FIXING the G90 M5's BIGGEST DESIGN FLAW: Kies Oil Cooler Skid Plate
Kies Engineering · G90 / G99 M5
Fixing the G90 M5's Biggest Design Flaw
BMW built a 700-horsepower super sedan and then left the oil cooler hanging in the wind. Here's how we scanned it, engineered around it, and built the fix in the USA.
The G90 BMW M5 is a 700-horsepower luxury rocket, fast enough for the track, big enough for the whole family. But BMW left one critical oversight: an exposed oil cooler sitting right underneath the car, completely vulnerable to rocks, road debris, and the kind of random impact that can drain your oil and destroy your engine in seconds.
Sound familiar? The same issue plagued the G80 M3, and Kies Motorsports fixed it then, too. Now we've done it again for the G90 M5.
The Problem
BMW does include a plastic undertray on the G90 M5, but it's designed for aerodynamics; not protection. It has a massive cutout positioned directly below the oil cooler, leaving the cooler completely exposed.
One sharp rock. One chunk of highway debris. That's all it takes for a catastrophic oil dump and a blown motor.
The short version: the factory undertray moves air. It does not stop rocks. The one spot that needs armor is the one spot BMW left open.
Engineering the Solution
At Kies Motorsports, we don't just sell parts; we design and manufacture them. Here's how the G90 M5 skid plate came together, in order.
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3D Scanning
We captured precision scans of the entire undercarriage using the EinScan Neo handheld scanner. Its built-in display and hybrid alignment system mean no tethered computer, the onboard screen shows exactly what's being captured in real time.
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In-House CAD Design
Our engineer rebuilt the scanned area in CAD, modeling every mounting point and clearance requirement against the factory geometry.
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USA Manufacturing
We prototyped, tested, and refined through multiple iterations before landing on the final design. Designed, engineered, and manufactured in the USA.
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Smart Engineering
Where spacers are needed, we welded them directly onto the plate. No loose hardware, no balancing act on your back in the driveway.
Installation: Dummy-Proof Bolt-On
The skid plate installs like an OEM part, no drilling, no fabrication, no trimming. Hand tools and a jack are all you need.
- Remove the large plastic undertray and the front trim strip (10mm bolts).
- Remove the two bolts holding the oil cooler.
- Transfer the factory plastic clips over to the Kies skid plate.
- Slide the skid plate over the bumper cover and align the front holes.
- Hand-thread three factory 10mm bolts to hold it in place.
- Install the larger bolts through the oil cooler.
- Secure the remaining screws and washers in the four open mounting holes.
- Reinstall the trim piece and push pins.
- Torque everything down.
Durability Testing: Rocks vs. Skid Plate
We put the plate through a real-world torture test. Team members hurled jagged chunks of concrete and asphalt at it, the same debris you'd catch off a highway. We even parked a brand-new Apex wheel behind the plate to make the stakes honest.
Kies Aluminum Skid Plate
Survived
Repeated direct hits from concrete and asphalt. Result: minor cosmetic marks. Nothing behind it was touched.
Unprotected OEM Oil Cooler
Destroyed
Same rocks, one hit. Punctured, oil out, engine gone. Even a small rock is enough.
That's the whole argument. A skid plate is cheap insurance against a bill that starts at a new engine.
Key Takeaways
- The G90 M5 has an exposed oil cooler, just like the G80 M3 before it.
- The Kies Motorsports skid plate is designed, engineered, and manufactured in the USA.
- 100% bolt-on installation: no drilling, no cutting, no modification.
- Welded-in spacers eliminate loose hardware during install.
- Field-tested against real road debris. It holds up.
Watch the Build & Rock Test
Frequently Asked Questions
Does the G90 M5 skid plate require drilling or cutting?
No. The plate is a 100% bolt-on part that reuses factory mounting locations and factory hardware. No drilling, cutting, or trimming of the bumper or undertray is required.
Which BMW models does this skid plate fit?
It's engineered specifically for the G90 M5 and G99 M5 Touring using 3D scans of the factory undercarriage.
Do I keep the factory plastic undertray?
The large plastic undertray comes off during installation. The factory plastic clips transfer over to the Kies skid plate, and the front trim strip and push pins reinstall over the top.
What is the skid plate made of, and where is it made?
It's aluminum, with spacers welded directly to the plate so there's no loose hardware during install. It's designed, engineered, and manufactured in the USA.
Why does the G90 M5 need a skid plate at all?
The factory undertray has a large cutout directly beneath the oil cooler for airflow, which leaves the cooler exposed to road debris. In testing, a single rock punctured an unprotected cooler — enough to drain the oil and destroy the engine.
How long does installation take?
Most owners complete it in about an hour with basic hand tools. The only fasteners involved are the factory 10mm bolts, the oil cooler bolts, and the supplied screws and washers.
Get the Skid Plate
Protect the cooler before the road finds it first.