Driver Knowledge Tests

How much weight can you carry over different types of axles on a truck or trailer?

To avoid excess wear on the road and to ensure that bridges and other road infrastructure can cope, there are limits to how much weight can be placed above different types of axle. The tyres on those axles transfer the weight through to the surface. The rules are anything but consistent.

Single axle, single tyresSteer axle*
Non-steer axle, tyres <375mm
Non-steer axle, tyres 375-449mm
Non-steer axle, tyres >450mm
6000kg
6000kg
6700kg
7000kg
*Some exceptions exist in Queensland and for road trains
Single axle, dual tyresPig trailer
Any other vehicle
A complying bus or a bus authorised to carry standing passengers
Ultra-low-floor bus with no axle groups
8500kg
9000kg
1000kg

11000kg
Twin-steer axle group, single tyresNon-load-sharing suspension system
Load-sharing suspension system
10000kg
11000kg
Tandem axle group, single tyres<375mm
375-449mm
>449mm
11000kg
13300kg
14000kg
Tandem axle group, dual + single tyresSingle on one axle, dual on the other
A complying bus
13000kg
14000kg
Tandem axle group, dual tyresPig trailer
Any other vehicle
15000kg
16500kg
Tri-axle group,single tyresSingle tyres <375mm, or a combination of singles and duals
Pig trailer >374mm, duals on all axles or a combination
15000kg

18000kg
Tri-axle group, dual tyresVehicle other than a pig trailer, single tyres >374mm, or duals or a combination20000kg

There are some associated rules:

Dog or pig trailers must not be heavier than the truck towing them.

The maximum GML (general mass limits) for a combination is 42500kg unless operating under a notice permit or specific scheme.

All heavy vehicle must be fitted with road-friendly suspension and accredited under the NHVAS (National Heavy Vehicle Accreditation Scheme).

Darren is an expert on driving and transport, and is a member of the Institute of Advanced Motorists

Posted in Advice

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