SMMT Guide on Couplings > 50mm Ball Brackets and Couplings

50mm Ball Brackets and Couplings

There are no specific regulations covering the ball bracket itself other than the requirements of EC Directive 94120 EC.

However, this Directive, together with BSI and ISO (International Standards Organisation) standards, specifies the dimensions of the ball, the clearances around the ball and the range of permissible heights when mounted on a laden vehicle.

It is strongly recommended that only units manufactured to meet these standards are fitted. These can be identified by a small flat area on top of the ball which is usually stamped with ISO 50.
Ball brackets may be one-piece fixed or detachable in one or more parts.

Most ball couplings fitted to trailers have a wear adjustment or indicator feature incorporated and they are designed to accommodate a ball bracket which is under size by 1mm, that is to say, 49mm. diameter.

Cheek for looseness and rattles as any more wear and tear than this can cause the coupling to detach from the ball.