GROSS TRAILER MASS
Gross Trailer Mass ( known generally as GTM ) is the mass transmitted to the ground by the tyres of the trailer when coupled to a tow vehicle and carrying the maximum load recommended by the manufacturer or importer , approximately uniformly distributed over the load bearing area .
In short , it is the limit of weight that can be placed over the axles of the trailer . It does not include the weight exerted on the towball or jockey wheel .
Important note : GTM is a weight rating . You ’ ll find it marked on the van ’ s vehicle plate and it must not be exceeded .
AGGREGATE TRAILER MASS
Aggregate Trailer Mass ( ATM ) is the total mass of the caravan / trailer when carrying the maximum load recommended by the manufacturer . This includes mass imposed onto the tow vehicle / jockey wheel when resting on a horizontal plane .
If you were to put your caravan on a weighbridge on its own , resting on the jockey wheel , this is the weight you would measure against ATM . Basically , it is the maximum total weight the trailer can be , as stipulated by the manufacturer .
Important note : ATM is also a weight rating that must not be exceeded .
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