Glossary of technical terms.

For those who sometimes get confused (me included!) with all the technical terms used in legislation and the trailer world here is a list of the most commonly used terms.

GLOSSARY

GROSS WEIGHT
The total weight of the trailer (or towing vehicle) and load Gross Vehicle Weight (GVW) or Gross Weight Mass (GWM) The total weight of the towing vehicle and its load.
GROSS TRAIN WEIGHT
The maximum allowable combined weight (combined MAM) of the towing vehicle and trailer as set by the towing vehicle manufacturer.
KERBWEIGHT
The weight of the towing vehicle (without payload), including all fluids required for operation, 90% full tank, 68kg driver and 7kg luggage.
MAXIMUM GROSS WEIGHT
The maximum figure set by the manufacturer for the gross weight. This will normally be the technically permissible maximum based on the carrying capacity of the tyres, axles, coupling, suspension and chassis but may have been adjusted downwards for commercial reasons.
MAXIMUM AUTHORISED MASS
As above
MAXIMUM TOWING LIMIT
The most weight a car may tow (specified by the manufacturer).
MTPLM
The maximum weight of the caravan, as stated by the manufacturer (pre-1998 caravans: MGW, or Maximum Gross Weight).
NOSEWEIGHT
The maximum downward force your towball can bear, or your caravan exerts.
MASS IN RUNNING ORDER (MIRO)
The weight of the caravan equipped to the manufacturer's standard specification.
UNLADEN WEIGHT
The weight of the trailer (or towing vehicle) less removable optional equipment and load.
USER PAYLOAD
The user payload comprises all extra items not included in the manufacturer's standard spec. The user payload is the MiRO subtracted from the MTPLM.
VERTICAL STATIC LOAD/NOSE LOAD
The weight imposed on the towball or eye by the trailer coupling.

* NB: For the purposes of determining the gross vehicle weight of the towing vehicle, the noseweight of the caravan is included as part of the car's payload. Consequently, the gross train weight is really the sum of the gross vehicle weight including the noseweight plus the axle weight of the caravan, not its total weight. If the noseweight is not included in the vehicle weight but in the weight of the caravan, there is a danger of overloading the car.

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