Pros and Cons of Each Side Skirt Material

Side skirts are more than just cosmetic add-ons—they serve the functional purpose of smoothing airflow along the side of the vehicle, reducing lift and drag. The material you choose directly impacts performance, longevity, installation complexity, and your wallet. Below we break down each of the three common materials in detail so you can match them to your specific driving needs and budget.

Plastic (ABS / Polypropylene) Side Skirts

Plastic side skirts are the most widely chosen material for budget-conscious owners or those new to body modifications. They are typically constructed from ABS (Acrylonitrile Butadiene Styrene) or polypropylene—both thermoplastic polymers that are lightweight and corrosion-proof.

  • Cost: Lowest among the three; a set of plastic skirts can range from $60 to $200.
  • Weight: Very light (approx. 2–4 lbs per skirt); minimal impact on fuel economy.
  • Durability: Flexible and resistant to minor impacts, but prone to cracking in extreme cold or under repeated stress. UV exposure can cause fading or warping over time if not properly painted or coated.
  • Installation: Easiest to drill and mount; many sets come with adhesive tape and screws suitable for DIY work. No special tools required.
  • Customization: Can be painted with flexible primer and automotive paint, but the plastic may need surface preparation to prevent peeling. Aftermarket colors and textures (e.g., matte black unpainted) are common.

Plastic side skirts are best for daily drivers where cost and ease of replacement matter. However, they lack the rigidity required for track use or harsh environments.

Fiberglass Side Skirts

Fiberglass enjoys a sweet spot in the side-skirt world—stronger than plastic yet lighter than aluminum. Made from glass fibers embedded in a resin matrix, fiberglass can be hand-laid or compression-molded for a smooth, paintable surface.

  • Cost: Moderate; typically $200–$500 for a quality set.
  • Weight: Slightly heavier than plastic (5–8 lbs per skirt) but still manageable.
  • Durability: Excellent resistance to cracking from impacts and fatigue; does not corrode or rust. However, fiberglass is brittle under extreme point loads—a sharp curb hit can cause spiderwebbing or a break.
  • Installation: Requires more care than plastic. Fiberglass needs to be pre-drilled with caution to avoid splitting. Professional fitting is recommended for precise alignment and to prevent stress fractures during mounting.
  • Customization: Fiberglass accepts paint exceptionally well. It can be sanded, primed, and painted to match factory finishes seamlessly. Custom shapes and aggressive styling are readily available.

Fiberglass is ideal for enthusiasts who want a sporty look that can handle moderate daily driving and occasional spirited cornering. It’s also a favorite for show cars because of the smooth finish.

Aluminum Side Skirts

Aluminum side skirts represent the premium tier. Often made from 5052 or 6061 alloy, they offer unmatched durability and a metallic appearance that can either be painted or left as raw brushed metal for a rugged aesthetic.

  • Cost: Highest; expect $400–$1,200+ depending on thickness, gauge, and finish.
  • Weight: Heaviest—typically 10–15 lbs per skirt. This can add up and affect vehicle balance slightly, though the difference is negligible for most street cars.
  • Durability: Extremely high. Aluminum resists dents better than plastic and won’t crack like fiberglass. It is corrosion resistant, but bare aluminum will oxidize (patina) unless clear-coated or painted. In salty or coastal environments, proper sealing is essential.
  • Installation: Requires metal-specific tools (drill bits, rivet gun or bolts for heavy-duty mounts). Aluminum can be drilled and riveted, but alignment is critical—poor installation leads to rattles or air leaks.
  • Customization: Can be powder-coated, painted with epoxy primer, or left with a brushed finish. Because aluminum is machine-formable, you can find wider profiles and integrated aerodynamic elements (e.g., vortex generators or rock guards).

Aluminum skirts are the go-to for trucks, off-road vehicles, and drivers who frequently encounter debris, gravel, or winter road salt. They also appeal to those wanting a long-term investment with low maintenance.

Head-to-Head Comparison Table

To make your decision easier, here’s a quick reference comparing key attributes across the three materials.

Property Plastic (ABS) Fiberglass Aluminum
Cost (set) $60–$200 $200–$500 $400–$1,200+
Weight per skirt 2–4 lbs 5–8 lbs 10–15 lbs
Impact resistance Good (flexible) Very good Excellent
Corrosion resistance Excellent Excellent Good (with coating)
DIY installation difficulty Easy Moderate Hard
Paintability Requires flexible primer Excellent Requires proper prep
Longevity 5–7 years (UV/thermal degradation) 10+ years (with care) 15+ years (indefinite with coating)

Key Factors to Evaluate Before Buying

Beyond material properties, your personal driving environment and vehicle usage will determine the best choice. Consider the following factors carefully.

Driving Conditions and Environment

If you live in an area with salted winter roads, aluminum is a smart pick because it doesn’t rust. For year-round dry climates, plastic or fiberglass will hold up fine. Off-road drivers should prioritize aluminum for its dent resistance; rock chips that would crack fiberglass are shrugged off by aluminum.

Aerodynamic Goals

Side skirts serve a real aerodynamic function by sealing the gap between the front wheel well and the side of the car. Aluminum skirts can be fabricated with a deeper profile and air dams that actually reduce drag. Plastic skirts are often thinner and more decorative than functional. If you plan to track your car or optimize fuel economy, choose a material that allows precise shaping—fiberglass or aluminum.

Paint, Finish, and Style

If you want a perfect color match to your factory paint, fiberglass is the easiest to work with. Plastic can also be painted but requires special adhesion promoters. Aluminum skirts look great in a brushed or powder-coated finish, but to match a glossy paint job you’ll need a professional shop. Some drivers prefer the contrast of a black plastic or raw aluminum accent—that can simplify your choice.

Maintenance and Repair

Plastic skirts are cheap to replace entirely rather than repair. Fiberglass can be repaired with resin and mat, but the repair may be visible without refinishing. Aluminum dents can sometimes be hammered out, but cracks in aluminum require welding or replacement. Factor in the cost and effort of repairs based on your local road hazards.

Installation Complexity and Tools

If you’re a weekend wrench-turner, plastic skirts are the most forgiving. Fiberglass requires careful drilling to avoid stress cracks. Aluminum demands metal drill bits, punches, and often rivets or threaded inserts. A professional install for fiberglass or aluminum can add $100–$300 to the total cost but ensures proper fitment and durability.

When to Choose Each Material: Scenarios

To help you visualize, here are three typical use cases and the material that fits best.

Scenario 1: Budget Daily Driver – Choose Plastic

You own a 2015 Honda Civic and want a subtle ground-effects look without breaking the bank. Plastic side skirts cost under $100, are easy to install with self-tapping screws, and if you scrape a curb, you can replace them for another $80. This is sensible for commuting and parking lot duties.

Scenario 2: Weekend Street/AutoX Racer – Choose Fiberglass

Your 2005 Mazda Miata sees spirited canyon runs and the occasional autocross. You need skirts that are lightweight, can be painted Brilliant Black, and will not flex at speed. Fiberglass offers the rigidity and smooth finish you want. You’ll have them professionally fit to avoid cracking and trust them for years of fun.

Scenario 3: Truck or Off-Road Rig – Choose Aluminum

Your 2020 Ford F-150 Raptor frequently traverses gravel roads and rock fields. Aluminum side skirts can take abrasion and small stone impacts without failing. They also match the truck’s utilitarian aesthetic. Spend extra on a powder-coated finish to prevent oxidation, and you’re set for the life of the vehicle.

Installation Tips for Each Material

Proper installation is critical for both function and form. Here are practical notes for each material.

  • Plastic: Use low-tack tape to hold the skirt in place while drilling. Pre-drill pilot holes to prevent the plastic from splitting. Use corrosion-resistant screws. After installation, seal the edge with silicone to prevent water ingress.
  • Fiberglass: Always test-fit and mark mounting points. Drill from the front side into the metal—never from the back into fiberglass (to avoid chipping). Use rubber grommets between the skirt and body to reduce vibration. Paint both sides before installation to seal against moisture.
  • Aluminum: Use a step-bit or sharp metal drill bit with cutting oil. Clamp the skirt securely to avoid shifting. Use stainless steel rivets or bolts with nylon lock washers. Consider adding a rubber edge trim to protect the paint.

For all materials, ensure the rocker panel mounting surface is clean and free of rust or debris. Use a rust inhibitor if necessary.

Long-Term Value and Resale Considerations

While plastic side skirts are cheap initially, they may look faded or cracked after a few years. Fiberglass skirts hold their value better if undamaged. Aluminum skirts, if properly maintained, can even outlast the car and be transferred to a new vehicle. However, note that some buyers prefer OEM looks, so heavy modifications may not always boost resale value.

Expert Recommendations

Based on feedback from body shops and performance builders, here are summary recommendations.

  • For a strictly cosmetic daily driver with minimal risk: Plastic is fine. Save your money.
  • For a car that sees regular performance or show use: Fiberglass is the sweet spot – light, strong, paint-friendly.
  • For trucks, SUVs, or vehicles exposed to road salt/gravel: Aluminum is the clear winner for durability.

Pro tip: If you’re still uncertain, buy a set of used factory plastic side skirts from a salvage yard for under $50 and test fit for shape and clearance. Once you confirm the design, then invest in fiberglass or aluminum for the final set.

Final Thoughts

Plastic, fiberglass, and aluminum side skirts each serve a purpose. Plastic gives you a low-cost entry point. Fiberglass offers the best combination of weight, paintability, and durability for most performance applications. Aluminum provides unmatched toughness for harsh environments and long-term ownership.

Remember: The best side skirt is one that fits your vehicle’s use case, your budget, and your tolerance for maintenance. Investing time in proper installation and care will extend the life of any material you choose.