Accurately determining the actual weight on a particular bridge is a critical step before leaving for a weigh control or trip. Truck driver DAF XF or Kamaz must understand that a visual assessment of the load on the body is often erroneous, since the center of gravity of the load may be shifted. Incorrect weight distribution leads not only to fines from the traffic police, but also to accelerated wear of the vehicle’s suspension and frame.
There are several proven methods that allow you to obtain reliable data on axle loading without having to stop at each stationary point. Modern logistics companies require forwarders to provide accurate figures, since an overload of even 2-3% can cause a refusal to accept goods at the recipient’s warehouse. Below we will analyze in detail the technical and legal aspects of this process so that you can feel confident on the road.
Regulatory requirements and acceptable values
Legislation strictly regulates maximum permissible loads, which depend on the type of roads, the distance between the axles and the design features of the tractor and semi-trailer itself. Axial load is calculated based on the fact that the wheel pressure on the road surface should not exceed established standards, otherwise the asphalt concrete pavement will be destroyed. For a single axle in a group with a distance between them of less than 2.5 meters, the standards will be significantly lower than for widely spaced axles.
It is important to take into account seasonal restrictions, which are often introduced in the spring to preserve the roadway. At this time, the permissible weight can be reduced by 40% or more, which requires special attention to route planning and cargo distribution. Violation of these temporary restrictions is punished as strictly as permanent norms, and weight control during such periods is strengthened by mobile groups.
⚠️ Attention: Exceeding the permissible axle load by more than 2% is already considered an administrative offense and entails a fine.
Different types of trucks have different passport characteristics, which cannot be ignored when making calculations. For example, for a three-axle trolley Scania or Volvo the total load is distributed unevenly, and the rear axles often carry more weight than the front. Understanding these nuances helps to avoid situations where the total weight of the car is normal, but the distribution along the axles is critically impaired.
Using stationary weight systems
The most reliable and legally significant way to find out the exact load is to weigh on a stationary truck scale. Such complexes, located at bases, warehouses or specialized points, provide high accuracy of measurements, since the platform is long and allows the vehicle to be installed completely. When entering the platform, it is important that the wheels of all axles are strictly within the boundaries of the weighing equipment.
The weighing procedure is usually carried out in two stages: first, the mass of the entire vehicle is measured, and then, if necessary, the axle groups are weighed in stages. To obtain correct data, the driver must turn off the engine, turn off all power consumers and leave the cab if required by the operator’s instructions. Any vibrations or operating air conditioning systems can introduce errors in the sensor readings.
- 🚛 Full weighing: the car drives onto the platform as a whole, which gives the total mass.
- ⚖️ Axis weighing: Each axle or bogie is weighed separately for detailed analysis.
- 📝 Receiving a coupon: an official document with a seal that has legal force in disputes with the traffic police.
- 🛑 Control check: re-weighing to eliminate technical equipment errors.
It is worth noting that modern electronic scales are calibrated regularly, but the human factor when installing a car can play a role. If the wheels rest on a slab joint or on an inclined part of the driveway, the readings will be distorted. Therefore, the driver should closely monitor the operator's actions and, if necessary, request that the vehicle be reinstalled.
Mobile and portable weighing platforms
Mobile weighing platforms are increasingly being used for rapid checks without visiting large bases. These devices are compact plates that are placed under the wheels of each axle in turn. This method allows you to quickly calculate the load directly at the loading site, which is especially important for construction sites or remote warehouses.
The accuracy of mobile scales is somewhat lower than that of stationary analogues, and greatly depends on the flatness of the surface on which they are installed. The use of such platforms on soil or asphalt with holes can lead to a significant error, so it is recommended to choose the most flat areas possible. The device connects to a tablet or smartphone, where data on each axis is displayed in real time.
The advantage of portable systems is their autonomy and the ability to operate from a built-in battery. Logistics companies that own large fleets of equipment often purchase such kits for self-monitoring of drivers before leaving for a flight. This allows you to identify overload in advance and redistribute the cargo, avoiding downtime and fines.
⚠️ Attention: When using mobile platforms, make sure that the surface underneath is firm and not sloped, otherwise the readings will be incorrect.
Load calculation using formulas and technical data
If you don’t have scales at hand, you can use the mathematical calculation method, based on technical documentation and known parameters of the load. To do this, you need to know the mass of the empty vehicle (its own mass), the mass of the cargo and the coordinates of the center of gravity. Weight distribution between the axles of the tractor and semi-trailer obeys the laws of physics and can be calculated with sufficient accuracy.
The basic formula takes into account the distance from the center of gravity of the load to the axles of the semi-trailer and the distance between the axles of the hitch. Knowing these values, you can determine what proportion of the weight will fall on the fifth-wheel coupling device, and what will be distributed along the axles of the trailer. Next, the load from the saddle is transferred to the rear axles of the tractor and its front axle in proportion to the base of the vehicle.
To simplify calculations, there are special tables and software calculators where you just need to enter the dimensions and weight. However, it is worth remembering that the theoretical calculation does not take into account the unevenness of the cargo, the presence of voids or the displacement of pallets during movement. Therefore, a small margin of safety should always be added to the obtained figures.
Formula for calculating the load on the front axle
Load = (Cargo weight * Distance from CG to trailer axle) / Trailer base + Curb weight
Electronic weighing systems in the cab
Modern premium trucks such as Mercedes-Benz Actros or MAN TGX, are often equipped with built-in axial load monitoring systems. These systems use air suspension sensors to detect airbag pressure and convert it into weight. The data is displayed on the in-cab display in real time, allowing the driver to monitor the load while working.
Although on-board systems are very convenient, their readings are for reference only and may have an error of up to 5-10%. For official reports and weight control, data from the on-board computer is not taken into account by inspectors. Nevertheless, for quickly adjusting the position of the cargo along the way, this is an indispensable tool.
| System type | Accuracy | Legal force | Cost |
|---|---|---|---|
| Stationary scales | High (0.1%) | Yes | Paid/Free |
| Mobile platforms | Average (1-2%) | No (for self-control) | High (buy) |
| Onboard sensors | Low (5-10%) | No | Included in the price of the car |
| Calculation method | Depends on the input | No | Free |
Drivers who often deal with heterogeneous loads are recommended to periodically check the readings of on-board systems with the data of stationary scales. This will help you develop a personal correction factor and better understand how a particular car behaves under different loads.
Practical advice on load distribution
Proper cargo stowage is a key factor in managing axle loads. Shifting the center of gravity forward or backward can dramatically change axle loads, even if the overall weight remains within normal limits. Shifting the load by just 10-15 centimeters can change the axle load by several hundred kilograms.
When loading, it is necessary to strive for an even distribution of weight over the body area. Heavy pallets should be placed closer to the center of the semi-trailer platform, avoiding mass concentration above the coupling device or, conversely, at the tailgate. The use of spreader bars and straps also helps secure the load and prevent it from shifting during travel.
☑️ Checklist before weighing
If you find that one of the axles is overloaded, do not try to solve the problem by bleeding the air suspension. This will not change the actual weight per wheel, but will only distort the sensor readings and may lead to damage to the suspension components. The only sure way is to physically move the cargo or partially unload it.
Main conclusion: Accurate knowledge of the axle load saves you from fines and breakdowns, so use proven weight systems before each trip.
Frequently asked questions (FAQ)
Is it possible to challenge a fine for overloading if the scale shows an excess?
You can challenge the fine if you prove that the weighing equipment is faulty or the weighing procedure was violated. This requires a scale verification certificate and a certificate of control weighing on working equipment.
Does tire pressure affect axle load readings?
Tire pressure does not affect the actual weight on the axle, but it can affect the area of contact between the wheel and the weigh plate. However, modern weight systems take this factor into account, and the difference in readings will be minimal.
What is the acceptable error when weighing trucks?
According to metrological standards, the permissible error for automobile scales ranges from 0.1% to 1% depending on the accuracy class and weighing range. For legal purposes, only certified devices are used.
What to do if there are no scales in the warehouse, but the cargo needs to be sent?
In this case, it is recommended to use the calculation method with a safety margin or call a mobile weighing platform. Sending a loaded vehicle without accurate axle load data is risky due to a possible fine along the way.