Many motorists sooner or later face a lack of space in the standard luggage compartment of their vehicle. This problem is especially acute during long vacation trips or when transporting large cargo such as skis or bicycles. At this point, a logical question arises: what is the correct name for the trunk on top of the car and how do different designs differ from each other?
In everyday life, this design is often simply called a “roof rack,” but the technically correct name depends on the type of device. The basis is luggage system or trunk-crossbars, which are installed directly on the roof of the car. It is these transverse arcs that are the foundation for attaching any additional equipment, be it a closed container or an open platform.
If we are talking about a sealed container that is attached to the crossbars, then its correct name is autobox or luggage box. This is an aerodynamic container that protects things from precipitation and dust. There is also an open modification called a "basket" or "platform". Understanding these terminological differences will help you choose the right equipment and avoid purchasing mistakes.
Terminology: box, basket or expedition rack?
When understanding what the trunk on top of a car is called, it is important to clearly separate the concepts, since the functionality and aerodynamics of the car depend on it. The main element is luggage system (crossbars), but users most often search for the name specifically for the container. The closed type of construction, made of impact-resistant plastic, is commonly known as autobox. Its key feature is complete tightness and streamlined shape.
Open structures, which are a metal lattice with sides, are called expedition racks or just baskets. They are designed for transporting goods that are not susceptible to moisture or have a non-standard shape. For example, it is more convenient to place construction materials or dirty tools in an open basket. Unlike a box, the basket does not create such air resistance, but also does not protect the contents from rain without the use of an additional cover.
⚠️ Attention: When choosing between a box and a basket, keep in mind that the open design has a much greater effect on the noise level in the cabin at high speeds. If you plan to drive on the highway frequently, aerodynamic box will become a more comfortable solution.
There are also specialized mounts that are often confused with the main types of racks. These are holders for bicycles, skis and even boats. All of them are mounted on base crossbars. It is important not to confuse the load-bearing capacity of the car roof itself and the load-bearing capacity of the elements installed on it. Exceeding the permissible limits can lead to roof deformation or body damage.
Design and fastening elements of the luggage system
Any top mount system consists of several key components, knowledge of which is necessary for proper installation. The basis is cross members (arcs), which can be made of aluminum or steel. They are connected to the roof of the car via supports (paws), the design of which directly depends on the body type of your car.
For cars with integrated roof rails (longitudinal arches along the roof), special clamps are used. Owners of cars with a smooth roof (without roof rails) will need supports attached through the doorway or to special fixing points. Fasteners must be made of corrosion-resistant materials to withstand aggressive environmental influences.
- 🔧 Cross members: load-bearing element that transfers the load to the body.
- 🔩 Supports (feet): adapters that provide fixation on a specific type of roof.
- 🔐 Locking system: locks and latches that prevent theft and spontaneous opening.
Build quality directly affects safety. Cheap models often have play in the places where the arches connect with the supports, which causes a characteristic whistle at speed. More expensive systems such as Thule or Yakima, use sophisticated engineering solutions to minimize noise and vibration. When purchasing, be sure to check for safety certificates, for example, standard City Crash, which ensures that the trunk can withstand sudden braking.
Before purchasing universal crossbars, measure the distance between the centers of the doorways. Too short arches may not fit on wide SUVs, and excessively long ones will protrude beyond the clearances, creating a danger for other road users.
Roof types and equipment compatibility
The answer to the question of what the roof rack is called and whether it will fit on top of the car lies in the design of the roof of your car. Manufacturers distinguish several main types of roofs, each of which requires its own mounting kit. Incorrect selection of supports can lead to damage to the paintwork or even deformation of the roof metal.
The first type is a roof with integrated roof rails. In this case, the longitudinal arches fit tightly to the roof surface, there is no gap between them. To install the crossbars, special clamps are used that cover the railing from below. Second type - standard roof rails with a gap. Here the longitudinal arches are raised above the roof on supports, which allows you to pass the fastening element under them.
The third option is a smooth roof without any elements. Here, installation is carried out either through the doorway (over the upper edge of the door), or at special fixing points (fixed points), hidden under decorative plugs. The fourth type is roofs with grooves (found on older car models), where the mount is inserted directly into the channel.
| Roof type | Support mounting type | Difficulty of installation | Risk of paint damage |
|---|---|---|---|
| Smooth (without rails) | Through the doorway / Fixed points | Average | High (requires rubber pads) |
| Integrated roof rails | Clamps | Low | Low |
| Standard roof rails (with clearance) | Grasping paws | Low | Low |
| Grooves (T-slot) | Groove insert | Low | Medium (risk of corrosion) |
When installing on a smooth roof through a doorway, it is critical to set the clamping force correctly. Excessive force can damage the door seal, while too little force can cause the load to shift. Always use a torque wrench if the support design provides one, or follow the instructions for the number of screw turns.
Load capacity and aerodynamics
One of the most important parameters that is often ignored is static and dynamic lifting capacity. The dynamic load capacity is the weight that the rack can carry while the vehicle is moving. Typically this figure ranges from 50 to 100 kg, including the weight of the luggage system itself. The static load capacity (weight when stationary) can reach several hundred kilograms, which is important, for example, when installing motorhomes on the roof.
Aerodynamics plays a key role in fuel consumption. Installing a bulky basket or box increases drag, which leads to an increase in fuel consumption by 10-20%. Aerodynamic bars oval or wing-shaped tubes create less noise and have less impact on fuel economy compared to square tubes. When choosing a box shape, you should also give preference to teardrop-shaped models.
⚠️ Attention: Never exceed the maximum dynamic load specified by the vehicle manufacturer in the owner's manual. Exceeding the limit changes the center of gravity of the car, which critically reduces road stability and increases braking distance.
To minimize noise, it is recommended to install crossbars across the air movement (perpendicular to the axis of the car) and use arches with built-in spoiler or a rubber seal that dampens vibration. If you only use the rack seasonally, it is better to remove it to avoid wasting fuel.
Effect of speed on fuel consumption with luggage rack
At a speed of 90 km/h, consumption increases by about 5-10%, but when the speed increases to 120-130 km/h, air resistance increases exponentially, and excess fuel consumption can reach 20-25%. In addition, at high speeds there is an increased risk of resonant vibration, which can loosen fasteners.
Installation and Safety Guidelines
Installation of a luggage system requires care and adherence to technology. Before installation, make sure that the contact points with the body are absolutely clean. Sand or small pebbles caught under the rubber seals of the supports can act as an abrasive and leave scratches on the varnish. It is recommended to pre-wash the roof and wipe the fastening points dry.
The installation process usually begins with arranging the crossbars at the required distance. It is important to maintain symmetry: the distance from the front edge of the arc to the edge of the roof on the left and right should be the same. After preliminary fixation, it is necessary to check the tightness of all screws. Many modern systems are equipped tension indicators (for example, a green window), which indicate that the effort is sufficient.
- 🚗 Distribute the load evenly, put heavy things down.
- 🔒 Be sure to use straps or nets to secure the load inside the basket.
- 👀 Check the reliability of the fastening after the first 10-20 km of the journey.
When transporting long cargo (boards, pipes, skis), they must protrude beyond the dimensions of the vehicle no more than 1 meter from the rear and be marked with a red flag or a lantern if they cover the standard optics. Lateral overhang is usually prohibited or strictly limited by traffic regulations.
☑️ Check before departure
Luggage system care and storage
In order for the trunk to serve for a long time and not lose its appearance, it must be looked after. Metal elements, especially welds on baskets, are susceptible to corrosion. Wash the system regularly with a soft sponge and car shampoo. Do not use abrasive powders or hard brushes, which may damage the protective coating or plastic.
Pay special attention to the rubber seals on the supports. Over time, they may dry out or crack. To extend its service life, it is recommended to treat rubber with special conditioners (for example, silicone-based) at least twice a year. This will maintain the elasticity of the material and prevent squeaks.
If you remove the trunk for the summer or winter, store it in a dry place. It is better to keep plastic boxes disassembled or opened to avoid deformation from pressure. Metal arches should be suspended or placed on a flat surface, avoiding contact with aggressive chemicals.
⚠️ Attention: When washing a car in automatic car washes with hard brushes, the presence of a roof rack can lead to damage to both the trunk itself and the washing equipment. Always remove the system or choose washes with hand washing and mild chemicals.
Regular maintenance of rubber seals and checking the tightness of screws is the key to quiet driving and cargo safety over many years of operation.
Is it possible to wash a car in an automatic car wash with the trunk installed?
Most manufacturers of rack systems and car washes do not recommend driving through automatic car washes with active brushes while the rack is installed. The brushes can get caught in the bars or box, causing damage to the vehicle's paint, damage to the trunk mounts, or even damage to the wash equipment. It is safer to use self-service manual foam washes or touchless washes while maintaining spray distance.
How to stop the trunk squealing at high speed?
Whistling usually occurs due to incorrect installation of the crossbars (they should be installed with the flat side up if the profile is asymmetrical) or due to gaps in the fasteners. Try turning the arches over, changing the distance between them, or using special aerodynamic pads (spoilers). The whistle can also come from unsecured loads or open locks.
What is the maximum weight that can be loaded on the roof of a car?
The maximum weight depends on two factors: the load capacity of the luggage system itself (usually 50-100 kg) and the permissible load on the roof of the car, specified in the manufacturer's instructions (often 75-100 kg dynamic load). Exceeding the limits specified in the instructions for the car is strictly prohibited.
Do I need to remove the trunk if it is empty?
From a technical point of view, an empty trunk increases fuel consumption due to poor aerodynamics and creates additional noise. If you do not plan to use it in the coming weeks, it is better to dismantle the system. This will also reduce the risk of theft (if the mounts are not secured) and reduce the height of the car, which is important when entering low garages or parking lots.