Common issue on these cars, it seems, to not be able to adjust rear camber within spec (-1.5 to -2.2 degrees).
Camber out of spec, and failed suspension components can lead to extremely fast tire wear on the inside shoulders of the rear tires.
On my 2001 E53 3.0i with spring suspension, the rear ball joints (33-32-6-767-748) were the root cause. Another common one, very easy to replace, and sometimes gets it done without needing to dive all the way in to the ball joints, is the rear upper control arms (33-32-6-770-859 and 33-32-6-770-860).
Some have found the swing arm bushings worn out. There are aftermarket replacements allowing replacement of just the bushings vs. the full swing arm.
I replaced my ball joints and rear upper control arms shortly after getting my x5 a few years ago. Aligned within spec (-1.8 and -1.9 on L+R), apparently easily (did not do it myself).
Years and miles later, I found a need (more of a want
) to do a quick alignment since the steering wheel was off by a few degrees. Car drove fine, as it always has (even with the multiple issues when I first got it).
In doing my homebrew alignment, I found the rear right camber was out of spec, at about -3.5 degrees, along with the beginnings of tire wear on the inner corner.
I found the camber adjustment back there to be already about at its limit. Here is a pic of the bolt end of the eccentric adjustment. The bolt end faces forwards, so this pic is looking back.
This shows why I am unable to dial in the camber adjustment I need, even with new, good suspension components.
Basically everything that could be affecting camber back there is new already except the swing arm bushings which do not look to have any problems.
The eccentric bolt head there is supposed to fit within the two ~vertical surfaces (stamped steel, reinforced with welds), so when the eccentric turns, the center of the bolt slides left or right, moving that suspension pivot point. In this case, wanting to reduce camber, making the wheel more upright, I want the center of that bolt to move inwards (to the right in the photo). Partly due to that surface being damaged / gone, partly that the nut-side of the setup has issues as well, and I think partly due to the whole suspension being stressed due to the spring, the center of that bolt does not move inward as needed.
The whiteout mark shows the "before" adjustment location. Made that mark and took this pic before I knew of this issue. Expected I'd be able to dial in the required adjustment.
So with this situation, no adjustment was possible and the camber remained at -3.5 degrees. With all new suspension parts already, I did not know what I'd do to solve this, and searching on here came up only with aftermarket adjustable rear upper control arms as documented solutions. I did not want to go that route, hoping to keep things stock.
This is the limiting problem I've got. If anyone is in a similar situation = known good suspension components back there, stock wheels, springs, etc., not lowered, and you're still getting excessive negative camber and tire wear, you might want to take a close look at the actual eccentric adjustments. The nut-side faces rear and is easily visible just looking under your car. If nothing else, before you take it in for an alignment, you can see if the eccentric is already trying and failing to get things more vertical. That would save you the alignment cost and effort.