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This is an installation guide for the CMST carbon-fibre kit on the 2021-2025 BMW 4 Series G22 coupe and G23 convertible, focused on the front lip and the rear lip. The front work involves removing the front bumper to access the radar and forward camera, and the rear lip requires transferring the original reflectors and reconnecting the tail-light wiring. The kit fits over the factory panels with 3M VHB tape, panel-bonding adhesive and self-tapping screws. Allow most of a day with two people and a hoist.

• Vehicle: BMW 4 Series G22 coupe / G23 convertible, 2021-2025
• Pieces covered: Front lip (with grille trim), rear lip
• Fixings: 3M VHB tape, panel-bonding adhesive, self-tapping screws, factory clips
• Difficulty: Moderate to involved; sensor and wiring steps need care
• Time: Most of a day with two people

Tools and preparation

Have ready a trim-removal kit, a cordless drill, degreaser, adhesion promoter, fine sandpaper, masking tape and a heat gun. As with any tape-bonded kit, surface prep decides the result: degrease every bonding face, key it lightly where instructed, apply promoter, and only bond when the car is warm and dry — above roughly 15°C. In cooler weather, warm the car and the parts indoors first.

The G22/G23 front job is more involved than a simple lip because the front bumper houses the forward radar and, on many cars, a camera. You will be removing the bumper, so set aside space to work on it off the car. Dry-fit the front lip and the rear lip before committing any adhesive, and mark their positions with masking tape.

Difficulty and time estimate

This is a moderate-to-involved install. The front lip is rated up a notch because it requires removing the bumper and working around the radar and camera. The rear lip is similar — it carries the reflectors and the wiring for the rear lighting. Neither is beyond a careful DIYer, but both reward patience. Budget most of a day and keep a second person on hand for the bumper and the long panels.

Step 1: Front bumper and front lip

Begin by removing the front bumper: take out the bumper screws, then disconnect the original radar unit and the forward camera so the bumper can come away cleanly. With the bumper off, fit the CMST front lip and the centre grille trim. Use self-tapping screws to mount the lip to the centre grille and the lip's fixing points, then run 3M tape and a few beads of panel-bonding adhesive along the top mating edge for a continuous bond.

Radar and camera: reinstall the radar and camera to the bumper as you reassemble. On cars with ACC, the centre grille trim has to be fitted to the correct cut-out so the radar aperture stays clear — line the trim up to the sensor opening rather than blocking it. Refit the bumper to the car, reconnect the radar and camera, and only then drive the lip's lower self-tapping screws to lock the bottom edge. Finish by refitting the number plate. If the front under-tray needs a clearance hole for a fixing, drill it yourself to suit — check clearance before you do.

Step 2: Rear lip

The rear lip is the second careful step. Remove the original rear lip and bumper together, then separate the factory reflector strips — these transfer across to the CMST rear lip so the car keeps its rear reflectors. Locate the CMST lip on the bumper's clip points and fix it with self-tapping screws, making sure it seats tight with no gap at the join. The rear lighting wiring follows the factory colour code as you reconnect it: red to positive, black to earth, and the yellow wire is not used on this fitment — match the original colours and do not guess. Reinstall the original bumper screws and refit the lip to the car.

There is a corner detail at each end of the rear lip that bonds with 3M tape and a few points of panel-bonding adhesive; align each corner to the bumper, press it home and let it set. If you are not comfortable around the reflector transfer and the lighting wiring, this is the step to hand to a workshop.

Fitment tips and cautions

• Plan the bumper-off front job. The radar and camera must be disconnected to remove the bumper and reconnected on reassembly — work methodically and label connectors.
• Keep the ACC aperture clear. Fit the grille trim to the sensor cut-out so the radar's line of sight is not blocked.
• Match the wiring colours. Red to positive, black to earth, yellow unused on the rear lip — follow factory colours exactly.
• Warm, clean surfaces. 3M VHB tape needs warm, dry, degreased paint; bond indoors in the cold.
• Dry-fit and mark. Tape is unforgiving — test-fit and mark positions before peeling backing.
• Cure time. Avoid rain and car washes while the adhesive reaches full strength.

After installation: checks, compliance and care

Once both lips are on, do a methodical walk-around before the car goes back into service. Check the panel gaps at the front lip corners and the rear lip ends are even side to side, confirm there are no proud edges where the tape could catch a car wash brush, and verify every connector you touched — radar, camera and rear lighting — works. Reverse the car slowly with a spotter to confirm the parking aids read correctly, and test the indicators, reflectors and reversing lights at the rear.

Give the adhesive time to reach full strength before exposing the car to a high-pressure wash or heavy rain; VHB-style tape continues to build bond strength over the first day or two. For the first week, avoid steam cleaning the lower bumpers and don't run the car through an automatic wash with rotating brushes, which can lift a freshly bonded edge.

On the compliance side, a carbon front lip and rear lip are low-mounted aero pieces, and the relevant consideration in Australia is ground clearance and protrusion. Make sure the front lip does not reduce clearance below your state's minimum and that no sharp edge protrudes beyond the bodywork. If you are unsure, a workshop can advise on whether your fitment is within the rules for road use in your state. Keeping the kit reversible — bonded and screwed rather than permanently bonded into the structure — also makes it easy to return the car to standard if needed.

Long term, treat the carbon like paint: wash and dry it normally, keep a wax or sealant over the lacquer to protect it from UV, and avoid abrasive polishes that can haze the clear coat. The G22's lips sit low and catch road grime, so a regular wipe-down keeps the weave looking sharp.

Frequently asked questions

Do I have to take the front bumper off?

For the G22/G23 front lip, yes — the bumper houses the radar and the forward camera, and removing it is the clean way to fit the lip and grille trim and to keep the sensors working. Disconnect those units before removal and reconnect them on reassembly.

Will my Active Cruise Control still work?

Yes, as long as the radar is reinstalled correctly and the centre grille trim is fitted to the sensor cut-out rather than over it. Verify the system once the bumper is back on the car.

What about the rear reflectors and lights?

The factory reflector strips transfer to the CMST rear lip, and the rear lighting wiring reconnects to the original colours — red to positive, black to earth, with the yellow wire unused. Test the lights before final reassembly.

Does the G23 convertible fit the same as the G22 coupe?

The front and rear lower pieces in this kit are shared between the G22 coupe and G23 convertible, which use the same bumpers. Confirm your exact model and any factory M Sport bumper differences when ordering.

Should I get it professionally fitted?

Given the bumper removal, the sensors and the rear wiring, professional fitment is the safer route for many owners. AME Motorsport can arrange installation in Australia so the radar, camera and lighting are handled correctly.

Get it fitted in Australia

Prefer to have it installed? AME Motorsport can help. Browse the full G22/G23 range in the CMST body kits for BMW, pick a carbon nose from the CMST front lip collection, finish the tail with a CMST rear diffuser, and explore the wider CMST catalogue. Contact us to book fitment or for current 4 Series pricing.