the tires in my Nissan Leaf, especially when the roads are a little wet. Much of the car's weight is in the battery, and it's FWD. When you start accelerating, it lifts even more weight off of the front of the car, which is not good when trying to accelerate in a FWD car.
           
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          • 17.088 ^2

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            Hmmmm...
            OK people, you've given me some food for thought.
            I guess, especially given all the examples from Norway, that I shouldn't worry too much about performance in the snow.


            (Especially given how pathetically little of the white stuff we had this year... but hey, global warming is a myth, global warming is a myth, say it three times, maybe I'll believe it.)
             
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            • Mark C

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              In a book I read about the Chevrolet Corvair, {rear engine / air cooled flat 6 / vw challenger}, a man went to pickup his car at the dealership in MI, but it had been snowed in when a snow plow went by. He asked the dealer to help him get the car out, but the dealer wouldn't, not until after he tried to drive it out first. He was very surprised that it actually did drive out.

              Perhaps having the right balance of weight over the driven wheels is more important than which end of the car the driven wheels are on. I do hope it has traction control though.
               
            • Badback

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              Front wheel drive is a traction solution. It puts the front mounted engine over the driven wheels. The extra weight improves traction. A front engine rear wheel drive car lacks good traction. IIRC, Citroen invented this design, called the Citroen Traction Avant, in 1934. This design also simplifies the vehicle by eliminating the drive shaft and integrating the differential with the transmission. Some claim, and I agree, that the ability to move the driven wheels side to side helps in slippery conditions. This also simplifies assembly because the whole drive unit goes in as one. Disadvantages include torque steer, limited turning circle and a tendency to 'plow' in turns because of unequal weight distribution.
              Rear wheel drive improves driving dynamics by permitting drifting in turns.
              For Tesla, the drive motor is over the driven wheels in any case, and most of the weight is in the battery pack in the center. So, comparing a Tesla to an ICE car is inappropriate, IMNSHO.
               
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              • Gary Moore

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                My first car was a Corvair. During a major blizzard in Flint, I once took a fellow student home who had made the mistake of riding his Yamaha motorbike to class before a couple feet of snow fell in a few hours. The side street that he lived on had not been plowed.

                I plowed it with my Corvair going home from his place. The scary part was judging deceleration as I hit the end of his street at Grand Traverse. I didn't want to slow too fast and get stuck in a snow drift, but I didn't think that cruising through a red light onto the main drag was a good idea either. Mission accomplished.

                As Badback noted, the weight distribution is key.

                In the Eighties, I used to drive home over that very stretch of I-85 in Altanta north of the Connector which burnt up and collapsed yesterday.

                Rather that take the Perimeter (I-285) home across the north side, I'd take I-75 south into town going home and take the left hand ramp back up I-85 north.

                One day, some guy in a BMW 318 came screaming up on the rear bumper of my Fiero GT as I'm approaching the hairpin turn of the ramp to I-85.

                I have had very few accidents, but most of them involve my being hit from behind, so I was a tad displeased.

                So, I demonstrated to Mr. Ultimate Driving Machine what having the engine over the rear drive wheels meant. I accelerated through the hairpin turn, and he was no longer on my bumper. Fortunately for him, he didn't try to keep up with me through the turn. That would have been a very severe error on his part.

                Please don't drive as I do, but if you do drive, always remember that the laws of physics are not the kind which you can violate.
                 
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                • MelindaV

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                  I've only had one FWD car - which was also my first 5-speed bought new in feb 2000. When it was a few months old, and I was driving it one Sunday morning with a migraine and apparently forgetting how to drive...
                  I was leaving a shopping center on the outskirts of town and while sitting at the light waiting to turn left onto the highway, I was laughing at the car pulled over just down the highway the other direction as I would be going. Light turned green and I pulled onto the highway. This is just about when 80's stations started coming up and Joan Jett's I Love Rock & Roll came on, which made me smile and headache much better (what can I say, I'm a product of the 80s...). a half mile later I was coming up on the reduced speed sign at the edge of town and looked down to see what my speed was (see I didn't even pay attention on a regular basis to my gauges behind the steering wheel then!) and saw I was right at the reduced speed limit but my RPMs were around 5500-6000 instead of half that as they normally would be. So quickly shifted up from 1st or 2nd to 4th (going 40! ha) and the car swerved a ridiculous amount once in the correct gear. Cop apparently had finished with the other car because he then was behind me pulling me over to see if I was drinking! When he got to my window first thing he he said was something like "I saw you swerve and thought maybe you were drunk, but can see you are not". I asked him how many drunk drivers he gets before noon on a sunday and he just looked at me like I asked if he's seen anyone speeding since he's been a cop. Still no idea how he decided I wasn't drinking before I even opened my mouth... but I tend not to laugh at others pulled over any more ;)
                   
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                  • S Gibb

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                    Their seems to be some misconceptions about front wheel drive. First off, you cannot compare weight distribution of an ICE car to that of an BEV. Most BEV's are now coming with battery packs that takes up the entire bottom of the vehicle, which is the majority of the cars weight. So it does not matter where you place the drive unit. Its just a matter of pushing VS pulling weight. i'll come back to this later.

                    Second. with a BEV torque steer is a thing of the past even with sophisticated traction and launch control. The reason torque steer happens is due to the lengths of the CV shafts (drive shafts). With an ICE vehicle with FWD this is mostly due to the fact that the engine sits on one side and the transmission (final drive) on the other. So the short drive shaft will always have more twist (torque) as it is closer to the output than the longer driveshaft, an unequal amount of twist = torque steer. With Tesla and possibly other manufacturers this is solved simply by having the final drive very close to the center of the vehicle therefore equal length drive shafts going to your wheels. The slight difference in driveshaft lengths on the Tesla is made up for by a small shaft directly splined to the final drive, which then allows for equal length drive shafts.

                    Last push VS pull. Mostly for the snowy climate folks. RWD is the superior way of moving a car around in dry to wet conditions. Snow and ice are a completely different story. Now lets say you're trying to move through snow with a FWD car, you stop, then you spin your wheels trying to get going again and eventually get up to speed no problems. Same situation with a RWD car, you stop, then you spin your wheels to try to get going again. ooops you put too much power down, now your rear wheels are moving faster than your front and your rear end overtakes your front end, you're spinning out. Try to stop a 4000lb spinning rock it takes a while. This situation applies to pretty much any speed as well not just from a stop in snowy/ice conditions.
                     
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                    • RickDeckard

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                      #11 RickDeckard, Apr 8, 2017
                      Last edited: Apr 8, 2017
                      I prefer front wheel drive because most of the time i dont care but in my situation the only time i Do care is when driving in snow or icy roads when it feels like you are sliding like a boat, and i have the impression that it makes a difference between having front wheels at an angle and just merrily sliding along vs having the wheels powerfully rotating in the direction you want to go to avoid crashing into the sidewalk, a car, a fence, or an 18 wheeler semi truck coming in the opposite direction seconds away from a head on collision (which is not an enjoyable situation), etc.

                      This said ill probably be looking at dual for all wheel drive, more so if theres no FWD option.
                       
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                      • Tom Bodera

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                        I live in the Snowbelt so yes a FWD car or AWD would be the best choices because of S Gibb's writeup. I will also have to wait for the big D.
                         
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                        • JWardell

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                          It's simply a matter of total traction of the contact patch of the tire's rubber on the road surface. The front tires are already using much of their traction for steering. FWD requires them share steering and propulsion, so in low traction situations it is very easy for them to lose traction and spin and not steer. RWD gives propulsion two dedicated wheels that do nothing else but push. Decades ago when cars weights were far from balanced and 70% of the weight was up front in a huge cast iron engine block the front wheels did benefit from the extra weight, but that has not been the case for a long time. I've driven many FWD cars, and I sorely miss my BMW 1 series, especially in the snow. Plus, Tesla's above average traction control will make this all moot.
                           
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                          • 17.088 ^2

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                            When it came to the issue of deciding that BEVs versus PHEVs, it took me a long time to decide in favor of Tesla and BEVs (versus PHEVs). Until the first week of October last year to be precise (i.e.: my $1000 down).

                            Likewise, it seems that it took me a (not quite as) long time to decide that a Rear-wheel drive BEV is good enough for my needs, and I don't have to hold out (cash or time) for All-wheel drive.

                            But, I'd like to be sure...

                            = = = = =


                            I'd like to pose these questions to those of you who have driven (especially those who OWN) a Telsa Model S or X in the Northern Climates. I'm thinking Norway, Sweden, All of Canada, and those US States (like MN) that border Canada:

                            What are your opinions re a Tesla's performance in Snow?
                            i.e.: If you've driven a Rear wheel drive S or X in snow, PLEASE tell me/us about it.

                            Or, to put it another way...
                            If you do NOT care about "Ludicrous Mode" or high-performance issues, and are primarily concerned about safety, reliability, economy, etc., then is there any justifiable reason to pay for All-wheel drive for primarily SNOW related reasons?


                            17.088 ^2

                            .
                             
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                            • Safe Daddy Driver

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                              I'm still debating whether to forgo AWD in order to save a little $ as well as enjoy RWD driving dynamics. Or is it worth the extra cost for additional safety and battery efficiency? Anyway here's a nice short video of Tesla RWDriving in snowy Norwegian winters. (Published on YouTube months before D announcement.)

                               
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                              • JBsC6

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                                Most luxury sports sedans today are rwd and offer awd as an option.

                                Rwd platforms or rwd biased platforms offer superior driving dynamics.

                                That is why rwd is the chosen drive wheels in sports sedans.

                                The logic given above in a few of the posts are somewhat inaccurate with regards to handling and drive wheels.

                                Asking the front wheel drive only cars to accelerate and turn creates multiple forces working against the tire at the same time limiting handling traction.

                                For a street car ? Who cares I'm sure as tire limits are so high these days.?

                                Still since the OP asked the question...this is the answer.

                                Fwd in the near luxury and luxury segment went the way of the dodo bird here in the United States...

                                Quite frankly it's awd for sport sedan segment volume...

                                The snow country states practically demand that awd be offered..

                                Most people don't want to own a set of dedicated winter snow tires any longer...(I do ) Most purchases in this segment in America are leases so to go through the hassle of dedicated winter tires is foolish I would imagine too.

                                So awd with all seasons seems to be the preferred setup...

                                Tesla was right in its decision for rwd and offer awd....

                                Fwd belongs on the utilitarian Chevy Bolt..


                                JMO in New Jersey I Drive my corvette in the winter with dedicated snow tires and wheels or I'm not going anywhere...(all season being a waste in snow for rwd) but with awd being offered in the tesla model3? No question....get the awd version....good luck deciding
                                 
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                                • RickDeckard

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                                  #17 RickDeckard, Apr 9, 2017
                                  Last edited: Apr 9, 2017
                                  Winter tires are a better in snow and ice imo, depending on the situation it could be that the difference is too small to notice as you are driving, but a small difference can sometimes make the difference between "oh shhh... oof, that was close" and "oh shhh.. BANG!". (Its quite annoying to be stopped at a red light and be rear ended by a driver that "almost" stopped in time.)






                                  and while being a bit off topic might as well add this :

                                   
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                                  • 17.088 ^2

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                                    Ooops. I did forget one minor issue:
                                    We routinely travel to the in-laws, a trip of 331 miles one way.
                                    {Yes, there are THREE (or four) superchargers along the way, so I admit the below is at least to SOME extent a moot point.}
                                    -----


                                    As I recall, an All wheel drive BEV has slightly more miles range, given the same battery, etc., versus a rear (or front) wheel drive BEV.

                                    1. Is my memory correct about this?
                                    2. Would it actually make a significant difference over a 331 mile trip, given a Model 3's expected smaller battery?

                                    .
                                     
                                  • RickDeckard

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                                    #19 RickDeckard, Apr 9, 2017
                                    Last edited: Apr 9, 2017
                                    no, based on the S ranges, it would not make a significant difference (8-9 miles) and maybe you would have to supercharge even with a 75 unless you like to live on the edge (unless the Model 3 75 has more range than Model S 100D which has about 335 mi). It sounds like you would have been a person that would have liked a bigger than 75 battery.(im lucky in the sense that in my case the base battery will be more than enough).
                                     
                                  • MelindaV

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                                    Here's a screenshot of the Model S range calculator (Tesla has quite useful info on their site - this is under the main Model S page)..
                                    so 6 mile difference between the 60 and 60D - so in your 331 example, the dual motor option would have an extra 9ish miles over the rear motor
                                    IMG_0237.jpg
                                     
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