e90 equivalent of e3/46 RTAB

[turbo 6 justin]

My family is a 328i family, and after years in the e3/46 world my brother and stepdad jumped into the e90 world hopefully I will be too. Anyway I am the mechanic so my familiarity needs to expand to the new e90 platform. In the past when a 3 series develops a lose feeling in the rear that I describe as a side to side shimmy or losenedd over bumps or potholes which I more accurately describe as rear bump steer it is always the rear trailing arm bushing. When in doubt replace the RTAB and 80% of the planted feeling comes back, the other 20% was in the rear ball joint and other bushings. The e36 and e46 rear suspensions were almost identical. The e90 is a whole new world with the 5 link.

My question is which is the go to bushings/arms in the e90? One of the vehicles has high mileage and that lose feeling. I am not looking to replace everything back there.
I am guessing the bushing labeled b2 is the problem based on the force it controls. The arm labeled 2 has the most side to side movement but probably has little to do with the side to side feeling the arm labeled 3 feels tight but probably has the most to do with the lose feeling. Just looking for a little guidance here, I'm not a big fan of killing flies with sledgehammers and the replace everything approach seams to be along that line. Many thanks!!

e90 labeled.png

[TurnerMS]

The stock rear controls arms are sheet-metal and flex a lot under moderate cornering loads. Might want to replace them on the higher mileage car to see if that solves the problem. Common "upgrade" would be M3 rear arms that are all aluminum. Here is a link if you wanted to check them out- M3 Rear Control Arms

Here is a link to both stock and M3 if you wanted to compare prices (also included 4 new trailing arm bushings)- Shopping Cart

Probably wouldn't hurt to check the subframe bushings as well. If you have any other questions, feel free to email me directly, seank@turnermotorsport.com.