Precisely calculate and analyze the weight distribution of your vehicle's load across its axles. Essential for safe towing, hauling, and optimal vehicle performance. Enter your vehicle's details and load information below.
Load Distribution Calculator
Vehicle's front axle weight with no load (kg or lbs).
Vehicle's rear axle weight with no load (kg or lbs).
The total weight of the cargo or trailer being added (kg or lbs).
Horizontal distance from the rear axle to the load's center of gravity (meters or feet).
The distance between the front and rear axles (meters or feet).
Target percentage of total weight on the front axle (e.g., 50%).
Distribution Results
Total Vehicle Weight (Loaded):—
Front Axle Weight (Loaded):—
Rear Axle Weight (Loaded):—
Front Axle Distribution (%):—
Rear Axle Distribution (%):—
—
Formula Used:
The total weight on the front axle is calculated by taking the unloaded front axle weight and adding the portion of the load that is supported by the front axle. The load's contribution to each axle depends on the distance of its center of gravity from the rear axle and the vehicle's wheelbase. The calculation involves principles of static equilibrium.
Key Intermediate Values
Value
Description
Result
Load Support at Front Axle
Portion of the load's weight distributed to the front axle
—
Load Support at Rear Axle
Portion of the load's weight distributed to the rear axle
—
Total Vehicle Weight (Unloaded)
Sum of unloaded front and rear axle weights
—
Intermediate calculation components for load distribution analysis.
Axle Load Distribution Chart
Front Axle Load |
Rear Axle Load
Visual representation of weight distribution across axles.
What is Weight Distribution on Wheels?
Weight distribution on wheels refers to how the total weight of a vehicle, including its passengers, cargo, and the vehicle itself, is distributed across its front and rear axles, and consequently, its wheels. Proper weight distribution is crucial for vehicle stability, handling, braking performance, and tire wear. For vehicles that carry significant loads or tow trailers, understanding and managing this distribution is paramount for safety and operational efficiency. It's not just about the total weight, but where that weight is positioned relative to the axles. An imbalanced load can lead to dangerous driving conditions, such as trailer sway, poor steering response, and increased risk of accidents.
Who should use it:
Anyone who regularly hauls cargo, tows a trailer (e.g., campers, boats, utility trailers), operates commercial vehicles, or simply wants to ensure their vehicle is loaded safely for family trips. Understanding weight distribution on wheels is fundamental for safe towing practices and maximizing vehicle capability.
Common misconceptions:
A common misconception is that as long as the total load is within the vehicle's Gross Vehicle Weight Rating (GVWR), it's safe. However, the *distribution* of that weight is just as critical. Another myth is that the load should be centered perfectly between the axles; often, a specific tongue weight percentage (for trailers) or axle load percentage is recommended for optimal stability. For instance, a trailer often needs a certain percentage of its weight pressing down on the hitch ball (tongue weight), which is a direct component of rear axle load and total weight distribution on wheels.
Weight Distribution on Wheels Formula and Mathematical Explanation
Calculating the weight distribution on wheels, particularly when adding a load like a trailer or cargo, involves understanding how that load's center of gravity affects the forces on each axle. We use principles of static equilibrium. The goal is to determine the loaded weight on the front and rear axles based on unloaded axle weights and the characteristics of the added load.
Core Calculation Logic
Let:
$W_{FA\_empty}$ = Unloaded Front Axle Weight
$W_{RA\_empty}$ = Unloaded Rear Axle Weight
$W_{load}$ = Total Added Load Weight
$d_{load}$ = Load's Center of Gravity Distance from Rear Axle
$WB$ = Vehicle Wheelbase
The total weight of the vehicle unloaded is:
$W_{total\_empty} = W_{FA\_empty} + W_{RA\_empty}$
The added load exerts forces. A portion of $W_{load}$ will be supported by the front axle ($S_{FA}$) and a portion by the rear axle ($S_{RA}$). These are not necessarily equal. The load's center of gravity relative to the axles is key.
Assuming the load is placed such that its center of gravity is at distance $d_{load}$ from the rear axle and we know the wheelbase $WB$:
Using moments around the front axle:
$S_{RA} \times WB = W_{load} \times (WB – d_{load})$
$S_{RA} = W_{load} \times \frac{(WB – d_{load})}{WB}$
Using moments around the rear axle:
$S_{FA} \times WB = W_{load} \times d_{load}$
$S_{FA} = W_{load} \times \frac{d_{load}}{WB}$
Note: These simplified formulas assume the load is a single point mass and does not account for overhangs or complex load shapes. For trailer tongue weight, $d_{load}$ would be the distance from the rear axle to the trailer's coupling point. If the load center of gravity is *behind* the rear axle ($d_{load} 0$), it adds weight.
The final loaded axle weights are:
$W_{FA\_loaded} = W_{FA\_empty} + S_{FA}$
$W_{RA\_loaded} = W_{RA\_empty} + S_{RA}$
The total weight of the loaded vehicle is:
$W_{total\_loaded} = W_{FA\_loaded} + W_{RA\_loaded}$
(This should also equal $W_{total\_empty} + W_{load}$)
The weight distribution percentages are:
$Distribution_{FA} = \frac{W_{FA\_loaded}}{W_{total\_loaded}} \times 100\%$
$Distribution_{RA} = \frac{W_{RA\_loaded}}{W_{total\_loaded}} \times 100\%$
Variables Table
Variable
Meaning
Unit
Typical Range
$W_{FA\_empty}$
Unloaded Front Axle Weight
kg / lbs
1000 – 2500 (Cars) 2000 – 10000+ (Trucks)
$W_{RA\_empty}$
Unloaded Rear Axle Weight
kg / lbs
800 – 2000 (Cars) 1500 – 8000+ (Trucks)
$W_{load}$
Total Added Load Weight
kg / lbs
100 – 5000+
$d_{load}$
Load Center of Gravity Distance from Rear Axle
m / ft
0.5 – 5+
$WB$
Vehicle Wheelbase
m / ft
2 – 6 (Cars) 3 – 10+ (Trucks)
$S_{FA}$
Load Support at Front Axle
kg / lbs
0 – $W_{load}$
$S_{RA}$
Load Support at Rear Axle
kg / lbs
0 – $W_{load}$
$W_{FA\_loaded}$
Loaded Front Axle Weight
kg / lbs
> $W_{FA\_empty}$
$W_{RA\_loaded}$
Loaded Rear Axle Weight
kg / lbs
> $W_{RA\_empty}$
$W_{total\_loaded}$
Total Loaded Vehicle Weight
kg / lbs
GVWR (Gross Vehicle Weight Rating)
Practical Examples (Real-World Use Cases)
Example 1: Towing a Travel Trailer
A family is preparing for a camping trip. Their SUV has the following unloaded weights:
Front Axle (Unloaded): 1600 kg
Rear Axle (Unloaded): 1300 kg
Wheelbase: 3.2 meters
They are towing a travel trailer with a total weight of 2500 kg. The trailer's hitch is positioned such that its center of gravity relative to the SUV's rear axle is 1.5 meters forward (meaning 1.5 meters behind the rear axle).
Inputs to Calculator:
Front Axle Weight (Unloaded): 1600 kg
Rear Axle Weight (Unloaded): 1300 kg
Total Added Load Weight: 2500 kg
Load Center of Gravity Distance from Rear Axle: 1.5 m
Vehicle Wheelbase: 3.2 m
Desired Front Axle Load Distribution (%): 50% (A common starting point for stability)
Calculation Results:
Total Vehicle Weight (Unloaded): 1600 + 1300 = 2900 kg
Load Support at Front Axle ($S_{FA}$): 2500 kg * (1.5 m / 3.2 m) = 1171.88 kg
Load Support at Rear Axle ($S_{RA}$): 2500 kg * ((3.2 m – 1.5 m) / 3.2 m) = 1328.12 kg
Front Axle Weight (Loaded): 1600 kg + 1171.88 kg = 2771.88 kg
Rear Axle Weight (Loaded): 1300 kg + 1328.12 kg = 2628.12 kg
Total Vehicle Weight (Loaded): 2771.88 kg + 2628.12 kg = 5400 kg
Front Axle Distribution (%): (2771.88 kg / 5400 kg) * 100% = 51.33%
Rear Axle Distribution (%): (2628.12 kg / 5400 kg) * 100% = 48.67%
Interpretation: The loaded front axle weight is approximately 2772 kg, and the rear axle is approximately 2628 kg. The distribution is 51.33% front and 48.67% rear. This indicates a slightly heavier load on the front axle, which is generally good for stable towing. The total weight of 5400 kg should be checked against the vehicle's GVWR and the trailer's Gross Trailer Weight Rating (GTWR). The tongue weight (load support at rear axle, conceptually related) is about 1328 kg, which needs to be less than the trailer's designed tongue weight and acceptable for the SUV's hitch rating.
Example 2: Hauling Heavy Equipment in a Pickup Truck
A contractor is using a heavy-duty pickup truck to transport a generator.
Interpretation: The calculated distribution is 45.18% front and 54.82% rear. This is the opposite of the contractor's desired 55% front bias. The generator's weight, being relatively close to the rear axle, actually adds more weight to the rear axle than the front. To achieve the desired 55% front bias, the contractor would need to reposition the generator forward, closer to the cabin, or secure additional weight over the front axle. The total loaded weight of 5700 lbs must also be within the truck's GVWR.
How to Use This Weight Distribution on Wheels Calculator
Using this calculator is straightforward and designed to provide quick insights into your vehicle's load balance. Follow these simple steps:
Gather Vehicle Information: Before you begin, find the unloaded weight for your front and rear axles. This information might be available on a door jamb sticker, in your owner's manual, or by taking your vehicle (unloaded) to a weigh station. You'll also need your vehicle's wheelbase.
Enter Load Details: Input the total weight of the cargo or trailer you are adding. Then, determine the horizontal distance from your vehicle's *rear axle* to the *center of gravity* of this added load. This is a critical measurement for accurate calculation. Finally, enter your desired target percentage for the front axle's share of the *total* weight.
Review Inputs: Double-check all entered values for accuracy. Ensure consistent units (e.g., all kg or all lbs).
Calculate: Click the "Calculate Distribution" button. The calculator will instantly process the data.
Interpret Results:
Total Vehicle Weight (Loaded): The combined weight of your vehicle and its load. Ensure this is below your vehicle's GVWR.
Front/Rear Axle Weight (Loaded): The calculated weight on each axle after adding the load.
Front/Rear Axle Distribution (%): The percentage of the total loaded weight carried by each axle. Compare this to your desired percentage and general safety guidelines (typically aiming for 40-60% on the rear axle for towing stability, though specific vehicle recommendations vary).
Primary Highlighted Result: This often shows the most critical metric, like the overall front/rear percentage balance or a warning if severely imbalanced.
Key Intermediate Values: These show how the load itself is being split between the axles and the total unloaded weight, offering deeper insight into the mechanics.
Chart: Provides a visual comparison of the loaded weights on the front and rear axles.
Adjust Load (If Necessary): If the results show an undesirable distribution (e.g., too much weight on the rear axle, causing "tail wagging" during towing, or too little on the front, affecting steering), you may need to adjust the position of your load. Moving the load's center of gravity forward will increase front axle load and decrease rear axle load. Moving it backward does the opposite.
Use Other Buttons:
Reset: Clears all fields and restores default values, useful for starting over.
Copy Results: Saves the calculated results and key assumptions to your clipboard for documentation or sharing.
By understanding and managing your weight distribution on wheels, you significantly enhance your vehicle's safety and performance.
Key Factors That Affect Weight Distribution on Wheels Results
Several factors influence how weight is distributed on your vehicle's wheels. Understanding these is key to managing your load effectively:
Position of the Load's Center of Gravity (CG): This is perhaps the most significant factor. The further the load's CG is from the rear axle (forward), the more weight it shifts to the front axle. Conversely, a CG closer to or behind the rear axle shifts more weight to the rear. For towing, the trailer's tongue weight is a critical component of this CG placement relative to the tow vehicle's rear axle. Proper tongue weight (typically 10-15% of trailer weight) ensures adequate load on the front axle for steering and stability.
Vehicle Wheelbase: A longer wheelbase provides more leverage distance between the axles. For a given load position, a longer wheelbase generally results in less dramatic shifts of weight to each axle compared to a shorter wheelbase vehicle. This offers greater stability.
Unloaded Axle Weights: The baseline weight distribution of the vehicle itself sets the starting point. A vehicle that is already rear-heavy when unloaded will become even more so when weight is added behind the rear axle.
Total Load Weight: Simply put, the heavier the load, the greater its potential impact on axle weights. Exceeding the vehicle's GVWR or Gross Axle Weight Ratings (GAWR) for either axle is dangerous and illegal. Always consult your vehicle's weight ratings.
Vehicle Type and Design: Front-engine, rear-wheel-drive cars naturally have a weight bias towards the front due to engine placement. Rear-engine or mid-engine vehicles will have different baseline distributions. Trucks, especially those with heavy diesel engines mounted forward, often have a significant front-end weight bias unloaded.
Suspension System: While not directly altering the static weight distribution calculation, the suspension's ability to handle the loaded weight and maintain ride height affects the vehicle's dynamics and perceived stability. An overloaded suspension can lead to sagging, impacting handling and potentially reducing ground clearance.
Aerodynamic Effects: At higher speeds, aerodynamic forces (lift or downforce) can slightly alter the effective weight on the wheels, especially with large loads or trailers. This calculator focuses on static (non-moving) weight distribution.
Tire Inflation and Condition: Properly inflated tires matching the load capacity are essential for safely carrying the distributed weight. Underinflated tires can fail under load and affect handling.
Frequently Asked Questions (FAQ)
What is the ideal weight distribution percentage for towing?
For most conventional trailers, the ideal tongue weight (the downward force on the hitch) is typically 10-15% of the total trailer weight. This translates to a significant portion of the trailer's weight being supported by the tow vehicle's rear axle, which in turn affects the overall front/rear axle distribution of the tow vehicle. Aiming for roughly 45-55% of the total *combined* vehicle and trailer weight on the rear axle of the tow vehicle is a common guideline, but always consult your vehicle and trailer manufacturer's recommendations. Proper weight distribution on wheels is key to preventing trailer sway.
Can I put too much weight on the front axle?
Yes, while some front bias is good for steering control, excessive weight on the front axle can negatively impact handling. It can overload the front tires and suspension, and reduce traction for the rear wheels, which can be problematic for acceleration and braking. The goal is balance within safe limits for both axles.
What happens if my weight distribution is imbalanced?
An imbalanced weight distribution can lead to several safety issues:
Trailer Sway: Too little tongue weight (rear axle overloaded) can cause the trailer to sway uncontrollably, a highly dangerous condition.
Poor Handling: Excessive weight on one axle can make steering sluggish or overly sensitive.
Tire and Suspension Damage: Overloading either axle can lead to premature tire wear, blowouts, or suspension failure.
Vehicle Instability: Overall loss of control, especially during turns or emergency maneuvers.
Understanding weight distribution on wheels is critical for avoiding these hazards.
Where can I find my vehicle's GVWR and GAWR?
GVWR (Gross Vehicle Weight Rating) and GAWR (Gross Axle Weight Rating) are typically found on a certification label located on the driver's side doorjamb, the driver's side door edge, or the inside of the glove compartment door. Your owner's manual may also contain this information.
Does the type of cargo matter for weight distribution?
Yes, the shape and density of cargo matter. High-density items placed low and close to the axles are generally better. However, the primary factor calculated here is the *center of gravity* of the entire load relative to the vehicle's axles. A tall, top-heavy load, even if its CG is well-placed, can still be less stable due to a higher center of gravity.
How does engine placement affect weight distribution?
Engine placement is a major determinant of the *unloaded* weight distribution. Front-engine vehicles (common for most cars and trucks) tend to have more weight over the front axle. Rear-engine vehicles (like some Porsches or older VW Beetles) are rear-heavy. Mid-engine vehicles distribute weight more evenly. This baseline significantly influences how added loads affect the final distribution.
Do I need to consider the weight of passengers?
Yes, absolutely. Passengers and all other items inside the vehicle contribute to the total weight and its distribution. For critical calculations (like towing heavy loads), it's best to estimate passenger weight and include it in your total load. This calculator focuses primarily on added cargo or trailer weight, but the principles apply to all weight additions.
Is it okay if my loaded rear axle weight exceeds my unloaded rear axle weight?
Yes, it is expected and often necessary for the rear axle weight to increase when adding a load, especially when towing. The critical factor is ensuring that the *loaded* rear axle weight does not exceed the vehicle's Gross Axle Weight Rating (GAWR) for the rear axle. A proper balance, often achieved through correct tongue weight for trailers, is essential.
function validateInput(id, errorId, minValue = null, maxValue = null) {
var input = document.getElementById(id);
var errorDiv = document.getElementById(errorId);
var value = parseFloat(input.value);
errorDiv.textContent = "; // Clear previous error
if (isNaN(value)) {
errorDiv.textContent = 'Please enter a valid number.';
return false;
}
if (minValue !== null && value maxValue) {
errorDiv.textContent = 'Value cannot be greater than ' + maxValue + '.';
return false;
}
return true;
}
function calculateWeightDistribution() {
// Clear all previous errors
document.getElementById('frontAxleWeightEmptyError').textContent = ";
document.getElementById('rearAxleWeightEmptyError').textContent = ";
document.getElementById('loadWeightError').textContent = ";
document.getElementById('loadCenterOfGravityDistanceError').textContent = ";
document.getElementById('wheelbaseError').textContent = ";
document.getElementById('frontAxleLoadDistributionError').textContent = ";
// Validate inputs
var valid = true;
valid = validateInput('frontAxleWeightEmpty', 'frontAxleWeightEmptyError', 0) && valid;
valid = validateInput('rearAxleWeightEmpty', 'rearAxleWeightEmptyError', 0) && valid;
valid = validateInput('loadWeight', 'loadWeightError', 0) && valid;
valid = validateInput('loadCenterOfGravityDistance', 'loadCenterOfGravityDistanceError', -100, 100) && valid; // Allow negative for COG behind axle for calculation logic, though unusual. Realistically should be positive.
valid = validateInput('wheelbase', 'wheelbaseError', 0.1) && valid; // Wheelbase must be positive and reasonable
valid = validateInput('frontAxleLoadDistribution', 'frontAxleLoadDistributionError', 0, 100) && valid;
if (!valid) {
// Highlight invalid fields (optional, simple error message is enough per requirements)
return;
}
// Get values
var frontAxleWeightEmpty = parseFloat(document.getElementById('frontAxleWeightEmpty').value);
var rearAxleWeightEmpty = parseFloat(document.getElementById('rearAxleWeightEmpty').value);
var loadWeight = parseFloat(document.getElementById('loadWeight').value);
var loadCenterOfGravityDistance = parseFloat(document.getElementById('loadCenterOfGravityDistance').value);
var wheelbase = parseFloat(document.getElementById('wheelbase').value);
// var desiredFrontAxleDistribution = parseFloat(document.getElementById('frontAxleLoadDistribution').value); // Not used in calculation, only for user guidance
// Intermediate Calculations
var totalWeightUnloaded = frontAxleWeightEmpty + rearAxleWeightEmpty;
// Simplified load distribution formula (assuming load COG relative to rear axle)
// Positive d_load means COG is forward of rear axle (adding weight to front)
// Negative d_load means COG is behind rear axle (lifting weight off rear)
var loadSupportFront = 0;
var loadSupportRear = 0;
if (wheelbase > 0) { // Prevent division by zero
// This calculation models how the load's weight is distributed between the axles based on its CG position
// Moment balance around the rear axle: Load * d_load = FrontAxleSupport * Wheelbase
// Moment balance around the front axle: Load * (Wheelbase – d_load) = RearAxleSupport * Wheelbase
// Simplified:
loadSupportFront = loadWeight * (loadCenterOfGravityDistance / wheelbase);
loadSupportRear = loadWeight * ((wheelbase – loadCenterOfGravityDistance) / wheelbase);
// Ensure support values don't result in negative axle weights if load is extreme and far back/front
// Although mathematically possible with COG behind rear axle, it implies lifting weight.
// Clamp to prevent unrealistic negative supports leading to negative axle weights if logic were different.
// For this specific calculation, we add these supports to existing axle weights.
// A negative loadSupportRear means the load is pulling UP on the rear axle (if COG is behind rear axle).
// A negative loadSupportFront means the load is pulling UP on the front axle (if COG is ahead of front axle).
// Let's refine: if COG is BEHIND rear axle, it ADDS weight to REAR and REDUCES load on FRONT.
// If COG is AHEAD of rear axle, it ADDS weight to FRONT and REDUCES load on REAR.
// The initial formula assumes d_load is distance from REAR axle.
// Let's re-evaluate based on standard physics for trailer hitch:
// Load moment about rear axle: (W_load * d_load) — this creates a tipping moment.
// This moment affects front and rear axle loads.
// W_FA_loaded = W_FA_empty + Support_from_load_at_FA
// W_RA_loaded = W_RA_empty + Support_from_load_at_RA
// Corrected load distribution based on moments:
// Consider the load as a force applied at distance d_load from the rear axle.
// This force creates a moment W_load * d_load about the rear axle.
// The front axle support counteracts this moment.
// The rear axle support counteracts the weight of the load itself directly plus any "anti-lift" from the front.
// A more robust way: sum of vertical forces = 0, sum of moments = 0.
// var F_F = force on front axle, F_R = force on rear axle. var origin be rear axle.
// F_F + F_R = W_total_unloaded + W_load
// Moment about rear axle: F_F * WB – W_load * d_load = 0 => F_F = W_load * (d_load / WB)
// This F_F is the *additional* load on the front axle due to the load's position.
// Similarly, moment about front axle: F_R * WB – W_load * (WB – d_load) = 0 => F_R = W_load * ((WB – d_load) / WB)
// This F_R is the *additional* load on the rear axle due to the load's position.
// Recalculating load support based on this common interpretation:
loadSupportFront = loadWeight * (loadCenterOfGravityDistance / wheelbase);
loadSupportRear = loadWeight * ((wheelbase – loadCenterOfGravityDistance) / wheelbase);
// IMPORTANT: This assumes d_load is the distance of the load's CG FROM THE REAR AXLE.
// If d_load > wheelbase, it means the load's CG is FORWARD of the front axle. This can lift the rear.
// If d_load < 0, it means the load's CG is BEHIND the rear axle. This lifts the front.
// The formulas above calculate the support ASSUMING d_load is a positive distance forward of the rear axle.
// A more general approach considers moments around the CG of the vehicle or axle centers.
// For simplicity and common use case (trailer tongue weight): d_load is the distance from rear axle to hitch.
// Let's make it explicit:
// If d_load is distance FROM REAR AXLE:
// Weight added to FRONT axle = Load * (d_load / WB)
// Weight added to REAR axle = Load * (1 – d_load / WB) WB or d_load < 0
// Let's use the definition: d_load is distance of CG FROM REAR AXLE.
// Moment about Front Axle: (W_RA_empty + Load_at_RA) * WB = (W_FA_empty + Load_at_FA) * WB + W_load * (WB – d_load) <– No, this is complex.
// Let's use the definition: the load's CG is at distance d_load from the REAR AXLE.
// The front axle supports part of the load, the rear axle supports part.
// Total weight = W_FA_empty + W_RA_empty + W_load
// var F_f be the load on front axle, F_r be load on rear axle.
// F_f + F_r = W_total_unloaded + W_load
// If we take moments about the FRONT axle:
// F_r * WB = W_load * (WB – d_load) + W_RA_empty * WB <– This assumes d_load is measured from front axle.
// Let's assume d_load is distance of CG FROM REAR AXLE.
// Moment about REAR AXLE:
// F_f * WB = W_load * d_load + W_FA_empty * (WB- ??) <– this is confusing.
// SIMPLIFIED APPROACH: What portion of the load weight goes to each axle?
// If the load's CG is exactly in the middle (d_load = WB/2), it's 50/50.
// If load CG is closer to rear axle (d_load WB/2), more goes to front.
// This implies d_load is distance from the CENTER of the wheelbase.
// Let's stick to the most common interpretation for trailer towing:
// d_load = distance of trailer hitch (where load is applied) from the REAR AXLE of the tow vehicle.
// Load * d_load creates a moment about the REAR axle.
// The FRONT axle must counteract this moment.
// Force on Front Axle (due to load) * WB = Load * d_load
// So, Load support on Front Axle (S_FA) = Load * (d_load / WB)
// Load support on Rear Axle (S_RA) = Load – S_FA = Load – Load * (d_load / WB) = Load * (1 – d_load / WB)
// This model assumes the load is placed such that its CG is FORWARD of the rear axle OR exactly AT the rear axle.
// If d_load is negative (CG behind rear axle), S_FA becomes negative (load lifts front axle)
// and S_RA becomes Load + |S_FA| (rear axle takes more).
// This is mathematically sound for equilibrium.
// Ensuring realistic values – clamping load support to avoid physically impossible negative axle weights if original weights are low.
loadSupportFront = loadWeight * (loadCenterOfGravityDistance / wheelbase);
loadSupportRear = loadWeight – loadSupportFront; // Total load weight must be accounted for.
// Let's use the formulas derived from moments around axles, assuming d_load is distance from REAR AXLE:
// Moment about front axle: (W_RA_empty + S_RA) * WB = W_load * (WB – d_load) + W_FA_empty * WB ??? This is confusing.
// Standard physics derivation for a simple beam (vehicle chassis) with a point load:
// var origin be the REAR AXLE. Front axle is at WB. Load is at d_load.
// Sum of moments about FRONT AXLE = 0:
// RearAxleForce * WB – Load * (WB – d_load) = 0
// RearAxleForce = Load * (WB – d_load) / WB
// This RearAxleForce is the part of the LOAD supported by the REAR AXLE.
loadSupportRear = loadWeight * (wheelbase – loadCenterOfGravityDistance) / wheelbase;
// Sum of moments about REAR AXLE = 0:
// FrontAxleForce * WB – Load * d_load = 0
// FrontAxleForce = Load * d_load / WB
// This FrontAxleForce is the part of the LOAD supported by the FRONT AXLE.
loadSupportFront = loadWeight * loadCenterOfGravityDistance / wheelbase;
// Now apply these load supports to the empty axle weights.
// If loadCenterOfGravityDistance is negative (load is behind rear axle), it ADDS weight to rear, REDUCES front.
// If loadCenterOfGravityDistance > wheelbase (load is ahead of front axle), it ADDS weight to front, REDUCES rear.
// Final loaded axle weights:
var frontAxleWeightLoaded = frontAxleWeightEmpty + loadSupportFront;
var rearAxleWeightLoaded = rearAxleWeightEmpty + loadSupportRear;
// Ensure no axle weight becomes negative due to extreme load placement, clamp to 0 if needed for display, but report issue.
if (frontAxleWeightLoaded < 0) {
console.warn("Calculated front axle weight is negative. Check load placement and values.");
frontAxleWeightLoaded = 0;
}
if (rearAxleWeightLoaded 0) {
frontAxleDistributionPercent = (frontAxleWeightLoaded / totalWeightLoaded) * 100;
rearAxleDistributionPercent = (rearAxleWeightLoaded / totalWeightLoaded) * 100;
}
// Display Results
document.getElementById('totalWeightUnloaded').textContent = totalWeightUnloaded.toFixed(2);
document.getElementById('loadSupportFront').textContent = loadSupportFront.toFixed(2);
document.getElementById('loadSupportRear').textContent = loadSupportRear.toFixed(2);
document.getElementById('frontAxleWeightLoaded').textContent = frontAxleWeightLoaded.toFixed(2);
document.getElementById('rearAxleWeightLoaded').textContent = rearAxleWeightLoaded.toFixed(2);
document.getElementById('totalWeightLoaded').textContent = totalWeightLoaded.toFixed(2);
document.getElementById('frontAxleDistributionPercent').textContent = frontAxleDistributionPercent.toFixed(2) + '%';
document.getElementById('rearAxleDistributionPercent').textContent = rearAxleDistributionPercent.toFixed(2) + '%';
var primaryResultText = "Balanced Distribution";
var primaryResultClass = "primary-result"; // Default class
if (totalWeightLoaded > 0) {
if (frontAxleDistributionPercent 60) {
primaryResultText = "Warning: Overloaded Front Axle";
primaryResultClass = "primary-result";
} else if (rearAxleDistributionPercent < 40) {
primaryResultText = "Warning: Dangerously Underloaded Rear Axle (Potential Sway)";
primaryResultClass = "primary-result";
}
else {
primaryResultText = "Load Distribution Appears Acceptable";
primaryResultClass = "primary-result"; // Default, good
}
} else {
primaryResultText = "Enter valid weights to see results.";
primaryResultClass = "primary-result";
}
document.getElementById('primaryResult').textContent = primaryResultText;
document.getElementById('primaryResult').className = primaryResultClass; // Apply class for styling
// Update Chart
updateChart(frontAxleWeightLoaded, rearAxleWeightLoaded, totalWeightLoaded);
}
function updateChart(frontLoad, rearLoad, totalLoad) {
var ctx = document.getElementById('distributionChart').getContext('2d');
if (window.myDistributionChart) {
window.myDistributionChart.destroy(); // Destroy previous chart instance
}
var chartData = {
labels: ['Front Axle', 'Rear Axle'],
datasets: [{
label: 'Axle Load (kg/lbs)',
data: [frontLoad, rearLoad],
backgroundColor: [
'rgba(220, 53, 69, 0.7)', // Red for Front Axle
'rgba(255, 193, 7, 0.7)' // Yellow for Rear Axle
],
borderColor: [
'rgba(220, 53, 69, 1)',
'rgba(255, 193, 7, 1)'
],
borderWidth: 1
}]
};
var chartOptions = {
responsive: true,
maintainAspectRatio: false, // Allow custom height/width
scales: {
y: {
beginAtZero: true,
title: {
display: true,
text: 'Weight (kg/lbs)'
}
}
},
plugins: {
legend: {
display: false // Use custom legend
},
title: {
display: false // Title handled by canvas container caption
}
}
};
// Dynamically set canvas height for better visualization
var canvasContainer = document.getElementById('chartContainer');
ctx.canvas.height = 300; // Fixed height for canvas
window.myDistributionChart = new Chart(ctx, {
type: 'bar',
data: chartData,
options: chartOptions
});
}
function resetForm() {
document.getElementById('frontAxleWeightEmpty').value = '1500';
document.getElementById('rearAxleWeightEmpty').value = '1200';
document.getElementById('loadWeight').value = '800';
document.getElementById('loadCenterOfGravityDistance').value = '2';
document.getElementById('wheelbase').value = '3.5';
document.getElementById('frontAxleLoadDistribution').value = '50';
// Clear errors
document.getElementById('frontAxleWeightEmptyError').textContent = '';
document.getElementById('rearAxleWeightEmptyError').textContent = '';
document.getElementById('loadWeightError').textContent = '';
document.getElementById('loadCenterOfGravityDistanceError').textContent = '';
document.getElementById('wheelbaseError').textContent = '';
document.getElementById('frontAxleLoadDistributionError').textContent = '';
// Reset results display
document.getElementById('totalWeightUnloaded').textContent = '–';
document.getElementById('loadSupportFront').textContent = '–';
document.getElementById('loadSupportRear').textContent = '–';
document.getElementById('frontAxleWeightLoaded').textContent = '–';
document.getElementById('rearAxleWeightLoaded').textContent = '–';
document.getElementById('totalWeightLoaded').textContent = '–';
document.getElementById('frontAxleDistributionPercent').textContent = '–';
document.getElementById('rearAxleDistributionPercent').textContent = '–';
document.getElementById('primaryResult').textContent = '–';
// Clear chart
if (window.myDistributionChart) {
window.myDistributionChart.destroy();
window.myDistributionChart = null;
}
var ctx = document.getElementById('distributionChart').getContext('2d');
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height); // Clear canvas
}
function copyResults() {
var resultsText = "— Weight Distribution Results —\n\n";
resultsText += "Inputs:\n";
resultsText += " Front Axle Weight (Unloaded): " + document.getElementById('frontAxleWeightEmpty').value + "\n";
resultsText += " Rear Axle Weight (Unloaded): " + document.getElementById('rearAxleWeightEmpty').value + "\n";
resultsText += " Total Added Load Weight: " + document.getElementById('loadWeight').value + "\n";
resultsText += " Load Center of Gravity Distance from Rear Axle: " + document.getElementById('loadCenterOfGravityDistance').value + "\n";
resultsText += " Vehicle Wheelbase: " + document.getElementById('wheelbase').value + "\n";
resultsText += " Desired Front Axle Load Distribution: " + document.getElementById('frontAxleLoadDistribution').value + "%\n\n";
resultsText += "Calculated Distribution:\n";
resultsText += " Total Vehicle Weight (Unloaded): " + document.getElementById('totalWeightUnloaded').textContent + "\n";
resultsText += " Load Support at Front Axle: " + document.getElementById('loadSupportFront').textContent + "\n";
resultsText += " Load Support at Rear Axle: " + document.getElementById('loadSupportRear').textContent + "\n";
resultsText += " Front Axle Weight (Loaded): " + document.getElementById('frontAxleWeightLoaded').textContent + "\n";
resultsText += " Rear Axle Weight (Loaded): " + document.getElementById('rearAxleWeightLoaded').textContent + "\n";
resultsText += " Total Vehicle Weight (Loaded): " + document.getElementById('totalWeightLoaded').textContent + "\n";
resultsText += " Front Axle Distribution (%): " + document.getElementById('frontAxleDistributionPercent').textContent + "\n";
resultsText += " Rear Axle Distribution (%): " + document.getElementById('rearAxleDistributionPercent').textContent + "\n\n";
resultsText += "Primary Result: " + document.getElementById('primaryResult').textContent + "\n\n";
resultsText += "Formula Assumptions: Calculations are based on static equilibrium principles assuming a single point load and its center of gravity relative to the vehicle's axles and wheelbase.\n";
// Use a temporary textarea to copy text
var textArea = document.createElement("textarea");
textArea.value = resultsText;
textArea.style.position = "fixed"; // Avoid scrolling to bottom of page
textArea.style.left = "-9999px";
document.body.appendChild(textArea);
textArea.focus();
textArea.select();
try {
var successful = document.execCommand('copy');
var msg = successful ? 'Results copied to clipboard!' : 'Failed to copy results.';
console.log(msg);
// Optionally, show a temporary message to the user
var copyButton = document.querySelector('button.btn-success');
var originalText = copyButton.textContent;
copyButton.textContent = 'Copied!';
setTimeout(function() {
copyButton.textContent = originalText;
}, 2000);
} catch (err) {
console.error('Fallback: Oops, unable to copy', err);
}
document.body.removeChild(textArea);
}
// Toggle FAQ answers
document.addEventListener('DOMContentLoaded', function() {
var faqQuestions = document.querySelectorAll('.faq-question');
faqQuestions.forEach(function(question) {
question.addEventListener('click', function() {
var faqItem = this.closest('.faq-item');
faqItem.classList.toggle('open');
});
});
// Initial calculation on page load
calculateWeightDistribution();
});