Oh sry!

Front right: 27.75
Front left : 28
rear left : 28
Rear right : 28.25

Holy Crap, the right side is off by .50 inches (Hopefully he didn't use a metric ruler) which will result in circumferences of
87.18 inches (27.75) and
88.75 inches (28.25)

Which result in a difference of 1.57 inches. One wheel is spinning faster then the other.

Any suggestion? And is it enough to cause problems? From your "Holy Crap" it can't be good :rofl:

I'll need to take those measurements again though. My driveway has some ice and snow and might falsify the measurements a little.

Make sure the air pressure in the tires are all the same. Are all the tires the same make and model? Could be that one tire was replaced and that is why there is such a big difference.

The difference between the two right tires is more than 5.6%. That is probably you problem. As it was pointed out earlier:

Where is the 5% value coming from? I get a 1.8% difference (FR and RR). Since the calculations include a constant (pi), its easier and faster to just divide the diameters by eachother, comes out at 98.2%, FR/RR. And technically, this isn't exactly the correct way to do it, since the front and rear differentials will balance the difference between sides. And someone correct me, because I'm probably wrong, but the average of the left right per axle is what is seen by the center differential. So, the center would see 27.88 Front and 28.13 Rear, which is 99.1%. I don't think this would cause the differential faults.

IMO tire +- tire diameters that will generate warning light(s) or error codes from side to side or front to rear are confusing and inconclusive.

One reason is that I see no indication that posts are about a particular transfer case or all E53 transfer cases or transfer cases in general. As many know, there are two E53 transfer cases. One used from 2000-2003 and one used with xDrive from 2004-2006. The earlier transfer case was mechanical with a constant percentage front and rear. The xDrive transfer case is infinity variable and operates in a very different way.

Another is that for most of the posts there is a counter-post. Since I don't know the credibility of one verses the other, I don't have a clue if either of the posts are correct.

In addition, I can't find a BMW technical paper on how each operate, the impact of tire size on the transfer case or on the intended operation. Nor have I read a BMW generated percentage of how much variance is too much. I would guess there is one and would like to read it. Anybody know a source?

I can find where BMW states that different makes of tires may cause DSC to overreact and another where BMW states tire size is critical to proper operation and also one that states if the DSC is not operating properly it will generate error codes--all without any details. The only thing I think I know is that some amount of tire diameter or tire brand differences will compromise the effectiveness of the DSC system.

From personal experience I have never had a DSC problem related to tire size. At 110,000 miles I still have the original transfer case and never had a problem. I have replaced a single tire due to a blowout where the tread depth was then quite different than the other side. I have replaced tires on one end or the other many times as I go through rears twice as often as front tires. I have had different brands on the front and rear. I have had two different brands front and rear where the tires on the other end were down to half the tread depth. I have had to drive over several miles on deflated tire. I have noticed a low tire and had to drive 20+ miles before I could correct the 8 pounds it was low.

Thus far my conclusion has to be that some degree of tire differences front to rear or side to side may cause error codes or cause the DSC to over react but nothing else that is significant enough to mention.

:iagree: that OP should, in some manner, get all tire diameters to as near to the same height as possible and see if the problem goes away because that would eliminate the question if variation in diameter is the problem. Might be able to safely achieve that goal using inflation.

Lets recap:

-Tires are same brand , same tread pattern, same model, all inflated at same PSI....etc
-Problem started AS SOON as I put my winter's 18
-Many different theories concerning tire size but nothing really conclusive .
-Battery is fine
-Actuator now makes the ratchet sound when I shut the engine off.

I myself don't know as much as most of you concerning mechanics but it's hard to believe that such a small variation in tire can cause all this S***T.

How about the Angle sensor (lws) signal code that was pulled out from the scan? Couldn't this cause the same symptoms? Could this have been dammaged while the rim swap?

I'm trying to find another lead here....it's going in to my Indy on Friday and would like to know as much as I can before I do and especially before I install the new actuator gear.

Guys , thanks for chipping in with all your precious knowledge. It's greatly appreciated , trust me. :thumbup:

Steering angle sensor, DCS and ABS work in conjunction with each other so theoretically the answer is yes. While I wouldn't call changing tires suspension work, working on the suspension can require re-calibration of the sensor to get the light(s) to go out.

I am not convinced the problem is tire diameter differences either but I would put the 20s back on to see if that cures the problem. It is easier and much cheaper than Indy diagnostic hours. I know you would rather not do that, I wouldn't either, but I would anyway.

Reason I asked if the codes were cleared is so you can see if, for instance, that code returns. Unfortunately, even if it has it may only steer you in a direction instead of identifying the core cause. That likely means the potential of the tire diameter differences being the cause will still be on the table.

I know I should put the 20's back on and check it out but it won't help much now that the gear is shot (I guess) . I would need to change ( or flip) the gear then put my 20's on. Since my indy erased all the codes , now I only have the 4x4 signal going on but when I hit ice and slam the brakes to intentionally activate the abs , the ABS and red brake light goes on also ( and I only noticed that by testing on ice). Before the codes were erased , all 3 light stayed on.
There is so much combinations for this single problem that I've decided I'd flip the old gear after the indy is done with it and test for a while. I'm just not convinced we will find the problem on the first try for this one.... I'll hold on to the new gear and when the time is right , it's not that bad of a job to get to the actuator to swap the gear.
The headache...hahahahha

I would just flip the gear over right now, keep the snows on, double check your air pressure on all 4 corners, and see what it does.

My guess is the lower weight of the 18s doesn't absorb the torque from the engine as well and exacerbates the worn gear in the transfer case, as opposed to the "boat anchor" 20s that don't get the case as rattled.