[NGT2]

Anyone know if the xDrive system works differently in my M550 than my X7 40i?

We’re supposed to get some snow (not a lot) and I’ve got to go somewhere later. Just curious if the X7 is better on snow than the M550. Both have AS run flats. Ground clearance won’t matter.

[adhrp]

I don't have the answer to your question but as for your concerns - even my RWD 328i on AS tires could handle a couple of inches of snow easily, and a little more than that with more careful driving. I think the M550i will easily exceed that and the X7 should be a breeze too.

[JoeFromPA]

The exact tire and condition of that tire matters more than the X drive system.

Chances are the g30 will do better due to lower center of gravity and less weight. Snow driving is rarely an issue of getting moving. Turning and stopping is everything, and that isn’t AWD

[NGT2]

I give it an A+. Never a slip.

[Qsilver7]

XDrive operates the same on the 5 series and X7. The only differences will be ground clearance, road visibility (due to height difference) and weight/length. But the way the AWD system performs in inclement weather will be the same.

[AP]

Do we know how rear biased xdrive is on the m550?
Reviews state that it is but I’ve never found any reference as to how much. Is it the same for all xdrive cars or is the 550 any different

I’m talking about it’s bias in normal driving and not having to compensate at a moment in time for loss of grip , ie it’s default setting

[Qsilver7]

Originally Posted by AP

Do we know how rear biased xdrive is on the m550?
Reviews state that it is but I’ve never found any reference as to how much. Is it the same for all xdrive cars or is the 550 any different

I’m talking about it’s bias in normal driving and not having to compensate at a moment in time for loss of grip , ie it’s default setting

Assuming all 4 tires have the same traction and the steering wheel is straight…the front/rear torque bias is 50/50 based on the info from BMW TIS.

This is different data from when xDrive first appeared back in 2005 on the e53 X5…back then it was a 40/60 (front/rear) torque bias.

The info below appears to be inline with the info in the video.

[AP]

Thanks. So why do reviews state it’s rear biased getting that info from?

[Qsilver7]

Originally Posted by AP

Thanks. So why do reviews state it’s rear biased getting that info from?

Again, probably from the past when xDrive originally debuted. I don’t really recall BMW doing a lot of press on changes in xDrive…so unless you drill down many probably assume that it has pretty much remained the same.

You can see in the info below that goes back to the e53/e70/e83 era…the torque split was 40/60 (front/rear) bias:

[AP]

Ok thanks

[Neusser]

Originally Posted by Qsilver7

Assuming all 4 tires have the same traction and the steering wheel is straight…the front/rear torque bias is 50/50 based on the info from BMW TIS.

This is different data from when xDrive first appeared back in 2005 on the e53 X5…back then it was a 40/60 (front/rear) torque bias.

The info below appears to be inline with the info in the video.

Post a link to this please. Does not look legit to me.

From a more-recent German press release:

"Unter normalen Fahrbedingungen arbeitet es mit einer Grundverteilung der Antriebsmomente von 40 bis 60 Prozent zwischen Vorder- und Hinterachse"

So a base torque split of 40/60 under "normal driving conditions"

https://automag.de/bmw/bmw-xdrive/


Aside from the dynamic 40/60 split BMW has touted for ages, 50/50 would harm fuel efficiency. Much as the Audi front-biased Haldex models operate in FWDish mode most of the time, BMW would operate in RWDish mode, as powering one axle is far more efficient.

[AP]

This is one example , Joe Achilles in this case where the rear bias is mentioned

Obviously have no reference where he has got this info from but just a guess is that as this was a bmw press event where he borrowed the car, it may have been mentioned to him in a briefing potential tially?

I love these technical discussions, it’s what it’s all about!

https://youtu.be/WaYZlWc8WTo?si=WrgIXIZ3Fg2cDmEu

[JoeFromPA]

Never forget that BMW is a marketing machine. They may have deliberately been saying read biased for a long time without ever clarifying what that actually means.

[AP]

Very true
You can expand that lots of their safety systems where the explanation is vague and it’s not entirely clear as to exactly what’s going on

[JoeFromPA]

Originally Posted by AP

Very true
You can expand that lots of their safety systems where the explanation is vague and it’s not entirely clear as to exactly what’s going on

“Dynamic”

[Alscoob]

Well I have to say that on my 540i x-drive G31, since I have owned it, some 7 & a bit months & 8K miles the tyre wear seems to be consistant front to rear. If it were 60/40 rear bias one could expect more rear tyre wear? especially as the car is driven to use the power.

Perhaps the 50/50 change came about to avoid the potential diff problems with the front / rear wear difference being only 2mm in tread depth... and they kept it quiet?

[Qsilver7]

Originally Posted by Neusser

Post a link to this please. Does not look legit to me.

Unfortunately I can't post a link because it is a screen shot from the BMW TIS site. You'd have to purchase a subscription. I cropped the top of the page that has info that can't be posted online.

You can see at the very top of the info for the M550...that the link is specifically from the G30 M550 info. I also verified several other more modern BMWs (a g12 7 series, an f15 X5 and an f06 650ix GC)...and both of those models data also said it was 50/50.

It was only when I went back to the earlier 1st gen models that had xDrive that the data mentions the 40/60 torque split. Again, xDrive debuted on the LCI e53 X5 and also on the e83 (not sure what year on that model).

And if my memory serves correct...the 1st X5s that were built from 1999 to 2004...they had a special AWD system that was a combination of the AWD systems used in the 1980s on the e30 3 series & e34 5 series...but now included DSC...I believe it was referred to "in house" as DSC-X and they may have had a 48/52 (front/rear) torque split.

If you have access to the BMW TIS or other BMW technical documents...do a search for ALL WHEEL DRIVE SYSTEM xDRIVE w/TRANSFER BOX to see what you find

And do keep in mind which transfer box is being discussed. I say that because some of the smaller BMWs with xDrive that share technology with MINI...they may have a different torque split due to some of those models being FWD biased.

[Qsilver7]

Originally Posted by Alscoob

Perhaps the 50/50 change came about to avoid the potential diff problems with the front / rear wear difference being only 2mm in tread depth... and they kept it quiet?

Good point. I also wonder if the change came about to help with fuel consumption.

I remember when watching several videos on xDrive...that they mentioned how changes were made to improve fuel consumption...but they never went into details. But I do remember that statement made me make a check-mark in my mental Rolodex...hmmm.

[AP]

All very interesting

Thanks

[Qsilver7]

Just FYI since I brought it up in this thread...here's more info about the introduction of BMW's AWD system on the first iteration (pre LCI) e53 X5 that debuted in late 1999...this is prior to the introduction of xDrive in late 2004. This is old info found in my archives from back then.

I have to make a correction...the torque split for these early pre-xDrive was 32/68 (front/rear)...not the 48/52 (front/rear) split I mentioned earlier. This is what would be found on the first e53 X5 3.0i (w/M52 engine), X5 4.4i (w/M62TU engine), and X5 4.6is (w/M62TU engine):

[img]

[Neusser]

Originally Posted by Qsilver7

Unfortunately I can't post a link because it is a screen shot from the BMW TIS site. You'd have to purchase a subscription. I cropped the top of the page that has info that can't be posted online.

You can see at the very top of the info for the M550...that the link is specifically from the G30 M550 info. I also verified several other more modern BMWs (a g12 7 series, an f15 X5 and an f06 650ix GC)...and both of those models data also said it was 50/50.

It was only when I went back to the earlier 1st gen models that had xDrive that the data mentions the 40/60 torque split. Again, xDrive debuted on the LCI e53 X5 and also on the e83 (not sure what year on that model).

And if my memory serves correct...the 1st X5s that were built from 1999 to 2004...they had a special AWD system that was a combination of the AWD systems used in the 1980s on the e30 3 series & e34 5 series...but now included DSC...I believe it was referred to "in house" as DSC-X and they may have had a 48/52 (front/rear) torque split.

If you have access to the BMW TIS or other BMW technical documents...do a search for ALL WHEEL DRIVE SYSTEM xDRIVE w/TRANSFER BOX to see what you find

And do keep in mind which transfer box is being discussed. I say that because some of the smaller BMWs with xDrive that share technology with MINI...they may have a different torque split due to some of those models being FWD biased.

Is this from US documentation?

Weird. Almost wonder if they adjust the system by country.

For example in Germany and the EU, they provide half-load tire pressures, and, ofc, the suspensions are typically set up stiffer for EU cars.

I wonder if they adjust the torque split to 50/50 for the US models.

The German site I linked is from 2024 and clearly states 40/60, and I do find my G31 to exhibit rear bias. Power oversteer in the dry is definitely possible, and depending on tire pressure I would even say easy.

[G30M]

Originally Posted by AP

Do we know how rear biased xdrive is on the m550?
Reviews state that it is but I’ve never found any reference as to how much. Is it the same for all xdrive cars or is the 550 any different

I’m talking about it’s bias in normal driving and not having to compensate at a moment in time for loss of grip , ie it’s default setting

in normal driving at constant speed going straight 100% rwd. front wheels activated on demand (actively by computer before the car slips) - eg accelerating, turning, driving on snow, etc

my m340i goes sideways driving at a constant 55mph on loose tarmac! but the dealer has found the front diff is whining, so i'm not sure it that's got anything to do with it.