1995 BMW M3 LWT Front Splitter R&R
Copyright © 2000 Andrew E. Kalman email@example.com
Here is some documentation I put together while removing and replacing the front splitter on my 1995 (E36) BMW M3 Lightweight. Since several people have asked me how difficult it is to add the Lightweight's splitter to a stock M3, I felt that they might be able to get a better feel for what such an installation will entail by reading this text and looking at the pictures.
Figure 1 shows the front of a Lightweight with the splitter in the fully extended (outwards) position. It can also be pushed back somewhat, or all the way back to be flush with the front bumper cover (the big one-piece white plastic thing). The one-piece splitter appears to be made from a dense foam-like core, wrapped in fiberglass, finished and painted black. It weighs about 13 lbs. The splitter itself is just one of many parts that are unique to the front end of the Lightweight, the others being primarily brackets, mounting hardware, radiator ducting and plastic pieces at the bottom of the front bumper covering.
Figure 1: Frontal View of M3 Lightweight
I needed to replace the splitter due to damage it incurred during a race basically the splitter dug into the ground, and threw up a soda-can-size rock that smashed the right front foglight, bounced up onto the hood, and broke the front window. It also bent some of the bracketry. In Figure 2 you can see the damage more closely a large chunk was torn out of the splitter, and it has additional cracks. In this picture I've already replaced the foglight and removed one of the damaged brackets (more on that later).
Figure 2: Damaged Right-hand Corner of Splitter
I also wanted to replace the splitter because of all the damage (Figure 3) that had been done to it from scraping against curbs and this lift the splitter greatly reduces front ground clearance when compared to a stock M3.
Figure 3: Scraping Damage on Splitter
Removing the bumper cover is easy. First, you have to undo the four M10 nuts that hold the aluminum bumper to the car's "outriggers." The bumper is anodized black, and is behind the bumper cover. There are two pairs of nuts, each behind that black molding that pops off, as shown below in Figure 4 (right-hand side):
Figure 4: RHS Nuts Holding Bumper Cover
Next, remove the hex-head screws that hold each plastic fender liner in place against the bumper cover. For each liner there are two screws one (Figure 5) that's roughly at the same height as the wheel hub center, and one (Figure 6) that's down low at the bottom. There are several other screws and nuts that hold each fender liner in place there's no need to remove them.
Figure 5: Upper Fender Liner Screw
Figure 6: Lower Fender Liner Screw
Once the liner screws are removed the liner should be "pulled away" from the lip of the bumper cover. Lastly, it's necessary to disconnect the fog light and brake duct sensor wires before pulling the bumper cover off there are two wires on each side. Figure 7 shows the wires on the right side.
Figure 7: RHS Fog Light and Brake Duct Sensor Wires
Now you're ready to pull the front bumper and bumper cover off (the bumper remains attached to the bumper cover), complete with the entire splitter assembly, the fog lights and brake ducts. It doesn't weigh too much probably around 60 lbs. In Figure 8 you can see the "outriggers" that the bumper mounts to. You can also see the plastic-and-aluminum radiator ducting that the Lightweight uses you'll note the waviness of the aluminum, due to accident damage.
Figure 8: Front of Car with Bumper Cover Removed
In Figure 9 you see a rear view of the complete assembly, less the brake ducts, which have conveniently fallen off. The bumper cover is attached to the aluminum bumper with plastic rivets, and the splitter is held by three brackets that are rigidly attached to the aluminum bumper. There are outer left and right brackets, and a single center bracket. All the brackets have slots in the flat portions that contact the splitter the mounting hardware rides in those slots, enabling the splitter to go in and out. The outer brackets apply spring pressure to hold the splitter tight against the brackets there is a detent setting for the fully retracted position. The center bracket simply holds the splitter not-quite-tight against it. The hardware is designed to prevent it being tightened to the point where the splitter won't move. Unfortunately, this design (especially with regard to the center bracket) is contingent on accurately counterbored holes in the splitter, and in practice the mounting hardware has to be fiddled with a little to get set the sliding tension of the splitter properly.
Figure 9: Complete Bumper / Cover / Splitter Assembly
In Figure 10 you can see one of the (albeit bent) exterior support brackets for the splitter. It's a bent tube with some angled sheet metal welded to it. The upper and lower portions of the tube should be in-line (axial), with an offsetting bend in the middle. The upper part of the tube goes up vertically through the front aluminum bumper and is held in place by a flat-head countersunk hex screw at the top. It's prevented from rotating by that little triangular piece 3-4" from the top it has a hole for an M6 bolt to go through it and the aluminum bumper. The hardware you see at the bottom is a pair of spring-loaded "clamps" that hold the splitter in place, against the flat bottom of the bracket.
Figure 10: Damaged Right-hand Bracket
Going back to the front of the car, on each side the radiator ducting (Figure 8) is held in place by two hex-head screws (Figure 12) going into the body, and one (Figure 13) going into a Tinnerman clip on the fender liner. I've found this mounting scheme to be inadequate, and so I made a few modifications. For the rear upper screw, I use a 2"x1"x1/16" aluminum plate with a hole drilled in it to distribute the clamping force over the plastic mounting "ear" the supplied washer just isn't big enough and the plastic is likely to tear. For the lower screw, I replace it with an M4 bolt, washers and Nylock nut, and also use the same aluminum plate. Until the damage to the car (notice the interim duct tape fix in Figure 12), this scheme worked very well and the plastic ears of the radiator ducting held up nicely.
Figure 12: Upper Screws for Radiator Ducting
Figure 13: Lower Bolt for Radiator Ducting
In Figure 14 you can see the two M3 ducting systems. The main difference is that the Lightweight's unit has to have a cutout to accommodate the center bracket that holds the splitter.
Figure 14: Stock (above) and Lightweight Radiator Ducting
The Lightweight's ducting is made from aluminum pieces and the cut-off "walls" of the stock ducting. The walls are riveted into place onto the aluminum floorplate. The Lightweight's ducting also incorporates a deflector in the middle that prevents air from going under the radiator. It's a combination of another plastic piece (probably also from the stock M3) and a length of aluminum right-angle bracket. All of this is riveted together.
Figure 15: Plastic "Walls" of Ducting are Identical
Well, that covers all of the removal and inspection. The re-installation is truly the opposite of removal. When re-installing the bumper assembly you can adjust the various body gaps by shifting the bumper assembly around on those outriggers before you tighten it down. So in terms of the differences between the stock and Lightweight front bumper assemblies, the Lightweight's incorporates the bracketry and the splitter, and the radiator ducting is different. There are also some differences in the large plastic pieces that finish off the bottom lips of the bumper cover. If you're interested in adding this splitter to a stock M3, you'll need to order about 35 new front bumper part types that are unique to the Lightweight.
Figure 16 shows the new splitter in place. I've riveted PTFE-based "rub strips" to the wear edges in an attempt to prevent the abrasive wear on the splitter. So far it's worked quite well
Figure 16: New Splitter in Place