Blog

This is a build case study of a BMW 5 Series F10 wearing the CMST carbon-fibre widebody kit, the wide-track version of CMST's F10 programme. Where the narrow-body F10 keeps the factory track, this car runs flared FRP arches that add roughly 5cm per side at the front and 6cm at the rear over a wider wheel-and-tyre package. The show panels are formed in dry carbon fibre, while the arch flares, fenders and side skirts are moulded in FRP so the wider, compound shapes stay paintable and affordable.

• Vehicle: BMW 5 Series, F10 generation (520i–535i and the F10 M5 share the body)
• Fitment years: roughly 2010–2017 F10 saloon
• Materials: dry carbon fibre (show panels) and FRP (arches, fenders, skirts, bumpers)
• Key pieces: FRP front bumper with 3-piece vacuum-carbon lip and carbon corners, vented carbon bonnet, +5cm front / +6cm rear FRP arch flares, FRP fenders and skirts with carbon skirt lips, FRP rear bumper with carbon rear lip and corners, adhesive-mount carbon wing, SUS304 valved exhaust with carbon tips
• Finish: gloss twill-weave clearcoat on the dry-carbon pieces; primed FRP sprayed to the car's factory colour

The build: from executive saloon to widebody F10

The F10 5 Series left the factory as a restrained executive saloon, its N-series turbo petrol and diesel engines and long wheelbase tuned for quiet motorway comfort rather than visual aggression. That is exactly why it makes a strong widebody base: the proportions are clean and the body sides are broad enough to carry serious arch work without looking forced. The cars in this case wear two colours from the build, a silver-grey saloon and a black "phantom" car, both on the same CMST widebody architecture.

The brief was width and stance, not a stripped-out track car. The silhouette stays recognisably 5 Series, but the flared arches, lower ride height and staggered forged wheels change the footprint completely. AME stocks the full CMST catalogue alongside the wider BMW body kit range.

Full parts list, piece by piece

Front bumper, lip and corners

The nose is rebuilt around an FRP front bumper with larger intakes. Mounted to it is a three-piece front lip formed by vacuum-infused carbon, a process that draws resin through the carbon under vacuum for a consistent, void-free part. The three-section split makes the lip easier to ship and lets you replace one damaged segment after a kerb strike rather than the whole spoiler. Carbon front corners wrap the outer edges of the bumper, tying the lip into the new fender line, and together they reduce the air slipping under the nose. Compare pieces in the CMST BMW front lip range.

Vented carbon bonnet

The steel bonnet is replaced with a vented dry-carbon item, and the two functions stack. Removing mass from the highest, most forward panel of the car helps the front end change direction, while the vents give hot air trapped above the engine and turbo a path out, which helps keep intake temperatures in check on a turbocharged F10. Visually it is the centrepiece, since the twill weave reads clearly across such a large surface. Browse the CMST BMW bonnet collection.

Widebody arches, fenders and side skirts

This is where the car earns the "widebody" name. CMST adds FRP arch flares that widen the body by about 5cm per side at the front and 6cm per side at the rear, with FRP front fenders and side skirts carrying the new width down the flanks. Carbon lower lips run along the bottom of the skirts for a show-finish edge. FRP suits this job: glass fibre forms the deep, compound arch curves more economically than autoclaved carbon, and since the arches are colour-matched to the body, an exposed weave would be hidden under paint anyway. The wider track is the point, letting the car run broader tyres. See the CMST BMW fenders and CMST BMW side skirts ranges.

Rear bumper, lip, corners and wing

At the back, an FRP rear bumper houses a carbon rear lip and carbon rear corners that frame the lower tail and the exhaust exit, with the lip dropping a diffuser-style edge to pull the car visually towards the road. Above the boot sits an adhesive-mount carbon rear wing: rather than drilling the boot lid, it bonds to the surface with high-strength automotive adhesive, keeping the boot skin sealed and the install reversible. A raised wing sits in cleaner air above the bootline and adds rear load at speed, balancing the front aero so the car stays settled as the needle climbs. The CMST BMW spoiler range covers the wing options.

SUS304 valved exhaust

Completing the car is a SUS304 stainless-steel valved exhaust with carbon tips. SUS304 is the corrosion-resistant grade used for quality aftermarket systems, standing up to road salt and moisture far better than mild steel. An electronically controlled valve stays shut around town to keep the car quiet, then opens under load to free flow and let the engine sound through, giving a quiet commute and a louder note on demand. To pair the kit with a matching system, see the CMST cat-back exhaust range.

Why dry carbon for the show panels and FRP for the structure

The kit deliberately mixes two materials, and the split is intentional. The standard F10 reads as understated and corporate; the widebody build keeps that identity but rewrites the stance, and the material choice is what makes it work without adding needless weight.

In short, CMST puts dry carbon where light weight and a visible weave earn their keep, and uses FRP for the wide arches, fenders and bumpers, where colour-matched paint is expected and the compound shapes are easier to mould in fibreglass. It is the same philosophy you will see across the CMST body kit range.

Fitment and finish in Australia

A widebody conversion is a workshop job, not a driveway one. Carbon and FRP panels are more brittle than the flexible factory plastics, so plan for trial-fitting, checking panel gaps against the adjacent OEM panels, and securing each piece with the correct mix of clips, bolts and panel-safe adhesive. Three points are worth flagging before you book the work:

• Paint-matching the FRP: the arches, fenders, skirts and bumpers arrive primed and must be sprayed to your car's factory colour, so budget for a painter who can match BMW paint, including any metallic or pearl.
• Widebody wheel and tyre fitment: the +5cm front and +6cm rear flares only work if the wheel offset, tyre width and ride height let the tyre clear the new arch through full suspension travel and steering lock. Confirm the package before the arches go on, and set the alignment afterwards.
• Dry-carbon clearcoat care: the exposed weave is protected by a clearcoat that degrades under prolonged UV. Park undercover where practical, wash with pH-neutral products, and consider a UV-stable ceramic coating or paint protection film to stop the weave yellowing under the Australian sun.

Because the kit ships as discrete pieces, a competent body shop can fit it in stages and correct gaps along the way.

Owner takeaways for an F10 build

A few lessons carry forward. Stage the work: the front bumper, lip and bonnet deliver the biggest visual change, so a build can start there and add the arches and rear later. Sort the wheel-and-tyre package early, since the flares are designed around it. And keep the material split in mind when budgeting, as the dry-carbon show panels cost more per piece while the FRP structure carries the width and the paint.

Frequently asked questions

Will the CMST widebody kit fit my BMW 5 Series?

The kit is designed for the F10-generation 5 Series saloon, built from roughly 2010 to 2017. The F10 body is shared across the 520i through 535i and the F10 M5, so the panels are shaped to that generation specifically. Confirm your car is an F10 saloon before ordering, as the earlier E60 and later G30 5 Series use different bodies.

How much wider does the widebody kit make the car?

CMST's F10 widebody flares add about 5cm of width per side at the front and 6cm per side at the rear. That extra width is what lets the car run a wider track and broader tyres for a more planted footprint, and it is why the wheel offset and tyre size need to be confirmed before the arches are fitted.

Why are some pieces carbon fibre and others FRP?

Dry carbon fibre is the lightest and stiffest option and carries a visible twill weave under clearcoat, so CMST uses it for the show panels: the front lip, corners, bonnet, side-skirt lips, rear lip and wing. FRP (fibreglass-reinforced plastic) forms the deep arch flares, fenders, side skirts and bumpers more economically and takes paint cleanly, which suits parts that are colour-matched to the body anyway.

Does the carbon rear wing need holes drilled in the boot?

No. The CMST F10 rear wing is an adhesive-mount design that bonds to the boot lid with high-strength automotive adhesive rather than bolting through it. That keeps the boot skin sealed against water and makes the install effectively reversible, though correct surface preparation by the fitter is essential for a lasting bond.

How does the SUS304 valved exhaust work?

The system is built from SUS304 stainless steel, a corrosion-resistant grade, and finished with carbon tips. An electronically controlled valve stays closed at low load to keep the car quiet around town, then opens under harder driving to improve flow and let more of the engine's sound through. It gives you a quiet commute and a louder note on demand from a single exhaust.

Should I have the kit professionally fitted in Australia?

Yes. A widebody conversion involves brittle carbon and FRP panels, colour-matched paint, and wheel-and-tyre clearance that all need a body shop and an experienced fitter. Professional fitment protects the parts, gives the clean flush result the kit is designed for, and lets the workshop set ride height and alignment to suit the wider track.

Build your F10 widebody with AME Motorsport

If you are putting together a carbon widebody package for a 2010–2017 BMW 5 Series F10, AME Motorsport can supply the CMST pieces and advise on staging the build with your painter and workshop. Start with the full CMST BMW body kit range, then get in touch to confirm fitment and the right wheel-and-tyre package for the widebody arches.