Project 1: Rear Subframe Bushings

Project 1 CAR rear subframe bushings whiteline

Words: Don Cheng

Photography: Don Cheng

Published: June 20, 2017

 



It’s been a long time since we’ve last touched Project One. Not to say that work hasn’t been done in the background, but with the car sitting on a set of bald Michelins and the Canadian winter looming in late 2016, it was best to leave it stored over the winter and pick things up where we left off.

 

We started ordering parts almost immediately after shutting off the 135i for the last time in 2016. Parts have been slowly streaming in throughout the winter and we’ve got a small stash now ready to address each of the weak points we found in our last track shakedown. To recap, the suspension, an integral part of the behaviour of the car felt underwhelming when pushed even remotely near the car’s limits. Combined with the fact that the car had developed a strange clunk coming from the front passenger side, and a blown front left strut it was high time to give the 135i’s handling the complete overhaul it deserves.

 

 

But before we address any of that, it’s time to address one of the biggest limitations in the 135i’s handling repertoire - the rear subframe bushings. Comprised originally of soft rubber, the bushings deflect under load causing the rear end of the vehicle to squirrel back and forth when putting the pedal to the metal. To address this, a common modification owners do is swap them in for the harder rubber bushings from an E9X M3. The only downside to this is the complexity of re-inserting the new bushings. We looked at the market and found a product from Whiteline that will do all the things of the M3 bushings, and then some.

 

 

These polyurethane bushings are a multi-piece design, allowing simpler installation without needing to remove the rear subframe entirely. Fresh from its winter hibernation, we took it over to our good friends at Unique Workshop to install the first step to our suspension overhaul.

 

 

Unique isn’t new to the automotive scene. They’ve been around for a number of years now primarily servicing the JDM Tuner scene. But that doesn’t mean they are strangers to the European market offerings. The N54B30 in the 135i is a familiar model to them and they know the E82’s chassis like the back of their hand.

 

 

Their approach to the swap involved lowering one side of the subframe bushing just slightly, installing the subframe bushings, and then moving to the next side. The first side was accomplished with relative ease. All it took was a short torching of the subframe around the housing to expand the metal and push the bushing out - though there was a few tense moments around the shop was we heated up the metal very close to the fuel tank. As the experts worked away, I took the opportunity to explore around the shop and see some of the other unique vehicles (get it?) that are present - taking extra time to appreciate the super clean Austin Yellow M4 that was receiving a precise detailing job.

 

 

With the left side wrapped up, we moved on to the right side (when I say “we” I really mean Unique’s very own Vincent), which quickly proved to be a pain. Even without driving the car, we could tell that these bushings work very well in limiting the subframe’s movement. As it turns out when we tried to lower the right side, the bushings wouldn’t allow for the subframe to drop enough to slide the bushing removal tool in. After some improvising and playing with a pry bar, the tool slid in place and the final pair of bushings came out.

 

 

With all the Whiteline bushings in place and everything bolted up, it was time to just see how much of a difference this seemingly small change makes. The result is staggering. It’s easily one of my favourite mods to the car.

 

The rear end feels much more solid and much more capable of taking a stronger spring rate. Previously, the springs felt they were on the verge of overwhelming the rear end. Hitting potholes in the past caused the back-end to squiggle left and right before settling down.

 

 

Bump steer was a serious concern when turning and hitting a manhole cover for example, causing the entire car to jump in an alternative direction, making fast turns a somewhat harrowing experience. With the bushings installed, the rear end feels more composed. The spring rate and dampers still don’t match the car but the nervousness of the rear end and side-to side flex are 90% alleviated.

 

It makes me wonder what the car would be like when equipped with a proper set of dampers and springs. Stay tuned. There might be an answer to that soon.

 


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