Carbon Fibre vs Fibreglass vs ABS: Which Material Is Best for Car Parts?
If you've spent any time looking at aftermarket body parts, splitters, spoilers, mirror covers, or engine bay pieces, you've probably noticed that prices vary wildly. A mirror cover set might be $40 from one seller and $170 from another. The difference usually comes down to one thing: the material it's actually made from.
There are three materials you'll run into most often: genuine carbon fibre, fibreglass (FRP), and ABS plastic. Each has its place, but they are not interchangeable, and the gap in quality between them is bigger than most people realise. I deal with this topic constantly, so here's a straightforward breakdown based on what I actually see and handle.
ABS Plastic: Cheap, but You Get What You Pay For
ABS (acrylonitrile butadiene styrene) is a thermoplastic. It's the same stuff used in Lego bricks, cheap bumper bar add-ons, and most of those budget "carbon fibre look" parts you find on eBay and Amazon. It's injection moulded, which makes it extremely cheap to produce in volume.
The appeal is obvious: low price. You can pick up an ABS splitter or mirror cap for a fraction of what a carbon fibre equivalent costs. But ABS has some real drawbacks for automotive use. It's relatively heavy for its size. It warps and deforms in heat, which is a genuine concern in Australian summers where panel surfaces regularly hit 60 to 70 degrees. It also becomes brittle over time with UV exposure, especially if it's been painted or given a cheap hydro-dip "carbon" pattern.
The biggest issue I see is fitment. ABS parts are mass produced from generic moulds, and tolerances are loose. Gaps, uneven edges, and parts that need heavy modification to sit right are common. If you've ever bought a $50 "carbon fibre" lip from an online marketplace and wondered why it didn't fit, this is usually why. It's not carbon fibre at all, it's ABS with a printed pattern on it. We covered how to spot this in detail in our guide on how to tell real carbon fibre from fake.
Fibreglass (FRP): The Middle Ground
Fibreglass reinforced plastic has been used in the automotive aftermarket for decades. It's what most wide body kits, replica bumpers, and budget aero parts are made from. The manufacturing process involves laying glass fibre matting into a mould and saturating it with polyester or vinylester resin, then letting it cure.
Fibreglass is stronger than ABS and holds up better in heat. It can be sanded, filled, and painted, which makes it popular for custom body work. It's also lighter than ABS in most applications, though still significantly heavier than carbon fibre.
The downsides are worth knowing about. Fibreglass is prone to cracking on impact rather than flexing, so a knock that would dent a metal panel or flex an ABS piece will often crack or shatter a fibreglass part. Surface finish out of the mould is usually rough and needs a fair bit of prep work before paint. And while fibreglass is fine for large body panels where some extra weight isn't critical, it doesn't offer the stiffness-to-weight ratio that makes carbon fibre so appealing for performance-oriented upgrades.
For things like replacement bumpers or wide body conversions where the part will be fully painted anyway, fibreglass is a reasonable choice. But for visible accent pieces, engine covers, splitters, and anything where you want the material itself to be the visual feature, it's not the right pick.
Genuine Carbon Fibre: Why It Costs More and Why It's Worth It
Carbon fibre composite is woven carbon filament set in epoxy resin, and the result is a material that's dramatically lighter and stiffer than both fibreglass and ABS. A well-made carbon fibre part will typically weigh 40 to 60 percent less than an equivalent fibreglass piece, and it's stronger in the directions that matter for automotive stress.
But not all carbon fibre is equal. The manufacturing method makes a huge difference. We broke down the differences between dry carbon prepreg and wet layup carbon fibre in a separate post, and it's worth reading if you want to understand why two "carbon fibre" parts can feel completely different in hand.
At RB Innovations, every part is genuine woven carbon fibre, either 2x2 twill weave or forged/dry carbon. Each piece is vacuum bagged and heat cured for proper resin consolidation, then finished with a UV-resistant gloss clear coat. That UV protection matters more than people think, especially in Australia. Without it, carbon fibre parts will yellow and degrade within a year or two of sun exposure. If you want to know how to keep your parts looking sharp over time, we put together a full guide to caring for carbon fibre parts.
The trade-off is price. Genuine carbon fibre parts cost more than fibreglass or ABS because the raw materials are more expensive, the manufacturing process is slower and more labour intensive, and the finishing requires multiple stages. But the result is a part that looks better, weighs less, lasts longer, and actually fits properly.
Quick Comparison at a Glance
| ABS Plastic | Fibreglass (FRP) | Carbon Fibre | |
|---|---|---|---|
| Weight | Heavy | Medium | Very light |
| Strength | Low | Moderate | High |
| Heat resistance | Poor, warps easily | Good | Excellent |
| UV durability | Poor | Moderate | Excellent (with clear coat) |
| Surface finish | Smooth but plain | Rough, needs prep | Visible weave, high gloss |
| Fitment | Often poor | Varies | Tight (quality dependent) |
| Price | Low | Medium | Higher |
| Best for | Temporary or budget builds | Full body kits, painted panels | Visible accents, performance, long term quality |
So Which Should You Choose?
It depends on what you're trying to achieve. If you're building a weekend drift car and the splitter is going to get destroyed anyway, fibreglass or even ABS might make sense. If you're putting together a show car or a daily driver where you want parts that look good and last, genuine carbon fibre is the clear winner.
The mistake I see most often is people buying cheap ABS parts thinking they're getting carbon fibre, then being disappointed when the part warps, fades, or doesn't fit. If a "carbon fibre" part costs $40, it's almost certainly not carbon fibre. Real carbon parts cost what they cost because of the materials and the work that goes into them.
For reference, our genuine carbon fibre parts start at $170 for mirror covers and range up to $650 for larger grille pieces. That includes proper UV-resistant clear coat, vacuum bagging, heat curing, and test fitting for each specific vehicle. We make parts for the Kia Stinger GT, BMW F80 M3 and F82/F83 M4, VW Golf MK7 GTI and Golf R, Ford Falcon FG/FG-X, and the Toyota GR Corolla.
The Bottom Line
ABS plastic is cheap but doesn't hold up. Fibreglass has its place for large painted panels but falls short on weight and visual quality. Carbon fibre costs more upfront but delivers on every front: lighter, stronger, better looking, and built to last if it's made properly and cared for.
If you're weighing up materials for your next upgrade, the question isn't really which is cheapest. It's which one you won't regret in twelve months.
Browse our full range of genuine carbon fibre parts at RB Innovations, or get in touch if you have questions about a specific vehicle or part.