Our Project E46 M3 is chilling in its updated garage. See that X-pipe on the right, leaning against the wall? That's a BimmerWorld unit that will be tested and installed with Epic Motorsports software on a 2012 BMW M3 with the S65 V8 engine next.

Project E46 BMW M3: Part 19 – Powerflex Rear Trailing Arm Bushings and Maintenance

We put on RTABs from BimmerWorld/Powerflex because the car's rear end was getting all over the place!

by Pablo Mazlumian

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 onramp 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. We put a call into BimmerWorld, which is Powerflex’s master distributor for all things BMW. I’ve run Powerflex bushings all around on a previous turbocharged E36 BMW M3 with no problem. In fact, I believe it’s the same part number for the E36 and E46 RTABs.


Powerflex comes from Great Britain, and is imported to the USA for all things BMW by BimmerWorld—yeah those light blue and yellow BMW 3 Series you see on TV racing. BimmerWorld recommends replacement of your RTAB if you’re a spirited driver and have a car that has over 50k miles. They run $94 + shipping for the set.

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.

With a quick glance underneath the car you can spot the tear in our Project M3’s factory bushing.

It’s that time again so we’ll be doing some maintenance updates using German-made Lubro Moly products from Bavarian Autosport, including 60 weight oil and oil filter, Lubro’s Engine flush to remove carbon build up, and Lubro’s Ceratec lubrication for the internals.
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Thursday, August 24, 2017 8:49 AM
Having the right tool for the job is always a huge time saver! Those stock bushings looked horrendous.
Pablo Mazlumian
Pablo Mazlumianlink
Thursday, August 24, 2017 9:21 AM
Indeed! I cannot tell you how unnerving the car was in a high-speed, concrete (!! So, high grip) fourth gear turn, and it was a little bumpy to boot. I knew something was up then.
Thursday, August 24, 2017 10:09 AM
shoulda went SuperPro
Thursday, August 24, 2017 2:25 PM

the trailing arm moves up and down and also in and out - it king of swings. A stiffer bushing restricts that natural motion. Seems like a monoball is a better solution - moves in both planes. Definitely more expensive and potentially noisier.

What are your thoughts? I would think if Bimmerworld sells this solution it's probably legit.

I put monoballs in the trailing arms of an e36 M3 years ago. I did not notice any additional noise.
Thursday, August 24, 2017 4:23 PM
A monoball setup is great but maintenance, noise transfer, and wear become an issue on a street car. That said, I think someone sells one that uses a factory BMW sealed monoball captive in a an adapter that allows it to be used as a RTAB.
Thursday, August 24, 2017 5:22 PM
This whole thing about binding with Polyurethane is way overblown. Also, I've never had any problems with it. The main reason that OEMs isolate all the suspension pivots with rubber is for NVH, and if you're willing to sacrifice a little of that, you can gain a TON of handling precision. It's a win-win, in my opinion.

Now, going with spherical bearings, you have to be careful, there's a lot of road vibration transmitted through the components that transmit the heave loads, like the shock. When you go with spherical bearings in these components you gain a lot of NVH, for not much change in handling. Obviously the shock is going to work a little better. There's always a compromise.
Thursday, August 24, 2017 5:28 PM
For example, I went back to first principles on building a strut tower brace, and said to myself, why not just brace the shock, which is the whole thing you are trying to stiffen up in the first place, instead of bolting a brace to the shock tower? So, I used some really nice rod ends in a threaded rod, and bolted them directly to the shock mount rod. Then I bolted the other end to a stiffened up part of the firewall. The change in handling was AMAZING. I mean, I really don't know why racers don't do this kind of modification. I still wonder if I'm the only one. Regardless, at high speed the NVH is also amazing. I wouldn't recommend it for the 'average' enthusiast. But, for the guys that want a cheap, and easy upgrade that will absolutely improve the handling of your vehicle, this is it.
Thursday, August 24, 2017 6:14 PM
I believe that the problem with bolting right to the top of the strut is that as the strut moves up and down the top of the strut moves back and forth. By making the top of the strut rigid you are forcing the seals in the strut to deform so this movement can happen. It will cause it to wear quickly - the increased in wheel rate is probably what you are feeling and that is a result of the binding inside the shock as the seals deform.
Mike Kojima
Mike Kojimalink
Thursday, August 24, 2017 10:34 PM
I think binding caused by urethane bushings is a big problem with many cars. A B13 sentra is so bad you can remove the rear strut and jack up the back of the car locked solid by bind. The suspension will bind before it bottoms out! One of the reasons why these cars sometimes transition to oversteer violently unless they are kept from rolling. My GD STI also binds badly in the rear due solid high durometer bushings. I am going to softer bushings that have some cavities molded in for articulation. The Z32 300ZX T/C rod goes into bad bind with solid urethane that can cause terminal understeer and even make the T/C rod break. The Scion TC can also bind up solid with the wrong bushings.
Friday, August 25, 2017 8:05 AM
Here it is:


I would have to think this is the best possible solution for this application. Quite clever.
Friday, August 25, 2017 8:05 PM
Which bushings cause the bind in your GD Mike? Trailing arm? I assume the lateral links mostly move in one plane. I'm running some of the STi aftermarket rubber bushings in my GC and I really like them. Reasonably priced, maintenance free, and nice balance between NVH and performance. And you know it's good because it's right from the manufacturer!
Friday, August 25, 2017 11:36 PM
@erikl - I sincerely appreciate your concern, but I am an Mechanical Engineer, so I do know what I am doing. Maybe I simplified my explanation, but in no way am I doing any harm to the strut whatsoever. It's the EXACT SAME THING as mounting to a 'pillow ball' or spherical bearing.

The only real downside is the NVH.
Friday, August 25, 2017 11:40 PM
@Mike - There certainly are exceptions to every rule. I shouldn't have made such a blanket statement.

All I can say is, in my experience car handling is usually improved with PU bushings, so much that I think it's the best 'bang for the buck' mod you can do. Personally, I wouldn't talk people out of it, unless I knew there was a specific vehicle design that was compromised by using PU, as you mention with the Sentra.
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