Towballs for towbars come in a variety of load capacities, sizes, shank widths and shank lengths; there are 20 different products in total! Add in material/finish options like chrome finish, zinc coating, stainless steel, 2 sizes of converter balls, high rise towball kits for European caravans and trailer, some unusual North American and super heavy duty towballs and the total escalates past 30!!
The towball size must match the size of the coupling on the trailer being towed; this is very important, a 50 ml coupling will fit on a 1 7/8 ths towball but is liable to pop off and is an illegal combination. Lighter trailers can be towed with a 2000 kg ball but heavier applications need a 3500 capacity. Towbars with a regular 16 or 20 mm thick tongue are suited to a regular length shank of 45 mm but a long shank towball of 50 mm or 65 mm should be used when a towbar has a backing guide, load leveler or an extra thick tongue is involved. It is also important that the shank size, 3/4″, 7/8″, or 1″” suit the size of the hole drilled in the tongue as the towball may work loose if the hole drilled for it is too big. High rise towballs, also called long neck towballs, are need to prevent damage to Alko trailer couplings on European trailers.
Quite often WOF failures arise from inspections revealing mis matched towballs and trailer couplings and shanks found to be too short; the towball shank must be long enough to stick out beyond the bottom of the nut.
The good news is that Megatyre Towbars Auckland stocks most of these towball options and can usually get other options within 24 hours.