Reverse Gear Member
Join Date: Aug 2011
Car: E91+a few others
E30 5-lug: a new idea
I'm slowly preparing my car for a bigger motor. Part of that involves upgrading the chassis and drivetrain, of course, but one cannot forget the brakes! I figured I'd get a bird multi-kill award by going 5 lug in an effective, simple and cost-effective way.
There are multiple websites and threads on the web dedicated to swapping the e30 to a 5-lug setup. As I found out, there are a couple of tried-and-true methods. E30M3 all around, E36M3 front/E36ti rear, E36M3 front/MZ3 rear, E30m3 or Z3 6cyl rear, to name the top five. At risk of sounding like a snob, none of those really suited my wishes. My goals are simple: bigger brakes and wider wheels and thus tires. Why not go BBK and wide 4-lug? It’s a good option, but I have too many 5-lug wheels, and I like the appeal of a brake system which costs a reasonable amount while retaining some upgrade capacity further down the road (more on that later)—and besides, I always like to engineer new things (see my seat brackets). Here’s the rundown of my logic.
E30M3 is the simplest (totally bolt-on), but also the hardest setup to source and by far the most expensive, easily topping $2000 without consumables (rotors and pads). The improvement in braking is marginal.
E36M3/E36ti was my first choice, until I did some maths and figured out the brake bias would be wrong. Essentially, the rear brakes would be about the same as the E30’s while the fronts would be far better. I did like the simplicity of the E36M3 front end, which is what I chose.
E36M3/MZ3 is probably the ideal solution, bar two details. First, have you ever seen a MZ3 rear end for sale? It is also more intensive, requiring replacement of the diff flanges and halfshafts along with the trailing arms. Second, the rear offset would be quite high, probably around the high 40s. Not many wide wheels available in ET35 front and ET48 rear.
The Z3 6cyl rear end was my next choice, as it is really quite simple: Z3 hubs and rotors along with E36 328i calipers. Braking would be better, but still somewhat unbalanced, and the offset would still be too high. E30M3 rear is also a simple hub, rotor and caliper swap; although the offset would be good, the brakes would again be unbalanced relative to the E36M3 front.
Ultimately, I decided I would go E36M3 front (inspired by the great deal I got on the necessary parts), and mimic the approach taken by Tino at 300mm.de for the rear, namely a custom adapter to mount E36M3 rear calipers on E30 trailing arms through a Z4 hub. Unlike Tino, however, I want E36M3 rotors as well, instead of his suggested E46 328i rotors. I chose this for two reasons: the cost of z4 hubs, and the effectiveness of the E36M3 brakes all around.
TL;DR: Going E36M3 front and hybrid Z4/E36M3/E30 rear.
I won’t cover the front setup, because it is dead simple and well-documented elsewhere. Get ‘96+ E36M3 front spindles and struts, and use the E30 spring perch. It bolts right up. Use 96+ E36M3 control arms with E30M3 offset bushings. Done. E36 and E30 springs have the same diameter, and Bilstein Sport inserts for E30 and E36 have the same valving, so you can reuse your suspension. I realize that E36M3 front ends aren’t exactly common—I got very lucky finding mine. If you can’t find one, look up Max399 on r3vlimited. He sells some pretty nice adapter hardware allowing you to run E36 hubs on E30 struts. Not as elegant, but it works, and it’s well-priced.
As such, I’ll focus on my rear setup.
The beauty of this setup, in my opinion, is fourfold. First, the Z4 hubs fit the E30 halfshafts and bearings directly. I can simply press them in, and presto. In fact, every E30 after 1985, every E36 non-ti and non-M, Z3, Z4 and E46 share the same bearing diameter. Makes things easy! The Z4 hub in particular is very cheap (I get mine in Germany for 45 euros each—versus about $150 for an E30M3 hub.
Second, the brake bias and balance of the E36M3 will be maintained, retaining a balance very close to the original E30’s. My goal in this project was to improve the car without changing its character, which is, after all, what makes the E30 so great in the first place!
Third, by using the entire E36M3 setup, I can later upgrade with any parts compatible with the E36M3 is I want. Hello E46M3 brakes or E38 4pot Brembos!
Lastly, the rear offset will end up around ET30-35. This will allow me to run my beautiful E39 style 42s, along with essentially any wheel I later want—E36, E46 or otherwise.
At present, I’m obtaining measurements to design my custom rear adapters. Given that I’m just starting a new job, progress will be slow as I accumulate capital, so please bear with me. I will soon post a link to my parts list for anyone interested in duplicating my setup, and the schematics for the brackets will be available once complete.