Short answer
Gross vehicle weight is the sum of the axle loads, and a sum cannot show how the load is spread. A truck can sit inside its gross limit while one axle carries far more than its own rating, which is why onboard systems report per axle and alarm per axle rather than only on the total.
Key takeaways
- Gross weight is a sum; only a per-axle reading shows distribution, which is where most overload violations live.
- The ROADEK listing supports up to 32 sensors on a single sensor bus with one controller, so a multi-axle combination is one system.
- Strain-gauge sensing measures deformation under load, which is why it works on old and new vehicles alike rather than needing a suspension type.
- Both per-axle and gross-weight alarms are listed separately, because they answer two different compliance questions.
- Sensors can be added later without replacing the controller, which matters when a tractor gains a different trailer.
01Why a sum is the wrong number to watch
Gross vehicle weight is the total mass of the vehicle and its load, and it is the figure most operators track because it is the figure most often quoted. The problem is structural: a total is the sum of the axle loads, and any sum can be reached by many different distributions. A truck loaded heavily over its rear axles and lightly at the front can sit comfortably inside its gross limit while the rear group carries more than its own rating. The gross reading in that case is not wrong, it is simply answering a different question from the one that matters for road damage, braking behaviour and axle-group limits. This is why an onboard system that reports only a total has solved the easier half of the problem, and why per-axle reporting is the capability worth specifying.
02What a strain gauge actually measures
The ROADEK listing specifies strain-gauge sensing using an analogue TBE0A element, and understanding the principle explains the system's reach. A strain gauge does not weigh anything directly. It measures the minute deformation of a structural member under load, and that deformation is converted to a load figure through calibration. Because the quantity being sensed is deformation of the vehicle's own structure, the method does not depend on a particular suspension design being present, which is why our listing states support for all vehicle types including trucks, tractors and trailers, both old and new. A system that inferred load from air-suspension pressure would be restricted to vehicles that have air suspension; a strain-gauge system is not, though our listing notes air suspension and auxiliary circuits are supported as well.
03One bus, up to thirty-two sensors
A multi-axle combination needs a sensor at each measurement point, and the architecture determines whether that is one system or several. The ROADEK listing states up to 32 sensors on a single sensor bus, driven by a single controller with a sensor-bus interface. That matters for two reasons. Practically, a tractor-and-trailer combination with several axle groups stays one installation with one data path rather than a set of independent devices to reconcile. Commercially, the listing also states that sensors can be added without replacing the controller, so a fleet that changes trailer configurations is not re-buying the expensive part each time. The installation is described as a single connection point that is rotatable, which reduces the fitting work per sensor.
04Two alarms, because there are two questions
The ROADEK listing carries an overload alarm per individual axle and, separately, a gross vehicle weight overload alarm. Listing them as two features rather than one is the correct design, because they can fire independently and each means something different. A per-axle alarm with the gross still inside limits says the load is badly distributed and needs re-stowing, not removing. A gross alarm with every axle inside its own rating says the total is simply too much and some load must come off. Treating either alarm as a proxy for the other loses that distinction, and the operational response differs: one is a loading-dock problem solved by moving weight, the other is a dispatch problem solved by taking weight off the vehicle.
05Online and offline calibration
Because a strain gauge reports deformation rather than mass, calibration is what turns its output into a load figure, and the ROADEK listing states both online and offline calibration modes. The distinction is practical. Offline calibration is performed against known reference loads, typically at a weighbridge, and establishes the relationship between deformation and weight for that vehicle in that configuration. Online calibration allows adjustment while the system is in service, which matters because the relationship is not permanent: a structural repair, a changed body, or a different trailer alters it. The general principle carries over from fuel-level calibration, a sensor reporting a physical proxy needs a calibration table, and that table is a property of the specific installation rather than of the sensor model.
06What the driver sees, and why it matters at the dock
The ROADEK listing includes a real-time live load reading, and a live display changes where the problem gets solved. An overload discovered at a checkpoint is a violation; the same overload seen on a display during loading is an instruction to move a pallet. That difference is the main operational return on an onboard system, and it depends on the reading being available to the person loading rather than only in a report read later. It also interacts with the per-axle point above: a live gross figure lets a loader stop at the limit, while a live per-axle figure lets them place the load correctly in the first place. The second is what prevents the compliant-total, overloaded-axle case entirely rather than catching it.
07Where weight data meets the rest of the telemetry
Load is most useful read alongside the other channels rather than alone, because it explains them. Fuel consumption per hundred kilometres is not comparable between a laden and an empty run, so a consumption figure without a load figure invites the wrong conclusion about a driver or a vehicle. The same applies to engine hours and brake wear. Our catalogue holds the pieces for that combination: the LV-CAN200 reads engine parameters from the vehicle bus, and the Eurosens Dominator reports tank level over RS-485. The practical requirement is that all three arrive with timestamps that can be aligned, which is a platform question rather than a sensor one, and it is the reason a weight system that reports into the same platform is worth more than one with its own separate display.
| Situation | Gross reading | Per-axle reading | Correct response |
|---|---|---|---|
| Load stacked over the rear axles | Within limit | Rear group over rating | Re-stow, move weight forward |
| Simply too much cargo | Over limit | Several axles over | Remove load |
| Load correct and evenly spread | Within limit | All axles within | Dispatch |
| Trailer swapped for a heavier one | May be within | Depends on the new axles | Recalibrate for the configuration |
| Uneven road camber during loading | Unchanged | Momentarily skewed | Read on level ground |
Figures and sources
- ROADEK onboard weight sensor bus capacity and controller architecture: up to 32 sensors on a single sensor bus; one controller plus sensor-bus interface (Source: ENTEK.AI product catalogue, as of 2026-08-31)
- ROADEK sensing technology: strain gauge (TBE0A analogue) (Source: ENTEK.AI product catalogue, as of 2026-08-31)
- ROADEK calibration modes: online and offline modes (Source: ENTEK.AI product catalogue, as of 2026-08-31)
- ROADEK alarm types, listed as two separate capabilities: overload alarm per individual axle; gross vehicle weight overload alarm (Source: ENTEK.AI product catalogue, as of 2026-08-31)
- ROADEK vehicle compatibility and suspension support: all types, trucks, tractors, trailers, old and new; air suspension plus auxiliary circuits (Source: ENTEK.AI product catalogue, as of 2026-08-31)
- ROADEK installation and scalability: single rotatable connection point; sensors addable without replacing the controller (Source: ENTEK.AI product catalogue, as of 2026-08-31)
- Teltonika LV-CAN200 role in the same telemetry set, reading engine data from the vehicle bus: CAN adapter reading vehicle bus parameters (Source: ENTEK.AI marketplace, as of 2026-08-31)
- SAE J1939 total vehicle distance resolution, for aligning load against distance-based figures: SPN 245: 0.125 km per bit (Source: SAE J1939-71, Vehicle Application Layer, as of 2026-08-31)
Questions
If my gross weight is legal, can an axle still be overloaded?
Yes, and this is the common case. Gross weight is the sum of the axle loads, and many different distributions produce the same total. A load stacked over the rear axles can leave the total inside its limit while the rear group exceeds its own rating, which only a per-axle reading reveals.
Does onboard weighing need air suspension?
Not with strain-gauge sensing. A strain gauge measures deformation of the vehicle's own structure under load rather than inferring weight from suspension pressure, which is why the ROADEK listing states support for all vehicle types including older trucks and trailers, with air suspension supported as well.
How many sensors does a tractor and trailer need?
One at each measurement point, and the architecture keeps that as a single system: the ROADEK listing supports up to 32 sensors on one sensor bus with a single controller. Sensors can also be added later without replacing the controller, which matters when a tractor is paired with a different trailer.
When does the system need recalibrating?
Whenever the relationship between deformation and load changes, a structural repair, a changed body, or a different trailer configuration. Our listing states both online and offline calibration modes, so an adjustment does not necessarily require taking the vehicle to a weighbridge and out of service.