Thanks for all of the input and history.

ZF Lemförder makes the upper and lower control arms for both MB factory OEM new, and aftermarket. The owl logo in the aluminum forging indicates this.

 

I re-read through your post and yes, I do know what you're talking about with the feeling that rear is pushing you around. I haven't done any work to the rear, and yes over rough road the rear feels like it will push the front around left and right a bit, but again; it's bushings... That was DRAMATICALLY reduced by new front bushings. I still have to do the rear bushings, and I'm going to do a full suspension rebuild when I do that, with all the rear bushings, tie rods, sway bar end links, sway bar bushings with Bilstein sport shocks (instead of the OEM Sachs shocks that have very low damping rates).

My primary theory about this behavior is as the rubber gets old and brittle, the jolts get sharper with near zero rebound damping in the rubber so you get oscillation in the chassis. (Undamped harmonic oscillator in 3 dimensions). Since there's L/R give in the front bushings, you're going to get tire wobble that moves you around trying to absorb this 'hit'. I have no doubt that when I replace the rear bushings that behavior will nearly cease entirely (shortly there-after completely remedied by having high damping coefficient shocks and progressive springs).

The sway bar links are supposed to soak up 'some' of this side to side energy instead of transferring it entirely to the chassis / shocks to deal with; but alas, that rubber is shot on my rig as well.

Instead of a 'ship moving' motion in the front; I now get a hard damped thunk feel in the front as the tire slips over whatever groove it's been pushed over and the car doesn't really move off track nearly as much. I don't think this is entirely able to be remedied by fixing either the front or the rear. The rear is still unbounded by the lack of sufficient shock damping (they're not bad shocks or leaking, just factory setting is BOAT).

'Maybe' it's possible that just dealing with the sway bar end links would improve this; but I'm a little doubtful as they only initiate some of the motion, and don't deal with the energy after the fact. So even if they were more elastic, the energy is still transferred, just damped a bit more. Anything on down the line that isn't damping and absorbing the energy will still 'wobble' and cause L/R issues in addition to any U/D motion.

The primary challenge with body and suspension control, movement issues, is it's all compounding. The weakest link will contribute the most; followed by the next weakest link, etc. With age, all suspensions components become weak links with various severity and non-factory dimensional contributions to unwanted movement and behavior.

I know it's been gone over in dramatic fashion, but the last vehicle I had that ate rear brakes, it was really just simply the calipers were slow to disengage and dragged a bit from the factory. Dealership always claimed it was normal, but calipers are pretty fickle beasts, and the tolerances are pretty tight to work perfectly. If they're dragging or slow at all on the slide / piston, they'll eat pad front or rear. The rear brakes are super tiny and undersized so any real additional wear is highly noticeable. The disks are super thin and calipers super tiny in the rear. The disks are dramatically thicker and pads much larger on the AMG sport brakes in the rear if you've looked (I'm retrofitting those in later as well next brake job). Ironically if your rear's are slow to release it might be contributing to your fronts releasing faster and wearing even less. I don't think either issue is really related at all unless you think the ABS is causing a caliper to lock and hold. The sensors won't even tell you that, only way to really tell is to take the caliper all the way out and test it manually hydraulically. (at which point your diagnostic fee has paid for a new caliper so if you suspect it just replace it). On one vehicle I had they actually had springs pinned to the pads to get them off the disks faster, but the dealership always left them off as the kits didn't include fresh ones and they tended to destroy them in haste to do the job. There was a shim/spring kit that was supposed to be ordered with the pads but the dealership didn't bother (I learned this after debugging and diagnosing it myself after warranty ended and they stopped just giving me infinite free brake jobs so I had to deal with it).

Anyways I know that's a longshot so I wouldn't count on that being an issue. All brakes drag a little, it's only when it's severe that it causes any real issue. The 4matic traction control relies on wheel braking on slip so it's theoretically possible to contribute? But that's just speculation on my part. I'm late to the party; and what I DO know for certain is the suspension on the W166 gets wibbly wobbly timey wimey when the rubber is bad. (insert Doctor Who joke here)