Why 3,500 kg does not tell the whole story
A vehicle may have a published 3,500 kg braked towing limit while its practical combination is constrained by GVM, GCM, towball download, axle ratings, fitted tow equipment or driver licence class. Manufacturer figures also vary by grade, cab, body, engine and drivetrain.
Towball download is part of the load carried by the towing vehicle. It is included in the vehicle-mass check, while only the trailer's remaining axle-supported mass is added to that vehicle mass for the operating combination calculation. This avoids counting the same weight twice.
- ✓Use the exact configuration, not a model-family headline
- ✓Include fitted structures and every added accessory
- ✓Use the trailer's real loaded mass and towball download
- ✓Measure axle loads in the intended loaded and hitched condition
Published plan or weighbridge check?
Plan a vehicle starts from a dated manufacturer payload, GVM and GCM record. It is useful before purchase, but individual vehicles and finished fit-outs vary. Chassis-cab users must include the completed tray or service body wherever it is excluded from the published baseline.
Check my fitted vehicle starts from the mass of your vehicle as actually weighed. Add only the people or load that were not on the vehicle at that weighing. A single total still cannot prove either axle is inside its rating, so obtain separate axle readings where that matters.
Licence and certification stay separate
NZTA describes Class 1 licence scope using GLW and GCW. For a combination, GCW is based on the GLWs of the vehicles—not simply today's operating mass. The optional licence check therefore asks for trailer GLW and uses the entered vehicle GVM as its GLW planning value.
This calculator is not a legal or engineering certificate. Modifications, loading position, tow hardware, trailer configuration and other rules can affect the real answer. Confirm the exact combination with current NZTA guidance and qualified suppliers or certifiers before use.