4x4 warning light when i turn (maybe my 20's?)

[vwsnaps]

I have aftermarket 20's on my X3 and when i turn and am under on the gas or going at a decent speed i get a funny noise that and feel to the steering wheel. Almost like ABS is acting up and trying to make an adjustment.

Yesterday coming off interstate ramp i was corning hard (i forget that the X3 is NOT the M3 i traded in )and my 4x4 warning light came on when it made that noise and a little rumble. Almost like its rubbing when i corner hard but there is still alot of clearance?

Anyone have this trouble when moving up to 20's ?

Here is pic of car

[DINANM3]

That light comes on when your DSC is working and active. And the feeling you get is the system applying the brakes automatically.

[B&DCalgary]

Definitely sounds like the DSC being activated. Turn off the DSC and, if it stops, this will confirm it. Normally on pavement the action of the DSC is hard to detect unless you're driving so hard that the tires are starting tp break loose, then you will get the slight shuddering you describe as the DSC kicks in to get the skid under control.

I've read on other threads about this happening with oversized wheels and wonder if the wheel and tire size somehow throws off the 'brains' of the system. When you put the 20's on your vehicle, did you reset the tire pressure measurement system? This is important because it actually measures tire rotation, not pressure, and feeds the information to the computer. If the computer is receiving tire rotation speeds that don't make sense to it under aggressive driving conditions, it might be fooling it into activating the DSC inappropriately. That's the only thing I can think of... but I might be off base

[xx3]

Sounds like you are a little unsure about DSC, so allow me to debrief you:

DSC or Dynamic Stability Control is a complex electronic system that measures many things (pedals, steering angle, yaw rate, vehicle speed, etc...) and figures out what it thinks is your 'intended path' and compares that to what the car is actually doing. If your car deviates from what it thinks is the 'intended path', DSC will intervene and attempt as best as it can to get you back on your intended path.

In doing so, DSC will apply brakes on any number of individual wheels and sometimes even cut engine torque.

DSC applies short bursts of full brake power when it intervenes. DSC doesn't slowly apply brake pressure as one does when they push on a pedal - instead its more of an on/off state. Theoretically DSC would is 'slamming on the brakes' for a very brief period of time. Therefore you are correct in saying you felt an ABS pulse, because the ABS system is indeed active when DSC is intervening.

Intervention is shown with a couple flashes of the 4x4 ! light in yellow.

DSC has several modes. It can either be on (like every-time you start the car) and exhibit no light in the dash. It can be in DTC mode (DSC simply intervenes later allowing you to have more fun), or Dynamic Traction Control, which is activated after a short press and a constant 4x4 ! light in the dash. Or it can be completely turned off by pressing the DSC button for 3-5 seconds again with the same 4x4 ! light in the dash. If however the 4x4 ! light is illuminated and you did not push the DSC off button at all, this could indicate a problem with the DSC system, or xDrive.

I would suggest finding a curve that always sets off DSC at a current speed, and then try it with DSC completely off. You won't skid that much, because xDrive does such a good job of moving the power around the car... But you should feel no pulsating and see now flashing light in the dash...

So to recap:
Flashing 4x4 ! light: DSC is active and intervening, or has just intervened.
Constant 4x4! light: You are either in DTC or DSC is completely off. Or something is wrong with your xDrive or DSC system.

DSC: Dynamic Stability Control, always unless you turn it off, no light in the dash.
DTC: Dynamic Traction Control, later intervention - allows more spirited driving, Constant 4x4 ! light is lit up. Brief press of the DSC button to activate.
DSC off: No electronic intervention whatsoever. Light looks the same as it does when DTC is off. 3-5 second press of the DSC button.

So what most likely occurred is that DSC intervened, which took you by surprise because you felt the ABS pulse even though you were not pushing on the brake pedal...

Originally Posted by B&DCalgary

I've read on other threads about this happening with oversized wheels and wonder if the wheel and tire size somehow throws off the 'brains' of the system. When you put the 20's on your vehicle, did you reset the tire pressure measurement system? This is important because it actually measures tire rotation, not pressure, and feeds the information to the computer. If the computer is receiving tire rotation speeds that don't make sense to it under aggressive driving conditions, it might be fooling it into activating the DSC inappropriately. That's the only thing I can think of... but I might be off base

This is referring to the run-flats and the tire pressure monitoring system. This is unique to BMW's with runflat tires as the car compares wheel rotations from what they are to what they should be in order to detect a flat. BMW's without run-flats don't have a calibration system and I guess are able to manage by themselves. I think DSC only measures the rotation of the wheels in comparison to other wheels - therefore it doesn't matter as long as you have the same sized rims on all four wheels...

You could still try re-calibrating it though. When parked on a flat surface and with the engine on, push and hold the run-flat button until the tire light with a ! illuminates in the dash. When slowly drive away until the light turns off - usually 10-20 feet. The system will have re-calibrated by then.

[B&DCalgary]

Originally Posted by xx3

This is referring to the run-flats and the tire pressure monitoring system. This is unique to BMW's with runflat tires as the car compares wheel rotations from what they are to what they should be in order to detect a flat. BMW's without run-flats don't have a calibration system and I guess are able to manage by themselves..

Good info, except incorrect on this point. The tire pressure monitoring system works on all wheel combinations, regardless or whether they're run-flats or not. Once calibrated, it measures a change in wheel rotation speed relative to the other wheels on the vehicle.

[simoncpw]

Originally Posted by B&DCalgary

Good info, except incorrect on this point. The tire pressure monitoring system works on all wheel combinations, regardless or whether they're run-flats or not. Once calibrated, it measures a change in wheel rotation speed relative to the other wheels on the vehicle.

That's right. It works with all non-run-flats tires as well. It successfully detacted one of my tires was loosing air frequently.. which turned out to be a nail had punctured thru.

[ChristopherM3]

1st time I've seen an X3 with some Style 87's on........I like it!

[vwsnaps]

Thanks, i figured it was something automated thing. Ill drive around and try to figure it out.

Thanks for the input.

[X3 of Miami]

I have the same problem when i moved up to 20"s ... the 4x4 lights up when i make u-turns and also regular sharp turns

[xx3]

Originally Posted by B&DCalgary

Good info, except incorrect on this point. The tire pressure monitoring system works on all wheel combinations, regardless or whether they're run-flats or not. Once calibrated, it measures a change in wheel rotation speed relative to the other wheels on the vehicle.

I never said it didn't work with non-run flat tires. I simply stated that non runflat equipped BMW's did not ship with a flat tire warning mechanism, unlike the X3 and 3 series models equipped with run-flats...