[atg4]

Originally Posted by Ali Shiralian

Now only if Subaru could design better interiors...

You could say the same about BMW, MBZ and Audi haha. E90 armrests, MBZ front air vents and Audi's touch sensitive buttons come to mind...

[tturedraider]

Originally Posted by venom4065

I thought xDrive is a permanent AWD system? That is what it is according to BMW website.

Originally Posted by Billfitz

It is. Normally most of the power goes to the rear wheels, but it will send more to the front if it detects the need.

The default split is 40:60. That's what xDrive delivers all the time, unless it detects a different need.

[N55Nick]

A lot of bad information in this thread. BMW xDrive is on all the time, with default 40:60 to rear. It changes that distribution based on slipt, up to 100% front or rear based on the need, than goes back to 40:60

With the very low center of gravity, xDrive and good winter tires, my 435 feels like a tank in winter storms (except for M sport bumper that acts like a snow plow)....

[Polo08816]

Originally Posted by __

The default split is 40:60. That's what xDrive delivers all the time, unless it detects a different need.

Originally Posted by N55Nick

A lot of bad information in this thread. BMW xDrive is on all the time, with default 40:60 to rear. It changes that distribution based on slipt, up to 100% front or rear based on the need, than goes back to 40:60

With the very low center of gravity, xDrive and good winter tires, my 435 feels like a tank in winter storms (except for M sport bumper that acts like a snow plow)....

We should elaborate a bit more on the xDrive "detecting" slip.

The xDrive is more of a utilitarian AWD system than a performance oriented AWD system like the Audi Quattro. It simply can't react fast enough compared to a gear driven center differential.

I would imagine wheel speed sensors plays a big part in the system input. Just like how the wheel sensors + brakes can't come close to replicating the effect of a true limited slip rear differential, it would be unrealistic to expect xDrive to be anything other than a utilitarian AWD system.

[lens]

Originally Posted by Polo08816

We should elaborate a bit more on the xDrive "detecting" slip.

The xDrive is more of a utilitarian AWD system than a performance oriented AWD system like the Audi Quattro. It simply can't react fast enough compared to a gear driven center differential.

I would imagine wheel speed sensors plays a big part in the system input. Just like how the wheel sensors + brakes can't come close to replicating the effect of a true limited slip rear differential, it would be unrealistic to expect xDrive to be anything other than a utilitarian AWD system.

I actually really hate the xDrive system as it intrudes when it doesn't need to most of the time. Sometimes it saved my ass (turned and hit black ice and it actually allowed me to get out of it by finding dry bit of road) but most of the time I turn off DTC and have a little fun around corners.

[strumbringer]

Originally Posted by chaungo

I actually really hate the xDrive system as it intrudes when it doesn't need to most of the time. Sometimes it saved my ass (turned and hit black ice and it actually allowed me to get out of it by finding dry bit of road) but most of the time I turn off DTC and have a little fun around corners.

That's not the xDrive, it's just the DSC and it is indeed annoying. I had the same experience in my RWD E92 until I decided to hit that DTC button every time.

[RM7]

Originally Posted by Polo08816

The xDrive is more of a utilitarian AWD system than a performance oriented AWD system like the Audi Quattro. It simply can't react fast enough compared to a gear driven center differential.

This. If it's trying to react and change the split, it's because it should have already done it to prevent the slip it's already experiencing. In other words, it's more reactive and you notice it driving.

[tturedraider]

Originally Posted by JamesNoBrakes

This. If it's trying to react and change the split, it's because it should have already done it to prevent the slip it's already experiencing. In other words, it's more reactive and you notice it driving.

The choice is it changes the split based on conditions (which it does in a split second) or the split is fixed and never varies. There is no "should have already done it to prevent the slip it's already experiencing." The only answer there is a fixed split system such as Subaru uses.

[RM7]

Originally Posted by __

The choice is it changes the split based on conditions (which it does in a split second) or the split is fixed and never varies. There is no "should have already done it to prevent the slip it's already experiencing." The only answer there is a fixed split system such as Subaru uses.

I'm glad you like it.

[atg4]

Originally Posted by Polo08816

We should elaborate a bit more on the xDrive "detecting" slip.

The xDrive is more of a utilitarian AWD system than a performance oriented AWD system like the Audi Quattro. It simply can't react fast enough compared to a gear driven center differential.

I would imagine wheel speed sensors plays a big part in the system input. Just like how the wheel sensors + brakes can't come close to replicating the effect of a true limited slip rear differential, it would be unrealistic to expect xDrive to be anything other than a utilitarian AWD system.

The audi guys seems to think differently.

"If you're pushing a car up a hill, it's nice if someone joins in to help. Nicer still if they were there from the start.

If the question is which is better, all things equal, any reactive system (Haldex) will be inferior to a full time proactive system (Torsen). With Haldex the skid or spin must begin before the other axle kicks in. Sensors, electronics and algorithms may smooth the transition, but it's there. Drive both in the snow and this will be readily apparent.

I'm not saying that Haldex is not good, but it's certainly not as good. You're 4motion Tiguan would easily best a FWD Tiguan through the snow, undoubtedly why you bought it. But you are quite right in noting that the reason your Tiguan goes better in snow than those BMW's and MB's is your choice in tires (and maybe the driver). Put good winter tires on the BM or MB and in really bad conditions, they'll out climb you handily, albeit at 2-3 times the price.

BTW, I don't believe that Subaru uses a Haldex system. They are full time AWD.


So yes, tires are everything. If the tire can't grip the surface, you got nuthin', no matter how many wheels are driving. That's where traction control is so misunderstood. Cutting power to a spinning wheel is great, but eventually that equals no forward motion."

http://www.audiworld.com/forums/perf...drive-2756530/

[strumbringer]

Originally Posted by alexandertg21

With Haldex the skid or spin must begin before the other axle kicks in.

Except he's wrong right there. Given that the default split is 60(R)-40(F) on the BMW, the other axle is already kicking in, all the time. What the system does is increase the torque to the non-slipping axle reactively... which a fixed system will not do.

BTW, LSD = "Limited" Slip Differential. So, err, it "limits" slip, but does not eliminate it.

Both systems can be implemented well. Go drive em. Pick the one you like. Let's stop arguing hypotheticals.

[Bob in IL]

I currently have one of each (X Drive and Quattro) and any differences are so slight it's not worth comparing. I think most of the differences are perceived.

[hollandog]

I had the G37x for 3 years.
It behaves like the xDrive for most part but the xDrive would let the rear slip a bit more.

I was able to survive the massive snow storm in Dec 2010 where the city decided to not plow the streets. My G37x with Goodyear Eagle All-season did an amazing job going through 6"-12" of unplowed streets. Took me 8 hours to get home from Long Island that supposed to be normally 2 hours trip. Along the way all kinds of cars were abandoned on the side of the highways. I was offered $350 to give a guy ride home because his Ford was stuck at an intersection.

Even the plow truck got stuck with chain around the block and left a big pot hole after.

[Polo08816]

Originally Posted by Bob in IL

I currently have one of each (X Drive and Quattro) and any differences are so slight it's not worth comparing. I think most of the differences are perceived.

When you say you have Quattro, are you referring to the system found in the Audi A4 or the Audi S4 (which has an optional rear limited slip differential)?

[Bob in IL]

Originally Posted by Polo08816

When you say you have Quattro, are you referring to the system found in the Audi A4 or the Audi S4 (which has an optional rear limited slip differential)?

Same system as in A4/Q5 etc.

[335BOY]

Originally Posted by pokerface

A4 quattro models are longitudinal engine setups (same as bmw) and torsen awd. All four wheels are always powered in the audi vs on the bmw defaulting to RWD until it senses a slip. Quattro feels way more planted for me while xdrive is a bit more fun. On an unplowed road with nannies off the audi will tend to drift if I crank the steering wheel and stomp the gas while the bmw will want to turn the tail around. That being said both cars driven sensibly are very safe and get you through pretty much anything.

I can do donuts in my Audi in snow. It starts 40% front 60% rear. This annual thread is great.

[335BOY]

Originally Posted by Bob in IL

I currently have one of each (X Drive and Quattro) and any differences are so slight it's not worth comparing. I think most of the differences are perceived.

Agreed!

[tturedraider]

Originally Posted by JamesNoBrakes

I'm glad you like it.

I didn't say I like it. I didn't say I like any one more than another.

[OldOne]

Originally Posted by __

Per CNET, Subaru uses at least four different versions of Symmetrical AWD.
http://www.cnet.com/roadshow/news/no...created-equal/

An ex-Subaru guy here. I think it's more like 5 or 6. I have a first hand experience with 3.

1. An older manual WRX: 50/50 split, 2 viscous LSDs center and rear, open front diff (note that newer manual WRX'es now have an open diff in the rear).
2. WRX STi: mechanical LSDs front and rear, mechanical + electronic center diff (DCCD), 40/60 default split
3. CVT Forester: open front and rear diffs, no center diff (rear axle is connected via an electronic clutch pack), 90/10 split (I don't believe 60/40 quoted in the article is correct).

They do feel differently. In the snow, both WRX and both STi feel more planted than the Forester: wheel slippage is harder to get under the same conditions, but the STi is a bit more tail-happy due to a slight rear bias (and is an absolute blast when you do break all 4 wheels free). The Forester, on the other hand, spins front tires easily, and there is a noticeable delay before the rear kicks in.

It is my understanding that the xDrive is functionally similar to the system in the Forester (and Haldex AWD) except it's backwards (rear biased). Basically, in this kind of a setup one axle *always* gets the power, and the other one gets variable power depending on the degree of lockup of the clutch pack, as decided by the computer based on various inputs.

I now drive a 340i xDrive, and while i don't have a lot of experience in the snow yet, it feels somewhat like the Forester in terms of a pronounced reactive response to wheel slippage on one axle: it seems like you do need to have some slippage on one axle in order to feel the other kick in. It obviously drives totally differently since it's rear-biased, and is very tail-happy with nannies off, a lot more so than the STi that supposedly has the same 40/60 torque split. I suspect that the xDrive in this car is actually more rear-biased than that, and the split ratio might vary between Comfort, Sport, and Sport+, but I'm not sure yet. Definitely need to play in the snow some more!

Anyway: my initial impression is that xDrive is totally adequate for winter driving for normal people as long as you leave the nannies on, but if you're Tommi Makinen, you want the STi for the snow.

That being said, I love the 340i.

My 2 cents.

[jbeene]

"my initial impression is that xDrive is totally adequate for winter driving for normal people as long as you leave the nannies on, but if you're Tommi Makinen, you want the STi for the snow."


Agreed. I could do flat spins with all 4 wheels spinning in the my Subaru. Never tried it in the xdrive but I will say that on the highway, in terrible conditions, the xdrive is very sure footed.

Bad driving conditions make for excellent skiing conditions - I've had more than a dozen powder days this year...and I don't give up much time to the road conditions. That said I'm running Nokian Hakka R2's. Killer tires.

[MomoM3]

What differential is in the 340i xDrive? Can't tell by driving it. Haven't been able to make the tires spin.

[pjohns21]

Oh Momo, you had to go and open this same can of worms again... Take heed- there are many xDrive "experts" on here. Please take their information with a grain of salt.