Polyurethane Bushing Upgrade for the CLK55

The rearward bushings in the front lower control arms of the W208 CLK are known to wear out rather quickly.  They are “loose” by design, having an air gap around more than half the perimeter of the bushing, meaning there is only about 2″ of rubber holding the outer shell to the inner sleeve.  This not only leads to premature failure, but often leads to vibrations in the car, even when the bushings are new.  I’m sure the Mercedes engineers had good intentions, but in practice these bushings have been a sore spot for many CLK owners.  You can replace the factory units with aftermarket polyurethane bushings from Powerflex if you want a performance and reliability upgrade.

You have three options when these bushings go bad:

  1. Replace the bushing with a new OEM-style piece
  2. Replace the entire control arm
  3. Upgrade to polyurethane bushings for better performance and longevity.

Spoiler alert; I chose option 3.  This article focuses on installing the Powerflex bushings in the front and rear positions of the lower control arm, but keep reading even if you opt for options 1 or 2.

What you’ll need for this job

Follow these links to purchase the items needed for this project:

Let’s Get Started!

This is not a general maintenance blog, so I’m not going to bore you with the tedious details about how to remove the control arms from the car.  Just check the list of tools above and you’ll figure out the rest.  Once you get the arms off the car we can talk about the bushing removal and installation process.  Go ahead.  Get started.  I’ll wait here.

Let’s take a closer look at the Powerflex bushings.  If you got sets for the front and rear of each arm you will notice that the front bushings are black and the rears are purple.  That’s because the rears are a softer polyurethane (lower durometer) than the fronts.  The engineers at Powerflex didn’t just slap together a polyurethane bushing that will fit in the hole; they actually designed the front and rear bushings to be different, sorta like the Mercedes engineers did, but better.  These will last much longer and will give a better, more connected driving experience.  The next thing to note is how thick the inner sleeves are.  If you compare them to other kits on the market you’ll see that the Powerflex sleeves are about twice as thick.

Removing the Factory Bushings

Start with the rears because they are pretty easy to get out, and they are probably the reason you’re here in the first place.  If yours are as bad as mine were, you can pretty simply whack the center section out with a hammer.  If not, then use a hacksaw blade to cut through the remaining rubber so you can remove the center sleeve.  That will leave you with the outer shell still pressed into the control arm.  Luckily the shell is aluminum, so it cuts very easily.  cutting_out_old_bushing_shellI used a sawzall with a hacksaw blade, but you can just as well use a manual hacksaw.  Just take the blade off the saw, feed it through the hole, reattach it to the saw and start cutting.  You only need to cut a slit through the shell, stopping just shy of going all the way through. (it won’t take long!)  Try to avoid gouging the steel of the control arm.  Once you have cut the slot, take a hammer and chisel and knock the shell away from the arm.  You are trying to collapse the shell so it releases its tension on the arm, then you can easily knock it out.

Now let’s do the front bushings.  They are not quite as easy, since they are probably still in decent shape (they don’t tend to go bad like the rears), and there’s not really any way to cut or press them out.  Luckily, they have a flange that extends out past the control arm so you can use a mini-sledge and a masonry chisel and beat the shit out of them until they pop out.

Installing the new polyurethane bushings

You can use a piece of threaded rod to squeeze the sleeve into the new bushings

The Powerflex poly bushings come with a small tube of grease that you’ll want to apply to the outer and inner surfaces of the bushings.  Failure to grease them will result in squeaks, so don’t forget!  It is important to install both halves of the bushing into the control arm first, and then slide in the center sleeve.  In my experience, the rear bushings go in much easier than the fronts.  I was able to squeeze the rears in-place using a C-clamp, but the fronts weren’t so easy.  I ended up using my arbor press; if you have a hydraulic press you should use that.  If you have neither, don’t despair!  You should be able to coax the sleeves into place using a piece of threaded rod (about 8″ long), with a nut and large washer on each end.   Just insert the rod through the bushings and the inner sleeve and begin tightening the nuts until the sleeve is pressed all the way into the bushing halves.


Now that the new polyurethane bushings are installed, you are ready to put the arms back on the car, but before you do there’s something you should be aware of.  The factory bolts that go through the bushings have an oblong shoulder on them.  The holes in the frame are slotted to accept this shoulder.  The frame holes on the threaded side of the bolt have a different type of slot.  This is to allow for three positions of camber/caster adjustment.  The OEM bolts with the shoulder will only work in the “middle” position.  If you want to use the inboard or outboard positions, you need a special fluted bolt that comes with a special washer.  Here’s why this is important to us: the Powerflex inner sleeves won’t allow the OEM shouldered bolt to fit properly.

Febi 07752
Febi eccentric bolt

You need to get a set of “eccentric bolts” and then use the inboard or outboard slots.  I recommend using the inboard slots, as this will pull the bottom of the wheels in a little, thereby reducing camber.  In my opinion, Mercedes spec’s too much negative camber anyway, which is why our tires tend to wear out on the inside prematurely.

Now that you’ve got the bushings installed, all you need to do is re-install the control arms in the reverse order that you took them off.  Be sure to check the lower ball joints while you’re in there and replace them if needed.  Good luck!

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