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The CMST BMW M4 G82 widebody kit pairs flared widebody arches with a dry carbon-fibre aero set — front lip, side skirts, rear lip and a ducktail spoiler — for the 2021-onward G8x M4. The approach is widebody first, carbon second: the kit widens the M4's body for a broader, more planted stance, then adds dry-carbon exterior pieces to sharpen the look and carry the weave detailing. It is shaped specifically for the G82 coupe (and the related G80 M3 and G83 convertible), so the flares and carbon parts follow the factory body lines and mount to the standard bumpers and boot lid.

• Vehicle: BMW M4 (G82 coupe, G83 convertible) and M3 (G80), 2021 onward; S58 3.0-litre twin-turbo inline-six, ~503 hp / 650 Nm
• Style: Widebody conversion with a dry carbon aero set
• Material: Widebody flares plus dry carbon fibre (pre-preg, autoclave-cured) front lip, side skirts, rear lip and ducktail spoiler
• Key pieces: Widebody front and rear arches, dry carbon front lip, carbon side skirts, carbon rear lip with corners, ducktail spoiler
• Finish: Gloss twill weave under clearcoat; flares painted body-colour (shown here on Sao Paulo Yellow)
• Reference: CMST dry carbon front lip CMS1-352G

Widebody first: why the order matters

The G8x M4 is already a wide, aggressive car with its large frameless twin-kidney grille and muscular haunches, so CMST's build philosophy here is to commit to the look: widen the body first, then add carbon. The widebody arches push the bodywork out for a broader track stance and the clearance to run a more aggressive wheel-and-tyre fitment, giving the M4 the planted, purposeful look that suits its hardware. Only then does the dry-carbon aero set go on — front lip, side skirts, rear lip and ducktail spoiler — to sharpen the edges and add the weave detailing. Doing it in that order means the carbon pieces are chosen and fitted to suit the wider body, so the result reads as one resolved build rather than carbon bolted onto a standard car. AME stocks the full CMST catalogue alongside the wider BMW body kit range.

The base car is no slouch. The G82 M4 runs the S58 — a 3.0-litre twin-turbo inline-six producing roughly 503 hp and 650 Nm — with an eight-speed M Steptronic transmission and, in Competition xDrive form, a 0–100 km/h time near 3.9 seconds. The widebody-and-carbon kit gives the bodywork the same intent as the running gear without altering the M4's silhouette.

Front end: widebody arches and a carbon lip

The front combines the widebody front arches with a dry-carbon front lip. The flared arches widen the front track and frame a wider wheel, while the carbon lip drops the leading edge of the M4's bumper and sharpens the already aggressive front. CMST's front lip for this kit carries the reference CMS1-352G and is dry carbon throughout, so it shows a crisp twill weave under clearcoat. On a bright colour like the Sao Paulo Yellow car shown here, the gloss-black weave of the lip contrasts hard against the paint and gives the nose a clear, low edge. Browse the equivalent parts through AME's CMST front lip for BMW and CMST fenders for BMW collections.

Sides: carbon skirts on a wider body

Down the flanks, dry-carbon side skirts extend the rocker line and visually pull the M4 towards the road, tidying airflow between the widened front and rear arches. CMST describes the skirts as following a racing-inspired design, and on the widened body they do more than usual: the extra arch width and the lower carbon skirt line together stretch the side profile and make the coupe look longer and lower. The gloss weave along the sills draws a clean horizontal line between the flares. See the related CMST side skirts for BMW range.

Rear: carbon lip and a ducktail spoiler

The rear pairs the widebody rear arches with a dry-carbon rear lip and a ducktail spoiler. The rear lip wraps the lower bumper with corner sections, framing the M4's quad exhaust and giving the tail a planted, diffuser-style edge that balances the front lip. Above it, CMST uses a ducktail-style spoiler with a clean, simple line rather than a tall fixed wing — it lifts the trailing edge of the boot lid just enough to finish the rear visually and add a subtle aero element, while keeping the look restrained and in keeping with the M4's lines. The combination of widened rear arches, carbon rear lip and ducktail gives the back of the car a wide, low, finished stance. For the spoiler and rear-lip options, AME lists the CMST spoiler for BMW and CMST diffuser for BMW collections.

The full widebody-and-carbon set

Seen together, the kit is a coordinated package: widebody front and rear arches to set the stance, then a dry-carbon front lip, side skirts, rear lip and ducktail spoiler to sharpen and detail it. The carbon pieces are all dry carbon (autoclave-cured pre-preg), so the weave reads consistently from the splitter to the ducktail. The white-background layout below shows the set as supplied — front bumper, diffuser, spoiler, arches, skirts, grilles and front lip — which makes the build logic clear: a wider body first, with carbon highlights placed where they are seen. The full carbon range sits in AME's CMST carbon fibre body kit and CMST body kit for BMW collections.

Rear-on: the widebody stance

From directly behind, the payoff of the widebody is obvious. The flared rear arches stretch the M4's hips out over the wider rear track, the carbon rear lip and diffuser-style corners drop the visual height of the bumper, and the ducktail finishes the boot line. The quad exhaust sits centred under the carbon rear lip, and on the yellow car the gloss-black carbon against the bright paint makes the whole rear read as wide and planted. It is the clearest angle for seeing how the widebody and carbon work together rather than as separate add-ons.

Fitment and finish in Australia

A widebody-and-carbon M4 build is a body-shop job. The widebody arches need trial-fitting, panel-gap setting against the adjacent OEM panels, and painting in primer-to-colour so the flares blend seamlessly into the M4's bodywork — on a colour like Sao Paulo Yellow, the paint-match has to be exact. The dry-carbon lip, skirts, rear lip and ducktail are mounted with the correct mix of bolts, clips and panel-safe adhesive, and trial-fitting matters because carbon panels are made to tighter, more brittle tolerances than flexible factory plastic. Dry-carbon clearcoat is UV-sensitive, so washing with pH-neutral products and adding a UV-stable ceramic coating or PPF on the leading edges keeps the weave from yellowing and guards against stone chips. Anything that changes the car's external width or ride height should be fitted with roadworthiness in mind, so keep wheel fitment sensible for road use in your state. AME can supply the CMST G82 pieces and advise on staging the work; start with the CMST body kit for BMW range.

Frequently asked questions

Which BMW does the CMST M4 widebody kit fit?

It is designed for the BMW M4 (G82 coupe and G83 convertible) and the related M3 (G80) from the 2021 model year onward. It is shaped to the G8x body, so confirm your car is a 2021-or-later G8x M3/M4 before ordering. It is not designed for the previous F82/F80 generation.

Why does CMST recommend the widebody before the carbon?

The build is designed widebody-first so the carbon aero pieces are chosen and fitted to suit the wider body. Widening the arches sets the stance and the wheel-and-tyre clearance; adding the carbon front lip, skirts, rear lip and ducktail afterwards sharpens and details that wider body. Done in that order, the result reads as one coordinated build rather than carbon bolted onto a standard-width car.

Are the aero pieces dry carbon?

Yes. The front lip, side skirts, rear lip and ducktail spoiler are dry carbon fibre — pre-preg carbon cured under heat and pressure in an autoclave. Dry carbon is lighter and stiffer than wet-layup carbon and shows a crisp 2x2 twill weave under clearcoat. The CMST dry carbon front lip for this kit carries the reference CMS1-352G.

Is the ducktail spoiler the same as a fixed wing?

No. The ducktail is a low, clean spoiler that lifts the trailing edge of the boot lid, giving a subtle aero element and a finished rear line while keeping the look restrained. A tall fixed wing sits up in cleaner air for more rear downforce but is far more aggressive visually. The ducktail suits the widebody M4's lines for a planted, OEM-plus stance rather than a track-wing look.

Does the widebody add downforce?

The widebody is about stance and wheel-and-tyre clearance rather than downforce. The carbon front lip and ducktail tidy airflow and add a measure of front and rear aero, but CMST does not publish specific downforce figures for the kit. Treat it as a styling-led widebody with carbon detailing, and budget separately for suspension and tyres if you want measurable aero performance.

Should I have it professionally fitted?

Yes. The widebody arches need expert trial-fitting and body-colour painting, and the dry-carbon panels are more brittle and less forgiving than factory plastic. Correct panel gaps, secure mounting, exact paint-matching and clearcoat protection all need a body shop, and professional fitment gives the flush, factory-grade result the kit is designed for.

Build your M4 with AME Motorsport

If you are planning a widebody conversion for a 2021-onward BMW M4 Competition or M3, AME Motorsport can supply the CMST widebody arches and dry-carbon aero pieces and help you stage the build. Start with the CMST body kit for BMW range to see the components, then get in touch to confirm fitment, paint-matching and the wheel package that suits your G8x M4.