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The CMST BMW 4 Series carbon-fibre kit is a two-path aero package for the G22/G23 4 Series (2021–2025), offered either as a wide-body conversion with a replacement front bumper or as a bolt-on set that keeps the factory bumper. Both paths use carbon fibre (with FRP reinforcement on the full bumper) and cover the front lip, bonnet, side skirts, fenders or wide arches, rear lip and a choice of rear wings. Every panel is moulded from the G22's surfaces and mounts to factory points, so you can build anything from a subtle carbon refresh to a full widebody on the same car.

• Vehicle: BMW 4 Series Coupe (G22) and Convertible (G23), 2021–2025; including M440i and 4 Series M Sport
• Two configurations: "with front bumper" (wide-body) and "with OEM bumper" (factory-bumper bolt-ons)
• Materials: carbon fibre throughout; FRP-and-carbon composite on the full front bumper for structural toughness
• Key pieces: front bumper + grille + vents, front lip, bonnet C, wide arches, side skirts, rear lip with corners, ducktail and goose-neck wings, front fenders
• Finish: exposed carbon weave or paint-matched

One car, two directions

BMW's 4 Series Coupe is the brand's style flagship in the mid-size class, and CMST treats it as a platform for two different owners. One wants the full aggressive widebody; the other wants to keep the factory bumper and add carbon where it counts. By tooling both a complete replacement front bumper and a set of bolt-ons that work with the OEM bumper, CMST lets a G22 owner choose how far to go without committing to one fixed look. The styling takes the G22's tense surfacing as its starting point and pushes it toward motorsport, blending light weight, aero function and a sharper stance.

Configuration 1: the wide-body (with front bumper)

Front bumper, grille and vents

The replacement front bumper is the most dramatic change. Built as a carbon-and-FRP composite — carbon for lightness, FRP for structural toughness in a large impact-prone panel — it has knife-sharp lines and a wide central intake that drops the factory restraint. An enlarged grille and carbon bumper vents complete the face, forming a wide-body front end that reads far more aggressive than stock. The composite construction is a deliberate choice: a full bumper benefits from FRP's resilience where pure carbon could be brittle.

Front lip, bonnet and wide arches

Below the bumper, a full carbon front lip sits low and sharp, stepping down from the bumper for a layered attack and adding front-axle downforce. The carbon bonnet (CMST's "C" design) draws a raised centre spine that strengthens the bonnet's lines while channelling air toward the cooling system and trimming weight over the nose. The wide arches are the defining wide-body element: they cover the front and rear wheel arches and integrate with the side skirts, flaring the body so the wheels and tyres fill a wider, more planted footprint with one continuous line from nose to tail.

Side skirts, rear lip and wings

Carbon side skirts carry subtle air-channel detailing and join the wide arches into one muscular profile. At the rear, the multi-stage carbon rear lip with corner sections tidies airflow leaving the tail and adds a downforce path under the back of the car. For the wing, owners choose between a ducktail-style carbon spoiler — elegant, integrated, guiding roof air to the tail with the rear diffuser to form a downforce channel — or a goose-neck big wing for a full track look, whose mounting structure improves high-speed stability and corner grip.

Configuration 2: keep the OEM bumper

For owners who like the factory bumper, CMST offers a parallel set. The OEM-bumper front lip has sharper, more defined edges than the wide-body lip, with a central rise that pulls down and outward and carries air-guide channels to manage flow and add visual punch. Carbon front fenders bring out the side-line's three-dimensionality and, thanks to carbon's strength, are a sensible companion to the wide arches if you later go wider. This path also offers the ducktail and goose-neck wings and an OEM-style carbon boot lid, so you can build a clean, carbon-accented G22 that keeps its standard bumper while still gaining aero detail.

Why carbon on the 4 Series

The G22 is a well-balanced rear-drive (or xDrive) coupe, and carbon helps in two ways. Weight: a carbon bonnet and carbon panels remove mass high and forward, sharpening turn-in. Aero: the lip, arches, diffuser-fed rear lip and wing build genuine downforce front and rear, which a fast coupe uses on a quick road or a track day. CMST designed the kit so each piece contributes to a front-to-rear downforce balance rather than loading one end, which is what keeps a modified coupe predictable at speed.

Fitment and finish in Australia

The bolt-on (OEM-bumper) parts are a straightforward carbon upgrade, but the wide-body configuration is an advanced install: the arches need precise alignment, and wider wheels and tyres with the correct offset are required to fill them. We recommend professional fitment for the wide-body path and for setting even panel gaps on any carbon piece. Australian UV is hard on lacquer, so protect the weave with a ceramic coating or paint-protection film. Parts ship clear-coated and can be painted to body colour.

See the range in our CMST Body Kit for BMW collection, compare wings under CMST Wing for BMW, explore wider options in BMW Body Kit, and read about the brand on the CMST page.

FAQ

Does the kit fit both the G22 Coupe and G23 Convertible?

Yes, the kit is designed for the BMW 4 Series G22 Coupe and G23 Convertible (2021–2025), including M440i and M Sport models. Some rear pieces (boot lid, wings) are body-style specific, so confirm coupe or convertible when ordering.

What's the difference between the "with front bumper" and "with OEM bumper" versions?

The "with front bumper" version is a wide-body conversion: it replaces the factory bumper and adds wide arches for an aggressive, track-style look. The "with OEM bumper" version keeps your standard bumper and adds carbon bolt-ons (lip, fenders, skirts, wings). They suit different goals and budgets.

Why is the front bumper carbon and FRP rather than full carbon?

A full replacement bumper is large and exposed to impacts, so CMST combines carbon for light weight with FRP for structural toughness. The composite resists cracking better than pure carbon would in that application while keeping weight down.

Should I choose the ducktail or the goose-neck wing?

The ducktail is integrated and elegant, guiding roof air to the tail for a subtle downforce gain — ideal for a street car. The goose-neck wing is the track choice: its over-mounted structure produces cleaner, stronger high-speed downforce for better stability and corner grip. Both are carbon fibre.

Do I need wider wheels for the wide-body version?

Yes. The wide arches are designed to be filled by wider wheels and tyres with the correct offset. Plan wheel fitment with the kit so the tyres sit flush within the arches without rubbing — it is essential to the wide-body look and is best set up by a professional.

Ready to plan a 4 Series build — subtle carbon or full widebody? Explore fitment, wings and finishes in our CMST Body Kit for BMW range and talk to the AME Motorsport team about your spec.