E46 M3 Bilstein B12 Pro Kit

With my 2002 M3 at 130k miles, and not knowing if the suspension had ever been refreshed, I decided it was time for an update. I wasn’t willing to spend the big money on coilovers and also wanted something that was similar to OE or a little better. After a little searching, I came across the Bilstein B12 Pro Kit on Turner Motorsports’ site that seemed to fit my needs.

The Kit

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The kit consists of Bilstein HD shocks and struts that are matched with a set of Eibach Pro Kit springs. This was sold as an improvement over OE and claimed to lower ride height by around an inch. It really appealed to me due to the reasonable price and the fact that the matched springs and shocks could be had in a kit. Depending on where this kit is ordered from, the prices ranged from about $800 to $1,100. I just did a Google search for the part number and ordered from the cheapest source.

Of course in addition to shocks and springs, mounts and a few other associated parts need to be ordered. I ordered these directly from Turner Motorsports in a kit that included the mounts, bearings, bolts, gaskets, and some reinforcement plates. The reinforcement plates are intended to prevent mushrooming of the front towers and tearing of the rear mount surface. Whether or not I needed these, I figured I might as well throw them in for peace of mind.

The Install

First step of the install was to get the car lifted up and take the wheels off. One of my favorite little things about working on the M3 is the central jack points. Only jacking it up in two places and being able to easily put jack stands on each corner is the best.

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Finally it was time to take all the old components off. Once the rear shock is removed from the arm, the assembly will hang down low enough that your “should” be able to reach in and easily take the rear springs out. I however could not get the assembly down far enough to get the spring out. After extensive researching, I came across a DIY that said to make sure the parking brake was released. I walked out to the car, released the parking brake, and the rear assemblies dropped another three inches or so and the springs were easily removed. Overall the rears were extremely easy to remove and replace with the new parts.

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The fronts were a little more time consuming but not too difficult. After getting everything detached, I couldn’t get the hub/brake assembly out of the way enough to pull the shock assembly out. I then had to take a spring compressor and compress the assembly about an inch to get enough wiggle room. Once those were out, the rest of the assembly was pretty simple. I was able to reuse a few of the minor components to rebuild the shock/spring assembly with the new stuff and it went back in without an issue. The only hiccup was that they gave me two left shock reinforcement plates so I had to drill out new holes on one of them.

The Results

I measured the height from the ground to the edge of the wheel well fender area before and the fronts were at 26.75 and 26.5 inches, and the rear was at 26.5 and 27 inches. So things were sitting a little crooked due to their age. Now all of them are sitting around 26.75 inches. The front would be a little lower but the reinforcement plate raised things up by its thickness. So the update didn’t lower the car by as much as I had hoped, but lowering it wasn’t all that important of a factor to me anyway.

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Finally, how it drives now. The handling definitely feels a little tighter. Going through corners it seems to stay flatter, but I can’t say for sure as it could just be a bit of a placebo affect. Before there was some brake dive, but it never stuck out to me at all. However, now there is next to no dive at all under braking. It really is pretty amazing how flat it stays. So overall I would say the handling is marginally improved.

By far the best and most significant difference is in the ride quality. It soaks up large bumps better also glides smoothly over the small stuff. There is a concrete road on my daily commute that has some pretty terrible expansion cracks. I would cringe the entire time I was driving as I bounced all over the place. There is a night and day difference as it just coasts through. I tried to capture video of this section with a before and after, but it’s tough to tell unless you walk very closely.

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Summary

Overall, it was worth the little over $1,000 for all the parts. While the handling wasn’t a drastic improvement, the ride quality certainly was. As I plan on driving the car for a few more years, it’ll be nice to have the peace of mind that the handling should remain constant and I won’t need to do another refresh.

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