[tturedraider]

I’m not going to comment on the contradictions to your claims present in the very text you posted.

I’m going to just post this here without comment.

[celsdogg]

This diagram for the E90 seems to prove sky right. . .

[tturedraider]

Originally Posted by celsdogg

This diagram for the E90 seems to prove sky right. . .

I’m not exactly sure how you get that from the diagram. Did you read the description? There is one weird sentence, “Driving torque is always transmitted to the rear wheels, and most of the time to all four wheels”, but the majority contradicts what he claims, based on how I read it.

It should probably be noted that diagram and description is from xDrive’s introduction at the beginning of E90 production in 2005 and xDrive today is somewhat different. Its capabilities have evolved and improved since that introduction.

[celsdogg]

You do you man, I dunno, lol.

That top right diagram shows a continuous shaft to the rear diff. Clutch plates that close for the roller chain for the front axle so it can get some torque love.

I also would be skeptical of that roller chain holding on to 300 lb/ft by itself for to long. . .

[Skyhigh]

Originally Posted by celsdogg

This diagram for the E90 seems to prove sky right. . .

It absolutely does…. By all means - both graphically and within the text!

“Driving torque is always transmitted to the rear wheels and most of the time to all four wheels”. —-> that’s exactly the split 50:50 to 0:100, where the rear driveshaft always gets min 50% torque distribution.

And it goes on:

“The multi-disc clutch is completely closed, sending the maximum possible torque to the front wheels (note it does not say “all”, but “maximum possible”!)

…

XDrive opens the clutch completely, sending no driving torque to the front wheels”

Again —-> there’s the 50% to 0 torque on the fronts

How much more clear can it be!? It is written in English and the words say it all. One just needs to think about the meaning of every word and why it is phrased like it is. The schematic supports the statements fully in addition. Don't even see how one can misinterpret it.

I mean honestly it is not so difficult to grasp - the rear shaft is ALWAYS mechanically connected. The front can be fully disconnected or fully connected.
The only way to achieve “virtually” 100% traction sent to the front axle (and the key word here is virtually), is when there is no traction on both wheels in the rear as they both slip. Then the car virtually becomes a FWD car for a fraction of a second And that is valid for any AWD, as torque requires traction. Simple physics.

Thank you for proving yourself wrong. Now is the time to simply admit it and move on…. We all make uneducated guesses sometimes.

[tturedraider]

I’m not going to parse out every single word you’ve posted. It isn’t worth the time to me. I know what I know about how xDrive operates. As the previous poster said to me I’ll say to you, “you be you”. I’ve spent more time here than I intended. I’m out.

[Skyhigh]

Expected nothing else I would have congratulated you for being man enough to admit your mistake if you had done so…

You are welcome though for correcting your understanding. That’s what forums are for.

Enjoy xDrive!

[happyhippo]

I'am very happy with x-drive. I have hankook goodyear winter tires and they hook up really excellent, car is stable and predictable.
My only issue is that is still behave like RWD car on wet conditions, but I may try xDelete to change front-rear power ratio

[Skyhigh]

You can’t change the ration with xDelete. Not on the F series.
And yes - it is rear-biased, it is supposed to feel a bit like RWD that’s per design.

[LongRoofTDI]

Originally Posted by thisismikeyb

xDrive is great with a good set of winter tires, it's also more fun with a proper LSD in the back.

When you say proper LSD, what do you mean?

[johnung]

Originally Posted by LongRoofTDI

When you say proper LSD, what do you mean?

He just means a mechanical LSD like the M Performance LSD, which works immediately when there is any rear wheel spin to transfer more power to the other rear wheel, rather than just the BMW electronic system that comes standard in our cars.

That BMW e-LSD system doesn’t activate until there is at least 30% spin at a rear wheel. Then it works by applying the brake to just the wheel that is spinning. If that doesn’t work, then it starts to cut throttle.

So the mechanical LSD actually makes the car go faster while keeping it safer, the e-LSD focuses on safety while actually slowing the car down.

When my MP LSD was first installed I immediately noticed that the car seemed to enter curves faster. Probably one wheel would normally spin, but the MP LSD was automatically sending power to the other wheel so it felt like I was now powering into curves. I also noticed that the car was much quicker off the line from a standing start for the same reason.

[LongRoofTDI]

Originally Posted by johnung

He just means a mechanical LSD like the M Performance LSD, which works immediately when there is any rear wheel spin to transfer more power to the other rear wheel, rather than just the BMW electronic system that comes standard in our cars.

That BMW e-LSD system doesn’t activate until there is at least 30% spin at a rear wheel. Then it works by applying the brake to just the wheel that is spinning. If that doesn’t work, then it starts to cut throttle.

So the mechanical LSD actually makes the car go faster while keeping it safer, the e-LSD focuses on safety while actually slowing the car down.

When my MP LSD was first installed I immediately noticed that the car seemed to enter curves faster. Probably one wheel would normally spin, but the MP LSD was automatically sending power to the other wheel so it felt like I was now powering into curves. I also noticed that the car was much quicker off the line from a standing start for the same reason.

Interesting…Did the MP LSD only come as an aftermarket unit or did it come with the M-Sport Package? Wonder if it’s a good mod for a daily driven, year around, 4 season Xdrive F31?

Thanks in advance, I’m new here.

[johnung]

Originally Posted by LongRoofTDI

Interesting…Did the MP LSD only come as an aftermarket unit or did it come with the M-Sport Package? Wonder if it’s a good mod for a daily driven, year around, 4 season Xdrive F31?

Thanks in advance, I’m new here.

Good question. Anything labeled as “M Sport” means that is a factory installed option. You should see it on the window sticker and in mdecoder if you enter the VIN.

“M Performance” is BMW’s aftermarket parts group. Sometimes people get confused thinking that an M Performance part was installed at the factory. MP parts can be ordered with a new car at the dealership (the car that I bought used came with MP parts) but MP parts are most often installed at the dealer. Someone once told me that some MP parts can be installed at the port after the car arrives from the factory.

“M Sport” is most of all a marketing term that BMW slaps on everything. So it’s really important not to see M Sport and jump to conclusions about what is installed on a particular car.

The most common mistake is for guys to see that a car is labeled as an M Sport model and assume that it has M Sport everything like MS Brakes, MS Suspension, etc. An M Sport model is mostly MS bumpers and maybe a different steering wheel and a few badges. If the window sticker doesn’t have a separate line item that says…
“M Sport Brakes”
then it doesn’t have M Sport Brakes regardless of whether it’s an M Sport model or not.

All F3x M Sport Brake calipers are blue, but even that doesn’t mean that they are all the same because some models came with Front 340mm Blue Calipers and other BMW F3x models came with Front 370mm Blue Calipers. They are both labeled “M Sport”, and installed at the factory but the parts are not identical.

Like I said, BMW slaps the marketing term “M Sport” on everything. It’s basically meaningless as a descriptor unless one knows the full context of how it’s being used.

Hope this helps!

[LongRoofTDI]

Originally Posted by johnung

Good question. Anything labeled as “M Sport” means that is a factory installed option. You should see it on the window sticker and in mdecoder if you enter the VIN.

“M Performance” is BMW’s aftermarket parts group. Sometimes people get confused thinking that an M Performance part was installed at the factory. MP parts can be ordered with a new car at the dealership (the car that I bought used came with MP parts) but MP parts are most often installed at the dealer. Someone once told me that some MP parts can be installed at the port after the car arrives from the factory.

“M Sport” is most of all a marketing term that BMW slaps on everything. So it’s really important not to see M Sport and jump to conclusions about what is installed on a particular car.

The most common mistake is for guys to see that a car is labeled as an M Sport model and assume that it has M Sport everything like MS Brakes, MS Suspension, etc. An M Sport model is mostly MS bumpers and maybe a different steering wheel and a few badges. If the window sticker doesn’t have a separate line item that says…
“M Sport Brakes”
then it doesn’t have M Sport Brakes regardless of whether it’s an M Sport model or not.

All F3x M Sport Brake calipers are blue, but even that doesn’t mean that they are all the same because some models came with Front 340mm Blue Calipers and other BMW F3x models came with Front 370mm Blue Calipers. They are both labeled “M Sport”, and installed at the factory but the parts are not identical.

Like I said, BMW slaps the marketing term “M Sport” on everything. It’s basically [...]

I appreciate the clarification. Truly a great explanation. Guess my best COA is to talk with my local dealer about ordering an MP LSD.

Thanks again.

[johnung]

Originally Posted by LongRoofTDI

I appreciate the clarification. Truly a great explanation. Guess my best COA is to talk with my local dealer about ordering an MP LSD.

Thanks again.

Here’s a link to some MP LSDs. The part number needed will depend on your F3x model, RWD or XDrive, manual or automatic. Below is a dealer in Maryland who discounts Genuine BMW parts online. Shop dealers in your area to see if someone will discount or match the price.
Installation is about $650 and it takes two special tools that many independent shops don’t have. This is one job that I’d do at the dealer rather than try to save a couple hundred bucks on labor.

https://www.getbmwparts.com/c-differentials-92

[LongRoofTDI]

Originally Posted by johnung

Here’s a link to some MP LSDs. The part number needed will depend on your F3x model, RWD or XDrive, manual or automatic. Below is a dealer in Maryland who discounts Genuine BMW parts online. Shop dealers in your area to see if someone will discount or match the price.
Installation is about $650 and it takes two special tools that many independent shops don’t have. This is one job that I’d do at the dealer rather than try to save a couple hundred bucks on labor.

https://www.getbmwparts.com/c-differentials-92

Thank you much! This is a huge help. I’m in an F31 328dx, and it seems none of the ones at the link fit….or is this more of a “fit thr 335i unit to any F3x”?

[johnung]

Originally Posted by LongRoofTDI

Thank you much! This is a huge help. I’m in an F31 328dx, and it seems none of the ones at the link fit….or is this more of a “fit thr 335i unit to any F3x”?

The list should be showing the available F3x LSDs. Send an email through the GetBMWParts website, give them your VIN and ask which MP LSD will fit your car. They are very helpful and responsive

[LongRoofTDI]

Originally Posted by johnung

The list should be showing the available F3x LSDs. Send an email through the GetBMWParts website, give them your VIN and ask which MP LSD will fit your car. They are very helpful and responsive

Thanks for the help. You’ve been great man.

[thisismikeyb]

Originally Posted by LongRoofTDI

Thank you much! This is a huge help. I’m in an F31 328dx, and it seems none of the ones at the link fit….or is this more of a “fit thr 335i unit to any F3x”?

Unfortunately, BMW never blessed the 328 cars with M-Performance LSD’s. As far as I can tell, I got away with it on my car due to it being an early production model, June 2013, which had the same diff and axles as the 335i. The 328d and newer 328i’s all have different axles and diffs.

[LongRoofTDI]

Originally Posted by thisismikeyb

Unfortunately, BMW never blessed the 328 cars with M-Performance LSD’s. As far as I can tell, I got away with it on my car due to it being an early production model, June 2013, which had the same diff and axles as the 335i. The 328d and newer 328i’s all have different axles and diffs.

Well that’s just unfortunate! All is good tho, I know FarKle did an aftermarket unit (either Quafe or WaveTrac) that he has enjoyed….gotta find that thread!

[Eddamoo]

Ooh spicy thread. I'd rather not get involved in the argument but just wanted to leave a comment to those at loggerheads. I can clearly see both points of view - to me, it depends where you're reading 'the Torque'. I think this was just causing the confusion here.

Gearbox Torque: Can only go up to 50% front. 50%+ will always go to the rear diff.

Wheel Torque (after the brakes): Infinitely variable - 100:0, 0:100 or anywhere between. BUT the front portion can only be up to 50% of the total gearbox torque.

When we talk X-Drive we often infer traction and therefore wheel torque. It is possible to have 100% of the cars wheel torque to be produced by a single front wheel. The only way to do that is for the DSC system, to apply the other 3 brakes while the car is moving.

This situation is obviously rare and the torque applied to that front wheel will only be <50% of the gearbox torque AND only able to match the rear wheel speeds, but it is possible. An example would be a driving on snow and the rear wheels have broken grip (thanks to being fatter on most BMW's) - apply brakes to the rears to allow the fronts to catch up.

[Skyhigh]

Exactly......