[kamek]

100% xi... car is a tank in the snow

[Amdahl]

Sorry for jumping in, but perhaps both sides are right on this tire-patch/weight/traction issue.

The extra weight issue would seem to be correct when you are on a solid surface, as it potentially improves contact with the ground..

The less-weight-is-better-principal would seem to be correct when you are on a semi-solid surface, such as snow. This might have some connection to those substances which act as a liquid under some circumstances, and a solid in others. In the case of snow, one second, you can stand on it, and the next your foot will slide right out from under you. Weight is clearly not beneficial in that case.

[Altima]

Originally Posted by TrackRat

Rule changes don't allow AWD in most cases to compete with RWD as it's now acknowledged that AWD is an unfair advantage, as Audi proved even after IMSA added a lot of weight on the Audis.

It depends on the type of racing (per wiki):
In 1969, Team Lotus raced cars in the Indy 500 and two years later in Formula 1 with the Lotus 56, that had both turbine engines and 4WD, as well as the 4WD-Lotus 63 that had the standard Cosworth engine. Matra also raced a similar MS84, and McLaren entered their M9A in the British Grand Prix, while engine manufacturers Cosworth produced their own version which was tested but never raced. All these F1 cars were considered inferior to their RWD counterparts, as the advent of aerodynamic downforce meant that adequate traction could be obtained in a lighter and more mechanically efficient manner, and the idea was discontinued, even though Lotus tried repeatedly.

I don't understand why every American thinks they need an SUV for 1 kid and a bag of chips. I also don't understand why every American thinks they absolutely need AWD to get anywhere. It's the same BS marketing that convinced the uneducated masses that FWD is better than RWD. I live 10 miles outside of Philly... We had a blizzard this year - first in 14 years. If we are unlucky, it will snow once or twice a year here and it's usually under 4 inches, and cleared within a day. Yet I see XI's and G37X's everywhere??? I have driven many types of vehicles in all kinds of weather (traveling north, or west where there is slightly more snow at times):

RWD:
1988 Monte Carlo SS, 1988 Chevy Caprice, 1990 2WD C1500 Pickup truck (5 speed), 1998 Lincoln Town Car Signature Series, 2006 Mustang GT (5 Speed)

FWD:
98 Ford Escort, 2002 Pontiac Grand Am GT, 2008 Nissan Altima 2.5S (Current)

4WD/AWD:
2003 Audi A4 Quatro Stick, 2003 Silverado Pickup (Never once had to use the 4 wheel drive in snow, ever)

Guess what? Never had a problem with any of them. In fact the car I felt MOST in control of in snow was the 88 Monte Carlo. The steering was unaffected by tractive forces, and the posi rear made for an unstoppable, well balanced machine - no BS electronics such as ABS or Traction Control to get in the way either. On my Altima, I actually experiment with the ABS and it seems like when I get the wheels to lock - it stops faster in snow than when the ABS kicks in and pulsates. I'm not saying I hate ABS or Traction Control, I just like 'non-intrusive'.
And whoever said FWD is SOO much better in the snow has never driven a RWD car before. And no, don't compare a 370Z with wide tires to a Civic... Compare a Monte Carlo to a Front Drive Lumina or something. RWD stops and turns better. The FWD traction advantage is barely noticeable, and up hill my RWD's faired much better.

My point is - AWD is not needed in 99% of driving conditions. I'm no engineer, but I don't see how higher ride height, added unsprung weight, higher drivetrain loss adds performance on dry pavement either?

All things equal:
Maybe someone can explain this to me. Accelerating in a RWD car thru a corner - the slip angle of the front wheels is less than the rear wheels because the tractive force of the rear wheels increases the slip angle of the rear wheels... (Oversteer)

In an AWD car - the slip angle and tractive forces are supposedly balanced at all 4 tires? (Not considering the added 3% of weight over the front wheels in an Xi which is 240 lbs heavier)

Wouldn't this result in more understeer because of the fronts having a higher slip angle than in a RWD?
In other words the Front Wheels will hang on to the corner better in a RWD car than an AWD because of less loading and no tractive force to accelerate the reaching of limits?


I wish someone had Nuremberg times for a 335i vs 335xi. I can't find this sort of thing anywhere!

[Nikolas]

Originally Posted by Altima

It depends on the type of racing (per wiki):


I wish someone had Nuremberg times for a 335i vs 335xi. I can't find this sort of thing anywhere!

There are recent Hockenheim times out there. The XI was faster.There was also a test done a year or so back between the 335i, 335xi, Acura SHAWD TL 6 speed and one other car. In that test which was a road course, the XI was also faster. C&D also recently tested both 0-60 and 1/4 mile and the XI was .5 second faster in both.

[Altima]

Originally Posted by Nikolas

There are recent Hockenheim times out there. The XI was faster.There was also a test done a year or so back between the 335i, 335xi, Acura SHAWD TL 6 speed and one other car. In that test which was a road course, the XI was also faster. C&D also recently tested both 0-60 and 1/4 mile and the XI was .5 second faster in both.

I find this really hard to believe... Do you have the link to the article? I do know sometimes (especially on C&D) the editors are extremely biased toward their favorite drive-train / manufacturer / etc. How can an identical but lighter car with less mechanical losses, lower ground clearance be slower?

[Nikolas]

I can't find the Hockenheim article, but here is another:

http://www.fastestlaps.com/compariso...MW_335_xi.html

and here:

http://www.motortrend.com/roadtests/...ual/index.html

[manbart]

I'm in Massachusetts and have a 330xi 6MT and will soon put coilovers on it. Then I have the best of all worlds with a AWD, Manual, with great sport handling!

Tilf

[Tiz113]

I like my XI in the snow it handles perfect, i drove around last winter in like 3-4 inches with two jeep wranglers and kept up no problem and i didnt have snow tires on

[zsqure]

Ok, I'll chime in too. I have had heavy 4 wd crew cab diesel p/u, awd pacifica and cx9, an awesome a4 and this 328xi. Take the xi over the i, great in the snow. My xi feels heavier than my a4 and more planted in the snow. It is absolutely hands down better in the ice/slush we get here in NE ohio. 16 in of heavy wet snow over last winter and no problem getting around.

[lux.sh]

If I move to an area where snow is not just occasional but everyday thing during winter, I would AWD it the day I move.
My 330i already suffers in rain. It has been raining here since last october.

[808AWD325xi]

The AWD system is an aid in the snow and rain. With an upgraded suspension and near neutral steering, it's a force to reckoned with in twisties as well as in a straight line. The only downside that I see is the additional horsepower needed to overcome the extra weight...the E90 XI being the epitome of this. I have yet to encounter another car at the track (including other AWD cars) that can launch like an XI...

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[GmanJeff]

BMW's own web pages reflects faster 0-60 times for the xi over RWD (.2 seconds for the automatic transmission model). If 0-60 times are important for the type of driving you do, in either wet or dry conditions, that data point may be useful.

[jeff g]

I own a 2008 335xi.
I live and drive daily in DEEP SNOW country.
My last car was an A6 AWD.
I much prefer my 335 to my A6. I run RFT Blizzaks all winter long and change
to non run flats for summer.
The 335xi IS the best AWD drive car I have ever driven. Period.

[ruxp]

Originally Posted by TrackRat

PeteB - the comments on acceleration are in regards to slippery surfaces, i.e. rain and snow. That's where AWD shows it's value for typical consumers. It's not in 0-100 drag races. On the track AWD is also superior in wet or dry but some folks prefer RWD for personal reasons. There is always a weight penalty with AWD but in return you get better traction. It just depends on your personal priorities but there is no escaping the reality that AWD provides better traction on any surface and that translates into more safety and for many drivers more fun.

I say buy what makes you happy as long as you're a technically informed consumer.

The 335i lacks a limited slip differential, so it will have trouble getting traction as easily as an AWD car will on a launch.. even on dry pavement.

Originally Posted by Altima

I wish someone had Nuremberg times for a 335i vs 335xi. I can't find this sort of thing anywhere!

I think you meant "Nurburgring"

[fdiprete]

my experience:
my e36i, rwd+snows = very good.
my e90xi, awd without snows = good
my e90xi, awd+snows = unstoppable TANK

[howiedds]

that should be changed to AWD with STUDDED snows = tank....my xi still slips and slides a little on snow Dunlop M3s

[fdiprete]

Originally Posted by howiedds

that should be changed to AWD with STUDDED snows = tank....my xi still slips and slides a little on snow Dunlop M3s

interesting - I'm running blizzaks. I get rooster tails as they bite into the snow (dtc off ) - but they are squirmy as hell on dry pavement.

[howiedds]

taking off is no prob...its the stopping. THAT is the most important thing about snow tires....... i drove like a granny, and the xi can still slide on some post snow storm days... (dreaded black ice)

[lux.sh]

Recently had an encounter with WRX. As I was pretty much drifting throughout the whole corner, the rex was confident and stable. It passed me as I was struggling to gain traction in the rear on corner exit point. Gave him big thumbs up.

If you ever planning on having competitions even when weather is not permitting, stick with AWD.

[darkmcs]

My first car was a '98 Impreza 2.5RS and I loved the AWD in every condition! I kept it for 5 years and decided to get a fun car... Sold the Scooby and got a MINI.

My Cooper S had 237hp (dyno-proven lol) and it really showed traction problems in a lot of driving situations... And I had a LSD diff on it!

When I decided to buy a 335, there was no doubt I would get Xdrive. The added weight is the only downside to almost flawless traction, proper F/R bias (40/60), extra grip in the corners (especially with Xdrive's intelligent AWD system! Feels like it corners on rails!), and added overall safety (aka confidence for some drivers...).

Xdrive was only $800 more and when I bought my car, I had no clue it was such an advanced system!

In summary, you have the right to think that a BMW should be a RWD car, but keep in mind that AWD systems are very good and in most case, they only increase MPG figures by a slight percentage and a many manufacturers are pushing their AWD systems to consumers because of all the advantages! (just an example: M-B E-Class are now mostly 4Matic... and M-B plans to sells more AWD than RWD C-class models in the near future...)

[BRAISKI]

Originally Posted by TrackRat

Rule changes don't allow AWD in most cases to compete with RWD as it's now acknowledged that AWD is an unfair advantage, as Audi proved even after IMSA added a lot of weight on the Audis.

lol I searched "unfair" if someone posted this, looks like you did

[GTR-Dad]

Originally Posted by TrackRat

Rule changes don't allow AWD in most cases to compete with RWD as it's now acknowledged that AWD is an unfair advantage, as Audi proved even after IMSA added a lot of weight on the Audis.

AWD becomes an advantage mainly when power levels exceed a threshold that depends on available traction.

In the dry, that number is about 350 whp in my experience. In the wet, it drops to about 200 whp. In the snow, AWD is a huge advantabe above about about 10 whp.

Dan