Truckscience Axle Weight Calculator

Truck Axle Weight Distribution Calculator

Distance from center of front axle to center of rear axle.
Center of Gravity of the cargo, measured from the front axle.

Calculation Results:

Total Gross Vehicle Weight (GVW): — kg

Calculated Front Axle Weight: — kg

Calculated Rear Axle Weight: — kg

function calculateAxleWeights() { var tareFrontAxleWeight = parseFloat(document.getElementById("tareFrontAxleWeight").value); var tareRearAxleWeight = parseFloat(document.getElementById("tareRearAxleWeight").value); var loadWeight = parseFloat(document.getElementById("loadWeight").value); var wheelbase = parseFloat(document.getElementById("wheelbase").value); var loadCgDistance = parseFloat(document.getElementById("loadCgDistance").value); var resultDiv = document.getElementById("result"); var totalGVWOutput = document.getElementById("totalGVWOutput"); var frontAxleWeightOutput = document.getElementById("frontAxleWeightOutput"); var rearAxleWeightOutput = document.getElementById("rearAxleWeightOutput"); var warningMessage = document.getElementById("warningMessage"); warningMessage.innerHTML = ""; // Clear previous warnings if (isNaN(tareFrontAxleWeight) || isNaN(tareRearAxleWeight) || isNaN(loadWeight) || isNaN(wheelbase) || isNaN(loadCgDistance)) { warningMessage.innerHTML = "Please enter valid numbers for all fields."; totalGVWOutput.innerHTML = "Total Gross Vehicle Weight (GVW): — kg"; frontAxleWeightOutput.innerHTML = "Calculated Front Axle Weight: — kg"; rearAxleWeightOutput.innerHTML = "Calculated Rear Axle Weight: — kg"; return; } if (tareFrontAxleWeight < 0 || tareRearAxleWeight < 0 || loadWeight < 0) { warningMessage.innerHTML = "Tare weights and load weight cannot be negative."; totalGVWOutput.innerHTML = "Total Gross Vehicle Weight (GVW): — kg"; frontAxleWeightOutput.innerHTML = "Calculated Front Axle Weight: — kg"; rearAxleWeightOutput.innerHTML = "Calculated Rear Axle Weight: — kg"; return; } if (wheelbase <= 0) { warningMessage.innerHTML = "Wheelbase must be a positive value."; totalGVWOutput.innerHTML = "Total Gross Vehicle Weight (GVW): — kg"; frontAxleWeightOutput.innerHTML = "Calculated Front Axle Weight: — kg"; rearAxleWeightOutput.innerHTML = "Calculated Rear Axle Weight: — kg"; return; } // Calculate total GVW var totalGVW = tareFrontAxleWeight + tareRearAxleWeight + loadWeight; // Calculate weight distribution from the load // Using the principle of moments: // Moment about front axle: Load_Weight * Load_CG_Distance = Weight_on_Rear_from_Load * Wheelbase var weightOnRearFromLoad = (loadWeight * loadCgDistance) / wheelbase; var weightOnFrontFromLoad = loadWeight – weightOnRearFromLoad; // Calculate total weight on each axle var calculatedFrontAxleWeight = tareFrontAxleWeight + weightOnFrontFromLoad; var calculatedRearAxleWeight = tareRearAxleWeight + weightOnRearFromLoad; // Display results totalGVWOutput.innerHTML = "Total Gross Vehicle Weight (GVW): " + totalGVW.toFixed(2) + " kg"; frontAxleWeightOutput.innerHTML = "Calculated Front Axle Weight: " + calculatedFrontAxleWeight.toFixed(2) + " kg"; rearAxleWeightOutput.innerHTML = "Calculated Rear Axle Weight: " + calculatedRearAxleWeight.toFixed(2) + " kg"; // Add warnings for unsafe conditions if (calculatedFrontAxleWeight < 0) { warningMessage.innerHTML += "Warning: Front axle weight is negative. This indicates the load's center of gravity is too far back, potentially lifting the front axle and causing loss of steering control. This is extremely dangerous! "; } if (calculatedRearAxleWeight < 0) { warningMessage.innerHTML += "Warning: Rear axle weight is negative. This indicates an impossible or extremely unstable load distribution. "; } if (loadCgDistance wheelbase && calculatedFrontAxleWeight > 0) { // Only warn if CG is past rear axle but not causing negative front weight (already warned) warningMessage.innerHTML += "Warning: Load CG is positioned behind the rear axle. Ensure this is within safe and legal overhang limits. "; } }

Understanding Truck Axle Weight Distribution

Proper axle weight distribution is one of the most critical aspects of safe and legal truck operation. It directly impacts vehicle stability, braking performance, tire wear, and compliance with road regulations. Overloaded axles or improperly distributed loads can lead to severe consequences, including accidents, fines, and damage to the vehicle and infrastructure.

Why Axle Weight Matters

  • Safety: Incorrect weight distribution can compromise steering, braking, and overall vehicle control. Too much weight on the front axle can make steering heavy, while too little can reduce traction and control. Too much weight on the rear can lead to instability and difficulty in braking.
  • Legality: Most jurisdictions have strict limits on the maximum weight allowed on individual axles and the total Gross Vehicle Weight (GVW). Exceeding these limits can result in hefty fines and require immediate load adjustment.
  • Vehicle Wear and Tear: Overloaded axles put excessive stress on tires, suspension components, brakes, and the chassis, leading to premature wear, increased maintenance costs, and potential component failure.
  • Road Damage: Heavy axle loads contribute significantly to road degradation, which is why regulations are in place to protect infrastructure.

How the Calculator Works (The Lever Principle)

This calculator uses a fundamental principle of physics: the lever principle (or moments). Imagine your truck as a beam supported by two pivots – the front and rear axles. When you place a load on the truck, its weight exerts a force at its center of gravity (CG).

The calculator determines how this load's weight is distributed between the front and rear axles based on:

  1. Tare Weight: The unladen weight of the truck itself, distributed across its axles.
  2. Load Weight: The total weight of the cargo being carried.
  3. Wheelbase: The distance between the center of the front axle and the center of the rear axle. This acts as the length of our "lever."
  4. Distance from Front Axle to Load CG: This is the crucial measurement. It tells us where the load's weight is concentrated relative to the front axle.

By calculating the "moments" (force multiplied by distance) around each axle, we can determine how much of the load's weight is supported by the front axle and how much by the rear. This load-induced weight is then added to the truck's tare axle weights to give the total loaded axle weights.

Using the Calculator Effectively

To get accurate results, ensure your input values are precise and consistent in their units (e.g., all in kilograms and millimeters, or all in pounds and inches).

  • Tare Weight – Front/Rear Axle: These are the weights on your axles when the truck is empty. You can usually find this information in your truck's specifications or by weighing the empty vehicle.
  • Load Weight: The total weight of the cargo you intend to carry.
  • Wheelbase: Measure the distance from the center of your front axle to the center of your rear axle.
  • Distance from Front Axle to Load CG: This is often the trickiest measurement. For a uniformly distributed load, the CG is at its geometric center. For irregularly shaped or unevenly distributed loads, you might need to estimate or use more advanced methods to find the combined CG. Measure this distance from the center of the front axle to the estimated center of gravity of your entire cargo.

Important Considerations

  • This calculator provides an estimate for a two-axle truck. Multi-axle configurations (tandem axles, tridem axles) involve more complex calculations.
  • Always verify your calculated weights with actual weighbridge measurements before operating on public roads.
  • Be mindful of legal axle weight limits in your region, which can vary significantly.
  • A negative front axle weight in the results indicates an extremely dangerous condition where the load is too far back, potentially lifting the front wheels off the ground.

Using this calculator can help you plan your loads more effectively, ensuring safety, compliance, and extending the life of your vehicle.

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