How to soundproof a fender liner: a complete guide

• 🛡️ Bitumen-based vibrating plasters with an aluminum foil layer - provide bulk and vibration damping.
• 🔇 Splen or Izolon with a closed cellular structure - serve as a barrier to noise and heat, do not absorb water.
• 🧱 Biplast or Accent (only if there is a guarantee of complete tightness of the external protection) - for deep sound absorption.

⚠️ Attention: Never use materials that absorb moisture (for example, ordinary foam rubber or felt without protection) directly on the metal of the arch. A wet material stops working, adds weight and becomes a source of corrosion that will be hidden from view until a through hole appears.

Necessary tools and workplace preparation

The quality of work performed depends 80% on preparation. You do not need complex industrial equipment, but a set of specific tools is required. First of all, it is necessary to provide access to the arched space. In most cases, complete processing requires removing the wheel and, often, dismantling the plastic fender liner itself.

To work you will need:

• 🔧 A set of keys and sockets (torxes or star keys are often required to attach lockers).
• 🌡️ A construction hairdryer is a must for warming up vibration materials and their high-quality rolling.
• 🖐️ Sealing roller - without it it is impossible to achieve monolithic adhesion of the material to the metal.
• 🧼 Degreaser (anti-silicone) and rags - for preparing the surface.

It is best to work on a level area with good lighting. If you plan to remove the fender liners, make sure you have a place to safely place them. Before starting active operations to clean the metal, it is recommended to cover the brake mechanisms with polyethylene so that dust and chemicals do not get on the calipers and pads.

Pay special attention to cleaning the metal. Old mastic, dirt and rust must be removed mechanically. You can use a wire brush or a soft abrasive. After mechanical cleaning, the surface is thoroughly degreased. Surface cleanliness - this is a guarantee that vibration isolation will not fall off after a month of operation.

Technology for applying vibration insulation to metal arches

The first and most important stage is applying a vibration-insulating layer directly to the metal of the body. The rule works here: the larger the coverage area and the better the rolling, the better the result. The material must be cut into convenient pieces, pre-heating them with a hair dryer until they become plastic. Hollow material will not stick well and will not be able to fill micro-irregularities in the metal.

The application process is as follows: heat a piece of material, apply it to the metal and immediately, while it is hot, begin rolling it with a roller. The movements should be from the center to the edges, expelling the air. Avoid the formation of bubbles - these are bridges for sound. In hard-to-reach places where it is difficult to reach with a roller, you can use a wooden spatula or a tool handle wrapped in rags.

For arches, materials with a thickness of 2-3 mm are usually used (for example, Vibroplast M2 or analogues). Thicker sheets (4-5 mm) may be too heavy and difficult to install on curved arch surfaces, although their efficiency is higher. If you are using thick material, be sure to heat it thoroughly.

After pasting the main part, do not forget about the internal stiffeners and hidden cavities where you can reach. Treating these areas reduces the overall resonance of the structure. However, do not try to push the material where it will interfere with the installation of the plastic fender liner or disrupt the fit.

Protection of plastic fender liners (lockers)

Plastic arch liners are often ignored, considering them simply protection against dirt. However, it is they, vibrating in the air flow and receiving impacts from stones, that create a significant part of the noise. Processing of lockers is divided into two directions: sound insulation of the inner side (facing the body) and protection of the outer side.

It also makes sense to stick sheets on the inside of the plastic vibration isolation. This will make the plastic heavier, remove its own ringing sound and prevent rattling in the places where the clips are attached. For the outer side, which faces the wheel, vibration isolation is not suitable - it will quickly wear off. Here it is better to use liquid fender liners or special mastic coatings that absorb the impact of gravel.

If you do not plan to use liquid noise insulation, you can cover the outside of the locker with thick splen or foil material, but this is a temporary solution. A more professional approach is to use ready-made soundproofing pads for fender liners, which are sold for specific car models, or to make such pads yourself from a dense rubber-like material.

Application of the second layer and final assembly

The second layer is traditionally sound absorber. On arches, foil splen or isolon with a thickness of 4-8 mm is most often used. It acts as a barrier, reflecting remaining noise, and serves as additional thermal insulation. It must be glued on top of the vibration insulation, carefully smoothing it out.

When installing the second layer, it is important not to block the technological openings if they are provided by the design for water drainage. There should always be drainage at the bottom of the arch. If you accidentally seal the drainage hole with a vibrator, be sure to cut it with a knife before installing the locker. Stagnation of water in the arch is guaranteed corrosion.

Final assembly requires care. The fender liners, weighted with sound insulation, can fit tighter, so the holes for fasteners sometimes have to be drilled out a little or longer screws must be used (but without fanaticism, so as not to pierce the body through). Check that nothing rubs against the wheel when turning the steering wheel all the way.

⚠️ Attention: When assembling, make sure that the wiring going to the ABS sensors or arch lighting (if any) is not pressed or pinched. Vibration can quickly wear down the insulation of wires, leading to a short circuit.

Common mistakes and how to avoid them

One of the most common mistakes is trying to save money on degreasing. Dust, invisible to the eye, reduces the adhesion of the glue significantly. As a result, after a couple of seasons the vibration insulation begins to peel off in pieces, creating even more noise than before treatment. Degreasing must be thorough, to the point of creaking.

The second mistake is using materials not intended for outdoor use. Some craftsmen glue interior materials into the arches (for example, cheap foam rubber or acoustic felt without a moisture-resistant layer). Under arch conditions, such materials are instantly saturated with water, freeze in winter and rot. Use only closed cell or foil/film protected materials.

The third mistake is careless rolling. Many people think that simply gluing a sheet of paper is enough. But without careful rolling with a roller, the material does not work as a single mass with the metal. The vibrations continue and the effect is minimal. Spend time on quality rolling of every square centimeter.

The effect of sound insulation on corrosion resistance

Properly performed sound insulation of arches is a powerful anti-corrosion barrier. Vibromaterial completely blocks the access of oxygen and moisture to the metal, preserving it. Even if a microscopic pocket of rust remains under the material, without air access it will not develop further.

However, if the technology is broken and water gets under the material (through poor-quality edges or holes), hidden corrosion begins. The metal rusts under a layer of vibration, and you will only know about it when a through hole appears. That is why it is so important to properly prepare the surface and seal the edges of the sheets.

For maximum protection, vibration isolation can be combined with anti-corrosion compounds. First, the metal is treated with a rust converter (if necessary) and primer, then vibration insulation is glued, and the joints and edges are coated with bitumen mastic or liquid fender liner. This “pie” provides protection for decades.

Regular inspection of the arches (at least once a year during washing) will allow you to notice material delaminations in time and eliminate them, preventing the development of corrosion. Remember that arches are a high-risk area, and neglecting their condition can lead to expensive body repairs.