E34 535i M-Tech Skirts Addition


Let’s face it: ground effects are cool and stock e34’s, with the exception of repaints, M5’s, and model year ’95 cars, just don’t have much going on for them around the rockers besides some black underbody coating garbage that would make the new pope weep.

After my three month long Style 5 acquisition fiasco, I finally got a set of wheels and was about to leave well enough alone when our friend Bret Luter informed us of an exciting opportunity. As I confirmed, Style 5’s with a set of skirts look bangin’! I bopped over to Bret’s farm and a few c-notes later, I was the owner of a set of M-Tech skirts from a mangled ’95 525. Although mine came with a little damage, painting (or repainting) a set of skirts should be a less-than-$100 affair. Lucky for me, they were already green – just Oxford Green, not Fritz’s current Islandgrun – so I’m leaving them alone for right now. The Oxford is a slightly darker green, and the two-tone effect that resulted is a nice variation on the US ///M5 color scheme.

Buying these parts from the $tealer is EXPEN-SIVE! Don’t believe me? Check the ETK. BMA can probably cut you a ~ $475 deal on the skirts alone. The body-colored lower door trim, black on non-skirted e34’s, costs about $50 a door. Additional expenses include the mounting hardware, which are comprised of a grommet and a pressure fastener (x8 on each side) as well as two piece “compound” clips (x5 on each side) on the underbody. Add the cost of paint and buying new becomes an expensive proposition. So, it behooves one to hunt around for a junked ’95 or ///M5 if you’ve just gotta have them. Once they’re on, though, the cool points are out the window.

Prep Work

The standard E34 ///M-Tech skirt setup is comprised of the following hardware: (2) skirts – left and right side, and there’s a difference, (2) front door body colored lower trim pieces, (2) rear door body colored lower trim pieces – appear to be the same on both sides, (10) compound/two piece black plastic clips for securing the underbody side of the skirt – 5 per side, (16) plastic grommets – 8 per side, (16) adjustable plastic fasteners for said grommets – 8 per side.

Part Numbers:

Skirts: 51712230339 & 51712230340
Trim: Front - 51212230373 & 51212230374; Rear - 51222230398
Clips: 51711938940
Grommets: 51131934160
Fasteners: 51711959929

Note: there may be other hardware that will be needed, such as the fastener that goes on the rear fender (could just as easily use a standard tappet screw) or the foam “gaskets” that form a seal around the jack points. Be sure to check your ETK software prior to attempting installation so that you know you’ve got everything. If there’s one thing that I know you *do not* need, it is the “drilling jig”: it serves no other purpose, to my knowledge, than to mark drilling points, easily and cheaply done with a red sharpie.

Necessary tools and materials

Installing the skirts doesn’t require much in the way of tools and shop materials. Snapping the fasteners into the grommets does take a bit of strength, especially if the holes aren’t dead on, so bring your A game. Also, I decided to attack a few underbody coating issues before I covered them up with the skirts, so I included some tools and materials associated with those repairs:

  • 10mm socket and an extension, for removing the fender bolts.
  • Needle nose pliers (easily take apart the compound clips with these)
  • Water pump/channel lock pliers (for setting aforementioned clips and bending the rocker lip back in place from bad jack placement over the years.
  • A good drill and a 1/4” bit (or slightly larger). Use a Milwaukee Magnum Hole Shooter if one’s available. I’d started with a pathetic 7.2v VersaPack B&D, not a good tool for driving 16 holes through metal with a reasonably large bit, and it quickly died.
  • A red sharpie or other implement (that’s visible when applied to the black underbody coating garbage) for marking the hole points.
  • Rags for cleaning stuff up.
  • Sandpaper or a good angle die grinder with metal brush (for removing rust).
  • Underbody spray or hard black enamel paint/stabilizer (for covering up repairs).
  • Wax or some kind of desiccant to keep as much road and rain water as possible out of the space between the rocker and the skirt, and for under the door trims.
  • A beer (I prefer a glass of Carlo Rossi’s finest vintage 2005 sangria – nothing as classy as CR while working on a bimmer, except maybe Franzia) and a good CD to listen to while you’re working.


The Install

  1. First things first: used the needle nose pliers to remove the black trim located on both front and rear fenders. At this point, I addressed some rust issues: the paint on the front of the pass front fender had deteriorated due to tire sandblasting.

    Clean dirt and address any rust issues before installing skirt

  2. The old, black lower door trims can also be removed at this point. Might as well get all the old (probably) nasty stuff out first. I was installing used parts and didn’t have enough confidence in myself to pull the old lower door trims off before I had the skirt on. It’s a bit harder to fit the lower trims once the skirt is in place, and having the new lower trims on the doors will also help when setting the skirt.

  3. Depending on how well your car has been treated over the years, some rocker panel lip R&R may be necessary. Given the idiocy of my car’s PO, I knew I’d have to do a little work straightening out things down there. If the lip is smashed or bent outward, the skirt will likely not end up flush against the rocker. I didn’t take any pictures of the process, because every situation will be different. The basic idea is to strong-arm the lip back to normal, remove and treat any rust spots, and fix any areas that have lost the underbody rubber coating. Also, if any of this work needs to be done, be sure to do it the correct way the first time – once the skirt is on, or even partially on, it’s a pain to get it off again.

  4. Mark and drill holes in the rockers for the grommets. Yes, it’s a frightening thing to think about. I held the skirt up to the rocker, got it as close as possible to where it should sit when installed, then used the red sharpie to mark the mounting points (8 per side) based on where the plastic fasteners hit the rockers. Check the marks twice: although the fasteners have some horizontal leeway, there is little room for error in vertical placement.

  5. Once you’ve got your marks, pull out the holeshooter and have at it. I used a ¼” drill bit, but had to make the holes slightly larger to accommodate the grommets, so it might be wise to use a slightly larger bit from the get go.

    Use a good holeshooter, Milwaukee/Magnum variant

  6. Set and press a plastic grommet into each hole. The first picture below is of the grommet itself, the second is with it “set” – use the needle nose pliers to pinch the two lobes.

    Grommet clip that needs compressing in order to set

  7. A set grommet can be pressed into the previously drilled hole (you may want to find something to help press it in – I used the water pump pliers with good success):

  8. Once all grommets are in, things should look like this:

  9. The frontmost fender bolt (one of the two that secures the fender to the body underneath the car) has to be removed. The other bolt can stay – the skirt has a hole to clear it. If applying a coat of wax or other desiccant to the rocker panel area, now’s the time to do it.
  10. Line up the skirt and (really) press it on. It may take some serious force to get some of those fasteners in the grommets. On the pass side of my car, I’d misaligned two holes bad enough that one fastener had to be omitted. They’ll set with a satisfying POP. It’s okay to leave one or two fasteners out if necessary – the other six or seven are more than adequate for holding the skirt to the rocker.
  11. Once the skirt is set at the top, sink the previously removed fender bolt, securing the skirt to the fender, and the fender to the body.
  12. Each side requires five “compound” clips. These clips secure the bottom of the skirt to the rocker lip. As mine were used, I had to disassemble them using a pair of needle nose pliers. I assume they come disassembled from the factory.

  13. There are five mounting points along the underbody side of the skirt. Here’s one of them:

  14. Fit the skirt part of the clip….

  15. Then compress the rocker side of the clip in with a set of water pump pliers:

  16. The clips should be snug (so that they can’t be moved with a hand).
  17. Once all compound clips were installed, I stuck on the lower door trims. It can also be done before installing the skirts. Because I was using used lower door trims, I had to improvise getting them on (new trims may be easier): I temporarily removed part of the end of the trim and slid it onto the door, then pressed the removed part back into place. You may also want to sink a fastener in the rear fender, but I left that for another day when I’ve removed the rear wheels.
  18. Stand back and admire your hard work. Looks good, doesn’t it? Forget the car FEELING faster, I bet it actually GOES faster :o)

    Best, Whit

Article By Whit Lowell / 1990 535iA