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      02-08-2015, 04:48 PM   #89
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Originally Posted by Sportstick View Post
I sense the indignation, but don't understand it in this thread. My comments were made recently to correct a simple misstatement of fact. No drive system, neither two nor four wheel, generates traction, and it had been posted to the contrary earlier. Traction occurs at the ground and is a function of the tires interacting with the surface. That is not a technical detail nor word game. Understanding this leads to being able to make informed decisions about buying vehicles and tires. Everyone can be just as enthusiastic as they wish and we all hope everyone enjoys their cars. The debate can easily end when everyone buys what they want, but doesn't try to mis-state facts.

BTW, in our corporate database I just checked, here are the top 5 U.S. states in descending order for all wheel drive intention for the next car purchased (excluding pickup trucks) n=~92,000:

1) New York
2) Michigan
3) Ohio
4) New Jersey
5) Wisconsin
It is a word game. C'mon.
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      02-08-2015, 05:06 PM   #90
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Originally Posted by 335BOY View Post
It is a word game. C'mon.
I think it's not a game. Here's why. To the degree that "AWD adds traction" becomes conventional wisdom, it leads some folks with less technical knowledge astray. They then go and buy a vehicle for non-enthusiast use, even a BMW, feeling safer with AWD and paying no attention to any having any different tires than if they selected the RWD base vehicle version. Some of these people wind up with injuries/damaged vehicles and are mystified as to why their AWD vehicle didn't take better care of them. My reason for pursuing this discussion is not to impugn anyone's car or informed personal decision, but to raise the issue that what we say to others about vehicles and tires can make a difference in someone's well-being.
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      02-08-2015, 06:20 PM   #91
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Originally Posted by Sportstick View Post
I think it's not a game. Here's why. To the degree that "AWD adds traction" becomes conventional wisdom, it leads some folks with less technical knowledge astray. They then go and buy a vehicle for non-enthusiast use, even a BMW, feeling safer with AWD and paying no attention to any having any different tires than if they selected the RWD base vehicle version. Some of these people wind up with injuries/damaged vehicles and are mystified as to why their AWD vehicle didn't take better care of them. My reason for pursuing this discussion is not to impugn anyone's car or informed personal decision, but to raise the issue that what we say to others about vehicles and tires can make a difference in someone's well-being.
Unbelievable.......again.
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      02-08-2015, 06:40 PM   #92
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Originally Posted by 335BOY View Post
Unbelievable.......again.
Sorry we can't communicate more effectively with each other. All points have been made, so let's just move on.
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      02-11-2015, 10:05 AM   #93
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Originally Posted by Mark's M View Post
With respect, these RWD vs AWD discussions ALWAYS end up talking about winter driving and a few people, me included, are really, really tired of it. AWD has it's benefits in normal weather which includes driving in the wet.

This ridiculous debate needs to end. Those with M235's in AWD format are just as enthusiastic about the performance of their cars (rightfully so, it's a blast) as those with the RWD version. Not everyone who bought the xDrive version of the M235 lives in permanent winter conditions, some of them don't see snow at all. So please, no more automatic "default to winter tire discussions" for this car, it's getting very lame IMHO.
^ + 1

Most of the discussions on RWD vs AWD focus on one being the correct choice and the other being unacceptable. I prefer to look at this as whether AWD is a viable alternative to RWD.

I can understand where some do not consider AWD a viable choice for the 3 / 4 series since the xDrive cannot be had with a sport suspension. But for the M235i, given both AWD and RWD have the same sport suspension and can be had with the same wheels and tires, I think the answer is yes.

To me, AWD is analogous to the Automatic Transmission- both are evolving. The 8 speed Sport AT in a BMW is to the point that it offers slightly better performance than a conventional MT, but driver interaction is different. Some prefer the interaction of a conventional MT so either one is a valid choice depending on personal preference.

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      02-11-2015, 10:25 AM   #94
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RWD. I'm in Montreal. Obviously I could get stuck in a snowbank. Accelerating on ice is slower. One you're moving the car is VERY stable, so IMO the pros outweigh the cons, unless you live in a city where it snows every day for 6 months.
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      02-11-2015, 08:37 PM   #95
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Quote:
Originally Posted by BruceOmega View Post
^ + 1

Most of the discussions on RWD vs AWD focus on one being the correct choice and the other being unacceptable. I prefer to look at this as whether AWD is a viable alternative to RWD.

I can understand where some do not consider AWD a viable choice for the 3 / 4 series since the xDrive cannot be had with a sport suspension. But for the M235i, given both AWD and RWD have the same sport suspension and can be had with the same wheels and tires, I think the answer is yes.

To me, AWD is analogous to the Automatic Transmission- both are evolving. The 8 speed Sport AT in a BMW is to the point that it offers slightly better performance than a conventional MT, but driver interaction is different. Some prefer the interaction of a conventional MT so either one is a valid choice depending on personal preference.

Bruce
Well reasoned Bruce. I think the key here, as you mention, is personal preference. Also key, for this particular car and also as you mention, is that their performance capabilities are relatively similar. Sure one of them will do a little better than the other in a couple of areas and vice versa. Bottom line though seems to be that both are a blast to drive. Lots of kudos to BMW for satisfying the performance needs of BOTH sides of the RWD/AWD argument
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      02-12-2015, 07:56 PM   #96
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I personally went AWD because that "X-drive" badge on the trunk is Super badass!

Actually, I went AWD because my Camaro is RWD, my Harley is RWD, my outgoing lease was FWD, and I have come to really appreciate my X5D's ability to be both smooth and capable is a wide variety of weather conditions.

I also had a turbo I-4 AWD car about a decade ago (Eagle Talon TSi) and found it a BLAST to drive. I hoped the 228xi would build off that same driving experience, and so far I've been very happy!
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      02-12-2015, 09:37 PM   #97
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Quote:
Originally Posted by Sportstick View Post
Respectfully, yes it does. As noted in the explanation above, asserting AWD has more (or any) traction is just as wrong as suggesting rear wheel drive has less or (or any) traction. Drive systems don't have traction.Tires do.
LOL, this is a total game of semantics...

Scenario:

6" of new snow falls on a hilly driveway. 4x4 SUV is left in RWD configuration, and fails to get up driveway. Driver shifts the vehicle into 4WD, and is able to make it up the driveway. Same tires, same conditions, but the 4WD mode makes the difference between being stuck and getting going. I call that traction - I'd be interested to see what term you have for that if it's not traction.
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      02-12-2015, 10:30 PM   #98
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Quote:
Originally Posted by whoosh View Post
LOL, this is a total game of semantics...

Scenario:

6" of new snow falls on a hilly driveway. 4x4 SUV is left in RWD configuration, and fails to get up driveway. Driver shifts the vehicle into 4WD, and is able to make it up the driveway. Same tires, same conditions, but the 4WD mode makes the difference between being stuck and getting going. I call that traction - I'd be interested to see what term you have for that if it's not traction.
OK. This topic was concluded a while back, but with your thought-out scenario, let's pick it up again. (Those who are tired of this topic might wish to stop reading now and find a different thread!) If I hold 4WD as a constant and vary the kind of tires on the front wheels, the potentially beneficial effect of engaging 4WD will change accordingly. Therefore, 4WD is not the ultimate source of the traction. It is determined by the tires, because the traction occurs between the tire and the road surface, not in the differentials nor axles of 4WD hardware. All 4WD does is enable two more tires to have motive power, and if the tires are of the proper type, gain traction with the ground underneath. Bald PSS up front would have essentially no helpful effect, exaggerating the scenario to point out the logic.

Depending on your age, you may recall the "Necessary but insufficient" type of questions in the old SAT. For improved overall vehicle traction vs RWD, 4WD is necessary in the vehicle but is insufficient without proper tires, as with tires with low-to-no traction on a low mu surface, there would be no beneficial effect of 4WD. Car mags have proven more than once that 4WD/all seasons cannot keep up with RWD on winters. So, while 4WD can help in the situation you describe, it helps not by adding traction of its own, but by enabling the two additional tires which the 4WD powers to gain the helpful extra traction.

This is a distinction with a difference and not relegated to mere semantics. The reason this is important to understand is for drivers to realize they need to pay attention to tire selection and not just rely on having 4WD . Far too many do not and wind up with their all-seasons facing skyward and the roof in the snow. Claiming 4WD, per se, "adds traction" just reinforces the misunderstanding. The caveat about tires should always be included.

Last edited by Sportstick; 02-12-2015 at 10:41 PM..
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      02-13-2015, 08:09 AM   #99
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Quote:
Originally Posted by whoosh View Post
LOL, this is a total game of semantics...

I call that traction - I'd be interested to see what term you have for that if it's not traction.
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Originally Posted by Sportstick View Post
<wall of text that fails to answer my question>
Totally agree that overall grip is dictated by the tires. A racing slick on an AWD car isn't going anywhere in snow.

If t = potential traction of a tire in any given situation or condition, then:

RWD total potential traction = 2*t
AWD total potential traction = 4*t

From the standpoint of total traction available to the vehicle, AWD does in essence add potential traction. However, in the above formula. If t=0 because of the wrong tire selection, 2*0 and 4*0 both equal 0... And the car goes nowhere.
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      02-13-2015, 08:24 AM   #100
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Quote:
Originally Posted by whoosh View Post
Totally agree that overall grip is dictated by the tires. A racing slick on an AWD car isn't going anywhere in snow.

If t = potential traction of a tire in any given situation or condition, then:

RWD total potential traction = 2*t
AWD total potential traction = 4*t

From the standpoint of total traction available to the vehicle, AWD does in essence add potential traction. However, in the above formula. If t=0 because of the wrong tire selection, 2*0 and 4*0 both equal 0... And the car goes nowhere.
Yes! Completely agree with your use of the term "potential traction" and the mathematical expressions. Potential is not the same as kinetic. The reasoning in my answer didn't come up with the same very descriptive term as did you, and well-done on your part , which might have helped earlier on in this thread.
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      02-13-2015, 08:36 AM   #101
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Quote:
Originally Posted by Sportstick View Post
Yes! Completely agree with your use of the term "potential traction" and the mathematical expressions. Potential is not the same as kinetic. The reasoning in my answer didn't come up with the same very descriptive term as did you, and well-done on your part , which might have helped earlier on in this thread.
Glad we could come to agreement, and in only 4 posts!!
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      02-13-2015, 08:50 AM   #102
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Originally Posted by whoosh View Post
Glad we could come to agreement, and in only 4 posts!!
Yeah! Usually I have to build a lot more "text walls" to finally say what you came up with in one phrase!
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      02-13-2015, 03:26 PM   #103
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Quote:
Originally Posted by Sportstick View Post
Yes! Completely agree with your use of the term "potential traction" and the mathematical expressions. Potential is not the same as kinetic. The reasoning in my answer didn't come up with the same very descriptive term as did you, and well-done on your part , which might have helped earlier on in this thread.
This is a very interesting discussion, and far be it for me to try to refute anything Sportstick says. BUT it seems to me that there would be a scenario, using the 4x4 on the hill example, where that vehicle, on 4 winter tires, wouldn't be able to make it up the hill in 2WD, but WOULD when switched into 4WD mode. Thus clearly, the xDrive DOES make a difference in some situations, no? What am I missing? Thanks.
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      02-13-2015, 03:42 PM   #104
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Originally Posted by CE750Jockey View Post
This is a very interesting discussion, and far be it for me to try to refute anything Sportstick says. BUT it seems to me that there would be a scenario, using the 4x4 on the hill example, where that vehicle, on 4 winter tires, wouldn't be able to make it up the hill in 2WD, but WOULD when switched into 4WD mode. Thus clearly, the xDrive DOES make a difference in some situations, no? What am I missing? Thanks.
You understand it perfectly. 4WD does do something. It sends power to two more tires so they can make use of their ability to gain traction. The earlier issue had been a wrong statement that the 4WD system adds traction, when there is an intervening factor which actually adds the traction....the tires! There is no traction to the ground generated in the differentials and axles which comprise the 4WD components. The descriptive of 4WD creating "potential traction" works well, which becomes "kinetic traction" once the tires start turning and not slipping.

It would be like telling a pilot that the hydraulic actuators add lift. No, the hydraulic actuators activate flaps and slats and they provide the lift. Hydraulic actuators in the absence of flaps and slats are useless. Think of 4WD as the hydraulic actuators and flaps and slats as the tires.

Last edited by Sportstick; 02-13-2015 at 03:54 PM.. Reason: Edited to add analogy
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      03-19-2015, 02:25 PM   #105
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I'm trying to figure out whether or not to order Xdrive, and today I had the opportunity to drive two 235's back to back...one Xdrive and the other RWD. I know the dealer well, and they let me take each car out without a salesperson, so I did not hesitate to push each car hard :-) Both cars had staggered Pilot Super Sports, and it was about 45 degrees here.

To give some perspective let me say that while I'm not a professional racer nor do I have extensive track experience, but I own a Porsche 996 and previously owned other sports cars including a Lotus Elise, so I'm reasonably acquainted with handling characteristics.

The extra weight of the Xdrive is noticeable, but only when you push the car very hard on entrance and exit ramps. I don't think an average driver would ever notice the extra weight, even if they were looking for it.

When pushed VERY hard, the Xdrive car had somewhat more tendency toward initial understeer. When I say "pushed the car hard", I do mean to or beyond the point that most passengers would likely be concerned for their safety.

Finally, it was far easier to achieve faster flat out acceleration from a standing stop with Xdrive. Without the LSD it was not difficult to overwhelm the rear tires on the RWD car with all the torque...of course traction would have been better with these tires had the weather been 30 or 40 degrees warmer.
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      03-19-2015, 04:16 PM   #106
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Quote:
Originally Posted by shark715 View Post
I'm trying to figure out whether or not to order Xdrive, and today I had the opportunity to drive two 235's back to back...one Xdrive and the other RWD. I know the dealer well, and they let me take each car out without a salesperson, so I did not hesitate to push each car hard :-) Both cars had staggered Pilot Super Sports, and it was about 45 degrees here.

To give some perspective let me say that while I'm not a professional racer nor do I have extensive track experience, but I own a Porsche 996 and previously owned other sports cars including a Lotus Elise, so I'm reasonably acquainted with handling characteristics.

The extra weight of the Xdrive is noticeable, but only when you push the car very hard on entrance and exit ramps. I don't think an average driver would ever notice the extra weight, even if they were looking for it.

When pushed VERY hard, the Xdrive car had somewhat more tendency toward initial understeer. When I say "pushed the car hard", I do mean to or beyond the point that most passengers would likely be concerned for their safety.

Finally, it was far easier to achieve faster flat out acceleration from a standing stop with Xdrive. Without the LSD it was not difficult to overwhelm the rear tires on the RWD car with all the torque...of course traction would have been better with these tires had the weather been 30 or 40 degrees warmer.
You just so happen to test drive? Dealer buddy?
I went for AWD and will be having winter tires.
I consider myself an enthusiasts, but dont plan to autocross or track.
(Ok, maybe one day, once...) But it sounds like it could be said unless you plan to track/autocross an xdrive isnt worse.
And if you do track, you should prob wait for the M2 and not even consider the M235i
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      03-19-2015, 04:32 PM   #107
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Originally Posted by williesm View Post
But it sounds like it could be said unless you plan to track/autocross an xdrive isnt worse.
Based on my experience today, I would say the X drive is close to invisible (except for the extra traction during hard acceleration, and of course, for winter traction) until you are driving the car at or close to the limit, and then, yeah, the RWD is going to be the more entertaining drive. Not really surprising assuming what the dealer said is true (that it's heavily biased toward rear wheel drive). I was also expecting (not really sure why) the xdrive's ride to be a bit more stiff, but I can't say I could detect any difference whatsoever.
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      03-23-2015, 10:47 AM   #108
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Quote:
Originally Posted by shark715 View Post
Based on my experience today, I would say the X drive is close to invisible (except for the extra traction during hard acceleration, and of course, for winter traction) until you are driving the car at or close to the limit, and then, yeah, the RWD is going to be the more entertaining drive. Not really surprising assuming what the dealer said is true (that it's heavily biased toward rear wheel drive). I was also expecting (not really sure why) the xdrive's ride to be a bit more stiff, but I can't say I could detect any difference whatsoever.
Thank you very much for your two posts. I was acutely interested in this comparison for the M235i.

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      03-23-2015, 12:48 PM   #109
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Quote:
Originally Posted by shark715 View Post
Based on my experience today, I would say the X drive is close to invisible (except for the extra traction during hard acceleration, and of course, for winter traction) until you are driving the car at or close to the limit, and then, yeah, the RWD is going to be the more entertaining drive. Not really surprising assuming what the dealer said is true (that it's heavily biased toward rear wheel drive). I was also expecting (not really sure why) the xdrive's ride to be a bit more stiff, but I can't say I could detect any difference whatsoever.
I drove rwd m235 on the track. and test driven the x-drive m235(3 separate test drives on street drives at different dealers). after driving the rwd version, I was expecting the x-drive version to be a letdown but I came away impressed by the x-drive version
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      03-23-2015, 08:41 PM   #110
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Quote:
Originally Posted by bimmercar View Post
I drove rwd m235 on the track. and test driven the x-drive m235(3 separate test drives on street drives at different dealers). after driving the rwd version, I was expecting the x-drive version to be a letdown but I came away impressed by the x-drive version
I'm interested to hear more... did you drive the S3 by chance? Your thoughts / comments? I had a chance to drive the S3 today and wow what a beast in normal mode and crazy fast in sport.
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