MHC+ BMW F80 M3 & F82/F83 M4 GTX Ultra Aggressive Undertray Add On In Pre Preg Carbon Fibre

Complete your GTX rear aero with the MHC+ GTX Ultra Aggressive Undertray Add On for the F80 M3 & F82/F83 M4, the lower section of the two-piece GTX rear diffuser system. Manufactured from 100% pre-preg (“dry”) carbon fibre, the undertray and corner sections extend the diffuser further underneath the vehicle for a far more substantial, track-inspired rear profile that balances the GTX front aero.

Please note: this is an add-on. The MHC+ BMW F80 M3 & F82/F83 M4 GTX Rear Diffuser is required and is sold separately, or buy both together as part of the complete MHC+ GTX Aero Kit.

Key Features

• Lower undertray and corner add-on for the MHC+ GTX rear diffuser
• Designed for the BMW F80 M3 & F82/F83 M4
• Requires the MHC+ BMW F80 M3 & F82/F83 M4 GTX Rear Diffuser (sold separately)
• Manufactured from 100% pre-preg (“dry”) carbon fibre
• OEM-style 2x2 twill carbon weave
• Deep high-gloss UV-resistant lacquer finish
• Developed using full 3D chassis scanning and CAD engineering
• Fits using OEM mounts, pre-applied adhesive tape and stainless steel screws
• Assembles to the diffuser on the bench with supplied M6 hardware
• 15-minute fit
• Backed by MHC LDN’s 3-year warranty

The Full GTX Rear Aero Appearance

Fitted beneath the GTX diffuser, the undertray and corners create:

• A more substantial and purposeful rear profile
• Enhanced visual depth underneath the vehicle
• Improved balance with the GTX front splitter

Add It Now or Add It Later

The GTX system is modular by design. The undertray bolts to the diffuser with six supplied M6 bolts, with a further four holding the corner sections in place – so you can run the diffuser on its own and add this whenever you are ready, without modifying anything you already own.

Fitment & Installation

Fits using: OEM mounting points, pre-applied automotive-grade adhesive tape and supplied stainless steel self-tapping screws, with supplied M6 nuts and bolts joining the sections together

Tools required – items marked (supplied) are included in the box:

• Drill
• 2.5mm drill bit (supplied)
• PZ2 driver bit (supplied)
• 10mm socket and 10mm spanner – M6 nuts and bolts, you need to hold both ends
• 8mm socket – rear bumper corner OEM fixings
• Panel wipe or IPA and lint-free cloths (alcohol wipes supplied)

Time to fit: 15 minutes
Difficulty: Moderate – pilot drilling required

Assemble the diffuser and undertray as a complete unit on the bench first, then fit it to the car. Aligning the faces of the corner sections with the arch is the alignment that matters most visually, so take your time over it.

All required fixings and consumables are supplied. Best fitted indoors, above 15°C, on a clean, dry car – trial fit before committing any adhesive tape. A full step-by-step GTX fitting guide is available, and professional installation is recommended for the best possible result.

Precision OEM-Level Fitment

MHC+ developed this component using:

• Full 3D scans of the BMW F8X chassis
• Advanced CAD modelling and engineering
• OEM-level panel alignment development

This ensures flush integration with the factory body lines, accurate panel alignment and OEM-style fitment quality. No cutting or compromise required.

Premium Pre-Preg Carbon Fibre Construction

Unlike conventional wet carbon fibre products, MHC+ uses genuine pre-preg (“dry”) carbon fibre, delivering:

• Increased strength and rigidity
• Reduced overall weight
• Superior weave consistency
• Minimal imperfections or air pockets
• Exceptional long-term durability

Each component is cured under controlled heat and pressure to achieve optimal resin saturation, producing a premium carbon fibre part suitable for high-end BMW builds.

Deep High-Gloss Finish

Finished in a premium UV-stable gloss lacquer, every GTX component offers:

• Excellent resistance to fading and yellowing
• A rich OEM-style appearance
• Seamless compatibility with other MHC+ carbon fibre components

Supplied Ready to Install

• M6 nuts and bolts for the diffuser and corner sections
• Pre-applied automotive-grade double-sided tape
• 4.8 x 13mm stainless steel self-tapping screws
• 2.5mm drill bit and PZ2 driver bit
• Alcohol wipes for surface preparation
• MHC LDN fitment guarantee

Compatibility

Requires the MHC+ GTX rear diffuser to be fitted.

• BMW F80 M3
• BMW F80 M3 Competition
• BMW F82 M4
• BMW F82 M4 Competition
• BMW F83 M4 Convertible
• BMW F83 M4 Competition

Why Choose MHC+?

MHC+ is recognised globally for producing premium BMW carbon fibre styling upgrades with precise fitment, OEM-inspired design and exceptional manufacturing quality.

Why Buy from R44 Performance?

R44 Performance supplies premium BMW styling and performance upgrades trusted worldwide.

• BMW specialists
• Genuine high-quality carbon fibre products
• Fast UK & international shipping
• Expert technical support

Finish your GTX rear end with the MHC+ GTX Ultra Aggressive Undertray Add On, delivering the complete GTX rear aero appearance, premium pre-preg carbon fibre construction and OEM-quality fitment for the F8X M platform.

Unless explicitly stated otherwise, all products sold by R44 Performance Limited are designated RACE ONLY and are solely for competition or off-road use limited to racing formally sanctioned by a recognized racing organization. Any other use, including recreational off-road use, may violate local, state, and Federal laws. R44 Performance Limited does not implicitly or explicitly confirm the legality of using any products it sells on public roads; that is entirely the responsibility of the consumer.

It is the responsibility of the customer to check with all federal, state local and environmental laws before ordering and installing a product. R44 Performance Limited is not responsible for any fees, fines or costs that a customer may incur as a result of failing to check with federal, state, local or environmental laws before ordering and installing a product.

We get a large number of custom orders and requests everyday, so as a result it is not always possible for us to keep every item in stock at all times in our warehouse. If you require the item urgently please contact our sales team here to check the stock before you make your purchase.

We totally understand if you're not certain a part will be compatible with your car, so we highly recommend contacting us here with your query. Our friendly sales team will then be in touch to confirm if this part is the correct part you are looking for.

All in stock products ship the same day if ordered before 2pm GMT

For out of stock items we will contact you with an estimated wait time if not otherwise specified above.

We offer worldwide shipping on all products. If upon receiving your product you wish to return; we offer a 30-day returns policy. For our in-depth returns information please follow the link. "R44 Returns Policy

All of our products come with a standard warranty of 1-3 years. This is dependant on the type of product however. For more details please see our warranty page here.