E30 M3 Suspension Swap

 

Well, I decided to convert my car to the E30 M3 5-lug setup. This is something that I have wanted to do for some time, but having to find the parts and likely needing to get them shipped prevented me from actually pursuing it. A guy near me wrecked his M3, so I decided to take the opportunity to get the parts and do the conversion.

Here is a list of parts which got from the M3:

Sway bars:
The front sway bar on an M3 mounts to the strut tubes rather than the control arm (which is where it mounts on all other e30s). Supposedly the sway bars are similar enough that either can be used, it is just the sway bar links that are different. The cabrio has a 21mm front sway bar, the standard 325i has a 20mm and the M3 has a 19mm. The M3 gets more leverage from the different mounting point, which is why it has the smallest size front bar. The M3 and some M Technic cars have 14.5mm rear sway bars, and the rest have a 12mm rear sway bar.

I cleaned up both M3 sway bars, but used the 21mm front sway bar and the 14.5mm rear sway bar. The M and standard e30 sway bars are definitely interchangeable.

Struts and arms:
From the M3, I took the entire front strut assemblies (including the aluminum control arms) as well as the entire rear trailing arms. The rear trailing arms are the same on all e30s, but it was easier just to remove them than all the individual brake and hub components. Once I got the parts back home, checked them out and cleaned everything up.

I pulled the old struts out, and removed the control arms by unbolting the tie rod levers. I took the new strut tubes in and had the existing spring perches cut off and the new Ground Control spring perches welded on.

Brakes:
Since I had the calipers off, I decided to rebuild them. I also figured it was a good time to paint them while they were apart. Along with the rebuild kits, I ordered stainless steel braided brake lines and some ATE Super Blue brake fluid from Turner Motorsport, which should finish off the brake upgrade nicely. Rebuilding the calipers is not too bad, but the pistons need to be blown out using an air compressor. The most difficult part is actually getting the dust covers on the front calipers. I tore one of them, which luckily the dealer had 1 front rebuild kit in stock. The rebuild kit did not come with any Disc Brake Caliper Lube, so I picked some up at a local auto parts store. I would consider this stuff a must-have while rebuilding the calipers. I also picked up a pressure bleeder, which should make bleeding the brakes much easier.

I had the front rotors turned, and was given a new set of rear rotors (and pads) when I bought the parts from the M3.

I decided not to rebuild the master cylinder, as it seemed to be in really good condition. I did pick up new self-locking nuts, o-ring and reservoir grommets. However, when I went to install the M3 master cylinder, I realized that it uses a 12mm fitting for one of the lines (the line itself uses a 12mm fitting on one end and 10mm on the other). I called the dealer, and the line was going to have to be shipped in from Germany. Since I did not really feel like waiting the additional time, I decided to just upgrade to the 25mm MC. The M3 has a 23.81mm MC stock, and the 325i MC as 22.20/17.46mm (front/rear). I ordered the 25mm MC from Bimmerworld for $199. I also decided to get a pressure bleeder as well.

I also picked up some misc parts for the swap. Some of these are really needed, and others just made sense to replace while everything was already out. Here is a list of the parts:

My current Ground Control coil-over setup will work with the new components, which is really nice. I did order a set of higher rate rear springs. I noticed that my rear suspension bottoms out occasionally, so some stiffer rear springs should help. I went with 550# (I was running 450#) and kept my existing 300#/F springs. When I received the new springs, I noticed that they were an inch shorter (5 vs. 6) and they were 2.25" I.D. instead of 2.5 I.D. I called Ground Control, and apparently different length and size springs are used for different spring rates. This apparently has something to do with optimum spring travel. Since the springs will not fit on my existing spring seats, they sent new spring seats out. Once I received these, I installed the new springs. Although the 550# rear springs made a good improvement, I realized that I need to go even more stiff. I ordered some 750# springs, which should definitely keep the rear from bottoming out. If not, I will need to replace the Bilstein Sports that I currently have, with some Koni adjustables.

The down side of this project was that I had to sell my 4-lug BBS RS wheels which I just had refinished. Bill Gosma was kind enough to let me use an extra set of bottlecap wheels/tires for the time being. After waiting for 8 weeks for my Compomotive CXN wheels to show up, I finally cancelled my order and started to look for something else. I decided to get some e34 M5 "M System" wheels, and just run them without covers. They are a 17x8 wheel, with a 20mm offset. For tires, I plan to use Nitto NT 555 225/40ZR-17. I have never used Nitto tires before, but have heard good things about them. This was also the only tire I could find in this size.

 

The install:

After 2.5 days of work (and the invaluable assistance from my friends Bill, Fred, Kris, Rich and Jeff), the car is about done. The front setup installed without too much trouble. The new sway bar bushings were difficult to compress into the brackets, but did finally go together. I am now using the cabrio 21mm sway bar with the M3 sway bar links. Rich gave me some 375# front springs, and installed them using an electric impact wrench (very cool).

The rear was definitely more work. Getting to the 2 inner rear brake lines is a real pain. I ended up dropping the exhaust and differential, then lowered the rear sub frame enough to get some room to reach the lines.

I also found out that the axles require a puller to seat in the hubs (beating on them with a mallet. I contacted Brett Anderson at Koala Motorsport, and he had the puller to me the next day. The puller made the job super easy, and the rest of the rear components went in without problems.

I picked up a set of stock M3 wheels, and bled the brakes. When I tried to install the wheels, I found out that the right front wheel rubbed on the strut housing. After some investigation, I determined that the strut tube is actually bent. It looks like this happened in the accident that the M3 was in, and is now obvious since the wheels that I am trying to use are rather wide (225).

I checked into whether or not the strut tube could be bent back into position, but I was advised to just replace it. I ordered a new housing from Bavarian Autosport, along with a new hub nut and dust cap. The hub was somewhat difficult to remove, but came off without a puller. The bearing came apart while pulling the hub, so I cleaned it up and repacked it. I had a new Ground Control spring perch installed, and also had the M3 sway bar link supports welded in.

I knew that the car would need an alignment when I was done, but I forgot to take into account the fact that I was going from standard to offset control arm bushings. The car had so much toe-out initially, that I really could not take it out for a test drive. I took it in the following Saturday morning for an alignment. They did a fine job, but my digital camera mysteriously disappeared from the glove box while it was in their possession. The car was never left unattended while it was at the shop, so it is obvious what happened :-(

I am really excited to have this project done! I have learned a ton, but it has really been a test of my patience and determination :-) Here is the car on stock M3 wheels with Kumho VictoRacer tires. This will be my autoX setup :-)

Here are some pics with the car on the M5 "M System" wheels. I may eventually have the silver lip polished, but I am happy with the way they look stock. The wheels weigh 19.5 pounds each, which is great for a 17x8 rim! They are also a forged wheel, so they should hold up fine even on the crappy SF roads :-)

I am really happy with the fitment, I think it is perfect. The offset on the wheel is et20.

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