25/05/2022
Interesting read…..
LITTLE KNOWN FACTS ABOUT THE 50MM TOW BALL THAT ALL SHOULD KNOW.
The most popular tow hitch is the standard 50mm tow ball but, is it’s time limited with so many better options available now.
Here is some interesting information about this popular tow hitch.
The 50mm tow ball is only rated to tow up to 3,500kg. Above that load, other hitch options must be used.
Larger 70mm balls or other hitch types are required above this weight.
All hitch types are rated so ensure you have the right one for your towing job.
Transport for NSW advise that 50mm ball couplings must comply to ADR 62 and Australian Standard AS4177.
A coupling complying with this standard must be permanently marked accordingly:
• the manufacturer's name or trademark;
• the mark ‘50’;
• the maximum rating for the coupling body in one of the following, as applicable,
• 750 kg; or
• 2000 kg; or
• 3500 kg;
• a code to indicate the serial number, batch, production date, or similar;
• the words ‘DO NOT WELD’ if the coupling body is manufactured from nonweldable materials;
• the words ‘WELD ONLY’ if the coupling body is specifically designed to be attached by welding only
Therefore, ensure you have the correct tow ball for your towing job, and beware of non-complying cheap overseas imports.
The 50mm tow ball must also be fitted at a height, when loaded, of between 350 and 460mm off the ground to be compliant.
WHY – Vehicle Standards at Federal Department of Infrastructure advise –
“The prescribed fitment height for ball couplings in AS 4177 is intended to ensure effective coupling articulation in normal operating conditions. When a ball coupling is operated with high levels of articulation it can become unhitched causing the trailer to become detached from the tow vehicle. The tow ball fitment height range ensures adequate levels of coupling articulation under normal driving conditions to ensure safe operation of vehicles and trailers operating ball coupling devices.”
This height limit will make safe coupling with many modern off-road caravans and lifted tow vehicles difficult to comply with, but it is still the law and should be complied with.
The 200 Series Landcruiser has one of the highest hitch receivers on the market, and most would need a drop hitch to ensure safe towing practice is followed.
NOTE: - This height limit is NOT noted relevant to other types of hitches. i.e., DO35, Hitch-Ezy etc.
Although they are by far the most used hitch, I am not a big fan of the 50mm ball use, apart from the suburban box trailer as a universal coupling.
The 50 mm coupling will have limited roll and once the limit is reached the caravan can in fact assist rolling over the tow vehicle in a caravan rollover situation. The cup rolls and pushes the ball stem to help tip the tow vehicle.
They are therefore not suited to, nor popular with serious off-road towing.
While we all have our own preferences, I recommend an articulated tow hitch, like the Hitch-Ezy, that has automatic double locking and is unusual which also reduces the chance of theft. I use the 5,000 kg unit to match my vehicle’s 4t towing capacity and even more rare.
The 3,500 kg units suit most needs.
The vehicle post is also one of the strongest on the market. No, they are not a sponsor.
I have a separate 380mm drop hitch with 50mm ball for borrowing / hiring a box or other trailers.
While many options are available, I have seen many photos of, and had a friend suffer broken hitch posts on another popular unit, so it pays to do some research of your own.
Popular hitches may not be the best or suit your individual rig needs.
NOTE :- TOWING WITH A TRUCK OR VEHICLE RATED OVER 5,000 GVM, FITTED WITH A 50mm BALL, THE 50MM TOW BALL CAPACITY MAY BE DERATED.
THIS WILL AFFECT MANY LARGE MOTORHOMES TOWING CAR TRAILERS ETC. ALSO.
If your tow vehicle has a GVM of 5,000 kg or above, a derating factor applies to the 50mm tow ball. It may no longer be able to tow a 3,500kg trailer.
Even though the ball may be originally rated at 3,500 kgs, when you attach it to a vehicle with a GVM of above 5,000kgs you will not be able to tow a 3,500 kg van with this set up in many cases.
A notice may also need to be fitted to the tow vehicle stating the maximum trailer weight that can be towed with the 50mm ball.
For example, a tow vehicle with a GVM of 6,000kgs can only tow a trailer / caravan to a max of 3,089kgs when using a 50mm tow ball. The trailer weight reduces dramatically the heavier the tow vehicle GVM gets. (7,500 GVM tow vehicle – 2,801kg van etc.)
A full explanation, calculations and chart is available from the National Heavy Vehicle Regulator (NHVR).
https://www.nhvr.gov.au/files/201709-0684-vsg16-50mm-ball-couplings.pdf
The towing capacity of your vehicle will be the LESSER weight capacity of the following: -
• Tow vehicle towing capacity
• Tow bar weigh capacity
• Tow hitch weight capacity
• Tow hitch coupling fitted to the tow hitch
• Common sense
Always check the weigh capacity of any replacement or drop hitches, as they often look the same, but load capacity may vary from 2,500kgs to 3,500kgs and above.
GVM and GCM weight limits must be adhered to as do other factors include rear axle loading as with most overhung type hitches the actual weight on the tow hitch is multiplied by 140 – 150% onto the rear axle when connected.
IE: - A tow ball weight of 300kgs will often be an additional 450kg on the rear axle, due to the leverage of weight off the front axle.
This makes many seemingly great tow vehicles exceed the rear axle loading and become unroadworthy. Some of the American ‘trucks’ come into this category.
Thank you for following Truck Friendly.
Stay safe everyone.
Cheers
Ken Wilson
