[ErkanTR16]

Go with what makes you happy. End of story.

[metallicpea]

You got that right.

Just hate to see common misconceptions being spread along.

[Polo08816]

Originally Posted by chaungo

Apparently, you can get the M performance LSD installed on the xDrive.

I was speaking to my SA at the dealer while my car was in service, and he told me that the m performance LSD is actually compatible with the xDrive now.

I have adaptive M suspension, and will buy dinan springs and bumpstops later.

I've heard that it was compatible, but is it the same part number as the M Performance LSD for the RWD Automatic model?

If not, there's a chance it's not available in the US. Just like how the ATF fluid for the ZF 8HP45 is not available for purchase even though it has a BMW Part Number. You would have to purchase the ZF Lifeguard 8 instead (which is the same thing).

[Musashi]

Originally Posted by metallicpea

"But do 60MPH in a RWD on black ice, and will discover rapidly why it spins with a micro wheel movement, versus an AWD which will not- not at that exact speed anyway. Maybe at 63.."

AWD has no effect on straight line traction at 60 MPH. Any loss of traction or correction at that speed is tires and driver.

You are referring to Friction (no AWD effect) Traction as in the main definition "action of drawing or pulling a thing over a surface, especially a road or track." I was referring to mechanical traction- the action of pulling. You can go in 100 yards from a full-traction zone to 10% of that due to changes in road Coefficient of Friction. Driver or tires - all being equal- have nothing to do with the physical changes on the road. Most often, from dry to wet or dry to ice, the car begins oscillating even if driving in a straight line. It is the freakiest feeling - very few have experienced- you have not- where you are doing nothing in terms of input but the road in front of you suddenly moves left an right and left and right across the windshield... The TC light flashes, and you know you are at CF 0 and oscillating. Road imperfection, minor bumps, and the ice- that is it, Cf is gone. Touch the brakes or the wheel and you are GONE in the concrete midlane walls. Expect to see a dozen ditched cars the next few miles.

First winter on my AWD, imagine this true scenario- light rain in Nov, 401 highway, 11PM nigh time, gentle long curb. 1 week old sport Pirelli Sottozeroes, winters. 75mph. Then a male deer's white butt emerges from the misty shadow reflections, walking on my highway lane, same direction, i'd say 50 m ahead, 0.7 s reaction time.. Had to swirl left, then right, TC lights flashing, somehow the deer remaining on my right side. Stopped, pulled aside, got out to check the road, was all black ice... Not wet- just iced. Drove at 35mph the next 40 miles and passed a dozen of crashed cars. No doubt that if I was in a FWD or RWD I would have been in a ditch. Had not expected it - too early in the season. No idea why so lucky- other than the road not being too saturated, and the all around AWD grip, enough for me to survive the 75mph sudden maneuver.

AWD doubles your traction. That is why for the same Cf AWD loose traction far less than either FWD or RWD.. In the curbed ramp pic example, if that was ice underneath, AWD traction and grip in the curb is far superior that any RWD. Even at slow speeds, that RWD on winters can just glide out unable to pull itself out of the spin. Come try it if uncertain of it. In Canada we see it all the time- usually some Ford GT or Corvette on winter tires.

We also know that Subaru has a better AWD traction system- tested and felt its superiority to BMW/Audi in winter as well.

Just enjoy your car and your climate.

[lens]

Originally Posted by Polo08816

I've heard that it was compatible, but is it the same part number as the M Performance LSD for the RWD Automatic model?

If not, there's a chance it's not available in the US. Just like how the ATF fluid for the ZF 8HP45 is not available for purchase even though it has a BMW Part Number. You would have to purchase the ZF Lifeguard 8 instead (which is the same thing).

BMW M Performance Limited Slip Differential 33107555607

Was given to me.

http://www.shopbmwusa.com/PRODUCT/47...P-DIFFERENTIAL

Apparently, it's the same exact part number.

[metallicpea]

I disagree.

You do not know what I have or have not experienced.

Traction required to maintain speed at 60 mph on straight line or gentle curve is very small and 99% tires. As soon as you hit ice and loose traction, as a driver you ease out of the gas, so there is no drive force at any wheel, again all tires. If your into the gas on frozen roads at those speeds you get what your asking for.

No evasive maneuver at 60 should involve more gas unless you think your Michael Schumacher...

Driver and tires...

[metallicpea]

I believe stability control reduces power and applies brakes, but does not apply more power to any wheel.

If this is old information, I will take back earlier comments and refresh my research, but otherwise AWD is not a factor in the cases I am discussing.

[Polo08816]

Originally Posted by Musashi

Nope. You can go in 100 yards from a full-traction zone to 10% of that due to changes in road Coefficient of Friction. Driver or tires - all being equal- have nothing to do with the physical changes on the road. Most often, from dry to wet or dry to ice, the car begins oscillating even if driving in a straight line. It is the freakiest feeling - very few have experienced- you have not- where you are doing nothing in terms of input but the road in front of you suddenly moves left an right and left and right across the windshield... The TC light flashes, and you know you are at CF 0 and oscillating. Road imperfection, minor bumps, and the ice- that is it, Cf is gone. Touch the brakes or the wheel and you are GONE in the concrete midlane walls. Expect to see a dozen ditched cars the next few miles.

First winter on my AWD, imagine this true scenario- light rain in Nov, dark, highway, and gentle long curb. brand new Pirelli Sottozeroes. 65mph. Then a male deer's but emerges from the misty shadow reflections,it is walking on my highway lane, i'd say 1 second reaction time, 50 m.. Had to swirl left, then right, TC lights flashing, somehow the deer remaining on my right side. Stopped, pulled aside, got out to check the road, was all black ice... Not wet- just mirror iced. Drove at 35mph the next 40 miles and passed a dozen of crashed cars. No doubt that if I was in a FWD or RWD I would have been in a ditch.

AWD doubles your traction- as in the main definition of traction "action of drawing or pulling a thing over a surface, especially a road or track." Do not want to mix traction and friction. That is why for the same Cf AWD loose traction far less than either FWD or RWD.. In the curbed ramp pic example, if that was ice underneath, AWD traction and grip in the curb is far superior that any RWD. Even at slow speeds, that RWD on winters can just glide out unable to pull itself out of the spin. Come try it if uncertain of it. In Canada we see it all the time- usually some Ford GT or winter driven Corvette on winter tires.

We also know that Subaru has a better AWD traction system- but that it another story, and tested and felt its superiority to BMW/Audi in winter as well.

Just enjoy your car and your climate.

LOL. Where are you getting this information or are you just making it up?

Your anecdotal evidence is basically the difference between a car equipped with snow tires and one that is not. Not drivetrain configuration.

Also, AWD doesn't "double" your traction. You can argue that it doubles your probability of attaining a level of traction, but I can assure you it's not double as you are imagining it is.

As for your pictures, I can do even better. They say pictures are worth a thousand words, but how much are videos worth?

That was RWD + snow tires and no issues, no oscillations, etc. at or above the posted speed limits.


Here's a RWD + snow tire recovery from black ice:

Fairly easy to control and manage if you have the right tires.


As far as mentioning Subarus, they're decent but I've also owned and driven a 2008 Subaru Legacy GT in quite a few winter seasons. AWD won't give you much additional stability or control when you're at speed, it will give you a bit more forward traction.

[metallicpea]

I think he was reading the description of DSC and thought it was somehow effected by AWD.

From BMWs website.

"Dynamic_Stability_Control
Nasty weather. Terrible road conditions. A deer crossing. When a driver loses control, there's usually more than one factor involved. Using built-in sensors to continually monitor multiple variables - such as speed, steering angle, yaw, brake pressure and traction - our Dynamic Stability Control system can detect and, more importantly, help correct the loss of wheel traction immediately. All of which helps to keep you in control, no matter what the circumstances"

[metallicpea]

This is something even BMW has given up trying to explain to it's customers. I don't know why I bother.

[MomoM3]

Seems like most of the folks siding with RWD+snows over xDrive+snows are from cold climates with flat terrain or major cities which get plowed out in hours.

[hollandog]

Originally Posted by Musashi

You 2nd point. Could very well be clockwise. In a rear mirror I cant tell for sure which waay it spins first as drivers compensate. But usually it always oversteers to the left.

Your 3d point- ridiculous. Tells me you have never interacted with any Canadian BMW dealership. Chances are that any Canadian members here do interact with local dealerships and local BMW owners. Not you.

I definitely think you need more training or would not have commented on driving realities you never experienced. Or list me a SLOOW uphill video- as if traffic moves at that speed. Also, a strawman fallacy- no one argued here that a RWD +W cannot drive up a hill. That tangent you inserted is a faulty argument on your part... Am comfortable coming out the Kommel straight on Les Combes at 320km/hr and hitting the brakes 100m before the turn. But do 60MPH in a RWD on icy roads, and will discover rapidly why it spins with a micro wheel movement, versus an AWD which will not- not at that exact speed anyway. Maybe at 63.

The driver who posted after your last reply merely confirms it that you cannot apply your geocentric driving experience in climates pushing the physics to limits you never experienced. Car so cold that it never warms up. Shocks and springs so cold that they barely flex. Engine so cold that the T needle still has not moved 20 min into the ride. Brakes so cold that they never warm up enough to bite. Most people who have accidents here have them on dry, cold days. Winter tires so cold they spin in Sport mode.

RWD owners STORE their cars in Canada- a vast majority. Often it takes that one slushy incident - usually a left/right turn and the rear of the car spinning into the adjacent lane before a lucky recovery. In our cold reality, that would happen 2-3 times every trip, every day, 4-7 days a week. Not that "3 days a year" NJ thing...On a FWD the driving wheels bail one out. On the xDrive it is a mix: rear begins skidding, the fronts pull you out of trouble. It is quite fun to try on empty lots with DSC off.

Perhaps the fol videos will drive the point. Winter tires or not, seen it identically to RWDs + W unable to move. And if you do not get it that this almost never happens to xDrive owners (never did to me any winter day, and last two winters were nasty for Dec to March) nothing can alter your biases:

You sure those idiots in the videos have winter tires on them?
Looks like summer/all season from the video.
I'm sure my RWD won't get stuck on that 2" of snow....with my Blizzak


It's easy to find these biased videos.

[Polo08816]

Originally Posted by hollandog

You sure those idiots in the videos have winter tires on them?
Looks like summer/all season from the video.
I'm sure my RWD won't get stuck on that 2" of snow....with my Blizzak

With WS80s + RWD, you'd probably be able to do 6-9" of snow depending on consistency/density. This is from a dead stop on level ground through constant depth of snow. It's about the same deep snow capability of my 2008 Subaru Legacy GT with Continental DWS tires.

I wouldn't want to drive a sedan in much deeper snow than that because at some point you're going to be risking body damage whether you are RWD or AWD.

At that point, an SUV/pickup truck with winter tires the way to go in deep snow.

[metallicpea]

Originally Posted by MomoM3

Seems like most of the folks siding with RWD+snows over xDrive+snows are from cold climates with flat terrain or major cities which get plowed out in hours.

Yes, flat land here. Good point, but I am in a smaller town surrounded by rural areas, so road clearing is not very good for me. I see deep snow every time we get it.

[BMW335iOn18s]

Rwd

[strumbringer]

FYI, the LSD is not available for the 340i xDrive AFAICT (I was all excited about the prospect for a bit until my hopes were dashed :-P)

[Musashi]

Originally Posted by Polo08816

LOL. Where are you getting this information or are you just making it up?

Your anecdotal evidence is basically the difference between a car equipped with snow tires and one that is not. Not drivetrain configuration.

Also, AWD doesn't "double" your traction. You can argue that it doubles your probability of attaining a level of traction, but I can assure you it's not double as you are imagining it is.

As for your pictures, I can do even better. They say pictures are worth a thousand words, but how much are videos worth?

That was RWD + snow tires and no issues, no oscillations, etc. at or above the posted speed limits.

Here's a RWD + snow tire recovery from black ice:

Traction is defined as: A physical process in which a tangential force is transmitted across an interface between two bodies through dry friction or an intervening fluid film resulting in motion, stoppage or the transmission of power. You got a Ct per wheel; combined Ct for the Rear wheels; RCt + Fct = TCt for Rear and Front wheels. Divide the traction in a 4x4 setting, and the combined effect exceeds x2 or even x3 that of a RWD which, for example, may have lost friction on on of its Rear tires and TC cutts off. Cannot remember, in winter, TC cutting power fully to the xDrive, rather re-distributing it. And why we can't just go and install an LSD on xDrive, it is v complicated.

Simpler argument: Road cycle Ct<xCross cycle Ct<Motorbye Ct<car etc. As you enter the argument, can you explain what are you calling traction, the basic math and definition. Sure not confusing it with Friction?

http://curriculum.vexrobotics.com/cu...n-and-traction
https://www.quora.com/What-is-the-di...n-and-traction

Very quick known video:

The video you provided is interesting, but below is a better one, eschewed as the Subaru is all-seasons.

- Grooved ice for months. 100+ days. Also, imagine parking that BMW on the side and, 3 hours later, as the Winters groov themselves in the ice, it cannot leave its location. Winters just spinning. Vehicle immobilization safety cutting power... And you have to get out and get help. Imagine that BMW taking a turn on that street, fast enough to spin. In the video one instance the BMW turns CCW; another, tail starts CW due to the ice grooving. Subaru with Winters, or an xDrive with winters, dart under control well ahead of the said BMW with winters. The rare RWD I saw on such streets, never saw it able to keep up with an AWD + W and I think you get the point. The AWD will start skidding but Front left still has traction, (and 6% more weight) giving you far superior directional control. Seen it, experimented, it is a WOW to feel the front bailing you out.

-100+days: Comfort and even Eco to suppress torque. No Sport mode = winter tires spin. Jan to Mid 2015 -5 to -10F weathe and Winters at that Temp become the All Seasons in your example. Winters have a T limit for grip/friction, we reach it often... At -0F your RWD + W become as good as RWD+ AS at 10F. One cold, dry sunny Ottawa day, -10F produced over 80 dry accidents in one day. Winters were barely useful. The main deterrent to RWD in Canada's snow belt are former RWD owners who advise their BMW/Audi brethren to not use one as DD... Cars got more expensive, heavier and powerful since the 32oolbs nimble E 36 series. RWD owners love to lower their already low F3x RWD cars. Ask Canadian AWD owners why ditching RWD for xDrive. There is no mass delusion at play.

Finally, the cost.. The nicer RWD cars now come with 19-20" + wheels and some with MSport brakes, etc. Winter- (Snowbelt), anything over 19" is begging for a wheel bend and chip every two weeks. Earlier series this was not the issue, profiles being different. 18" wheel sets, + sensors and winter tires are over 3500$ CAD (if quality) and must keep them on until roads are patched in mid april. So just slapping winters on a brand new modded 340i RWD +20" is a far more expensive proposition up north. Use your summer 19/20" as winters = the blue chemicals eat your finish and the roads will destroy your rims. Most xDrive here buy them with stock 18", regular brake-sets, and go 17"/18" BMW approved winter coated wheel-sets. M3 with CCBs? fuggetabbouit - the 19's get wrecked the first pothole (and thousands pop up each winter per small city) ;18" do not fit. M3 with BBK = winter indoor car in Canada.

No debate, however, that AWD cannot improve braking nor cornering, but can be a heck of a control and recovery tool.

Awesome forum, the knowledge on these threads is fantastic. Bottom line: enjoy your RWD where you live. Would also drive one where I live, on selective winter days at the winter tracks:

http://www.theglobeandmail.com/globe...ticle28550698/

[Polo08816]

Originally Posted by Musashi

No debate, however, that AWD cannot improve braking nor cornering, but can be a heck of a control and recovery tool.

Most of your post is true.

In skilled hands, AWD would provide you greater recovery capabilities. But my take on it is that it would take a professional driver to perform that type of recovery consistently. In that type of situation, the average driver would have lost control whether it was AWD or not.

But if that matters so much, why not go for an Audi S4 with Sport Differential? It's a much better and more capable AWD drivetrain than the xDrive. We've already established that xDrive is not a performance oriented system, but rather a more utilitarian system.

[hollandog]

Originally Posted by Musashi

The video you provided is interesting, but below is a better one, eschewed as the Subaru is all-seasons.

- Grooved ice for months. 100+ days. Also, imagine parking that BMW on the side and, 3 hours later, as the Winters groov themselves in the ice, it cannot leave its location. Winters just spinning. Vehicle immobilization safety cutting power... And you have to get out and get help. Imagine that BMW taking a turn on that street, fast enough to spin. In the video one instance the BMW turns CCW; another, tail starts CW due to the ice grooving. Subaru with Winters, or an xDrive with winters, dart under control well ahead of the said BMW with winters. The rare RWD I saw on such streets, never saw it able to keep up with an AWD + W and I think you get the point. The AWD will start skidding but Front left still has traction, (and 6% more weight) giving you far superior directional control. Seen it, experimented, it is a WOW to feel the front bailing you out.

-100+days: Comfort and even Eco to suppress torque. No Sport mode = winter tires spin. Jan to Mid 2015 -5 to -10F weathe and Winters at that Temp become the All Seasons in your example. Winters have a T limit for grip/friction, we reach it often... At -0F your RWD + W become as good as RWD+ AS at 10F. One cold, dry sunny Ottawa day, -10F produced over 80 dry accidents in one day. Winters were barely useful. The main deterrent to RWD in Canada's snow belt are former RWD owners who advise their BMW/Audi brethren to not use one as DD... Cars got more expensive, heavier and powerful since the 32oolbs nimble E 36 series. RWD owners love to lower their already low F3x RWD cars. Ask Canadian AWD owners why ditching RWD for xDrive. There is no mass delusion at play.

Finally, the cost.. The nicer RWD cars now come with 19-20" + wheels and some with MSport brakes, etc. Winter- (Snowbelt), anything over 19" is begging for a wheel bend and chip every two weeks. Earlier series this was not the issue, profiles being different. 18" wheel sets, + sensors and winter tires are over 3500$ CAD (if quality) and must keep them on until roads are patched in mid april. So just slapping winters on a brand new modded 340i RWD +20" is a far more expensive proposition up north. Use your summer 19/20" as winters = the blue chemicals eat your finish and the roads will destroy your rims. Most xDrive here buy them with stock 18", regular brake-sets, and go 17"/18" BMW approved winter coated wheel-sets. M3 with CCBs? fuggetabbouit - the 19's get wrecked the first pothole (and thousands pop up each winter per small city) ;18" do not fit. M3 with BBK = winter indoor car in Canada.

No debate, however, that AWD cannot improve braking nor cornering, but can be a heck of a control and recovery tool.

Awesome forum, the knowledge on these threads is fantastic. Bottom line: enjoy your RWD where you live. Would also drive one where I live, on selective winter days at the winter tracks:

http://www.theglobeandmail.com/globe...ticle28550698/

The RWD + Winter M3 seems to do alright in the video you posted. I don't think people are argue if AWD + Winter is better than RWD + Winter. They said RWD + Winter is enough for NJ.

My 340i with Msport brake comes with standard 18" summer MPSS. I'm using 18" winter so 18" fits no problem.

The mass prefer AWD because of marketing. If AWD is the all and done solution, Canada would mandate the AWD instead of winter tires. But I understand people who lives up there prefer AWD for the extra peace of mind. Most people simply do not understand the importance of winter tires. Look at the GTR that got stuck on his summer performance.

If I lived in Quebec I'd probably go for AWD or a winter beater SUV for higher ground clearance. It's a quiet hilly city which RWD + winter might not be enough.

[hollandog]

Found these 3 awesome threads of the M3 on snow.

BMW Snow and Ice Training Experience Event in Arjeplog Sweden

Storm Chasing Jonas in my M3 - Feast your eyes

Photos: BMW M4 Coupe Plays in Snow at BMW Driving Experience

[lens]

Originally Posted by hollandog

The RWD + Winter M3 seems to do alright in the video you posted. I don't think people are argue if AWD + Winter is better than RWD + Winter. They said RWD + Winter is enough for NJ.

My 340i with Msport brake comes with standard 18" summer MPSS. I'm using 18" winter so 18" fits no problem.

The mass prefer AWD because of marketing. If AWD is the all and done solution, Canada would mandate the AWD instead of winter tires. But I understand people who lives up there prefer AWD for the extra peace of mind. Most people simply do not understand the importance of winter tires. Look at the GTR that got stuck on his summer performance.

If I lived in Quebec I'd probably go for AWD or a winter beater SUV for higher ground clearance. It's a quiet hilly city which RWD + winter might not be enough.

Oh, it's hilly alright.

And bumpy.

And cold.

And icy.

And has ridiculously retarded drivers.


...I can't wait for spring/summer to arrive.

[Musashi]

Hilly with pot holes, enough to tear a lowered RWD apart. Was March 2015 and June 2015 in QC city for conferences, and the SUV rental was quite bumpy. However, seen some nice RWD summer cars driven at 30km/hr on the pedestrian full, nicely paved, Grande Allee..