[pjohns21]

That being said, to flip the car surely DSC would have intervened to the highest degree, even in Sport +. You were under conditions that were beyond the physical limitations of the system, and you were only going 40mph? Did you hit anything else? One wheel on mud (as seen in the pictures) with no traction at all and a light tap of the brakes to distribute the brake force to the other three wheels (with traction) along with ABS should have maintained the vehicle's stability. Did you panic and overcorrect? I have crashed two cars that way.

[_MotoMa83_]

Sorry to hear buddy !

[lazyrhino]

Originally Posted by Cloudguan

Hi all, it's merely past 1 month since I owned my AW M235i. I've always kept her like a baby & wash her by myself almost every week. Picked her up in LA and directly jumped to California 1 to San Francisco, had tons of fun with this car. Yet, bad things happen. Last Saturday I was driving to Napa valley with a friend, through my favorite canyon road. Of course I was familiar with the road and knew the braking zones of each corner. However, in one tight corner, my rear wheels span out and brought my car complete sideways. Next second, the frond went off the road and hit the hill, then my car kept climbing up until it fell down on the left side. It's fortunate my friend and I was able to climb out of the car from the moonroof almost dustless, the side airbags protected us well. By the time of the incident there was only my car in that section so no others were involved. After the accident I checked the scene, found the road on my side was all wet and covered by mud due to the rain the day before, maybe the cause of my car losing traction. It was a bad day but I still felt blessed since I didn't turn into another direction and fell into the cliff, that definitely gonna end worse.
Now the car sits in the body shop and waits for the diagnosis, the guy taking care of my car said it was damaged pretty bad and it's probably gonna be a 11k fix.
Anyway, it is my first accident since the day I got my license, so hopefully some expert can tell me what to do in this kind of case?

Brace yourself - I expect there are still plenty more unhelpful comments to come from other 'self appointed traffic cops' about your driving (based on assumption of course).

No one can fairly comment on your driving as they weren't there. What happened happened, and no one was killed (fortunately). If you were driving like a tw*t then I'm pretty sure you'll have learnt from it - anyone else would after an accident like that, and such a lucky escape.

One thing is for sure though, think yourself lucky you don't live in the UK...

If you went through your insurer:
- With damage like that, the car would be instantly 'written off' (i.e. no insurance company would touch it for love nor money, so it certainly wouldn't be getting repaired).
- The car would end up scrapped, and you'd get the absolute pittance in return that is its 'current market value' (pretty much absolutely naff all).
- Your insurer would then need to cover the costs for the repair of the road (repainting, resurfacing etc.) which they'd probably try and steal from your payout.
- Once the claim was settled and you had your payout, your next insurance quote for whatever vehicle you chose to replace the car with would be so astronomically expensive, you'd have to re-mortgage your house just to be able to legally drive again.

If you decided not to tell your insurer:
- Genuinely, if you could even find a repairer who'd be willing to have a crack at it, it'd cost you more than the value of the car. Even then it'd be a poor job, so a total waste of money, time and effort. Putting the cosmetics aside, it'd certainly never run nicely again.


Of course whichever route you chose, you'd still probably find yourself being ruthlessly investigated by the local council (responsible for the roads) and the Police, and more than likely face dangerous driving charges also. Lovely!

Anyway, gutted for you about the accident - learn from it though!
Drive safe!

[ThreeToTwo]

Originally Posted by pjohns21

That being said, to flip the car surely DSC would have intervened to the highest degree, even in Sport +. <snip>

But it wouldn't. I see your point but there are those that would criticise BMW if turning off DSC didn't really turn off DSC, however much one might instantaneously regret having turned it off. The manual says (p113 in the US edition): " Sport+: Sporty driving with ... DTC is switched on. The driver handles several of the stabilisation tasks". DTC is a version of DSC, you have one or the other and DTC has "forward momentum ... optimised ... Driving stability is limited during acceleration and when driving in bends" (p112)

I think I'm agreeing with your previous post but I don't see public roads as a place to get the car's tail out (that's for the track or the skid pan). That being the case, why turn off DSC? If the challenge is to keep the vehicle within the limits of adhesion then, when you fail, why not have a little flashing light that tells you rather than sliding the car and potentially - well we know the rest and thankfully in this case only the car was hurt. DSC can't repeal the laws of physics but it can and does prevent many accidents.

[pjohns21]

Originally Posted by ThreeToTwo

But it wouldn't. I see your point but there are those that would criticise BMW if turning off DSC didn't really turn off DSC, however much one might instantaneously regret having turned it off. The manual says (p113 in the US edition): " Sport+: Sporty driving with ... DTC is switched on. The driver handles several of the stabilisation tasks". DTC is a version of DSC, you have one or the other and DTC has "forward momentum ... optimised ... Driving stability is limited during acceleration and when driving in bends" (p112)

I think I'm agreeing with your previous post but I don't see public roads as a place to get the car's tail out (that's for the track or the skid pan). That being the case, why turn off DSC? If the challenge is to keep the vehicle within the limits of adhesion then, when you fail, why not have a little flashing light that tells you rather than sliding the car and potentially - well we know the rest and thankfully in this case only the car was hurt. DSC can't repeal the laws of physics but it can and does prevent many accidents.

DSC will intervene 100% at some point unless it is turned off completely. It is not turned off completely in Sport +, even with the dash indicating that it may be off. It is just reminding you that the intervention limits are less strict. Now, you can turn it off completely by holding the button down for 5 seconds, but xDrive will still have the power 40/60 split and all of the braking safety features will still be active when the brake pedal is applied, i.e. electronic brake force distribution, ABS, etc. In Sport + DSC will intervene, but only after the wheels have significantly began sliding or drifting. This is why it's not appropriate for amateurs to use, especially on public roads. At the point of DSC intervention in Sport + mode, it may be too late for an amateur driver to correct and may cause said driver to panic and over-correct by slamming too hard on the brakes or throwing the car's steering wheel one way or the other to try to maintain control of the car. From reading this dude's story again, it sounds like the car went up a steep hill sideways and turned over, at which point all of these systems are rendered useless if the wheels are not connected to the ground... DSC is DTC in Sport + mode, but you can activate DTC by hitting the button on the console once, exclusive of being in Sport + mode. I prefer DTC in the snow as I can get moving more quickly, even though it allows more wheel spin... Without DTC on, if I press on the gas too hard, power is cut and the brakes are applied, which means I am going nowhere. Regardless, I have put the car into Sport + and learned my lesson very quickly in the rain- that it is not appropriate to use given my level of driving skill, especially on public roads.

[ThreeToTwo]

Originally Posted by pjohns21

I prefer DTC in the snow as I can get moving more quickly, even though it allows more wheel spin... Without DTC on, if I press on the gas too hard, power is cut and the brakes are applied, which means I am going nowhere.

Thanks for the clarifications.

Your point about using DTC for traction in slippery conditions is of course valid - it's what it's for and I didn't mean to exclude it. Point is, it lets you go sideways as well as forwards

[Zooks527]

Originally Posted by pjohns21

...but xDrive will still have the power 40/60 split....

That's certainly the old school xDrive fixed split. The current clutch-based transfer case can run from 0/100 to 100/0. It will start at 40/60 on a dry road with all 4 tires on a solid grip, but as soon as any wheel starts to spin, it will start throwing torque at the opposite axle. Only if wheel slip begins to occur on wheels on both axles will it start differentially braking single wheels.

[pjohns21]

Originally Posted by ThreeToTwo

Thanks for the clarifications.

Your point about using DTC for traction in slippery conditions is of course valid - it's what it's for and I didn't mean to exclude it. Point is, it lets you go sideways as well as forwards

To a point, and then it will still reign you in when it thinks you've lost control. It's extremely intuitive as a machine, because of course the Germans engineered it that way. However, when you drive up a steep hill sideways and flip over due to gravity, there's nothing Hans or Mr. F22 can do to save you, unfortunately.

[pjohns21]

Originally Posted by Zooks527

That's certainly the old school xDrive fixed split. The current clutch-based transfer case can run from 0/100 to 100/0. It will start at 40/60 on a dry road with all 4 tires on a solid grip, but as soon as any wheel starts to spin, it will start throwing torque at the opposite axle. Only if wheel slip begins to occur on wheels on both axles will it start differentially braking single wheels.

Nothing is old school about what I said. With DSC completely off, which can happen after holding the button for 5 seconds, xDrive will still be split 40/60. I do not think it will transfer 100% to either axle and use individual brakes to control wheel spin when it encounters a loss of traction with DSC off. Otherwise, there would be no difference between DSC off and DSC on in xDrive vehicles. I mentioned xDrive because many people think it can be defeated by this way or that, and it cannot. With DSC off, I still have loads of more control over the vehicle because of xDrive. xDrive gives you a traction advantage in all circumstances because the default is at least a 40/60 split, no matter what buttons you press. What you're alluding to is when DSC is on, in which case yes, DSC can put 100% of the power to the front or rear wheels and use individual braking to control wheel spin. When DSC is off, you get the traditional 40/60 split. With DTC, you may get less DSC intervention and some shifting of power between the front and rear axles, depending on conditions.

[Zooks527]

Originally Posted by pjohns21

Nothing is old school about what I said.

One should be careful of one's direct assertions.

Originally Posted by pjohns21

With DSC completely off, which can happen after holding the button for 5 seconds, xDrive will still be split 40/60.

At normal driving speed on dry roads with no spin at any wheel. Much older xDrive systems would maintain this no matter what. The current xDrive system varies this all the time. As an example, regardless of DSC setting, the F22's xDrive system will fully open the transfer case clutch at low speeds (parking speed) to go fully RWD. It will vary continually at road speeds depending on sensed wheel slip.

Originally Posted by pjohns21

I do not think it will transfer 100% to either axle and use individual brakes to control wheel spin when it encounters a loss of traction with DSC off.

No, this is incorrect. There is no setting that allows you to change the system's control of the torque split, and it is capable of running to 100% to either axle at any time. This is the source of the "xDrive isn't as much fun" meme, as it makes it difficult to induce oversteer in corners. The system will always try to put the power the engine is producing down to the ground without wheel spin. You only get to spin a wheel or wheels in DSC off once you exceed the traction limits on both axles.

This link will download a BMW press release from about 10 years back: https://www.google.com/url?sa=t&rct=...92291466,d.cWc
Once you ignore the incredibly annoying font, pages 12 thru 14 talk about torque splitting (albeit in the 3 sereis) and commnet on DTC/DSC interaction.

Originally Posted by pjohns21

Otherwise, there would be no difference between DSC off and DSC on in xDrive vehicles.

Same reference, same pages. The transfer case torque distribution function remains the same across the board. The system will always transfer power away from an axle with a spinning wheel if it sense no spin on the other axle.

The difference is in the amount of yaw allowed before system intervention (DTC) or no intervention due to yaw (DSC off). Similarly, in DSC off, the car won't pull off power once wheels are spinning on both axles. However, in an xDrive car, there will always be differential wheel braking once there's a wheel spinning on an axle, unless the system determines that a brake is overheating.

Originally Posted by pjohns21

I mentioned xDrive because many people think it can be defeated by this way or that, and it cannot.

You are correct here, but do not seem to realize this sentence contradicts your previous assumption of how the system works with DSC off.

Originally Posted by pjohns21

With DSC off, I still have loads of more control over the vehicle because of xDrive. xDrive gives you a traction advantage in all circumstances because the default is at least a 40/60 split, no matter what buttons you press. What you're alluding to is when DSC is on, in which case yes, DSC can put 100% of the power to the front or rear wheels and use individual braking to control wheel spin. When DSC is off, you get the traditional 40/60 split.

This is flat out wrong. Provide a reference to support this, or retract it. If you go to the one I provided, you'll find absolutely no support for the assertion.

It was past that point even back in 2003 on the E83. See page 22 here: http://share.qclt.com/bmw%E8%B5%84%E...3%20xDrive.pdf

The 5 series carried the same strategy in 2005 when it added xDrive. See page 17of the xDrive section (page 41 of the overall file) here: http://bmw5ser.ru/manuals/e60/manuals-5er-e60-12.pdf

"Even when DSC is turned off, TCC (ed: Transfer Case Control) is still active to ensure maximum traction and vehicle dynamics."

Originally Posted by pjohns21

With DTC, you may get less DSC intervention and some shifting of power between the front and rear axles, depending on conditions.

Again, unsupported by any documentation or reference provided to date. You don't get "some" shifting, rather, the car retains the capacity and function of being able to shift 100% either way. Feel free to provide documentation to the contrary and I'll change my view.

[pjohns21]

...

So you're telling me with DSC off xDrive is still braking individual wheels to control wheel spin? Wheel braking is not a function of xDrive it is a function of DSC. This is not the case in my driving experiences with DSC off- the car won't do a donut as in a car with RWD but it will certainly make a perfect arc aka 4-wheel drift with all four wheels spinning.... The car does not try mercilessly to find the wheel or axle with the most grip... It lets all 4 wheels spin. In this case, since all 4 wheels have similar grip is it just static in the power distribution between the two axels? 40/60 as I am suggesting...

Rereading your post, I'm still disagreeing. Take the car out in a parking lot with a few inches of snow, turn DSC completely off, and let 'er rip. The car will rotate, albeit not in a tidy donut fashion like a RWD car.

From Wiki, with references:
"This setup allows xDrive to modulate the torque split between the front and the rear axles, which is normally split at 40:60 ratio. If wheel slip is detected by the ABS/DSC system, xDrive can react within a tenth of a second to redistribute up to 100% of the engine power to the front or rear axle.[1] The wet clutch is applied through a high speed electric servo motor turning a cam-shaped actuator disc.

xDrive is connected to the ABS and DSC systems. In the case that wheelspin or directional instability still occurs while xDrive is or has been modulating the torque split, DSC will brake independent wheels to regain traction and improve directional stability without driver intervention.

The front and rear differentials in xDrive vehicles are typically an open differential design, thus relying on brake application by the DSC system to transfer power from the slipping wheel to the wheel with traction."

All of this relates back to the DSC system... with DSC off it reverts to the traditional 40/60 split. If it did what you are saying, the xDrive system would transfer 100% to the front and 100% to the back endlessly which would make for a pretty uncontrollable vehicle, especially in conditions with very little traction.

From BMW:
"With xDrive a BMW takes full advantage of the benefits of rear-wheel drive: precise handling, optimum cornering and a clear separation between the engine and steering. Dynamic Stability Control (DSC) is only activated if it is necessary to redistribute engine power when conditions deteriorate: the system effectively counters over- or understeering by engaging the electronically controlled multiple-plate clutch, which reacts within a tenth of a second, to distribute up to 100% of the engine power to the front or rear axle and then back to the normal 40:60 ratio. With the BMW xDrive all-wheel drive system each axle optimally uses its traction to provide stabile acceleration out of every bend."

Once again, it continues to refer to DSC- the brains of the system. DSC is defeatable by holding the button. We have already determined that xDrive is not. BMW's explanation also refers to controlling understeer and oversteer... With DSC off I am able to oversteer the car in a circle (because the rear wheels are getting 20% more power by default), Obviously, this circle is a very large one compared to doing a donut with a RWD vehicle.

Does this video suggest that xDrive is attempting to find the axle with the most grip during that "donut?" No, it's stuck in the 40/60 split because DSC is OFF. Even though you cannot turn off xDrive due to the mechanical nature of the system, BMW even says it is electronically controlled, so what I am suggesting is possible- with DSC off the wheels are getting "the normal 40:60 ratio."

[Zooks527]

Originally Posted by pjohns21

...
So you're telling me with DSC off xDrive is still braking individual wheels to control wheel spin? Wheel braking is not a function of xDrive it is a function of DSC. This is not the case in my driving experiences with DSC off- the car won't do a donut as in a car with RWD but it will certainly make a perfect arc aka 4-wheel drift with all four wheels spinning.... The car does not try mercilessly to find the wheel or axle with the most grip... It lets all 4 wheels spin. In this case, since all 4 wheels have similar grip is it just static in the power distribution between the two axels? 40/60 as I am suggesting...


Rereading your post, I'm still disagreeing. Take the car out in a parking lot with a few inches of snow, turn DSC completely off, and let 'er rip. The car will rotate, albeit not in a tidy donut fashion like a RWD car.

Yes. That is what I'm telling you. If you want to split the "it's not xDrive, it's DSC" hair, have a good time. A BMW with xDrive will brake individual wheels all the time to match wheel speed across the axle. If you have DSC off, it will let the wheels spin if you put enough throttle into the system, but it will be braking individual wheels to have them spinning at the same rate.

Go the the references in #76 above. Search for the quote "ADB-X remains active when DSC is deactivated." Then read what ADB-X is. To save you the time, let me quote it for you: "Automatic Differential Brake X (special function for all-wheel drive vehicles)". xDrive cars are set up with different controllers and functions than the RWD ones, but use the same terminology in the owners manuals for convenience.

Disagree all you want. Net of a valid reference, it doesn't mean anything.

Originally Posted by pjohns21

...
From Wiki, with references:
** long Wikipedia quote snipped ***
All of this relates back to the DSC system... with DSC off it reverts to the traditional 40/60 split. If it did what you are saying, the xDrive system would transfer 100% to the front and 100% to the back endlessly which would make for a pretty uncontrollable vehicle, especially in conditions with very little traction.

No, it does not. Go back and re-read the references in post #76 above. What part of "Even when DSC is turned off, TCC is still active to ensure maximum traction and vehicle dynamics." are you struggling with?

Part of your confusion may be that, even though it is referred to as DSC, the actual stability control system in an xDrive car is more correctly referred to as DSC/DXC, with a set of additional functions that don't exist in the RWD cars.

But, again, you have provided ZERO references that support your statement that "with DSC off it reverts to the traditional 40/60 split." Zero. None. Bupkis. As opposed to the BMW training document that explicitly states otherwise.

Originally Posted by pjohns21

...
From BMW:
***BMW quote snipped***
Once again, it continues to refer to DSC- the brains of the system. DSC is defeatable by holding the button. We have already determined that xDrive is not. .

No, you again are extrapolating in the face of contrary documentation from BMW that it is not.

Again, what you think is not relevant. Find a reference that supports your claim that in "DSC off" mode, the car sets a locked 40/60 split. You can't. You've found a bunch of things that you think support the contention, but you have no reference that states it. Against that, we have multiple references that say otherwise.

Originally Posted by pjohns21

...
With DSC off I am able to oversteer the car in a circle (because the rear wheels are getting 20% more power by default), Obviously, this circle is a very large one compared to doing a donut with a RWD vehicle.

Does this video suggest that xDrive is attempting to find the axle with the most grip during that "donut?" No, it's stuck in the 40/60 split because DSC is OFF. Even though you cannot turn off xDrive due to the mechanical nature of the system, BMW even says it is electronically controlled, so what I am suggesting is possible- with DSC off the wheels are getting "the normal 40:60 ratio."

No, it suggests that the system is allowing wheels spin on both axles. It shows nothing regarding individual wheel rotation speeds, nor can any meaningful information be gleaned from a home video of someone doing donuts on a wet parking lot, past the maturity level of the driver.

Wait a minute. You know what else it's showing? It's showing a car with an open rear differential where both rear wheels are spinning. Huh. You know what that means? It means that the car is differentially braking the rear wheels, because if it were not, only one wheel would be spinning. Huh. The car is differentially braking the wheels even though DSC is off. Where have I heard that before? More importantly, who thinks that doesn't happen?

Now, read the highlighted section above. "Even though you cannot turn off xDrive due to the mechanical nature of the system" shows you do not understand how the clutch-based xDrive system works. You clearly do not understand that the system can be and is shut off in 3 specific conditions (high rate of turn at low torque, speed in excess of 180 kph, and detection of excessive understeer). An xDrive is not a hard mechanical LSD, it's a clutch based system that can be completely unlocked.

It looks like you're devolving into waving your "I think" flag until the cows come home, but go take another shot. Go find a reference that says what you claim, specifically, that in "DSC off" mode the torque is a fixed 40/60 split. Not "well, it says A controls B, so if I turn A off, B will do something completely speculative". That's not a reference, that's an inference.

And, just a heads up, the next thing that's going to be asked is how a car with a fixed torque split can function if one axle has no traction.

[pjohns21]

...trols B, so if I... [/QUOTE]

Well I'm waiting for someone to back either of us up. I understand you have better references than me but those in which you use don't prove your points either. You said TCC is still on- that means that the car always remains an all wheel drive vehicle except in the three situations you described, then the references state the vehicle is no longer all wheel drive in those conditions. This doesn't say that the car always uses the brakes for maximum traction or will continuously shift power back and forth 0/100 to 100/0 until it regains traction. There has to be some electronic algorithm to allow the car to oversteer as it can do with DSC off and this is stated in your references. There is no braking going in an oversteer 360 degree situation with no traction as is shown on the video above, nor is the torque being transferred back and forth 100% to and fro in order to try to regain traction, otherwise one wouldn't be able to oversteer the car. I get what you're trying to drive home that you can never shut off xDrive but with DSC off I am very sure there is no individual wheel braking going on- otherwise you couldn't rotate the car as you can in wet/snowy/icy situations. You're all text but not practically thinking of what's happening when a xDrive vehicle is able to rotate 360 as is possible because I have done it! You're also making the DSC braking more complicated than it is... DSC detects wheel slippage and sends torque to the axel that has more traction, then DSC applies the left or right brake to the wheel with less traction, thus allowing the opposing wheel to to use its torque and traction to move the car forward. THIS IS ONLY WITH DSC ON or DTC ON. In a no traction situation at all 4 wheels, the system would send 100% of traction to each axle back and forth if what you're suggesting is the truth- meaning you wouldn't be able to rotate the vehicle 360 degrees, nor would you be able to control the vehicle. This is why DSC cuts the power with the system on and applies the brakes. Which is also why it's sometimes difficult to get moving in these situations because the system sends power back and forth, which then causes excessive wheel spin and the engine power is cut and the brakes are applied. With DSC off I can spin all 4 wheels at a time at my leisure and all day long in the snow. Try it. There's no wheel braking going on in terms of controlling wheel spin, as there would be with DSC on- the wheels are spinning freely up to redline. Try it. Also, I'm using braking in the traditional sense, whereas I think you're referring to it as changing or reducing power from one axle to the other via the transfer differential without the use of the actual brakes- to the axle that has more traction. I'm talking specifically about the process of braking one wheel or the other to limit wheel spin and allowing the opposite wheel to move the car forward with its traction, which is required as xDrive can only transfer power to either axle not directly to one specific wheel (as Audi's system can without using individual wheel braking). xDrive has to rely on wheel braking to limit the power to the left or right wheel at that axle, otherwise the wheel with less traction would continue to spin with no forward momentum.

[Zooks527]

OK, that's a really long rambling stream of consciousness post at 1 am, so why don't I give you until, say, lunchtime to beat it into something a bit more coherent. Things you're going to need to address to make a bit more sense (this is not an exhaustive list):

"DSC detects wheel slippage and sends torque to the axel that has more traction, then DSC applies the left or right brake to the wheel with less traction, thus allowing the opposing wheel to to use its torque and traction to move the car forward. THIS IS ONLY WITH DSC ON or DTC ON"

You've posted a video of a car doing donuts. We'll assume DSC is off, as that is the point you were trying to make at the time. We'll presume it's an unmodfied 335xi, as a modified car wouldn't be relevant to the discussion. As such, it has an open rear differential. Why are both rear wheels spinning?

"With DSC off I can spin all 4 wheels at a time at my leisure and all day long in the snow. Try it. "

A ) How can all 4 wheels be spinning on a car that has open differentials in the front and back?
B ) Assume one axle is on wet ice with zero traction. Define the torque going to each axle with an arbitrary value of X. Then, place the opposite axle on a surface with good traction. If the torque distribution ratio between the two axles is a fixed constant, what will happen at both driveline and macro levels?




One without a quote. Jack the back of the car up so both rear wheels are off the ground. Turn DSC off. Start the car and put it in gear. Apply throttle. Define (a) what the computer is going to do to the driveline, (b) the torque applied at the rear wheels as a numeric value, and (c) the torque applied to the front wheels. What will happen a second after you press the throttle? Why did that happen?


And from a use of references standpoint: Still waiting for anything that says disabling DSC locks a 40/60 torque split,effectively creating a Torsen differential. However, if you think through what that would mean coupled with the questions above, you'll understand why BMW puts out all those videos of other types of AWD cars on roller beds being unable to move, and also why you'll be unable to find any such reference.


Through all of this, remember how xDrive is configured: a rear drive shaft hard-coupled to the transmission and a clutch-pack transfer case that can send torque to the front axle through a separate drive shaft. Ask what sensors are available for the system to know how to set the clutch parameters. Finally, ask yourself how you could establish the conditions where 100% of the torque is going to either axle, and then ask the conditions required for each case. That will answer your "back and forth" question on its face.

[pjohns21]

[/QUOTE]

You're way overthinking it. What you're suggesting is that there is no difference in a xDrive car with DSC on and DSC off. To hell there isn't. You're still thinking the system is more mechanical than it is... it is electronically controlled, the computer can decided what it wants to do and when. Do you have a xDrive car? Again, what you are suggesting isn't supported by what the car does with DSC off- oversteer with all four wheels spinning and sliding with the power given to all 4 wheels. xDrive has some sort of electronic algorithm to control how the xDrive power is pushed to both axels with DSC off- they designed it to purposefully oversteer to maintain the same sort of fun you could have with a RWD Bimmer. If 100% of the power was sent to the front with DSC off, the car would completely understeer, if 100% of the power was sent to rear with DSC off you would get total oversteer as in a RWD car. There has to be some sort of split with more power to the rear in order to oversteer like an xDrive model does with DSC off. You've pretty much told me over and over that because of what you're saying my car or anyone else's with xDrive can't oversteer into a "donut," for lack of a better word, in the rain or snow. I cannot prove to you that it is a 40/60 split, but that is what the default is when no slippage is detected in normal conditions. The DSC control unit does not send info to the xDrive system that the wheels have no traction when DSC is not active. Hence, I am able to spin all 4 tires on snow with no braking intervention for as long as my heart desires. All four wheels can spin with DSC off in snow or low traction conditions and this lack of traction and more power being sent to the rear axel produces the resultant oversteer we see in the video. It does not understeer like a FWD car and it does not rotate in a tidy circle like a RWD car. In order to do what the video shows, there has to be some portion of power to the front and some portion of the power to the rear. We can infer that there is more power being sent to the rear which is why the rear of the car is rotating more so than the front in order to create such a circular path of motion. Are you suggesting that in the video all four wheels are not spinning and sliding? I just stated three times what would happen if the front or the rear of the axle received 100% of the power, no one would be able to oversteer in such a way. Once again, that is why I suggested that with DSC off the system defaults to the 40/60 split as it would not taking demands from DSC or responding to the loss of traction and stability in relation to where the car is going, what the steering angle is, and the yaw rate. My explanation is logical and doesn't require discussion of clutch this and clutch that and open and closed diffs. If you place one axle on ice there is still power going to the other axel either by default (as in DSC off) or actively with DSC on. Similarly, if the rear wheels are off the ground there is still power to the front so by default the car would move forward when pressing on the gas (with DSC off or on). Those videos from BMW are always with DSC on, so how can you use them to apply to this situation? With DSC off the xDrive model would be the same if not worse in trying to gain forward momentum against the competitors. Your last paragraph doesn't say anything beyond the fact that yes there are almost a dozen sensors related to DSC and that many of them are disabled with DSC off. Again, many of these sensors are disabled with DSC off so they aren't transmitting data to xDrive. Therefore, xDrive functions as if it is performing on dry pavement, where it would be splitting the power in a 40/60 action. This is supported by the BMW documents that in a straight line on a dry road the power is split 40/60. It's very logical when you piece together what BMW says about xDrive and what I have seen the car do with DSC off and having very little traction to all 4 wheels. You have to understand that it is electronically controlled even though the xDrive system is mechanical. What you are suggesting would not allow a car to spin all 4 wheels to redline in the snow or ice, nor would it allow the car to smoothly pull off an oversteer maneuver which people are able to do in the snow with xDrive and DSC off. I was also at work, and it's getting hard to respond when your posts are aimed at getting around explaining how one can have their cake and eat it to with a xDrive vehicle and DSC off. Your explanation doesn't match up with what the car does in situations with no traction and DSC off, mine does. BMW explains this in the literature very plainly that with DSC off the system acts similar to a RWD vehicle in terms of how it performs when the tires are beyond the limits of adhesion to the road. It's not exactly the same because there is still some amount of power being sent to the front at all times, except in those three situations you described OR when DSC is ON and it's responding to the loss of traction at one axel and sending up to 100% of the power to the other.

[pjohns21]

Sorry to jack the thread... any word on the dude's car?