I bought my car used, with 123,000 miles on it and it has driven pretty well. It has survived track days, autocrosses, and daily driving in Atlanta.

Over the last two years though, I noticed two things:

  1. The car felt a lot like a go-kart
  2. Leaving garages or hitting speed bumps would sometimes bottom out the vehicle if I did not let the suspension rest.

Debating Between Coilovers and Stock Spring, Struts

I debated over buying a set of coilovers, Bimmeworld.com sells and supports ISC coilovers, they have a review in e46fanatics of surviving 5 years of heavy track use. And they’d be height, damper, and preload adjustable. And they are a Chinese import so they were the same price as…

What I went with, Koni Special Actives (formerly FSDs). I decided to go with these because, despite a willingness to track my car, mostly drive on streets. Tirerack has a great analysis of the special Active’s too, where they performed as well as the Koni Sports (a known good option), and were hypothesized to perform even better.

I also kept the stock springs, which had no signs of damage, partially because of ride height concerns. Having the factory ‘sport’ package means understanding that new springs will lower the car 3″ intimidating, but also unclear. And, performance wise, I just want that stock feel.

The Install

So, over Christmas, my shop mechanic (my father) and I bonded installing a new suspension. A task we’d done before on my 1989 Mazda RX-7 and he had done on his 1974 260z and 1999 Nissan Maxima. In all, the most of the work in the rear was removing the carpet — seriously, it took about 20 minutes otherwise bc they aren’t coilovers – and probably about 2 hours on the fronts (at a calm pace).

Based off of some suggestions, I spent a little extra on common wear items and some reeforcement plates. The stock sway bar end links that connect to the shocks are plastic and have a rubber boot; so the upgrade to a metal joint, an HD rod, and fresh rubber was obvious. The front and rear, but especially the rear strut mounts are known to wear out at the bushing, so I upgraded the rears to an American made aluminum and poly mount. The front strut sheet metal is also a known weak point – which I’ve countered on the front and rear with strut braces – but now I added steel reinforcement plates, basically big washers.

The Results

Well, I’m writing this post, and based off my introduction, you can probably already guess, but,

new struts are one of the best investments for a used car.

I say that, and even though I knew it from a similar experience in the RX-7; we start driving a new to us car and it feels okay, then it degrades slowly, but without objective ways to know it (oil leaking out of a strut, always bottoming out) it’s hard to know how much of an improvement it will be.

e46fanatics thinks that the stock 330i Sach’s struts start showing their age before 50k miles. And, on dis-assembly, at 170k miles, my rears were shot and running on the bump stops; the fronts were somewhat alive in those regards.

Now, my car doesn’t bottom out when leaving the parking garage bumps. It doesn’t squat when I accelerate. It shifts more smoothly. And it definitely corners at speeds better. And it feels a little bit less like a go-kart.