Tow balls

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robbief, Feb 22, 10:29am
can anyone tell me the advantages dis advantages 50mm tow ball to.1.7/8 tow ball
mugenb20b, Feb 22, 10:37am
50 mm tow ball is slightly bigger but also less common.
robbief, Feb 22, 10:40am
so why are there two sizes! 1/8: inch dif
johnf_456, Feb 22, 11:00am
No disadvantages as long as you have the right towball that matches your trailer. Most common is the 1 7/8
bjmh, Feb 22, 11:08am
can be a real trap for young players if you have the type of tow coupling on some bigger trailers,that can fit both.just by lifting up and turning coupling handle.It is marked but most couplings get covered in dirt etc.
sas777, Feb 22, 11:09am
Maybe because of UK import vehicles.
The old size was phased out in Britain after they joined the Common market; the 50mm size was introduced. Whilst the authorities didn't stop drivers using the old ball size it was not possible to pass an MOT with one fitted so they gradually died out.
This would have occurred late seventies / early eighties
rsr72, Feb 22, 11:10am
50 mm the standard in many countries. European OE fitments are 50mm with their sophisticated forged tow bar equipment.
About time we phased out supplying and fitting 1 7/8.
skin1235, Feb 22, 11:15am
the old style tow ball was a bolt through the center ( now illegal)
it was 1 7/8ths, and real easy to shear the bolt
they upped the size to allow heavier bolts to be used, but then outlawed the entire bolt system
the more common size is the 1 7/8ths as above has said, but there is also a legal aspect to the sizes, a trailer or caravan over a certain weight is supposed to use a 2 inch
inconvenient to be changing the balls for differing vehicles though so we tend to ignore that rule - the 2 inch has a larger mount stub which often means redrilling the towbar too - more inconvenience, and once redrilled you have to use a spacer if you put a 1 7/8th back on, even more inconvenience
but the larger mount stub means the 2 inch is a stronger unit, should be used for heavier tandems and caravans
phillip.weston, Feb 22, 11:16am
Yes most countries use 50mm (including Australia) yet NZ seem to lag behind using 1 7/8" balls. You can buy balls with a turn of a lever change between 1 7/8 and 50mm but you'll find you will use 1 7/8" the most.
gman35, Feb 22, 11:23am
As an aside , why do so many tow ball nuts/threads appear to have never been greased on initial installation when you go to remove them , and find the bloody ball is turning also ! !
pauldw, Feb 22, 12:01pm
The 50mm isn't always on a larger mounting stub. I have 1 that is marked 2000kg and is the same as my 17/8. I've seen a larger mount marked 3500kg.
bigfatmat1, Feb 22, 2:36pm
1 7/8 & 50mmis 19mm shank up to 2000kg. 2001kg to 3500kg is 22mm shank
skin1235, Feb 22, 4:20pm
Fair enough, all the 2 inch ( 50mm) ones I've had have had the larger shank, I assumed that to be normal for 50mm balls
matarautrader, Feb 22, 4:32pm
I have a Alco 50mm towball for our English caravan. Its rated at 3500kg
franc123, Feb 22, 8:21pm
50mm balls are just a nuisance, the vast majority of trailers (including rentals) in NZ still use the old size couplings, even newish ones, and again in the majority of cases a higher strength rating offered by a metric ball isn't needed. If you do come across a metric coupling at least its still possible, albeit not advisable, to fit it to an imperial ball, the other way round you can't. Really its best to just get a duofit ball such as those marketed/made by Trailcom.
rsr72, Feb 23, 9:17am
Just what NZ needs to start introducing, and standardise to the modern 50mm.
therafter1, Feb 23, 9:49am
For sure ??
bjdw, Feb 23, 10:41am
If you hire a trailer from a hire place the coupling is most likely to be . !
bjdw, Feb 23, 10:43am
5omm or 1 7/8" tow ball is $22.Duofit tow ball is $98.
therafter1, Feb 23, 10:54am
Zachary, and a good percentage of the problems relate to hire/borrowed trailers etc.

Yep, she fits, it??
rsr72, Feb 23, 11:33am
#21- Yet strangely enough, other countries don't require safety chains, obviously not seeing any problem with their 50mm.
Expensive European forged demountable, folding, OE tow fittings don't have provision for a safety chain.
therafter1, Feb 23, 11:41am
Probably because the original ball size in this country with its corresponding narrow shank has already been identified as having safety related issues identified with it but for some reason nothing has ever been done about it. And the original ball and shank size was probably designed to cope with a 6x4 trailer load of garden vegetation to the dump now and again, but has graduated over the years to being of sufficient strength to drag a u-haul trailer full of household contents from Invers to Kaitaia lol
therafter1, Feb 23, 11:47am
But the law is the law and as john say??
bigfatmat1, Feb 23, 12:14pm
nothing a tea towel over the town all wont fix
franc123, Feb 23, 12:33pm
The difference is the duofit can be changed without tools, a standard ball can't be unless you carry a large enough socket and strongbar and a pipewrench about with you.If you had to buy these to keep permanently in your vehicle plus $44 worth of balls what have you saved!