Modernizing the appearance of a vehicle or restoring its factory geometry often requires replacing standard body elements. In the modern automotive industry and tuning industry, you can increasingly see plastic fenders on cars, which are replacing traditional metal parts. This is due not only to aesthetic considerations, but also to the practical benefits that car owners who choose polymers receive.
Replacing standard metal with composite materials opens up wide opportunities for aerodynamic tuning and protecting the body from corrosion. Plastic does not rust, is easier to mold into complex geometric shapes and often costs less than original spare parts. However, the process of selecting and installing such elements has its own technical nuances, ignoring which can lead to poor-quality results.
In this article, we will analyze in detail what types of plastic are used in the automotive industry, how to choose the right arches for your model, and whether it is worth undertaking the installation yourself. You'll learn the differences between ABS plastic, fiberglass and polyurethane, and get practical tips for preparing surfaces for painting.
Advantages of polymer arches over metal
The main enemy of metal body elements is corrosion, which inevitably occurs when the paintwork is damaged. Plastic wings are completely free of this drawback, since polymers are chemically inert to the effects of water, reagents and salts. This is especially true for vehicles operated in harsh climates or on roads with aggressive chemical coatings.
In addition to corrosion properties, polymer parts have high elasticity. In the event of small collisions or impacts from branches, plastic can be deformed and return to its original shape, while metal will receive a dent that requires straightening. The weight of the part also plays an important role: reducing the weight of body elements has a positive effect on fuel efficiency and acceleration dynamics.
⚠️ Attention: Despite their flexibility, some types of plastic become brittle at low temperatures. It is not recommended to carry out installation or aggressive car washing at temperatures below -15°C.
From a tuning point of view, plastic gives designers unlimited creative freedom. You can create body kits of any complexity that cannot be made from a sheet of metal without expensive stamping. ABS plastic and polyurethane make it possible to replicate complex shapes with high precision, ensuring perfect repeatability of geometry.
Material overview: ABS, polyurethane and fiberglass
Not all plastic fenders are created equal, and understanding the differences between materials is critical to making the right choice. There are three main types of composites on the market, each of which has unique physical and mechanical properties. The wrong choice of material can lead to the part bursting in the cold or melting in the sun.
ABS plastic (acrylonitrile butadiene styrene) is the most common material for factory and high-quality tuning elements. It has high impact strength, scratch resistance and good temperature characteristics. ABS parts are easy to paint and sand, behaving almost identically to metal when painted.
Polyurethane is characterized by exceptional elasticity. If you are looking for fenders that are almost impossible to break in a minor accident, then this is your choice. However, polyurethane is more difficult to process: it requires special primers and paint adhesion additives, otherwise the coating may peel off over time. Fiberglass (fiberglass) is a material for exclusive tuning, allowing you to create any shape, but it is fragile when subjected to pinpoint impacts.
The Secret to Fiberglass's Durability
The quality of glass fiber directly depends on the vacuum infusion technology. Cheap, hand-made options often have voids and uneven resin impregnation, which leads to delamination and cracks after a year of use.
When choosing a material, you should take into account not only the price, but also the operating conditions. For daily driving, it has the optimal balance of strength and maintainability. ABS plastic. It combines the rigidity necessary to maintain geometry with enough elasticity to absorb small impacts.
Criteria for choosing quality wings
Buying low-quality body parts means you risk spending double the amount on remodeling and painting. The market is overflowing with offers, and it can be difficult to visually distinguish good plastic from a cheap analogue. There are a number of signs by which you can determine the quality of a product even before payment.
First of all, pay attention to the geometry and seating. A high-quality plastic fender should perfectly follow the contours of the body for which it is intended. The gaps between the door, hood and fender should be uniform. If during fitting (even visually) strong distortions are visible, it means that the matrix used to make the part is of low quality or is distorted.
- 🔍 Check the back of the part: the surface should be relatively smooth, without protruding fibers (in the case of fiberglass) or large holes.
- 🔍 Try to press lightly on the part: good plastic should spring, and not crunch or sag like plasticine.
- 🔍 Assess the thickness of the walls: it should be uniform over the entire area, thinning in the corners is unacceptable.
Also an important criterion is the presence of a soil layer. Many fenders are sold in black, already coated with primer. This speeds up the process of preparing for painting, but requires checking the quality of the primer itself. It should not crumble when held with a finger and should have a homogeneous structure without bubbles.
Ideal seat geometry is more important than material. A crooked wing made of expensive polyurethane will spoil the appearance of the car more than a straight wing made of budget ABS.
Comparative table of material characteristics
To systematize the data and simplify the choice, we provide a comparative analysis of the main characteristics of the materials. This table will help you quickly navigate the advantages and disadvantages of each type of plastic in the context of the specific tasks of the car owner.
| Characteristics | ABS plastic | Polyurethane | Fiberglass |
|---|---|---|---|
| Impact resistance | High | Very high | Low (fragile) |
| Elasticity | Average | High | Missing |
| Difficulty painting | Low | High | Average |
| Price | Average | High | Various |
As can be seen from the table, polyurethane wins in strength, but loses in the complexity of coloring. Fiberglass Great for creating unique shapes, but requires careful handling. ABS remains the "sweet spot" for most applications.
Surface preparation and painting technology
The quality of the final result depends 80% on proper surface preparation. Plastic, unlike metal, has a different adhesion (adhesion) and coefficient of thermal expansion. If you ignore special compounds, the paint will begin to chip at the first temperature changes or pressure washing.
The first step is always degreasing and washing the part. Even new fenders can be covered in factory grease or dust. After washing, it is necessary to matt the surface with an abrasive. P400-P600. This will create micro-scratches that the soil will adhere to. It is important not to overdo it and not to rub the part through, especially if it is thin.
The key is to use adhesive primer (primer) for plastic. This is a special composition that is applied in a thin layer before the main acrylic primer. It penetrates the polymer structure and creates a reliable bond between the flexible base and the rigid paint layer.
☑️ Checklist for preparation for painting
After applying the primer and base (color), it is necessary to use varnish. The varnish protects the color layer from ultraviolet radiation and mechanical influences. When drying, it is important to follow the temperature conditions specified by the material manufacturer, since overheating can deform the thin plastic wing.
Installation and fastening instructions
Installing plastic fenders requires care and the right tools. Unlike metal, plastic cannot be hammered, so all holes must line up the first time. It is often necessary to drill technological holes or use new fastening points.
For fixation, special screws for plastic or bolts with wide heads are used. Metal screws for metal can split plastic when screwed in. It is recommended to pre-drill the holes with a drill of a smaller diameter, and then carefully screw in the fasteners.
The installation process is as follows:
1. Trying on the part without fasteners, assessing the gaps.
2. Marking holes with a marker through technological holes in the body.
3. Drilling holes in the wing (if there are none or they do not match).
4. Applying sealant or anticorrosive to the inside of the wing before final installation.
⚠️ Attention: Never tighten fasteners “all the way” without control. An overtightened self-tapping screw will create tension in the material, and over time a crack will form around the cap, which will spread further along the entire wing.
Use a center punch to mark holes before drilling. This will prevent the drill bit from slipping and damaging the face of the new fender.
Common mistakes when tuning and repairing
Even experienced craftsmen sometimes make mistakes when working with polymer parts. One of the most common is an attempt to glue a cracked polyurethane fender with regular glue or epoxy. Polyurethane is chemically inert, and its repair requires special two-component polyurethane-based compounds or a hot welding method.
Another mistake is ignoring temperature gaps. Plastic expands and contracts more than metal. If you fasten the wing “tightly” at several points without taking into account backlash, when heated in the sun, the part may turn “boat” or crack at the attachment point. It is necessary to use standard attachment points and not add extra ones unless absolutely necessary.
Savings on preparation materials are also common. When buying an expensive wing, owners save on high-quality adhesive primer by using a regular universal one. This leads to the fact that after six months the paint begins to peel off, especially on the edges and bends, where the stress on the material is maximum.
The myth of “eternal” plastic
There is a misconception that plastic does not require maintenance. In fact, unpainted plastic (black) quickly fades and turns gray when exposed to UV rays. It must either be painted or regularly treated with protective polymer compounds.
FAQ: Frequently asked questions
Is it possible to weld a plastic fender to a metal body?
No, welding in the traditional sense is not possible. Plastic and metal have different melting points and chemical structures. Fastening is carried out only mechanically (bolts, screws, clips) using sealants to eliminate gaps.
Do I need to remove old paint from a used plastic fender before painting?
If the old coating holds tightly and has no swelling or cracks, it is enough to matte it (make it matte) with an abrasive P400-P500. Complete paint removal is only required if there are defects or the type of previous coating is unknown.
Why can a plastic wing squeak while driving?
The creaking occurs due to friction between the plastic and the metal of the body at the points of contact. To eliminate this, vibration isolation should be glued to the contact points (flanges) or a layer of anti-corrosion compound with rubber crumbs should be applied, which will act as a damper.
How long does it take for adhesive primer to dry?
Drying time depends on air temperature and soil type. Typically, initial drying takes 10-15 minutes, but complete drying and polymerization can take up to 24 hours. Always read the instructions on the can or can of the specific manufacturer.
Is it possible to straighten a dent on a plastic fender with a hairdryer?
Yes, if the plastic hasn't burst. Heating with a heat gun makes the material elastic, and the dent can be squeezed out from the inside or pulled out with a suction cup. However, after cooling, the plastic may partially return to its original deformed shape, so the method does not always give an ideal result.