Aug 20, 2018 update to the BMW 318is project car

Project BMW 318is: Suspension Planning

We had a plan for our 318is’s engine, but now we needed one for the suspension. Our goal? Build a comfortable street car that could still out-corner a real E30 M3. We didn’t need to reinvent the wheel, but we did need to make some careful choices: should we run expensive coil-overs, for example? What about the bushings: rubber or polyurethane.

Of course, anything we build needs to be up to track duty, too, but we wanted to keep costs reasonable and stick to off-the-shelf parts. We also wanted to build this car once, rather than take any chances on old suspension pieces. That meant we’d be replacing almost everything under the car.

Fortunately, this isn’t our first E30-chassis BMW. We pretty much know the formula for making one handle at this point, and it’s simple: Control body roll, add negative camber, and stiffen up the springs. We’ll get into all of the components and their installation individually, we picked Eibach springs and anti-roll bars, Koni dampers, Ground Control camber plates, and Powerflex polyurethane bushings and rear strut mounts.

We also ordered two sets of brake pads: Akibono pieces from FCP Euro for street duty, as well as a set of Pagid pads for track days. And of course, all of our stock replacement parts (control arms, tie rod ends, brake rotors and caliper rebuild kits) came from FCP Euro.

Our goal? Completely rebuild the suspension over the course of a single weekend. We’ll cover that project next.

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Comments
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mazdeuce - Seth
mazdeuce - Seth Mod Squad
8/20/18 2:43 p.m.

How do Eibach's spring rates compare to stock or an M3 of the era? How are bar sizes compared to those two? 

duke906
duke906 New Reader
8/24/18 12:31 p.m.

I once owned a 318is (why I sold it I'll never know) but I installed the Bilstein BTS spring/shock combo and it was fantastic, just as advertised, ride firm but not uncomfortable with handling limits far beyond my driving ability.  Great HPDE combo.

I would love to compare them when yo are done, but alas mine is gone

Sounbwoy
Sounbwoy New Reader
9/16/18 12:36 p.m.

Most of the suspension stuff also applies to the 325is, does it not? I have an '89 and my goals are pretty similar to this project.

LanEvo
LanEvo HalfDork
9/17/18 7:31 p.m.

With my old 318is track car, I ran:

  • Turner Motorsports J-Stock springs
  • Bilstein Sports revalved to “Firehawk spec”
  • Ireland Engineering front & rear ARBs, mounts, and bushings
  • K-MAC camber plates 
  • Urethane engine, trans, diff, and rear subframe mounts (don’t remember the brand...AKG?)
  • Various low-end tires: generally Toyo RA1s

Handling was completely neutral and benign. You could easily 4-wheel drift through pretty much any corner. Fast as heck around Tremblant.

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