Calculation of the maximum permissible weight of the cargo for the trailer begins with the analysis of the technical documentation of the tractor and the trailer itself, since exceeding the permitted values leads to fines or denial of insurance compensation. Owners often mistakenly believe that if a car can tow 2 tons, then the trailer can be loaded to the limit of its design, ignoring the curb weight of the vehicle itself and the load on the coupling device. Real. load-carrying capacity The difference between the total weight of the trailer and its own weight, and this parameter is strictly limited by the manufacturer and the legislation.
Ignoring technical limitations leads to the destruction of the frame, overheating of the transmission and loss of controllability of the road train at high speeds. In the technical documentation of each trailer, whether MMZ, scythia European ThuleThere are always two key numbers: the proper mass and the maximum allowed total mass. The second number determines how many kilograms you can put in the body without violating the laws of physics and traffic rules.
For legal use of the equipment, it is necessary to understand that the total weight of the road train should not exceed the parameters declared by the manufacturer of the car. If the PTS of your crossover indicates the mass of the towed trailer without brakes 500 kg, and with brakes 1500 kg, then buying a heavy trailer with a total weight of 2000 kg will require category rights "E" or make operation impossible without re-registration and changes in the design.
Categories of rights and mass restrictions
The legislation clearly regulates which vehicles and with what mass can be towed, having a standard category "B". The main criterion here is the total mass of the road train, which consists of the maximum permissible mass of the car and the maximum permissible mass of the trailer. For category B, this amount should not exceed 3,500 kg, which is a critical parameter when choosing equipment.
If you plan to transport heavy machinery or building materials, you will need a trailer with a gross weight of more than 750 kg. In this case, it is important to check whether the weight of your car allows you to stay within 3500 kg for the entire road train. For example, if a car weighs 2,000 kg, the trailer may have a mass of no more than 1500 kg so that the category “BE” is not required.
- 🚗 Category B allows trailers to be towed up to 750 kg without additional weight restrictions.
- ⚖️ For trailers heavier than 750 kg, the total mass of the vehicle and trailer shall not exceed 3,500 kg.
- 🚜 The category "BE" is required if the total mass of the trailer exceeds 750 kg and together with the car is more than 3500 kg.
- 📜 The braking system on the trailer is mandatory if its total mass exceeds 750 kg.
It is worth noting that the presence of brakes on the trailer is not just a formality, but a necessary condition for safety. Inertial-inertial or electric braking system allows you to effectively stop heavy load without overloading the brake pads of the car. The absence of brakes on a heavy trailer significantly increases the braking distance and can lead to the folding of the road train during emergency braking.
Specifications and axle load
When choosing a trailer, it is not enough to look only at the total load capacity, it is critical to take into account the weight distribution along the axles. Axle load shall not exceed the values specified in the documents for a particular model of trailer. Overloading one of the axles leads to rapid wear of the tires, deformation of the suspension and, most dangerously, to loss of stability on the road.
Multi-axle trailers, such as biaxial platforms for transporting cars or boats, require special attention to cargo balancing. Incorrect weight distribution can lead to the fact that one axle will be completely unloaded, and the other will work with overload, which is prohibited by the rules of operation. The technical documentation always indicates the maximum load on each axle separately.
⚠️ Warning: Exceeding the permissible load on the axle of the trailer is the basis for prohibiting further operation of the vehicle by traffic police officers and issuing a fine.
There are also strict rules for calculating the load on the coupling device (breather). Normally, the vertical load on the farcop ball should not exceed 10% of the mass of the laden trailer, but not more than the values specified by the manufacturer of the car. Excessive pressure on the farcop can lead to damage to the car body and deterioration of the handling of the front axle.
How to check the load on the breath
Stand on a flat platform, substitute a scale under the breather (or floor scales through the sling), lower the trailer on the ball. The readings of the scales are the vertical load. It should be between 25 and 75 kg for passenger trailers.
Calculation of payload and curb mass
Understanding the difference between full and curb weight is the key to competent operation. Mass in curb This includes the weight of the trailer itself, all liquids (if any) and standard equipment. Payload This is the weight of the load you can place on the platform. The formula is simple: payload = Total mass - curb weight.
In practice, however, the situation is complicated by the availability of additional equipment. Installation of an awning, side, winch or additional toolbox increases the curb weight, thereby reducing the payload capacity. Therefore, when buying accessories, always recalculate the residual load capacity.
Let’s consider an example of calculation for a popular model of trailer. If the total weight is 750 kg, and the finished (with an awning) is 250 kg, then you can load 500 kg of cargo. If you add another 50 kg of equipment, the payload will decrease to 450 kg. Ignoring this rule will lead to overload.
☑️ Pre-loading check
Effect of body type and design on load capacity
The frame design and body type directly affect how the trailer will carry the load. The board, the awning, the frame - all these elements that have their weight. Open platforms are usually lighter than on-board counterparts, which gives a payload gain. However, for bulk cargo or protection from weather conditions, boards and awnings are needed, which “eat” part of the load capacity.
Specialized trailers, such as boat trailers or snowmobiles, have a specific geometry of the lozenges. It affects the center of gravity. If the center of gravity is shifted too high or too far back, the stability of the road train falls. It is important to distribute heavy loads (e.g. engines or building materials) closer to the trailer axis and as low as possible.
| Type of trailer | Average curb weight (kg) | Typical gross mass (kg) | Payload (kg) |
|---|---|---|---|
| Onboard (uniaxial) | 150-200 | 750 | 550-600 |
| Trailer | 600-800 | 1000-1500 | 400-700 |
| For the transport of boats | 100-150 | 750 | 600-650 |
| Platform for technology | 300-400 | 2000-3500 | 1600-3100 |
The materials from which the trailer is made also play a role. Aluminum models are lighter than steel, which allows you to increase the payload at the same dimensions. However, the cost of aluminum trailers, such as Alu-Ko or analogues, much higher. Steel trailers are stronger to twist when transporting heavy loads, but are subject to corrosion, which over time also increases the mass due to rust and dirt.
Advice: When buying a used trailer, be sure to weigh it on the car scales. Over the years of operation, the frame could become overgrown with layers of dirt, bitumen and corrosion, which significantly increased its real curb weight.
Security rules and distribution of goods
The safety of the road train depends not only on the technical characteristics, but also on the correct load stowage. Heavy objects should be placed in the front of the trailer, closer to the coupling device, but not overloading the breather. Light and overall things (furniture, empty containers) are better placed behind and above.
Fixing the cargo is a separate and most important aspect. The use of only sides for fixation is unacceptable. It is necessary to use tensioner belts, chains or nets. The load shall not be displaced by sharp turns or braking. Shifting the centre of gravity sideways may cause the trailer to roll over, especially at high speeds or in side winds.
⚠️ Warning: Unsecured cargo falling on the road creates an emergency situation. The driver of the towing vehicle, including administrative and civil, is responsible for this.
When loading, the load height should also be monitored. If the cargo covers the tail lights, license plate or protrudes beyond the dimensions of more than 1 meter, special designations (flags, signs "Large-sized cargo") and, possibly, a permit for transportation are required. At night, the protruding parts shall be marked by retro-reflectors.
The main rule: 60% of the weight of the load should fall on the front half of the trailer (closer to the farcope) to ensure downforce on the coupling and stability of movement.
Frequent errors in the operation of trailers
One of the most common mistakes is ignoring the pressure in the tires. For trailers that stand idle for a long time, a decrease in pressure is characteristic, and when fully loaded, this leads to overheating of the rubber and the explosion of the wheel. The pressure must correspond to the load: the heavier the load, the higher the pressure should be (within the normal limits indicated on the sidewall of the tire).
Another mistake is the use of abnormal breathing or lengthening the frame on your own. Any change in the geometry of the trailer changes the distribution of loads and can lead to breakage. In addition, such modifications make it impossible to legally operate and pass the inspection. Registration data must strictly correspond to the actual state of the technology.
Drivers often forget to check the condition of the wiring. Oxidized contacts in the socket of the farcope or broken wires lead to the fact that the turn signals and stop signals on the trailer do not burn. This is a direct path to an accident and a penalty. Regular lubrication of contacts and checking the integrity of the insulation is a mandatory procedure before each season.
Seasonal storage
If you do not use a trailer in winter, lift it to the stands to unload the tires and springs. Reduce the pressure in the tires to 0.5-1 atmosphere or pump to normal, roar. Cover with an ultraviolet awning.
Maintenance of the chassis to maintain the load capacity
Over time, the trailer suspension elements wear out, which can lead to a decrease in actual load capacity and safety. Ressors lose elasticity, shock absorbers cease to extinguish vibrations, and hub bearings require regular lubrication. Ignoring chassis maintenance leads to the fact that the trailer begins to “walk” on the road even with a small load.
Particular attention should be paid to the condition of the axis and breath. The appearance of cracks in the metal, especially in welding sites, is categorically unacceptable. If deformations or deep corrosion are detected, operation must be stopped before repairs are carried out. Restorative repair of the frame is possible, but requires a professional approach and subsequent geometry check.
Regular maintenance extends the life of the trailer and ensures that the load capacity declared by the manufacturer will remain relevant. Lubrication of the bearings of the hubs should be made every 5-10 thousand kilometers or once a year. The use of quality lubricants that are resistant to water and high temperatures is critical to prevent wheel jamming.
How often do I need to go through the trailer inspection?
For trailers owned by individuals and having a total weight of up to 3500 kg, a planned technical inspection is not required in Russia. However, this does not relieve the owner of the obligation to keep the vehicle in good condition. Selling a trailer or traveling abroad may require a valid diagnostic card.
Can the loading capacity of the trailer be increased?
Factory increase in load capacity is possible only by the manufacturer or specialized services with changes in the design and PTS. Independent replacement of springs with more powerful or axles with reinforced ones without official registration is considered a change in design and is prohibited. This leads to a refusal to register and problems with insurance.
What to do if the trailer is overloaded?
If you find an overload already on the way (for example, at weight control), you must immediately remove part of the cargo. The operation of an overloaded trailer is prohibited. The penalty for overloading can be significant, and in the case of an accident, the insurance company can refuse to pay, citing a violation of the rules of operation of the vehicle.
Does the age of the trailer affect its load capacity?
Formally, age does not change the numbers in the PTS, but physically the metal gets tired. An old trailer with a corroded frame and tired springs may not withstand the load that the new one easily carried. Before loading the old trailer at the mass limit, make a thorough defect of the frame and chassis.
Do I need a tent for the load capacity?
The awning does not affect the carrying capacity of the frame, but it is included in the curb mass. By removing the awning, you increase the payload. However, for bulk cargo, the awning is mandatory under the rules of transportation to prevent cargo from scattering on the road, regardless of how this affects the weight.