Drivers planning to expand the usable space of their vehicles often look for the exact name for a sealed container that is mounted on roof rails or arches. In the professional environment and manufacturer catalogs, this element is most often referred to as autobox or airbox, which emphasizes its streamlined shape and purpose for high-speed driving. Exactly sealed plastic case is a key difference from open structures, protecting cargo from precipitation and oncoming air flow at high speeds.
There is confusion in terminology when users refer to any roof add-on as a “box”, but technically they are different devices with distinct characteristics. Thule, Atlant and Luxs They produce models that are divided into closed boxes and open baskets, and the choice depends on the type of items being transported. Understanding the differences between these designs will help you avoid mistakes during purchase and installation, ensuring the safety of your cargo.
Exact terminology: autobox, airbox or trunk?
The main name used by manufacturers and sellers of additional equipment is autobox. This term covers all closed containers made of durable plastic, most often ABS or polypropylene. The design is designed to minimize aerodynamic drag, so the second common name is airbox. Unlike metal boxes or fabric bags, such a box has high rigidity and does not require internal packaging of cargo from dust.
You may often hear the word “rack”, but it is a broader concept that includes any system for securing cargo on the roof. Open metal baskets, bike platforms and ski racks are also classified as roof racks. However, if we are talking specifically about a closed volume with a lid, then it is more correct to use clarifying terms so that there is no misunderstanding when ordering accessories.
- 🚗 Autobox - an airtight container to protect items from weather and theft.
- 🌬️ Aerobox — a model with improved streamlining to reduce noise and fuel consumption.
- 🔧 Fastening — a fixation system (paws, clamps), which can be sold separately.
It is important to distinguish between these concepts, since the type of equipment chosen will determine the roof load requirements for your vehicle. Some machine models have static and dynamic load limits that cannot be exceeded. Therefore, choosing between an open basket and a closed one autobox, always check the technical passport of the vehicle.
Design features and materials of manufacture
Modern airboxes are produced by vacuum molding from impact-resistant polymers. The most common material is ABS plastic, which combines lightness, UV resistance and frost resistance. More expensive models can be made from carbon or glass fiber reinforced polymer, which reduces the overall weight of the structure and improves aerodynamics, but significantly increases the cost.
The box lid is usually equipped with a system double-sided opening, which allows you to access things from any side of the car. This is especially convenient when parking close to other cars or the garage wall. Locking mechanisms such as Click & Go or analogues, provide quick installation without tools, securely fixing the box to the crossbars.
⚠️ Attention: Cheap models made of thin plastic can crack in the cold when hit or heavily loaded with snow. Choose boxes with a wall thickness of at least 3-4 mm.
The interior space is often equipped with stiffening ribs and places for attaching belts so that the load does not move while driving. Some manufacturers add special compartments for long items such as fishing rods or ski poles. Tightness is ensured by sealing rubber around the perimeter of the lid, which must remain elastic in all weather conditions.
Open bins vs. closed boxes
Choose between open metal basket and closed autobox depends on the nature of the trips and the type of cargo transported. The baskets are a welded structure made of steel rods or pipes, often coated with a polymer to protect against corrosion. They are ideal for transporting large items that are not afraid of moisture: construction materials, dirty equipment, fuel cans.
Closed airboxes benefit in terms of security and protection against theft, since access to the contents is only possible after opening the lock. They are indispensable for traveling with valuables, electronic equipment, clothing and groceries. Additionally, the box's streamlined design creates less noise on the track compared to an open cage that can whistle at high speeds.
Comparison of characteristics
An open basket is cheaper, but creates more noise and does not protect against rain. A car box is more expensive, but it keeps things dry and clean, and also improves the aerodynamics of the car.
When choosing, it is worth considering the seasonality of use. In winter, the open basket becomes covered with an ice crust, which is difficult to remove, and snow clogs all the cells. Plastic box in this regard, it is more practical: it is easy to brush snow off it, and the things inside will remain dry and warm. However, if you frequently carry objects with sharp corners, the risk of damaging the plastic is higher than scratching the metal.
Technical characteristics and load capacity
The key parameter when choosing is lifting capacity, which consists of the weight of the box itself and the weight of the cargo. It is important to understand that the maximum load on a vehicle's roof is limited by the manufacturer and is usually between 50 and 100 kg when in motion. Exceeding this limit can lead to deformation of the roof, damage to mounting points and, most dangerously, to poor handling and vehicle rollover.
The volume of boxes is measured in liters and varies from 300 to 900 liters. For compact city crossovers, models with a volume of 300-400 liters are optimal, while for large SUVs and station wagons, options with a volume of 600+ liters are suitable. The dimensions must correspond to the length of the roof so as not to block the view through the rear view mirror or interfere with the opening of the trunk or hatch.
| Parameter | Small box | Middle box | Big box |
|---|---|---|---|
| Volume (l) | 300 - 400 | 400 - 600 | 600 - 900 |
| Length(cm) | 120 - 160 | 160 - 190 | 190 - 235 |
| Width(cm) | 60 - 75 | 75 - 85 | 85 - 95 |
| Empty weight (kg) | 12 - 16 | 16 - 22 | 22 - 28 |
The dynamic load (while moving) is always less than the static load (while parked). This means that if the roof can support 300 kg in a parking lot, it does not allow carrying that much weight at 110 km/h. The car's center of gravity shifts upward, which increases roll in corners and braking distance. Therefore, distribute the load inside autobox it is necessary evenly, fixing heavy objects at the bottom.
Installation and safe operation rules
Installation airbox requires preliminary installation or the presence of standard crossbars (rails). The distance between the centers of the arches must comply with the requirements of the box manufacturer, usually in the range from 60 to 90 cm. Violation of this requirement may lead to the bottom of the container sagging or tearing off at high speed.
☑️ Check before travel
After installation, it is necessary to check the reliability of fixation. To do this, it is recommended to drive a few kilometers at low speed, then re-tighten the fastenings, since plastic and metal can have micro-shrinkage. During operation, the condition should be checked regularly seals and locks, lubricating them with special compounds to prevent freezing in winter.
⚠️ Attention: The driving speed with a loaded roof box should not exceed 130 km/h, and in windy weather or when transporting sailing cargo - 90-100 km/h.
Particular attention should be paid to the height of the vehicle with the load installed. The standard height of garage doors or barriers may be less than the dimensions of your car with autobox. Many drivers forget about the added 30-50 cm of height and damage the roof when entering underground parking lots. It is recommended to place a visible reminder sticker on your dashboard or windshield.
Legal aspects and restrictions of traffic rules
The traffic rules do not directly prohibit the use of autoboxes, if they are certified and installed correctly. However, there are requirements for the dimensions of the vehicle. The load should not protrude beyond the side dimensions of the vehicle by more than 40 cm (20 cm on each side) without special signs, and from the rear by more than 1 meter. If the load protrudes more than 1 meter from the rear, it must be marked with the “Large Load” sign and