[Robin_NL]

Audi and Subaru aren't BMW. BMW offers X-drive (to people in mounainous and sticky/snowy aereas) when they already have the 'almost' perfect layout: Front engine, rwd 50/50.

Audi has fwd standard and an engine over/above the front lip
Audi NEEDS quattro in their bigger engined cars. BMW doesn't.

AWD doesn't corner better in general than a good rwd.
TRACTION and GRIP are 2 separate things.

Tyres are very important in this case too.

[soj]

Originally Posted by ward

yet another brainwashed soul


so sad..........................

Give me your source to validate your opinion and lets see who's the sad brainwashed one.

Here's mine from Autozine:

RWD versus 4WD

Basically, 4WD does not introduce power oversteer. However, most people still prefer it simply because it provides superior cornering grip thus improve cornering speed. As I have promised earlier in the Cornering Grip section, here I'll explain how 4WD improve cornering grip :

Consider a driving wheel running in a corner. Due to the frictional force applied from the road surface, the tread in the contact patch distorts and creates slip angle. The faster the car corner, the more centrifugal force generates thus the larger the slip angle becomes. You can interpret this as the elastic distortion of the tyre generates a counter force to keep the car fighting with the centrifugal force. When the car is accelerated fast to the extent that the elasticity of the tyre reaches its limit, it could not distort anymore, thus more speed will lead to the tyre slide, and the car lose grip. This point is what we call "Cornering Limit".

A FWD or RWD car has already a lot of tyre distortion (slip angle) in the driving wheel because the tractive force is shared by only two wheels. Therefore there is not too much space left before the tyres running into their cornering limits. On the contrary, 4WD cars distribute tractive force to all wheels, thus each wheel shares considerably less tractive force thus create smaller slip angle in cornering. The car can corner at higher speed before the slip angle reach the cornering limit.

* * *
Grip aside, we concentrate back to our current topic - steering tendency.

There is always argument that whether the neutral steer of 4WD is better than RWD's oversteer. Although neutral is more favourable in the entry phase and mid corner phase during cornering, it doesn't provide the "correctability" of power oversteer in the exit phase. Remember, no driver could avoid miscalculation, no matter Mrs. Robinson or Michael Schumacher. Normally we need to feel the car's attitude and the road condition every moment before deciding how to control the car in the next moment. In this sense, RWD's controllable power oversteer is what we want.

Moreover, power oversteer of RWD ask the driver to intervene the throttle during cornering. This let him feel more involving and that he is mastering the car. In contrast, 4WD cars let the tremendous grip, the limited-slip differential and even the computer to rule the car's cornering. Therefore we always hear road testers said RWD is more fun to drive.

I am not saying 4WD cannot have power oversteer. Bugatti EB110, with its 30/70 front-to-rear torque split, did that beautifully while providing tremendous grip. Even though a 50/50 4WD car like Mitsubishi Lancer Evo V could achieve slightly power oversteer by means of well-sorted suspension geometry. For example, if the suspension is setup such that to introduce rear outside wheel positively cambers when subjective to body roll, the contact patch area decreases thus slip angle increases, then power oversteer is also available. However, you cannot set the suspension to provide power oversteer as much as RWD car since there is a trade-off in total grip and straight line stability.

[Robin_NL]

Originally Posted by soj

Give me your source to validate your opinion and lets see who's the sad brainwashed one.

Here's mine from Autozine:

Ever driven a Donkervoort/Caterham/Lotus Elise soj?

Fastest car on roadlegal tyres on the Nuerburgring Nordschleife is a rwd front engined Donkervoort.

Basically It's about tyres/grip.

4wd offers traction when needed in rainy/snowy situations.

Sometimes 4wd corners faster but more often rwds do.

[Robin_NL]

Excuse me, soj, in your bigger story: GRIP isn't TRACTION.

When talking about GRIP they mean Traction...

[soj]

Originally Posted by Robin Hood

Basically It's about tyres/grip.

4wd offers traction when needed in rainy/snowy situations.

Sometimes 4wd corners faster but more often rwds do.

Its about tires and grip. But if you have the SAME tires on a AWD and a RWD, the AWD will corner better. The interesting thing is that most AWD cars will come with all-seasons while enthusiasts who drive RWD will have a set of summer and winters, thus providing better handling under most normal conditions (dry, rain, light snow).

[soj]

the whole point of the original question was the ask why the ride height was different. The XI's are marketed to a different group of ppl. People interested in rain/snowy drivability. If you were looking for performance, you'd get the RWD and get a set of winter tires.

I don't see why the poster should even question the ride height of the XI. The need for the XI is so small, one would question why anyone would even want to get one. A RWD with good winter tires will suffice for most of America's needs. And if the weather is THAT bad in your area that you require an XI, you'd probably need the extra ride height too.

[Robin_NL]

Originally Posted by soj

Its about tires and grip. But if you have the SAME tires on a AWD and a RWD, the AWD will corner better. The interesting thing is that most AWD cars will come with all-seasons while enthusiasts who drive RWD will have a set of summer and winters, thus providing better handling under most normal conditions (dry, rain, light snow).

depends on the road surface. AWD is heavier, more understeer.
Layout is very important too.

On a dry surface the rwd 330i wins. On snowy thingies the 330xi.

[Robin_NL]

Shortly: 4wd is about TRACTION, not about grip.
Ever driven a 4wd in the snow?

Noticed the SAME stopping distance as a FWD/RWD with the same tyres?

Right then

example E39(former) M5 vs RS6 plus Audi, driven them both. Dry track.RS6 has a lot more understeer. and the M5 is the faster one(lacks 50BHP)

How come?

You tell me

[LEDZEP]

Originally Posted by visor

It's because BMW's X-drive cars are not designed from the beginning as an AWD car like Audi's and Subaru's are. In those cars, there is room designed under the chassis to accomodate the transfer case between the front and rear differentials.

What year is your Subaru? We traded our 2003 Subaru Outback LL Bean for the E91. The Subaru had several inches MORE ground clearance. No comparison.

BMW doesn't offer a lowered x-drive model for the same reason they don't offer a large coffee table rear spoiler, ground effects, or spinning wheel inserts. The engineers at BMW probably missed the class on "how to ghetto your ride", and they are stuck with having to focus on practical design aspects.

BTW, the ground clearance and wheel gap on the xi is virtually indistiguishable from the non x-drives. I've even measured my two and can't find a difference except maybe 1/8" here or there.

[soj]

Originally Posted by Robin Hood

Shortly: 4wd is about TRACTION, not about grip.
Ever driven a 4wd in the snow?

Noticed the SAME stopping distance as a FWD/RWD with the same tyres?

Right then

example E39(former) M5 vs RS6 plus Audi, driven them both. Dry track.RS6 has a lot more understeer. and the M5 is the faster one(lacks 50BHP)

How come?

You tell me

I never stated that AWD has less understeer. The article I posted clearly states that AWD steering is more neutral while RWD will provide oversteer. It also uses science to determine that given all things equal (the same car), the AWD will provide better grip and cornering. Comparing an RS6 and an M5 proves nothing since it isn't the same car. There are way too many variables so its a botched experiment.

The real test would be to get a 330i and 330xi and do a test using the same tires.

Oh yeah, no sports package on either so they can have the same ride height.

[Robin_NL]

Originally Posted by soj

I never stated that AWD has less understeer. The article I posted clearly states that AWD steering is more neutral while RWD will provide oversteer. It also uses science to determine that given all things equal (the same car), the AWD will provide better grip and cornering. Comparing an RS6 and an M5 proves nothing since it isn't the same car. There are way too many variables so its a botched experiment.

The real test would be to get a 330i and 330xi and do a test using the same tires.

Oh yeah, no sports package on either so they can have the same ride height.

You're right about the RS6 and M5 being different cars
AWD has better TRACTION, not grip.


A 330Xi is slower on a track, I give you my word for it. Why?
1)(Nose)heavier(kgs)=more understeer
2)4wd (X drive) takes more hp in the driveline

Neutral steering: Rwd has neutral steering, AWD sometimes suffers from (heavy) understeer.

Greetings
Robin(former Subaru GTT and Audi S3 quattro driver)

[Robin_NL]

Shortly: Many 4wd terms in car brands are MARKETING.

You NEED 4wd on:
1)ICE/Northpole/snow
2)In a WRC rallycar and then on gravel/mud/ice/snowy stages.

(Did you know that on a tarmac stage the FWD Citroens without the turbo and less torque/hp were faster than the 4wd Subs/Mitsus/Pugs?)

[LEDZEP]

x-drive is slower. Is this a mystery to someone? 200+ lbs more weight. Power to all wheels...

You don't buy and xi for performance. And you don't buy a Z4 to go on ski trips... deal with it.

[ska///235i]

the gap aint that bad...here's my 325 XI

[soj]

Originally Posted by Robin Hood

You're right about the RS6 and M5 being different cars
AWD has better TRACTION, not grip.


A 330Xi is slower on a track, I give you my word for it. Why?
1)(Nose)heavier(kgs)=more understeer
2)4wd (X drive) takes more hp in the driveline

Neutral steering: Rwd has neutral steering, AWD sometimes suffers from (heavy) understeer.

Greetings
Robin(former Subaru GTT and Audi S3 quattro driver)

I disagree about AWD causing heavy understeer. In my experience, RWD is more geared towards oversteer, just like FWD suffers from understeer. AWD tends (key word being "tends") to be neutral in steering. But sometimes oversteer is preferred over neutral steer in my opinion.

But we can just agree to disagree.

[soj]

Originally Posted by LEDZEP

What year is your Subaru? We traded our 2003 Subaru Outback LL Bean for the E91. The Subaru had several inches MORE ground clearance. No comparison.

BMW doesn't offer a lowered x-drive model for the same reason they don't offer a large coffee table rear spoiler, ground effects, or spinning wheel inserts. The engineers at BMW probably missed the class on "how to ghetto your ride", and they are stuck with having to focus on practical design aspects.

BTW, the ground clearance and wheel gap on the xi is virtually indistiguishable from the non x-drives. I've even measured my two and can't find a difference except maybe 1/8" here or there.

In the e90, ground clearance is the same for i and xi for non-sport models.

[ward]

SOj, that big silly article just says exactly what I've been saying putting drive force to the front wheels reduces their cornering power and makes the car push/understeet/plow.............


what was your point again?

[jmatero]

I don't understand why there should be any real difference in dry weather handling between Xdrive and RWD..... Here's the text straight from BMW regarding Xdrive on the E90 for 2006:

"Ask any driving enthusiast: for balanced handling and sports-car-like agility, you want rear-wheel drive. But what if, 20% of the time, you need an all-wheel drive vehicle that can tackle steep slippery hills? Must you sacrifice the thrilling, responsive handling of rear-wheel drive the rest of the time? Not if you have XDrive All-wheel drive. On roads with good traction, xDrive sends 100% of the power to the rear wheels for legendary BMW handling. The instant xDrive detects wheel spin, it smoothly redistributes up to 100% of available power to the front wheels. So when you need it, you enjoy surefooted grip on steep, slippery roads - and pure driving fun all year 'round."

[ward]

if any power at all goes to the fronts you're loosing cornering grip (in exchange for forward force)

if the system worked as planned then it would be OK, but any power to the front wheels at all encourages plow/understeer/badness

[icedragon]

Originally Posted by soj

I don't see why the poster should even question the ride height of the XI. The need for the XI is so small, one would question why anyone would even want to get one. A RWD with good winter tires will suffice for most of America's needs. And if the weather is THAT bad in your area that you require an XI, you'd probably need the extra ride height too.

The need for AWD in North America is small. The desire for AWD is HUGE. That is why Subaru's are selling well, BMW xi's are selling well, and why Porsche, Lexus, Acura, and Infiniti have also introduced rear-wheel-biased AWD. The AWD market is BOOMING.

Originally Posted by LEDZEP

What year is your Subaru? We traded our 2003 Subaru Outback LL Bean for the E91. The Subaru had several inches MORE ground clearance. No comparison.

My family also has a 2005 Subaru Legacy. The ride height is not as high as the E90. The Subaru Outback was specifically designed for more offroad purposes, so it has a much higher ride height.

[LEDZEP]

^ Gotcha... I was thinking of the Outback. It actually has more ground clearance than most SUVs. And you're right about the demand for AWD. I like to have one car with it because it's nice in bad weather. Too bad that most of the soccer moms that are buying those vehicles are doing so because they think it's magic...

[Bimmerista]

BTW, the ground clearence is similar for the e90 xi vs i because the e90 is higher off the ground than the e46 was even in stock (non sport package) trim.