What Are Onboard Scales and How Do They Work on Commercial Trucks?

Updated

Onboard scales are weighing systems mounted directly on a commercial vehicle that measure load weight in real time, so the driver or fleet can see how much the truck is carrying before it ever reaches a roadside or platform scale. They are most useful when you need to load to the maximum legal limit on every trip, avoid overweight fines, and cut the time spent waiting in scale lines. Systems are available for air, spring, and mixed suspensions, which matters if your fleet mixes tractors and trailers.

What onboard scales actually measure

An onboard scale does not weigh the whole truck the way a platform scale does. Instead, it measures the force carried at specific points on the vehicle and converts that into a weight reading.

  • Load cells are the sensing element. They are mounted where they can detect the load being carried — for example, in the suspension path.
  • Instrumentation in the cab takes the load cell signal and displays it as a usable weight figure, typically as axle weight or total vehicle weight.
  • Because the reading is live, it updates as material is loaded or unloaded, so the operator can stop at the right point instead of guessing.

Vulcan states that every part of its onboard weighing systems — including the strain gage, load cell, EDOC coating, and instrumentation — is designed, manufactured, and supported by VPG itself, which is relevant if you want a single-source supplier rather than a system assembled from multiple vendors.

Why fleets use them

The core value is knowing your weight while you load, not after you leave. According to Vulcan, the practical benefits break down like this:

Goal How onboard scales help
Maximize payload Load to the maximum legal limit every time instead of under-loading out of caution
Avoid overweight fines Catch an overweight condition before the truck is on the road
Reduce loading time Eliminate readjustment and waiting in scale lines
Lower maintenance cost Properly loaded vehicles put less strain on brakes, tires, and suspensions
Reduce liability Keeping weights within legal limits supports vehicle stability and safety

The maintenance and liability points are worth separating from the obvious fine-avoidance argument. A truck that is consistently overloaded wears brakes, tires, and suspension components faster, and an overweight vehicle can behave differently in an accident. Vulcan frames these as reduced maintenance cost and reduced liability exposure, which are operational and risk arguments rather than purely financial ones.

Where they are used

Vulcan reports its onboard scales are proven in a range of applications, and the list is a useful guide to whether your operation fits:

  • General trucking and delivery
  • Waste and refuse
  • Aggregate hauling
  • Timber and forestry
  • Aerospace, marine, medical equipment, heavy machinery, and process control (non-truck applications)

If your loads are variable — bulk material, mixed freight, waste with unpredictable density — an onboard scale is more valuable than in an operation where every load is a known, fixed weight.

Suspension compatibility is the main selection question

Before choosing a system, confirm what suspension your vehicles run. Vulcan offers solutions for air, spring, and mixed suspensions, and states that fleets can mix and match tractors and trailers without adjustment. That last point matters if you drop and hook: a system that requires recalibration every time you change trailers creates work instead of removing it.

Ask these questions when comparing options:

  1. What suspension type do your tractors and trailers use? Air, spring, or a mix determines which system family applies.
  2. Do you swap trailers? If yes, confirm the system handles mixed combinations without adjustment.
  3. Do you need axle weight, total weight, or both? This affects what the instrumentation must display.
  4. Who supports the system? Vulcan's position is that it designs, manufactures, and supports every component itself, which simplifies service if something fails.

What to verify before buying

Vulcan's page does not list pricing, so cost has to come from a direct quote. What the page does support:

  • The systems are designed and assembled in the US, with a manufacturing history dating to 1984.
  • Vulcan operates offices in North America, Europe, and Asia, and its solutions are used in 30+ countries.
  • The company describes its overload protection systems as relied on by an estimated 50,000+ vehicles worldwide.

Those are scale and support signals rather than performance guarantees for your specific application. The practical next step is to match your suspension type and trailer-swapping pattern to a specific system, then confirm accuracy expectations and support terms with the supplier directly.