Noise inside a car is not just discomfort, but a factor that significantly increases driver fatigue and reduces concentration. Many owners of cars, especially those in the budget and mid-size segments, are faced with the hum that the wheel arches emit when driving on a highway or uneven asphalt. The source of this sound is often plastic fender liners, or lockers, which resonate from gravel impacts and wheel vibrations. High-quality sound insulation of these elements can radically change the driving experience, making the interior quieter and more comfortable.
However, this process requires not only accuracy, but also the correct selection of materials. The wrong choice of components can lead to moisture accumulation, metal corrosion, and even peeling of the coating after a couple of months of use. In this article, we will look in detail at how to make noise with lockers, what modern solutions exist, and how to do the job so that the result will please you for many years.
Before you start purchasing materials, you need to understand that soundproofing wheel arches is a complex task. It includes not only the suppression of airborne noise from tires, but also the fight against vibrations of the metal of the body itself. Vibration absorption and soundproofing are different physical processes, and their implementation requires different types of coatings. Ignoring this principle will nullify all efforts.
Nature of noise and requirements for materials
Wheel arches are exposed to perhaps the most severe operating conditions among all elements of the car body. Constant temperature changes, exposure to moisture, salt, reagents, impacts of gravel and sand - all this destroys conventional finishing materials. This is why standard solutions for soundproofing doors or roofs will not work here. The material for lockers must have high adhesion, moisture resistance and resistance to mechanical damage.
The main source of noise in the arch area is the impact of small stones and gravel on the metal and plastic of the fender liner. This sound is transmitted to the body, causing resonance. The second component is aerodynamic noise and hum from tire rolling. To combat the first type of noise, heavy and dense materials that dampen vibration are needed. For the second - porous structures that scatter the sound wave.
⚠️ Attention: The use of conventional construction insulation or cotton wool in wheel arches is strictly prohibited. These materials are hygroscopic; they instantly absorb moisture, turning into a breeding ground for corrosion and mold, completely losing their insulating properties.
The most important parameter when choosing is the operating temperature. In summer, the surface of the metal under the arch can heat up to 80-90 degrees, and in winter it can cool to extremely low values. Cheap bitumen vibration isolators can crack and fall off in the cold, and when heated, they can leak, emitting an unpleasant odor into the interior. Therefore heat resistance is a key selection criterion.
Review of materials: vibration isolation and noise absorption
The market for auto tuning materials offers a wide range of solutions, but not all are suitable for wheel arches. The leaders in this segment are composite materials based on bitumen or mastic with an aluminum or polymer coating. They provide the necessary weight to dampen the resonant frequencies of the metal and create an airtight barrier.
For the top layer, which is applied over vibration isolation or directly onto the plastic of the locker, liquid compounds or dense sheets with a closed cell structure are best suited. Liquid sound insulation is good because it fills all the cracks and hard-to-reach places, creating a monolithic layer. Sheet materials are easier to install and have a predictable thickness.
Let's compare the main types of materials suitable for this task:
| Material type | Main function | Pros | Cons |
|---|---|---|---|
| Vibroplast (bitumen + aluminum) | Vibration absorption | Ease of installation, accessibility | Less effective in high heat |
| Vibroplast (mastic+aluminium) | Vibration absorption | High efficiency, heat resistance | More weight, harder to cut |
| Liquid sound insulation | Sound insulation + anticorrosive | Tightness, anti-corrosion properties | Long drying time, requires a compressor |
| Splen (SPE) | Thermal and sound insulation | Does not absorb moisture, lightweight | Low effectiveness against low frequencies |
Materials with foil layer. They not only dampen vibrations, but also reflect thermal radiation from brake discs and hot asphalt, which is especially important in the summer. However, if the foil comes into contact with the body where the paint has chipped, it can cause galvanic corrosion, so having an adhesive layer on both sides or proper insulation is critical.
The secret to the durability of the coating
For maximum metal protection, before gluing vibration insulation, it is recommended to treat the surface with a degreaser and apply a thin layer of anti-corrosion primer. This will prevent rust from appearing under the layer of material, even if adhesion is broken at one point.
Surface preparation: the key to success
The quality of surface preparation determines 80% of the success of the entire operation. Even the most expensive and effective material will not adhere to dirty, rusty or greasy metal. The process begins with removing the wheels and plastic fender liners. In some car models, access to the arches is possible only after removing the bumpers or suspension elements, which should be taken into account in advance.
After dismantling the lockers, it is necessary to thoroughly clean the metal part of the arch from dirt, sand and old anti-corrosion treatment. You can use a high-pressure washer for this, but the metal must be perfectly dried afterwards. The presence of moisture under the vibration insulation layer is unacceptable. The next stage is degreasing. Use special anti-silicones or White spirit, avoiding aggressive solvents that can damage the factory paintwork.
If pockets of corrosion are found on the metal, they must be cleaned to bare metal, treated with a rust converter and primed. Only after this can you begin to apply insulating materials. Don’t forget about the inside of plastic lockers - they also need to be washed and degreased if you plan to glue material to them.
☑️ Checklist for preparing for sound insulation
It is important to ensure good ventilation in the work area as degreaser fumes can be toxic. It is also worth protecting the brake mechanisms and suspension elements from contact with chemicals or pieces of materials if the work is carried out in an assembled state.
Vibration insulation technology
The first layer of the noise insulation “pie” is always a vibration-absorbing material. Its task is to increase the mass of the metal panel and change its resonant frequency, turning a ringing sheet of metal into a dull, inert surface. For wheel arches, it is recommended to use materials with a thickness of 2 to 4 mm. Thinner sheets may not give the desired effect, and too thick ones will create excess load on the body.
The application technology requires heating the material. The bituminous or mastic base becomes elastic and sticky at a temperature of 40-60 degrees Celsius. To do this, use a hair dryer. Do not overheat the material to the point of boiling or losing its shape, it should simply become soft. Glue the sheets with an overlap of 10-15 mm, carefully rolling them with a hard roller. Rolling is a critical step: it removes air bubbles and ensures tight contact with the metal.
Do not try to cover 100% of the arch surface. The optimal coverage is 70-80%. The remaining areas will allow the metal to “breathe” and will not create closed cavities where moisture can condense. Pay special attention to the areas around the fender liner fastenings and the service holes - it is better to close them completely to cut off the penetration of noise from under the wheels.
Use a stitching roller with a hard working surface. Soft rollers will not be able to squeeze out air from under heavy mastic, which will lead to the appearance of bubbles and a decrease in the effectiveness of vibration isolation.
After cooling, the material should become solid and monolithically connected to the body. Check the quality of adhesion by tapping the surface: there should be no ringing areas. If the material peels off or “plays,” the procedure must be redone, since there is no point in such protection.
Final sound insulation and locker protection
The second stage is the application of a noise-absorbing layer. Here the choice depends on what you are using: sheet materials or liquid sound insulation. Sheet materials such as Blockator or analogues based on closed-cell polyurethane foam, glued on top of vibration insulation. They work as a barrier, reflecting and absorbing sound waves. It is important that this material is also moisture resistant.
Liquid sound insulation is applied by spraying. This creates a seamless layer that provides excellent protection against gravel impacts. For application you will need a compressor and a spray gun. The material is applied in several layers (usually 3-4) with intermediate drying. Each layer must dry for a certain time, specified by the manufacturer, so that bubbles and “craters” do not form.
If you are working with plastic lockers, you can also glue them on the inside. This will reduce the rattling of the plastic itself and reduce the overall noise level. For plastic, it is better to use lighter vibration materials so as not to weigh down the structure that is attached to the pistons.
⚠️ Attention: When applying liquid noise insulation, be sure to cover all adjacent body elements, glass and chrome parts with masking tape and film. It is almost impossible to clean the hardened polymer composition from the paintwork without damaging the paint.
The final result depends on an integrated approach. The combination of heavy vibration isolation on metal and a porous or liquid layer on top gives a synergistic effect. Not only do you eliminate metal clanging, but you also cut out high-frequency tire and wind noise.
The combination of mastic vibration insulation (first layer) and liquid sound absorber (second layer) is considered the “gold standard” for wheel arches, providing maximum silence and anti-corrosion protection.
Common mistakes and how to avoid them
One of the most common mistakes is saving on materials. Cheap bitumen sheets without reinforcement with foil or mesh turn into crumbs in the cold. As a result, after one or two winters you will find that there is nothing in the arches except bare metal, which may have already begun to rust. High quality material costs more, but lasts for decades.
Another mistake is poor surface preparation. A sticker with dust or oil residue will cause the heavy layer of vibration isolation to simply slide down to the drainage holes under the influence of vibration and temperature changes. It can even block water flow, causing moisture to accumulate in hidden car body cavities.
Also, beginners often forget about technological holes. Arches often provide access to the internal cavities of the side members or sills. By sealing the outer part of the arch "tightly" but leaving the internal channels open, you create a resonator that can even increase the noise. All sound paths must be blocked.
Do not ignore the condition of the plastic fender liners themselves. If they are old, cracked or do not fit well, their replacement or repair should precede soundproofing. It is useless to make noise to the arch if the plastic locker dangles and rattles on bumps.
Is it possible to use regular mastic for sound insulation?
Conventional bitumen mastic for waterproofing foundations is not suitable for car arches. It does not have the necessary vibration-absorbing properties, may contain aggressive solvents that destroy plastic and paint, and cannot withstand the thermal expansion of metal, causing it to crack quickly.
Do I need to remove the suspension for good sound insulation?
In most cases, complete disassembly of the suspension is not required. It is enough to remove the wheels and plastic lockers. However, to access the inner surfaces of the arches in some cars, it may be necessary to remove shock absorbers or levers, which is best done in a service setting.
How long does liquid sound insulation take to dry?
Curing time depends on temperature and humidity. Typically, interlayer drying takes 30-60 minutes, and full readiness for use occurs after 24 hours. During the cold season, drying time can double.
Will the weight of the car increase after soundproofing?
Yes, the weight will increase. One arch can take from 1 to 2 kg of materials, depending on the chosen technology. For the entire car, this will add 4-8 kg, which is absolutely not critical for dynamics and fuel consumption, but will significantly improve acoustic comfort.