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Rear wheel drive

You may want to rethink the rear wheel drive on the Model S. I guess performance on dry pavement is best with real wheel drive but that is not the case in difficult conditions. Front (and of course all wheel) drive vehicles are sooo much better in snow and ice. I would much rather be in my old Honda or even my old Plymouth van in snow than than in my current BMW. Please reconsider.

I am most concerned with the condition of icy roads on an incline, especially when starting from a stop. With 4 wheels available to propel the car it is likely that one may gain sufficient traction to get the thing going. Granted my FWD and RWD experience is with older non-stability controlled vehicles I found the FWD would at least drag you (albiet slowly) in the direction you wanted to go. The RWD would tend to have the back end of the car wobble or try to pass the front end.

I suppose I will need to wait until Tesla is actually ready to ship the 'S' and test drive it before making any moves towards getting one.

I am interested in the vehicle for safe, comfortable transport. If I wanted a drag car, I would definitely go RWD, my racing days, however, are behind me. Although I'd be tempted to Auto-X the 'S' once.

Loki, you could take a Roadster out for a winter test drive and experience the Roadster's RWD + TC...then you would see first hand that the RWD Roadster does not wobble in any way, shape or form.

I have a few comments in other AWD / RWD threads on here...wished the Model S would be AWD rather than RWD.

I have had my Roadster almost 60 days (driving in the snow here in Canada). If the Model S performs as well as the Roadster in the snow, I've changed my mind and think AWD is unnecessary.

When I hear comments by roadster owners like Jaffray, it really temps me to reserve a M-S here in vermont. I am guessing a large part of the reason that roadster owners experience good winter traction has to do with how the low battery pack keeps the tires engaged in the road surface without higher up weight to throw the vehicle in turns the wrong direction, something I have experienced down hill with my AWD SUV in slush (of coarse AWD helps zero in down hill situations). The M-S should have this same battery design and thus ver similar weight distribution characteristics. This leads me to believe that it should also handle well in winter conditions. But this is all theory until the real deal shows up.

As a side note, it is interesting how much I feel from peoples posts that they expect the M-S to drive like the roadster at half the price and significantly larger size. I wonder how the drivers at Tesla of the current alpha M-S feel that the vehicle performs relative to the roadster or if even Tesla is designing the M-S with that as a goal?

You are all completely totally wrong about rear wheel drive. The entire point of Tesla is to produce an electric car that isn't a boring econobox that understeer's around corners. Front wheel drive is NOT safer in any way shape or form. Rear wheel drive allows the steering wheels to freely accomplish that task (while maintaining more lateral traction without acceleration forces) and the rear wheels to propel the vehicle forward. This also allows for a 50/50 weight distribution between the front and rear axles which is optimal for SAFE handling ESPECIALLY IN THE SNOW. And you guessed it, when going up hill FORWARD, the weight transfers to the rear of the vehicle increasing traction on the rear wheels along with the acceleration! This is not a 1975 Buick with a big block engine and 60% of the weight on the front. This is why BMW's and all other high end cars are not front wheel drive. All wheel drive is a good option too, but not necessary for 99% of the driving conditions in north america. Keep in mind, AWD reduces efficiently and adds weight to the car. More weight means longer stopping distances, more under-steer. The car is supposed to be efficient, and AWD may reduce the range of this car. It is all marketing! AWD is total complete marketing. Today's RWD is totally different than in the past. Especially when you factor in stability and traction control. It's all in the tires my friends.

mvbf;
The weight in the M-S will be much lower than the Roadster. The R's battery is a block behind the seats. The M-S' is a flat layer under the floor, as low as you can get. The plant interview vid wasn't kidding when it kept coming back to the superior handling characteristics this will have.

Not only that puts the center of gravity very low, it also puts it into dead center between the wheels. Can't be more ideal placement if you think of handling of the car. It also removes mass from extremes like they are in traditional ICE car (stopping spinning of a stick with weight at both ends is harder than stopping spinning a stick with that same weight at the middle of the stick. That is why all supercars have middle-engines).

The beauty of having two electric motors (one front and one rear) is the fact that you do not need a physical center differential and associated drivetrain losses. Also, the balance between front and rear can be controlled 100% electronically. Therefore, under low loads, low acceleration, the rear motor can be operated by itself while the front motor freewheels. As such, you don't have as much of an efficiency penalty (just the added weight of the front motor/drivetrain). However, when you want to stomp on it, the front motor can kick in to add a substantial boost to acceleration. Having two separate motors controlled electronically, allows for a lot more freedom with traction control in slippery conditions and hard cornering. The Nissan GT-R is one of the best performing cars for the money and uses all-wheel drive with an electronically controlled center differential and laps the Nuremburg Ring faster than a Porsche 911 Turbo. Sure, from a purist's point of view, RWD is the only way to go, but if you are truly seeking the ultimate in performance, AWD is king.

I do agree that keeping the M-S RWD works towards Tesla's goal of lower cost. However, having a higher trim level with AWD at the GT-R's price point that matches or beats the GT-R's performance would be awesome and well worth the extra money. Keep in mind that the R34 GT-R and earlier versions were nothing more than modified Skyline luxury sport sedans. The same strategy Nissan used for decades can be applied to the Model S. FYI the Infiniti G37 is called a Skyline in Japan and is RWD.

Best performance, cost, efficiency and space is 4 inside wheels motors like hydro-quebec electric car developped and destroyed in 1995(before gm ev1) too much for our world some info here:

http://www.dailymotion.com/video/x5m2nf_moteur-roue-sa-naissance-et-sa-m...
and
mms://medias-wm.radio-canada.ca/diffusion/2009/medianet/CBFT/Decouverte200911221900_m_1.wmv?MSWMExt=.asf

@joesontesla Tous d'abord, c'est une bonne chose que je comprends le francais pour voir ce video. Second of all, the problem with in wheel electric motors is the additional unsprung mass. The more unsprung mass you have, the stiffer the spring and damper system have to be to control it. Which translates to high NVH and an unconfortable ride (or unsafe handling characteristics if you use softer springs). Besides, they were talking about 25kW motors, which even with 4 of them is only 100kW. Combine weak sauce acceleration with a harsh ride, and you've got yourself an expensive paper weight sitting on your showroom floor.

70 kw x4 280kw tu ne comprend pas bien le francais.

Brian, that is interesting that the roadster puts much more weight over the rear wheels in a RWD car. On the one hand, I do see the general performance advantages to have a lower more distributed weight profile especially with the longer 4 door, 7 passenger M-S. On the other, it makes me less confident that it will perform as well as the roadster in uphill slippery conditions. More weight over the tires with power just seems like it would handle that uphill ice/slush/mud what have you better. Of course I do not pretend to be be even close to an expert in understanding these technicalities, so I welcome other possibly more educated opinions on this.

70 kw and 1200nm of torque per wheel. this tv show cause a shock in quebec in 1997. here fuel cost is 1.20$ per liter and 0.07 cent per kw almost produced by carbon free public hydraulic power plant.

I live in the northeast U.S.. First car I ever owned was a RWD and hills were murder. It simply could not be driven on some winter days. TCS can be overwhelmed b/c of the degree of incline and degree of slipperiness. Second car I had was a much older FWD car with no TCS and driving in slippery conditions was MUCH easier. Still one can get stuck with a FWD car. Noone has mentioned that AWD can be turned off and on if designed that way, such that efficiency is better with it off, but it is available with slippery conditions. If anyone is still wondering whether AWD is any better than RWD for handling, just check the Motor Trend video of the new Nissan GT-R AWD VS. an Ultimate Vette Z06 Carbon option VS. the latest maxed out Shelby Mustang GT 500. BTW, the Mustang had the highest horsepower, the Vette was much lighter due to use of carbon fiber and the GT-R had AWD making it the heaviest of the 3.
See it it at: http://www.youtube.com/watch?v=wfzqmpQQfOs

If you invest in *real* snow tires, you'll be shocked at how fantastic the traction is, regardless of vehicle. Once I swapped out the ultra high performance tires with real snow tires on my MR2 (a mid engine, balanced weight car with RWD and NO traction control), it went from useless in the snow, to awesome. I never found a hill I couldn't climb (ok, be reasonable here).

It really was night and day. I swapped the wheels/tires in December, and back in late February. Obviously, the street racing performance suffered, but I never got stuck. Life is full of tradeoffs.

No doubt, the original poster's BMW has performance tires.

This was stated previously but just to re-state simple facts:'

With current ICE engines the reason why FWD is preferred over RWD and why AWD is the most preferred is because of the ICE. In most cars the ICE sits right over the front wheels adding the extra weight needed for traction in slippery conditions. So FWD is better than RWD

AWD is just addition points of traction and power and if it is tuned correctly with traction control and smart stability so power is sent from slipping wheels to gripping wheels then obviously better

With Tesla on the Roadster and Model S, they put the massive amount of weigh (the battery) over the driving wheels. SO you will have as good or better control and traction as a FWD car.

With Model S because of the placement of the battery it will most likely have as good of traction as your typical AWD car. When Tesla does release the AWD version in 2013 or so, I would venture to guess that it would be one of the most superior driving experiences in slippery conditions

Not much of a debate regarding this topic beyond that

You folks want to see something funny. Here in south if we get two or three inches of snow or ice storm everything shuts down, stores empty of bread etc. Some driving that would really make you cold climate guys laugh. I could tell an epic tale here but will just shorten it down to "took me four hours to go twelve miles" during snow storm where ice quickly formed. Found out that the key was certainly slow in '74 Chevy Nova RWD but made it. This car would slide around easy. Had a '59 Ford would slide around some. But once had a '54 Dodge as long as went slow and steady and no "herky jerky" driving it was like a "mountain goat" maybe becase had dodge "red ram v8 engine",ha. It was heavy, had big broad tires, high off ground. One of the best, most dependable cars I have ever owned. Then there was the "65 GTO, mixed with a few beers, a newly adjusted hair trigger clutch, it did some slidding around to into a parked car{during my ancient night club days} not a good outcome on this particular episode.

All to say guess even RWD cars are different as they probably all are regardless of what kind of drive, but of course I know you folks are talking in general terms about the various drive set ups. Must really be a pain in some of your areas at times and no doubt a critical issue to each of you. Good luck.

(New member here)
While many car enthusiasts will drool over this or that high performance race car, take driving lessons at the track, and imagine being there while driving in rush hour, please note there are other drivers out there who have their own perspective. Here's mine.

In dry conditions with a powerful engine, rear wheel drive cars will increase traction with more power applied, while front wheel drive cars will lose traction. Above a certain amount of power, FWD just can't pull any more, while RWD (with wide enough tires) will be able to push. So, those who want to really move should have RWD on dry pavement.

I'm not one of those people. I like to have power to pass someone on the cell phone, but I don't like to be surprised and excited by an unexpected loss of traction when it's raining or icy. I like to be able to go when the light turns green, even on a slight uphill while on ice.

I don't yet have a Tesla car, but I am putting a deposit down, probably right after this entry, on a Model S. I'm hoping for all the great driving experiences owners of the Roadster claim.

Now to the point: I haven't driven a RWD car in years for a couple of reasons. (1) Family members drive the car, including the wife, who's even less into cars than me. If skidding occurs, it's easier to remember (when driving FWD, not RWD) to just turn where you want to go and try to modulate the accelerator to get back under control. Maybe traction control negates this need, I don't know. (2) With the ICE over the wheels, I can get moving on ice more often than with RWD. About 18 months ago I watched everyone with cheap and expensive cars drive circles around someone in a BMW who couldn't get up a mild incline in winter.

My take on all this, after reading EVERY item in this discussion: It would be nice to have a little bitty motor on the front wheels which would get the car going to, say, 5 MPH, then shut off. Advantages of this: (1) small weight gain (2) possibly only small additional cost (3) motor can be specific to very low speeds, possibly making it very energy efficient to get the car moving - I don't know if the big motor's windings are inefficient or slow to do this where a smaller one would be better, or maybe I'm just imagining things. [I've been trained as an electrical engineer, but my days of analyzing motor windings are in the distant past.] (4) the control of this front motor would be trivial - no real changes needed to controls for the rear wheels, as above 5 MPH it wouldn't exist and (5) allowing a little motor to spin up to high speeds while the car is going slowly means that, while braking, more regenerative energy can be recouped before friction brakes are applied, saving electricity (perhaps not enough to make a difference, but I'm not crunching the numbers).

Anyway, when you're stuck on a little, slightly icy uphill with your gorgeous new car having its rear wheels on the ice, and the local kids are walking past and watching while your own kids drive by in the Subaru, you might remember this post.

Wishing us all luck with our Model S's to come!

@EdG, thanks for the post. I enjoyed reading it. :-)

I've got a bmw 335d which is RWD. Yes FWD does a little better in the winter when you're on an icy incline, but I've never "not been able to move" or anything like that. As far as losing control of the car, skidding etc. it never really happens, traction control (and winter tires) pretty much prevent it from happening. (and I push the car in the ice and snow often to see how it responds) Yes without traction control you'd have to have a very light right foot, but traction/stability control keeps things straight and tidy.

Could be I saw the only BMW and BMW driver who would get stuck on that incline. Could be that I was just too smug, driving my Honda minivan right on by.

I heard once that Rolls Royce gave owners a car cover to put onto a disabled car: not a good ad if a premium car is out of action, and the passers-by can think up their own reasons for it.

So, if you're proud of your car, you don't want to be spinning tires while others, using far older technology, pass you by. Embarrassing. Much more fun is when everyone else is frantically trying to keep from sliding off the road while you casually move on. With 7 passenger capability, you could offer all those stuck drivers a lift, as long as you're SURE you can get moving again once you've stopped. Hence my prior post; it's great to have confidence.

But I'll have to drive the S for myself before I'm convinced it's at least as good as a $20K Subaru, which works wonderfully even without snow tires.

Performance over ice and snow has more to do with the type of tires mounted than whether or not the car is front wheel drive. I have only owned 1 front driver in almost 40 years of driving and the only time I had a problem was when I attempted a winter with summer performance tires. I put modern winter tires on a BMW and drove every where my friends did in their 4wheel drive SUVs.

The other thing different about the Tesla is that there is no engine at the front and the weight/mass of the vehicle is much better centered. If an ICE vehicle had more weight in the back, a RWD would handle well in the winter. That being said, I wouldn't mind AWD coming from my Audi TT which handles quite well in the winter.

I am still big AWD fan. Tis has to do with me having kids and a spouse and going on a trip I don't want to get stuck... If I slide off the road, I want some chance of being able to get myself back on the road... I also am a physician and it is a real big deal for me to be able to get to my hospital. Good weather, bad weather, apocalypse... It does not matter, lives are at stake... I choose AWD. It increases my confidence...

Interestingly, Lightning ditched the proposed in-wheel motors in favor of a rear-drive setup for their Electric GT. At 300k per vehicle, I doubt that cost was the primary driver of this decision:
http://green.autoblog.com/2011/06/06/electric-lightning-gt-ready-for-lon...

Probably they couldn't find powerful enough hub-motors worth of that car. Hub-motors in general are quite weak.

Another problem is road handling with heavy unsprung masses...

Regarding the pros and cons if different drivetrain layouts, I came across a very interesting post by a German auto journalist. He sheds some light on Audi's history and particularly on the rivalry between Audi and BMW. I found it very entertaining to read and even enlightening.

Unfortunately it is only available in German, but since there are quite a few forum member from Germany, Swiss and Austria among us, I post the link nevertheless:
http://motor-kritik.de/node/77

Bottom line: AWD is better than RWD under very specific circumstances. It is worse in all other, due to added cost, added weight, double-purpose of front wheels (steering and propulsion), added internal friction (and consequently added consumption/lower range), and more points of failure.

An RWD vehicle with a low center of gravity, a long wheel base and an even weight distribution between front and rear axle offers optimal driving dynamics under (almost?) all practically relevant conditions. Attributes which, incidentally, all apply to the Model S. :-)

Some of the disadvantages inherent to AWD will be much less prominent in an electric AWD (Model X) than they are in an ICE AWD vehicle, because shafts are replaced by cables and the compensating gearbox is replaced by software. Yet, the gist of it may still apply.

Very interesting, VB! It occurs to me to wonder if the X's front regen capacity is beefed up somewhat to handle the disproportionate load it will have.

It seems to me that based on that information it would make sense on an EV to put a smaller drivetrain at the front and only enable it as needed -- however for energy optimization purposes it seems that if you're not going to use AWD most of the time it'd be best to do away with the front motor increasing range due to both less drivetrain to consume energy and less weight.

It depends a bit of the surface is it better to have AWD or RWD. If you drive in bad conditions non-powered front wheels act like an brake. Also with two motors you don't need to have as much power / motor which reduces the required weight and weight of the cables.

Anyway, AWD strong point is in ability to move when both FWD and RWD cars would get stuck and better handling in slippery conditions, hill climbing etc. You don't buy it to save fuel/energy, you buy it for better handling.

Anyone who has driven AWD in slippery conditions in a place which has some hills knows that difference is huge between it and two wheel drives.

You could describe it like having to push a car up to hill with four blokes, one scenario only two of them push the thing up and two only walk with it keeping it in straight line, and other all four push it. Strain / person is halved with latter case and because they need less power to move slippage is also less likely.


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