Safety chains
All pig trailers with rigid drawbars (with or without breakaway brakes but excluding converter dollies) and, any other trailer
without breakaway brakes, must be fitted with safety chains that are marked in accordance with the relevant Australian
Standard complying with the following:
- trailers that do not exceed 2500 kg ATM must have at least one safety chain complying with Australian Standard
AS 4177.4-1994 or Australian Standard AS 4177.4-2004 ‘Caravan and light trailer towing components Part 4:
Safety chains up to 3500kg capacity’, or be a safety cable with a certified load capacity of the same
- trailers over 2.5 tonnes and not exceeding 3.5 tonnes ATM must have two safety chains of designation of 3500 kg
complying with Australian Standard AS 4177.4-1994 or Australian Standard AS 4177.42004
- trailers over 3500 kg ATM must have two safety chains made from steel of a minimum 800 MPa breaking stress
that conforms to the mechanical properties of Grade T chain as specified in Australian Standard AS 2321-1979
‘Short Link Chain for Lifting Purposes (uncalibrated)’ or Australian Standard AS 2321-2006 ‘Short Link Chain for
Lifting Purposes.’ Each chain must be sized such that the minimum breaking load exceeds the ATM.
The length of the safety chain/s must prevent the trailer’s drawbar hitting the ground if the trailer is detached from the
towing vehicle. The safety chains must be properly connected to the tow bar with attachments capable of withstanding the
specified breaking load of each chain. Do not use padlocks.
For further information regarding couplings, brake requirements and safety chains please refer to the Vehicle Standard
Bulletin – Building Small Trailers (VSB1) available on the Department of Infrastructure and Regional Development website
(www.infrastructure.gov.au)
Safety Chain Connections to Tow Bar
Safety chain(s) must be suitably and appropriately connected to a tow bar. The use of a shackle is permitted, provided the
shackle used is fit for the purpose and compatible with the safety chain in terms of strength and size.
It is the responsibility of the vehicle owner/operator to ensure that a shackle, if used to attach safety chain to tow bar, is fit
for the purpose and compatible with the safety chain. This can be demonstrated in a couple of ways:
- Use of a shackle that is compatible with the safety chain AND complies with AS 2741-2002 “Shackles”. In this case
the shackle will have appropriate markings.
Table-1 Selection of D Shackle (Guide only)
Trailer ATM (kg) Chain size
classification
AS 4177.4-2004
Chain Marking
AS 4177.4-2004
Suitable rated D shackle size
AS 2741-2002
Grade “S” or“6 dee” or “6 bow”
Minimum Proof Load
Strength (kN)
Chain / Shackle
up to 1 000 1 000 4177-10 6mm S WLL 0.5T 4.9 / 9.9
up to 1 600 1 600 4177-16 6mm S WLL 0.5T 7.9 / 9.9
up to 2 500 2 500 4177-25 8mm S WLL 0.75T 12.3 / 14.8
up to 3 500 3 500 4177-35 10mm S WLL 1.0T 17.2 / 19.7
- Alternatively, the use of a shackle that is compatible with the safety chain AND is of a reputable brand. In this case,
the shackle will have appropriate markings to show the brand and/or part identification sufficient to trace its brand
and strength.
Safe Towing – All about safe towing – 6 –
It should be recognised that a shackle that does not have any markings makes it difficult to establish its strength
