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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > All-Wheel-Drive (Xi / xDrive) Talk > dumb question no seriosously its dumb.



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      07-20-2015, 06:53 PM   #1
E46toE90
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dumb question no seriosously its dumb.

I know with awd you need to keep it under 1% rotational difference. Over 1% ,awd thinks you are slipping and constantly tries to fix the error which then something blows up.

Can i drive temp with dcs off. if my wheels are over 1% ?

Doesnt that stop the system from trying to correct its self?
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      07-20-2015, 07:01 PM   #2
AceOnShake
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I wouldn't risk your transfer case!
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      07-20-2015, 07:21 PM   #3
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Quote:
Originally Posted by AceOnShake View Post
I wouldn't risk your transfer case!
Thats what it comes down to but my curiousity wants to know.

I was on 19 had a blow out through on a spare 18. Traction light would come on so untill i repaired wheel i drove with dcs off
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      07-21-2015, 08:53 PM   #4
gtaccord
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T case is electronically controlled regardless of traction control setting. It will always try to "fix" it.
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      07-21-2015, 08:55 PM   #5
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So how with dsc off are you allowed to spin tires with it stopping it. Find it hard to belive
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      07-23-2015, 03:47 PM   #6
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Quote:
Originally Posted by E46toE90 View Post
So how with dsc off are you allowed to spin tires with it stopping it. Find it hard to belive
Traction control via brakes and throttle is different than front/rear clutch engagement
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      07-23-2015, 08:43 PM   #7
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I think it's more that the wheels are all trying to mechanically spin at the same rate, connected through the transfer case creating a lot of unwanted torque and bind on the gears and shafts if they are not all the same size.

The 335i doesn't deal with the front drive train and transfer case so it doesn't matter what they run.
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      08-05-2015, 08:34 AM   #8
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Quote:
Originally Posted by E46toE90 View Post
So how with dsc off are you allowed to spin tires with it stopping it. Find it hard to belive
Mismatched wheels effect three different systems.

DSC - will assume the shorter wheels are slipping under acceleration, even when they are not. This will cause traction control intervention.

ABS - will assume the taller wheels are skidding during braking, even when they are not.
This will cause ABS intervention.

Xdrive - will read the different sized wheels as traveling different speeds, even though they are not. This will cause wear within the transfer case.

You can turn DSC off.
ABS cannot be turned off, but the mismatxch is less noticeable here, unless you are braking hard OR the mismatch in size is great.
Xdrive cannot be turned off either. You can get wheelspin with DSC off, but remember Xdrive doesn't split power 50/50. Xdrive is rear biased. With the majority of power going to the rear, you can still spin a tire on low traction surfaces or while turning and accelerating if DSC is off. This design preserves sporty rear drive dynamics but sacrifices a bit of grip.
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