About this calculator

Estimate static load transfer between two support planes from measured baseline axle-group loads and cargo center positions. A rear tandem or tridem is represented as one support.

Inputs

How to use this calculator

Added cargo load point

  1. Added load at this position (lb)Weight of one cargo group or pallet; add rows for separate center-of-mass positions.
  2. Load center behind the front axle group (ft)Measured longitudinal distance from the front support plane.

Shared inputs

  1. Distance between front and rear axle-group support planes (ft)Use the centers of the tire-contact groups as an approximation; the model has only two vertical supports.
  2. Measured front axle-group baseline (lb)Actual scale measurement for this configuration before the added rows.
  3. Measured rear axle-group baseline (lb)Actual scale measurement for this configuration before the added rows.
  4. Front axle-group gross axle weight rating (GAWR) (lb)Use the manufacturer rating for this axle group; check tire and rim limits separately.
  5. Rear axle-group gross axle weight rating (GAWR) (lb)Use the manufacturer rating for the combined rear axle group; this model does not split individual tandem axles.

Enter the shipment or scenario values, then select Calculate result.

Method

Formula and variables

Set the front support position to 0 and the rear support position to wheelbase L. For each load W at distance x from the front, added front reaction = W × (L − x) ÷ L and added rear reaction = W × x ÷ L. Add the load-point reactions to the measured front and rear baseline axle-group loads.

Added load at this position (lb)
Weight of one cargo group or pallet; add rows for separate center-of-mass positions.
Load center behind the front axle group (ft)
Measured longitudinal distance from the front support plane.
Distance between front and rear axle-group support planes (ft)
Use the centers of the tire-contact groups as an approximation; the model has only two vertical supports.
Measured front axle-group baseline (lb)
Actual scale measurement for this configuration before the added rows.
Measured rear axle-group baseline (lb)
Actual scale measurement for this configuration before the added rows.
Front axle-group gross axle weight rating (GAWR) (lb)
Use the manufacturer rating for this axle group; check tire and rim limits separately.
Rear axle-group gross axle weight rating (GAWR) (lb)
Use the manufacturer rating for the combined rear axle group; this model does not split individual tandem axles.

Interpret the result

Front and rear reactions add to baseline loads. Remaining gross axle weight rating (GAWR) headroom is a separate comparison; individual axle and bridge-formula checks require additional measurements.

Outputs: Estimated front/rear reactions and rating headroom

Two-support static estimate only. Treats the rear tandem/tridem as one support, cargo as stationary point loads and the frame as rigid. It does not model suspension equalization, fifth-wheel/pin forces separately, braking/dynamic transfer, individual axle spacing, tires, bridge formula, state limits or scale uncertainty. Load centers must lie between the two entered support planes. A scale ticket is needed for operating decisions.

Worked example

Check the arithmetic

This example uses the starting values shown above. The arithmetic below is calculated independently of the interactive result.

Work through the calculation

  1. Added front reaction = 1,000 × (20 − 5) ÷ 20 = 750 lb; rear reaction = 1,000 × 5 ÷ 20 = 250 lb.
  2. Estimated front = 8,000 + 750 = 8,750 lb; rear = 12,000 + 250 = 12,250 lb.
  3. Combined axle-group load = 8,750 + 12,250 = 21,000 lb.

Compare the displayed result

Expected displayed result: 21,000 lb combined axle-group load

FAQs

Does this split weight across individual tandem axles?

No. The rear axle group is one support. Suspension equalization, individual axle spacing and dynamic transfer are outside this two-support model.

Example inputs and options

Starting values are examples unless a field identifies a dated rule. Unit selectors convert only fields marked for conversion. Rates and model options keep the units and basis shown in their labels.

Added load at this position (lb)
Example: 1000
Load center behind the front axle group (ft)
Example: 5
Distance between front and rear axle-group support planes (ft)
Example: 20
Measured front axle-group baseline (lb)
Example: 8000
Measured rear axle-group baseline (lb)
Example: 12000
Front axle-group gross axle weight rating (GAWR) (lb)
Example: 12000
Rear axle-group gross axle weight rating (GAWR) (lb)
Example: 20000