"These build journal entries are part of a Special Series covering BMW M's most popular wing designs.
Written in collaboration with Silvano at CarbonProduction GmbH, I take you into the historical development of these wings all the way to my unboxing impressions of the GTS, GT4 and M235/240i Racing wings.
In this entry, drill here baby! I document the installation process of the GTS wing with my E92 CSL composite trunk and the little things that should make for a durable installation."
Measure [...] never.
The benefits of working with professionals in the custom paint & body world is obvious: they've done a lot of wing installation over the years.
Jonathan will be the first to tell you that wing & trunk quality differs tremendously. For once, he was glad this wasn't a chassis mounted spoiler that required cutting into the trunk.
I put together a reel showing the complete process here.
He quite literally put the wing at its sweet spot intuitively, without first measuring or pulling out the laser.
In this current position, wing handily clears the back window with the standard mounts. The extended mounts would also clear, as it pushes the wing even further back.
You'd have to drill so far forward on the trunk to hit the glass that I'd have to question your sanity.
Still, we didn't actually do without measurements. We did, multiple times - before drilling, and after drilling.
The outline was marked with a sharpie along with the drilling holes for the mounts. Drilling templates are not included with this wing.
The CSL composite trunk's design makes this a slightly trickier positioning as there is no straight line by the ducktail. These mounts were put on the most outer position that remains flat.
Once we were satisfied with the overall potential aesthetics, Jonathan made the markings official.
That officially makes it official! The composite trunk was relatively easy to drill into, but it felt thicker than stock.
Looking at the underside, only 1x of the two holes was visible. This was a design difference between the OEM metal trunk and this one. This section is usually sandwiched with thinner, visible metal layers.
The further outward drilling location was right at a reinforced angled of the composite trunk. We decided to skip on reinforcements considering the cuts involved would weaken the area further that we felt we could reinforce.
He pulled out a hole saw and made a wider hole to fit the ratchet's box.
We previously believed I got hustled with a replica Vorsteiner trunk due to its shoddy fitment. The confirmation this was a full fiberglass trunk confirms it. I'll try to reach out to Peter at Vorsteiner to validate.
Old bear's tricks.
Drilling is really half the way there, bolting the wing right for a leak-free, vibration-less installation is the other half.
It's in that section of the installation that Jonathan's dad got involved. We needed a second pair of hands and mine were busy filming. Bilo loves playing around with custom fitments to create simple solutions to issues that are often overlooked by most without his experiences.
The trunk bolts.
The mounts and this GTS wing come without hardware to bolt through the trunk due to the variety of trunk designs and materials. They are M8x1.25 bolts, the length will depend on your mounts and trunk.
This was a matter of finding the right bolt. We had a variety of zinc plated bolts on hand to avoid long term corrosion from water and weathering.
Adding a 5-6 kg / 10-13 lbs wing & mounts on a trunk will usually incur vibrations. The goal is to limit vibrations and its transfer into the cabin to eliminate noises and long term damage to the trunk's paint.
We use a rubber seal in between the bolt holes directly under the mounts.
Eliminating water infiltration.
Water kills: it seeps into electrical systems, the amp, or our battery and make a mess of things. It also exposes unprotected metals to corrosion and accelerated rust.
E60 M5 owners know this quite well, and some E9x M3 owners have had the unfortunate luck to experience it. Fried amps and soaked batteries are no fun.
Solution #1: OEM GTS.
The OEM M3 GTS mounts were machined with channels to fit o-rings, these weren't. We still tried, it didn't work as it added too much thickness and made the mounts unstable.
This will be a design revision for the to-be-released 1:1 replica of the mounts.
The channels are already integrated on all current race pocketed GTS mounts and extended GT4 mounts.
Solution #2: a custom seal.
The chosen solution is one known by professionals. It involves create a custom seal with windshield polyurethane. It's a potentially messy job that I don't particularly recommend if you DIY.
With the first solution chosen, we officially bolted the wing. Some minor adjustments to the drilling holes had to be done to fit the ratchet's box properly.
We fitted washers to each bolt location, this is mandatory to spread the torque load and avoid cracking on composite trunks. I highly recommend it on OEM metal trunks as well.
With the wing firmly bolted, it confirmed our seal solution was needed. The front section of the mounts was slightly eating into the paint already The fiberglass construction makes it softer and susceptible to this.
Precise paint lines were made to leave a small section for the seal. This is precision work to obtain a clean line.
The urethane got applied, and was evened out by Jonathan to create a uniform, sleek seal.
The seal is sleek, and is ultimately better solution to the OEM o-rings as it eliminates any perspective on paint damage that will occur at the mounting points.
The seal also further eliminates any water infiltration under the mounts, even if it doesn't seep into the trunk with the OEM O-rings.
The seal is hardly noticed, unless you put your face to it.
The liner got put back on and it was like nothing ever happened :D
The final aesthetics.
I like it, I like it more than I expected - and the reasons are precisely why it was loved and hated when it got released.
TUV / ABE certification mandated, at the time, that wings cannot exceed the trunk lines. This restricted BMW M in creating a 122cm board: the width of the trunk.
This restriction creates symmetry, aligning the end plates vertically with the trunk's outer lines.
See what I mean? The end plates appear to dive into the trunk's lines.
The side view is nice. I am glad I got the wing painted in satin black to mimic the OEM GTS appearances. It's most subtle, for a wing.
No matter the 16mm focal length, it will always feel a bit small for some. There's the GT4 Mk2 and its 18cm wider board if you feel that way.
It looked even better out in the sun. The standard mounts' height does impede on your rear view when driving.
If I lowered the angle of attack by a single point, it would probably perfectly align with the CSL ducktail.
After driving it up to downforce appropriate speeds, I report no vibrations of any kind.
The wing is sturdy and the carbon board doesn't distort or flap about. It's a refreshing sight as I had anxieties from my Subaru STI days.
After 2 years procrastinating my wing fitment, I am ultimately glad I did it.
It follows the original idea of BMW M and adds character to the car at a moment in time the build was far enough to justify sporting a wing.
It also eliminates rear end lift at speeds, eh!
You can source the GTS 1:1 carbon wing year long here in various options. The GTS replica mounts will be offered later this year.