[moldcad]

So, I've made up my mind and have an M235i on order (was debating between that and the 435i, and decided that even coming from an F10, the 4 is still too large for my specific purposes).

Now seeking advise on whether to spend some of the money I saved by not buying the 435i on the LSD. I'm a sporty driver (I think getting rid of otherwise great, but for me - underpowered, 528xi can give you the idea of the way I like to drive), and for over 43 year now - with the exception of the last 2 years - I've been driving RWD cars. Only the last one of those (my old good E46 330i) offered the now obvious electronic "nannies" (and not just the obvious ones like DSC/DTC, but also brake-based e-diff); with my previous RWD cars everything was being taken care of by myself (I do hope I still have the reflexes and muscle memory I learned then).

However - even with e-diff - I remember embarrassing moments when I just couldn't move my 330i from a standstill (like at traffic lights) when both rear wheels were standing on ice (additionally, I didn't have a clutch with that one - it featured the infamous SMG gearbox - so I couldn't use the traditional way of rocking the car and getting it out of being stuck).

My M235i is going to be a SAT car (I did think of a "full return to the basics" and ordering 6MT, but after surgeries my right arm is so weak I can't use it for shifting for too long without a serious fatigue, so I've given up on that; this means no traditional clutch again ).

So, now a question to those savvy and experienced with the BMW 30% LSD available for the M235i: apart from its obvious advantages in track use, will it also help with traction on snow thereby helping somewhat to get used again to RWD after 2 years of the "AT + xDrive laziness" I indulged with my F10?

Please try to take my question seriously, and answer candidly using technical argumentations and terminology (as an engineer, I'm prepared to understand). Unfortunately, here in Poland there is absolutely no chance of a test drive an LSD-equipped car like the 2 series... So - considering I will probably never track my M235i, and only use LSD-assisted drifts and power-exiting corners sporadically - is it worth the price also as a sort of making for the lack of AWD in wintery conditions (OK, OK, good winter tires are the most important )?

Thanks for any constructive input!

[Bahuba]

I'd like to know if installing the LSD disables the e-diff. Otherwise, wouldn't that mean you'd need to disable the DSC (stability) in order to disable the e-diff to realize the benefits of LSD. I'm not so sure I want to disable DSC in winter.

[tke743]

Originally Posted by moldcad

Now seeking advise on whether to spend some of the money I saved by not buying the 435i on the LSD. I'm a sporty driver (I think getting rid of otherwise great, but for me - underpowered, 528xi can give you the idea of the way I like to drive), and for over 43 year now - with the exception of the last 2 years - I've been driving RWD cars. Only the last one of those (my old good E46 330i) offered the now obvious electronic "nannies" (and not just the obvious ones like DSC/DTC, but also brake-based e-diff); with my previous RWD cars everything was being taken care of by myself (I do hope I still have the reflexes and muscle memory I learned then).

However - even with e-diff - I remember embarrassing moments when I just couldn't move my 330i from a standstill (like at traffic lights) when both rear wheels were standing on ice (additionally, I didn't have a clutch with that one - it featured the infamous SMG gearbox - so I couldn't use the traditional way of rocking the car and getting it out of being stuck).

So, now a question to those savvy and experienced with the BMW 30% LSD available for the M235i: apart from its obvious advantages in track use, will it also help with traction on snow thereby helping somewhat to get used again to RWD after 2 years of the "AT + xDrive laziness" I indulged with my F10?

Good questions and I've had the opportunity to test this exact situation. I was at a light and the road was ice. When the light changed the car instantly spun the drivers side for a fraction of a second and then the e-dif arrested that and the car moved. This was a zero traction event on the one wheel and very limited traction on the other and it handled it fine.

The e-dif is actually quite good, and with that I wold say that the LSD might not fit your requirements. With no track time and anything under 8/10 street driving will not need it. (This is not your father's e-dif, or more accurately your older brother's.)

Let me be clear in saying this, I'm getting the LSD, but I track my car at least 10 times a year. The e-dif is good enough for track time, but not 100%. Also on a track it would cook the rear brakes.

Originally Posted by Bahuba

I'd like to know if installing the LSD disables the e-diff. Otherwise, wouldn't that mean you'd need to disable the DSC (stability) in order to disable the e-diff to realize the benefits of LSD. I'm not so sure I want to disable DSC in winter.

It does not disable the e-dif, it keeps it there but lessens it's use, at 10/10 they are designed to work together. You would not have to disable the e-dif to feel the effects of the LSD. The LSD limits slip but it also limits the amount of time the e-dif has to work.

[///MCFC]

even with the lsd, the traction control light still flashes constantly (except in sport+), which is a bit disappointing tbh.

[moldcad]

Thanks for the answer tke743. Do you happen to know iff e-diff system was already present in the 2003 E46 330i? Because I swear that when I happened to have both rear wheels on ice, it was virtually impossible for the car to move forward... So perhaps the e-diff system was only introduced later on, and indeed would be sufficient in the M235i?

[tke743]

Originally Posted by moldcad

Thanks for the answer tke743. Do you happen to know iff e-diff system was already present in the 2003 E46 330i? Because I swear that when I happened to have both rear wheels on ice, it was virtually impossible for the car to move forward... So perhaps the e-diff system was only introduced later on, and indeed would be sufficient in the M235i?

I'm coming from a 2004 330i ZHP and it had the same system as yours. No the e46 did not have an e-dif. It has a rudimentary traction control that wasn't all that good. I've had the same situation you describe, where you are just sitting there looking dumb, and everyone gets a good laugh.

The e-dif is technically in the same family, but the analogy I can give is that the one in the e46 was a slide ruler, the e-dif (and other nanny systems in the M235i) are a modern computer.

[Killramos]

I am dailying my M235i in Calgary and i have the M perf diff installed. It has never been stuck ( look at a webcam and you will see why thats impressive). That's with not exceptional OEM tires (winters obviously). I find it helps alot with turning on ice across traffic, and the nannies do a great job still keeping you in a line.

It is also alot more fun for hooning in snow covered parking lots or if you drive an ice course etc.

For me the LSD was the key missing piece in the car, and imo would have been a great distinguishing feature of the Mperformance car line. But it is hella expensive

For those dissapointed by their traction control light still flashing you need to do some more reading on how an LSD works.

[moldcad]

So your answers guys point me to opposite directions - but thanks nevertheless. Killramos - did you have an opportunity to drive the same route you're enjoying so much with LSD before you installed it, and if so, was the improvement worth it and immediately noticeable?

[scrape1]

Originally Posted by moldcad

Thanks for the answer tke743. Do you happen to know iff e-diff system was already present in the 2003 E46 330i? Because I swear that when I happened to have both rear wheels on ice, it was virtually impossible for the car to move forward... So perhaps the e-diff system was only introduced later on, and indeed would be sufficient in the M235i?

If both your rear wheels are on ice, your car won't move even with a spool rear end. The LSD allows transferring an unequal amount of torque to the two wheels, as opposed to an open diff, where the torque is always equal between the two wheels. If there is no traction to either wheel, you are dead in the water LSD or not.

[scrape1]

Also, mu hunch is that for getting unstuck in slippery conditions, the eDiff is perfectly adequate. In fact, the LSD might even need some help from the eDiff if 1 wheel is on bare ice or up in the air. I read that the LSD offers 30% lock, which may or may not be enough to move the car if one wheel is getting very low or no grip.

[moldcad]

Originally Posted by scrape1

If there is no traction to either wheel, you are dead in the water LSD or not.

In 99,99% of real life situations there is always some traction to at least one wheel (you must be very, very unlucky to have none). And this - considering the other wheel with no traction at all doesn't add to the moving resistance by getting broken dead by e-dif - should suffice for LSD to move the car out of trouble...

This is just mho, based on theoretical divagations only, though - so I may be wrong.

PS. The problem with getting real, unbiased advise on things like this is that from somebody who already spent the $$$ you will likely get an enthusiastic "pro", while somebody else who just cannot afford it (or it's not high enough on his list of priorities) will always point to the cons

[///MCFC]

Originally Posted by moldcad

PS. The problem with getting real, unbiased advise on things like this is that from somebody who already spent the $$$ you will likely get an enthusiastic "pro", while somebody else who just cannot afford it (or it' not high enough on his list of priorities) will always point to the cons

wtf? i feel like I'm taking crazy pills.

[Bahuba]

Even in snow covered roads (like today) I drive in sport+ (traction control off). My biggest beef is the inconsistency of the stability control. Sometimes it lets you do a power turn, other times it kicks in takes all the fun away. I wonder if the e-diff is somehow indirectly responsible. I'm talking about low speed power turns, and power turns from a standing stop.

[///MCFC]

Originally Posted by Killramos

I am dailying my M235i in Calgary and i have the M perf diff installed. It has never been stuck ( look at a webcam and you will see why thats impressive). That's with not exceptional OEM tires (winters obviously). I find it helps alot with turning on ice across traffic, and the nannies do a great job still keeping you in a line.

It is also alot more fun for hooning in snow covered parking lots or if you drive an ice course etc.

For me the LSD was the key missing piece in the car, and imo would have been a great distinguishing feature of the Mperformance car line. But it is hella expensive

For those dissapointed by their traction control light still flashing you need to do some more reading on how an LSD works.

pls do enlighten me, b/c i always believed that an LSD helps to increase the available traction and therefore reduce the need for those "nannies" that rob power. but surely you know something i don't.

[scrape1]

Originally Posted by moldcad

In 99,99% of real life situations there is always some traction to at least one wheel (you must be very, very unlucky to have none). And this - considering the other wheel with no traction at all doesn't add to the moving resistance by getting broken dead by e-dif - should suffice for LSD to move the car out of trouble...

This is just mho, based on theoretical divagations only, though - so I may be wrong.

PS. The problem with getting real, unbiased advise on things like this is that from somebody who already spent the $$$ you will likely get an enthusiastic "pro", while somebody else who just cannot afford it (or it's not high enough on his list of priorities) will always point to the cons

Maybe. Anecdotally, I had an S2000 with LSD and snow tires and never managed to get stuck. I also drove an E46 330i with snows and no LSD, and had one case where the car couldn't make it up a slope in an icy parking lot. Keep in mind, it was so icy that I had trouble walking up it. But there is no question which car was easier to drive in snow. The E46 felt more stable to me. The S2000 required more attention. Whether that's because the S2000 had zero electronic stability nannies, or because the LSD made it easier to spin both wheels, I am not entirely sure. But I think the experience most people have is that the eDiff with good tires makes for a very capable winter set up.

[foamie]

Today it was -10 degrees F (-23 degrees C) on my way to work, there were lots of areas of packed snow and ice patches on the road especially on intersections. My daily driver/weekend track toy is a S2000 CR currently equipped with winter tires. The prospect of driving without an LSD on a lightweight RWD car would be difficult at best and almost impossible to use here in Minnesota when the weather turns sour. I would have never considered the M235i coupe that I ordered without the possibility of having a LSD since I will destroy the rear brakes either in winter or on track days.

An open differential will direct power on the wheel with the LEAST amount of traction, which is really counter intuitive on low traction conditions. A LSD will direct power on the other wheel once the predetermined slip is achieved on the wheel which is slipping/no/poor traction. An e-diff is an open differential which will direct power on the other wheel once it senses slippage on one wheel by applying the brakes momentarily or pulsing them.

If you really like the M235, then the best option might be having X Drive and winter tires.... on those really bad days, you will still have an e-diff that you can depend on.... UNLESS both rears and 1 front are on ice and uphill .... then it is time for a car with perhaps a torque vectoring or LSD front differential (or move). I have driven the M235i xDrive this winter and it was very impressive IMHO and every bit as good as the RWD version, but I like the simplicity of RWD and doing track days. Good Luck !!!

[moldcad]

Originally Posted by foamie

I have driven the M235i xDrive this winter and it was very impressive IMHO and every bit as good as the RWD version, but I like the simplicity of RWD and doing track days. Good Luck !!!

I dismissed xDrive for exactly the same reasons, even though I don't do tracks any more

[Killramos]

Originally Posted by moldcad

So your answers guys point me to opposite directions - but thanks nevertheless. Killramos - did you have an opportunity to drive the same route you're enjoying so much with LSD before you installed it, and if so, was the improvement worth it and immediately noticeable?

I had my LSD installed this summer so no sorry i cant answer that. All i can say is I love it and the summer performance was definitely noticeable ( merging onto roads with gravel as an example, or kicking the rear out with power down).

As for the other poster who wanted enlightenment. An LSD ( particularly a clutch pack one like the Mperf) is an Open Differential UNTIL you start slipping(for ours wheel spin is needed to trigger lockup, more aggressive diffs can lock up just by turning sharply ). Traction control will notice the slip and will flash (though potentially not engage depending on software). The differential locks up when you reach the predetermined amount of difference in slip between the wheels (30% forward 9% rear), it is designed to engage BEFORE the eLSD (ediff) which basically means the ediff wont really engage when you have the Mperf.

The new electronic 0-100% locking diffs on the M cars this year are different beasts entirely.

Hope that helps.

[foamie]

Originally Posted by moldcad

I dismissed xDrive for exactly the same reasons, even though I don't do tracks any more

We do have similar reasons

Good luck on your decision but something tells me that even if you do not track cars anymore; like a lot of people here, you like playing with cars and breaking traction is a lot easier to do come winter time

[Kgolf31]

My evidence.

My 128i has the OE E-Diff still in the car, ordering a clutch soon, but that's beside the point
My dad's M235 has the MP Diff.

Night and day difference from standstills with the M235i and the differential.


PS - If you're in heavy snow press TC once. It will turn off the throttle control that starves the engine when it senses slip. It will, however still have yaw control active which will keep the car straight.

This will get the rear wheels turning, thus achieving lock, throwing out snow and getting grip

[ska///235i]

Bmw's open diff is assisted by ADB (auto diff braking) also know as an EDiff (electronic lsd)

The system will apply resistance to one wheel to balance traction between the rear wheels. So we always think of this as a 1 wheel wonder. However this isnt true. The Ediff "apply resistance" which means applying brake pressure to wheel with less traction to get the rear going. It does what a proper LSD is doing...well kind of, the concept is the same as both diff is applying pressure to the spinning wheel. One is doing it by braking and the other (MP diff) is applying it thru the clutch plates inside the diff.

So whats the difference? In my opinion a proper lsd will always have a faster reaction time cuz everything is almost realtime (controlling the drive shaft from the inside) where a Ediff is relying on sensors and transmit it to the ADB to apply braking (controlling the wheelspin from the outside) and someone have already mention...you'll toast your rear brake pads sooner

[pikcachu]

Originally Posted by Bahuba

Even in snow covered roads (like today) I drive in sport+ (traction control off). My biggest beef is the inconsistency of the stability control. Sometimes it lets you do a power turn, other times it kicks in takes all the fun away. I wonder if the e-diff is somehow indirectly responsible. I'm talking about low speed power turns, and power turns from a standing stop.

Sport+ is not "traction control off"

there are 3 traction states:

DSC on - mode when you start the car
TC on - 1 touch to the traction button or sport+
DSC off - hold 5 secs the traction button... everything is off

Also this implies that the LSD will only take full effect with DSC off

"A highlight in the suspension area is the BMW M Performance limited-slip differential available for the BMW M235i Coupé. When the dynamic stability control function DSC is deactivated, the torque-sensitive mechanical limited-slip differential in the rear axle ensures traction-optimised distribution of drive torque between the rear wheels. It reduces the slip that occurs on the wheel with less grip by transferring more drive power to the other wheels using a blocking effect. This converts engine power into forward momentum as effectively as possible so as to be able to accelerate out of a bend even more dynamically, for instance."
http://www.2addicts.com/forums/showt...&highlight=lsd

Quote:
Originally Posted by pikcachu
Hey,

Given that you were at the M perf Las Vegas event...

Do you know what this means ?

When the dynamic stability control function DSC is deactivated, the torque-sensitive mechanical limited-slip differential in the rear axle ensures traction-optimised distribution of drive torque between the rear wheels. It reduces the slip that occurs on the wheel with less grip by transferring more drive power to the other wheels using a blocking effect.

Is the LSD always on or only when you turn DSC off?

Thanks in advance

"Hey there,

I have not asked this exact question to the BMW staff, but here is what I think is happening.

A mechanical LSD is always 'on'. It is a mechanical locking device.

However, with DSC engaged, your inside wheel slip will be curbed much sooner by the DSC braking the individual inside wheel, well before it has had enough slip to engage the LSD.

The LSD is always on, but can't be felt until you turn off DSC. Otherwise, DSC will interrupt your power well before the LSD even has a chance to take hold.

Hope this helps. This is not an official BMW answer, and is my educated guess.

Sam

here is also a good video about LSD

http://www.2addicts.com/forums/showt...&highlight=lsd