Purchasing or renting a car often confronts the owner with the question of expanding the useful volume for transporting goods. A standard trunk may not be enough for large items such as skis, bicycles, a boat or a large travel box. It is at this moment that the driver begins to look for information about the names car roof bars and what function they perform. In everyday life, this design is often referred to simply as “arcs”, “sticks” or “crossbars”, but the technically correct name is roof rack or cross members.
Understanding the correct terminology is necessary not only for a competent dialogue with salespeople in car dealerships, but also for the safe selection of accessories. The design can consist of various elements, such as longitudinal guides and removable cross members. It is important to distinguish between them so as not to buy the wrong kit, which cannot be installed on a specific model body.
In this article we will look in detail at what a cargo securing system consists of, what types of installation exist, and what to look for when purchasing. You will learn why some cars require special adapters, while others require standard adapters. A key parameter when choosing is the type of roof your car has: the presence or absence of factory gutters, roof rails or fixing points. The wrong choice can result in damage to the paintwork or, worse, loss of the load at high speed.
Terminology: roof rails, crossbars and arches
The first thing a car enthusiast encounters is confusion in names. When they say "arcs", they most often mean cross members. These are horizontal elements that span the roof from one side to the other. It is on them that boxes, baskets or special holders for sports equipment are subsequently attached. However, the crossbars themselves are not always installed directly on the metal.
If your car already has fixed or removable longitudinal guides installed along the roof, then they are called roof rails. Rails are part of the body structure or a standard addition, and it is to them that the cross members are attached. Owners of crossovers and station wagons often see them immediately after purchasing a car. Owners of sedans or hatchbacks may have hidden mounting points or a smooth roof.
There is also the concept of “integrated roof rails,” which are low arches that fit tightly to the roof surface. They require special crossbars with a unique type of grip. Luggage system assembled - it is always a combination of longitudinal elements (if any) and transverse arcs. Without understanding this difference, it is easy to make a mistake when ordering a kit through an online store.
⚠️ Caution: Do not attempt to attach crossbars to roof decorations unless they are designed to bear the load. This can cause plastic parts to come off and cause serious damage to the body while driving.
Once you understand the terms, it’s easier to navigate through manufacturers’ catalogs. The main elements are always supports (hooks), arcs (pipes) and a fastening mechanism. Modern systems often use an airfoil that resembles an inverted letter A or an airplane wing, which reduces noise when moving.
Types of fastening of arches to the car body
Choosing the right type of fastening is 90% of the success in using the trunk. Auto accessory manufacturers have developed many solutions for different roof configurations. The most common option for modern cars is mounting in regular places. There may be hidden plastic plugs on the roof with threaded holes underneath. By removing the plug, you can screw the roll bar supports directly into the body.
For cars without roof rails and standard openings, a doorway mount is used. In this case, the trunk feet have special rubber stops that fit under the door seal. When the mechanism is tightened, the paw is securely fixed to the side of the roof. This is a universal method that is suitable for most sedans and hatchbacks produced in recent decades.
If longitudinal rails are installed on the roof, the task is simplified. The crossbars have special “feet” with clamps that cover the railing from below or from above. It is important that the clamp profile matches the shape of the railing: round, oval or rectangular. Some systems allow you to adjust the working width, which makes them universal.
Separately, it is worth mentioning the mounting on gutters. This is an old but still relevant type for some SUVs and classic models. The arch supports have a screw clamp that engages the gutter along the roof. This method is considered one of the most reliable, since the load is transferred to a powerful power element of the body.
Manufacturing materials and aerodynamics
The durability and appearance of the arcs directly depend on the materials. The classic option remains steel. Steel bars are usually powder coated or chrome plated. They are cheap and durable, but are susceptible to corrosion if the coating is damaged and are heavy. In addition, the round steel profile creates significant noise at speeds above 80 km/h.
More modern and popular material - aluminum. Aluminum arches do not rust, are lighter than steel and often have a more aesthetic appearance. They can be anodized or painted matte black. Aluminum allows you to create complex profiles that improve aerodynamics. The drop-shaped cross section of the arc helps the air flow around the structure with minimal resistance.
There are also arches made of composite materials or plastic with a metal core. They are used in specific systems where weight or design is important. However, the base still remains metal. When choosing, you should pay attention to the quality of the plastic at the fastening points: it must be frost-resistant and not crack in the cold.
To reduce noise, choose arches with an aerodynamic profile (wing-shaped) and be sure to install them across the roof, and not along it, if the design allows it.
Aerodynamic whistling is the main problem with cheap square bars. If you plan to frequently drive on the highway with a luggage rack, the overpayment for the aero profile will be compensated by the comfort in the cabin. Some manufacturers even conduct wind tunnel tests to prove the low noise levels of their products.
Load capacity and weight distribution
One of the most critical parameters is lifting capacity. Many drivers mistakenly believe that if the bars can withstand 100 kg, then the car will carry the same amount. This is wrong. The limitation is imposed by the car itself, or rather by the roof and mounting points. The vehicle instructions always indicate the maximum weight of cargo on the roof.
Typically, the static load (when the car is stationary) can reach several hundred kilograms, but the dynamic load (in motion) is limited to 50–75 kg for most passenger cars. This weight includes the mass of the arches themselves, the box and the load. Exceeding the limit can lead to deformation of the roof, detachment of fasteners or a change in the center of gravity, which is dangerous for handling.
| Vehicle type | Typical load (kg) | Features |
|---|---|---|
| Sedan (C-class) | 50 - 60 | Fastening to a doorway, uniformity is important |
| Station wagon / Crossover | 75 - 100 | Often there are roof rails, the load is higher |
| SUV | 100 - 150 | Powerful regular places or gutters |
| Minivan | 70 - 80 | Large roof area but weak attachment points |
Weight distribution also plays a role. Heavy objects should be placed closer to the center of the roof and closer to the front axle, but not above the windshield, so as not to block the view. The load must be securely secured with ratcheting straps. Using nets over the load will prevent it from falling out during heavy braking.
What happens if you exceed the load?
If the dynamic load is exceeded at high speed, arches may be torn off, doorways may be deformed, and, most dangerously, the vehicle may suddenly roll when turning due to a shift in the center of gravity.
Installation and Safety Guidelines
Installation of arches is a procedure that requires care. Before installation, the roof must be thoroughly washed and degreased. Grains of sand or dirt under the support can scratch the varnish when tightened or vibrated in transit. The rubber pads on the paws must be clean and intact. If they are worn out, it is better to replace them to avoid metal sliding on the body.
Fasteners must be tightened to the torque recommended by the manufacturer. Insufficient force will cause the arches to slip, while too much force can damage the door seal or deform the thin metal of the roof. After installation, be sure to check the tightness of the screws for the first 100–200 km, as new parts may “shrink” a little.
When driving with a load, the dimensions of the vehicle change. Don't forget about heights: driving into an underground parking lot or driving under low bridges can be fatal for the luggage box and roof. The windage also increases, so side winds become more dangerous. The braking distance of a car with a loaded roof also increases.
☑️ Check before departure
⚠️ Attention: Remove the archwires when not in use. Constant operation increases fuel consumption by up to 15% due to aerodynamic drag, even if the trunk is empty.
Review of popular brands and models
The car accessories market offers solutions from budget to premium. The leader of the segment is the Swedish company Thule. Their products are distinguished by high quality, excellent aerodynamics and a wide range of models for specific cars. However, the price of such arches can be comparable to the cost of a budget car.
Another famous brand - Atlant (Russia) and Amos (Poland). They offer more affordable alternatives. The quality of their products varies, but for seasonal use (for example, only in the summer for vacation) they are quite suitable. It is important to monitor the quality of painting and the condition of rubber seals.
Chinese manufacturers are now actively occupying a niche, offering copies of well-known brands. When purchasing such arches, you should pay attention to the certificates of conformity and the actual load capacity. Often stated characteristics may not correspond to reality. It is better to choose a proven manufacturer with an average price than to risk the cargo for the sake of saving.
When choosing, also consider compatibility with additional equipment. If you already have a box or bike racks of a certain brand, it is logical to choose arches of the same system or universal ones with standard grooves T-slot. This will simplify the installation of accessories without the use of unnecessary adapters.
The optimal choice is a balance between cost and frequency of use: for rare trips, a universal kit will suffice; for regular trips, it is better to invest in model bars with ideal aerodynamics.
Is it possible to make roof arches with your own hands?
Theoretically, it is possible to weld a structure from a profile pipe, but this is highly not recommended. Homemade arches are difficult to make aerodynamic and safe. The risk of corrosion, improper load distribution and roof damage is too great. The cost of factory-made universal arches is now affordable, which makes independent production economically and technically infeasible.
How to reduce noise from arcs at high speed?
It is difficult to completely remove noise, but it can be minimized. Use airfoil arcs (teardrop shaped). Install the front bar at the level of the front doors, and the rear bar at the center of the rear window or closer to the rear edge of the roof. It also helps to install special whistle-dissectors (if they are not included in the kit), which break up the air flow.
Do I need to remove the bars to wash them in an automatic car wash?
Most modern automatic car washes (portal and tunnel) require removal of the trunk. Brushes and dryers can snag the bars, damaging them or the vehicle. You can wash a car with roll bars in self-service manual car washes, but you should be careful with the water pressure at the fastening points so as not to drive water into the interior.