4x4 vs. AWD
 

So I went up to Big Bear Mountain again over the weekend and it was snowing pretty hard. Once again, the X w/ Dunlop summer perforamce tires handled beautifully (no chains). I had the car in AWD mode half the time and 4x4 mode the other half. Didn't notice any handling difference. My question is this:

Is it better to leave the car in AWD mode or 4x4 mode in the following conditions.

- Snow w/ no chains.
- Snow w/ chains.
- Heavy rain.

wowowowow...

Since when does the X3 have an AWD switch ?!? Its permanent 4 wheel drive !

Actually the X5 uses BMW's intelligent xDrive system and Dynamic Stability Control (DSC-X) to provide a safe, driving experience. It is all wheel drive.

uhhhhh... ... Are you saying X3 does not have X-Drive? Reading page 50-51 of your manual. Normally the X3 is in AWD unless if you push the DSC button lighting up the 4X4 light which enables 4 wheel drive.

Edit: The X3 does not have a 4X4 switch. It is permanently AWD. It is capable of 4x4 but that is determined by x-drive, not by the push of a button.

Actaully, pressing the DSC button activates the 4x4 light indicating that you have turned portions of the AWD system off. Therefore, travelling in snow, I would not turn the system off.

Turning the DSC button off simply makes your vehicle a rear-wheel drive vehicle (at least that is what a tech told me). Leaving DSC engaged allows for all 4 wheels to be used.

Seems like this thread has brought up another issue of DSC and x-Drive. Let me see if I can get things cleared up.

x-Drive: Always on and can not be turned off. xDrive is the all-wheel drive system of your BMW X3. The all wheel drive system xDrive variably distributes
the drive torque to individual wheels depending on the driving situation and prevailing road conditions.

DSC: Normally on. Can be turned off by pushing the DSC button. 4X4 light is on when DSC is turned off. The system optimizes the driving stability during acceleration and when starting from a standstill. The system recognizes any tendency for the vehicle to assume an unstable attitude such as oversteer or understeer; it then ounteracts this tendency with a combination of graduated reductions in engine torque and selective braking intervention at individual wheels.

Now can anybody help me with my initial question? I think this is the answer.

Snow w/ no chains - DSC ON
Snow w/ chains - DSC OFF
Heavy Rain - DSC ON

Are there any other instances where you guys feel that it is better off to have DSC OFF? This is what the manual suggest.

> When rocking the vehicle and starting off in deep snow or on loose road surfaces
> On sandy road surfaces
> On poor surfaces with deep ruts
> If the wheels churn on muddy surfaces
> When driving with snow chains

Same discussion was covered in this post not too long ago. It was entertaining. Enlightenment started somewhere around post #21 :)

http://www.xoutpost.com/x5-e53-forum/...on-ever-3.html

Post #22 covers MysticBlue's original question. The short version is, leave the button alone and take advantage of DSC (light off) except if you are stopped on an icy hill, or in deep snow, and pressing the accelerator has no affect since their is no traction and the DSC is overriding your throttle input. Then, turning DSC off (light on) allows the wheels to spin, and you can churn your way out. When you are moving again, press the button to turn DSC back on.

Haven't used chains, but that is BMW's other recommendation for when to defeat DSC; presumably the DSC system fights the traction characteristics of wheels with chains on. You don't have to turn DSC off, but if you smell brakes (and it won't take long, since that is how it restores traction) it is a good idea.

Jeff

I used to punch off my DSC button my first few weeks
of "1st Winter on the Mtn", before I got my spare winter
oem 17" wheels and winter tars...it worked well for controlled
wheelspinning and forward go, (w/serious steer.wheel correction),
as JCL, et al, described.

So, has anyone punched off their DSC on a pre-XDrive X and
rolled down the highway for any length of time, at speed?

Just wondering if it would "turn it into" RWD and goose the
mpg a tad...

The more I think about it, the more I think it wouldn't work
or, be "good" to the AWD sys. for that kinda treatment/speed/
time. Any thoughts?
BR,md

Since we all know now that turning off DSC does not equal to 4 wheel drive. What was BMW thinking putting that 4x4 in the light? :confused: I bet you majority of the X3 owners actually think turning off DSC = 4 wheel drive. Me and my friend had the longest argument about whether to leave the car in 4 wheel drive or all wheel drive in the snow storm. I guess that arguement was all for nothing. hahahahaha.