BMW 3 Series M340i G20 G21 Pre-LCI Carbon Fibre Rear Diffuser by Adro (2018-2022)

The ADRO rear diffuser replaces the factory undertray section at the rear bumper with a structured carbon fibre component that adds visual presence to the rear of the car. Its design was developed specifically for the G20/G21 pre-LCI bumper profile, ensuring a seamless integration that requires no cutting, trimming, or modification of the vehicle. All installation hardware is included. Forge Automotive can supply this diffuser on its own, or fit it at our Darwen or Leeds site.

Key features

• ADRO carbon fibre 2x2 weave - same specification as BMW Genuine M Performance parts
• Engineered specifically for BMW G20/G21 pre-LCI bumper (2019 - 2022 build dates)
• Direct bolt-on to existing rear bumper - all installation hardware included
• Part of ADRO's full carbon kit for the M340i (front splitter, side skirts, spoiler also available)

What's in the box

• 1 x carbon fibre rear diffuser
• Fitting hardware

Fitment

• BMW M340i 2019 to 2022, Saloon, Pre-LCI only
• BMW M340i 2019 to 2022, Touring/Estate, Pre-LCI only
• BMW 3 Series M Sport 2019 to 2022, Saloon, Pre-LCI only
• BMW 3 Series M Sport 2019 to 2022, Touring/Estate, Pre-LCI only

Supplied, fitted and finished by Forge Automotive

Forge Automotive can fit this diffuser at either of our sites: Darwen in the North West or Gildersome, Leeds in Yorkshire. Forge Automotive can also finish this diffuser before fitting: paint protection film (PPF) to guard the carbon, a colour change or satin wrap, or colour matching to the car. Ask when ordering. See more BMW 3 Series G20/G21 parts.

Common questions

What is a 2x2 twill weave?
The weave pattern in the carbon cloth. In a 2x2 twill each strand passes over two and under two, which gives the diagonal pattern BMW use on their own M Performance and M carbon parts. Choosing 2x2 means aftermarket and factory carbon on the same car match.

How do I look after a carbon fibre part?
Treat the lacquer like paint: wash with pH-neutral shampoo, avoid harsh solvents, and wax or seal it. UV is what ages carbon, so a protected finish lasts longer. Forge Automotive can apply paint protection film to any carbon part before fitting, which guards against stone chips and keeps the weave clear.

Is this the same quality as BMW Genuine M Performance carbon?
The ADRO diffuser uses the same 2x2 weave specification and gloss lacquer finish as BMW M Performance carbon parts. Visually indistinguishable - though it is an aftermarket component, not produced by BMW.

Can I install this at home?
Yes. The diffuser attaches to existing rear bumper mounting points with all hardware included. Most owners complete the installation in under an hour.

Fitting is available on every part at our North West (Darwen) and Yorkshire (Leeds) workshops. Prefer to fit it yourself? Fitting instructions ship with every part.

In-stock parts ship in 3–5 working days, fully insured. Every part is fitment-checked before dispatch.

Covered by the manufacturer warranty. Fitting through our workshop keeps it intact.