BMW 3-Series PowerFlex Trailing Arm Bushings (RTAB), install, E36, E46, Z4, X3
Bavarian Autosport has been sponsoring BMW project cars for the online automotive performance magazine, MotoIQ, for some time. BAVauto, in partnership with author and BMW performance geek, Pablo Mazlumian, has assisted in various E36 and E46 M3 project car builds as well as maintenance.
In Part-19 of the Project E46 M3 articles, pablo installs PowerFlex RTABs (Rear Trailing Arm Bushings), using the BAVauto RTAB remover/installer tool, which allows easy bushing replacement “on the car”.
We have found that the BMW models that use these rear trailing arm bushings will show unstable road manners and even a sense of “rear steering” as the bushings age and become soft (or worse). Additionally, worn RTABs can cause a clunking over bumps or when transitioning between acceleration and deceleration.
In Pablo’s article, he notes:
“The rear trailing arm bushings (RTAB) on BMWs are rubber and are prone to cracking. I’ve had them go bad on previous E36 M3s, and the symptoms were simple to discover and quite obvious. One of the easy ways was to accelerate the car hands-free of the steering wheel. If the rear pulled to a side, you most likely had bad bushings.
I didn’t figure it out so easy on this car, however. It wasn’t until I took a high-speed, four-gear turn on an uneven cement on-ramp that I could feel the rear end dancing around with so much grip from the surface (cement usually has higher grip than asphalt). It was very unnerving, and quickly made me lose confidence in the car.
Upon a quick look underneath, it was obvious the car’s RTABs were wasted. The car just clicked 70k miles, so it was no surprise.”
Here are some highlights from Pablo’s MotoIQ, Project M3 article:
These polyurethane pieces are modular and go together like so. These bushings allow for an easier install, because with a rotating mass there is no pre-tensioning. These particular RTABs should fit all E36 (except ti), E46 and Z Series cars.
Trying to remove a factory bushing without the proper tools can become an act of futility. Bavarian Autosport sells its own trailing arm bushing tool that is specific for this job. It will be used both for removing the old ones and installing the new Powerflex units. The Bav Auto trailing arm tool appears to be very high quality, and it features CNC machined components.
With the bolt out, the bushing was now able to be free of the housing. That sucker is really torn up! It’s no wonder the car felt so unsafe during high speed cornering, especially mid-turn when you’re trying to maximize the G-load to the front tires so you can get pointed where you want to and immediately get right back on the gas. It was all over the place, feeling like something was loose or practically broken. It was like driving a car with a mild, yet unpredictable rear steering!
These bushings are going to be really on there so to remove them, line up the Bavarian Autosport tool like so. Now simply start tightening the inside nut with your wrench or gear ratchet. You’ll notice the bushing’s stickiness start to give way, and little by little come on out.
Here’s another look at the original bushing fully removed. One can opt to purchase factory bushings again, by why when you’ve got polyurethane units from Powerflex that will give you a tighter feel and much crisper response without really any drawbacks.
What we did was mount up the tool again in order to start pressing the new bushing in.
“With the new Powerflex RTABs in there, the confidence in the car is back. You can throw the car into a turn under hard trail-braking and not worry about that back end stepping out. Also, the worry of driving over an uneven payment is a thing of the past. That new, tight feel is back!”