About this calculator
A truck whose total weight is still below its JBB (permitted gross vehicle weight in Indonesia) can still overload an axle when the cargo sits too far back or too far forward. An overloaded rear axle wears out tyres, springs and roads faster, while a steer axle that is too light makes steering and braking unstable. It happens often when heavy items such as machinery, coils or dense pallets are placed only at the tail of the deck near the doors.
The calculator uses a beam on two supports. A load W with its centre of gravity at distance x behind the front axle puts W × x ÷ wheelbase on the rear axle and the rest on the front axle. For a tandem, the rear is taken at the centre of the axle group. The empty vehicle weight per axle is added, and the results are compared with each axle's capacity and the JBB. You also get the window for the cargo centre of gravity, measured from the front of the deck, in which neither axle is overloaded, and a warning when the front axle carries less than 20% of the gross weight (a rule of thumb).
Default figures for CDD, Fuso, tronton and other types come from the catalogue and are only typical. Use the figures from your KIR book and the vehicle manufacturer: wheelbase, tare per axle, axle capacity and JBB. The heaviest permitted axle load (MST) on a road depends on its road class, so check the official rules that apply to your route.
Worked example
A CDD box truck (wheelbase 3,350 mm, deck starting 700 mm behind the front axle, deck length 4,300 mm, tare 1,850 kg front + 1,400 kg rear) carries 5 t spread evenly over the whole deck.
- Centre of gravity: 700 + 4,300 ÷ 2 = 2,850 mm behind the front axle (2,150 mm from the deck front)
- Rear axle: 5,000 × 2,850 ÷ 3,350 ≈ 4,253.7 + 1,400 = 5,654 kg (capacity 6,000)
- Front axle: 746.3 + 1,850 = 2,596 kg (capacity 3,300); gross 8,250 kg = JBB
- Safe centre-of-gravity window for 5 t: 1,678.5–2,382 mm from the deck front
- The same 5 t on the last metre of the deck only: rear axle 8,116 kg (over the limit) and the front axle drops to 134 kg
An evenly spread load is fine; the same load at the tail overloads the rear axle and makes steering dangerous.
How to use it
Choose the truck
Pick a truck from the catalogue, then adjust wheelbase, front axle to deck distance, tare per axle, axle capacities and JBB from the KIR book.
Place the cargo
For each item, enter its weight, its start position from the front of the deck and the length it occupies. Add a line for each other item.
Read the axle loads
See front and rear axle loads, gross weight, the front axle share and warnings when an axle or the JBB is exceeded.
Shift the load if needed
Use the safe centre-of-gravity window to move the cargo, then continue to the 3D Planner or the ODOL check before departure.