Originally submitted by Mike Wednesday, 21 April 2004
Weights, a guide through the maze.
A quick count reveals no less than 14 different weights, weight limits and recommendations applicable to caravans and towing vehicles, some, extremely important, others, less so. This guide will help newcomers to become familiar with weights before stepping further into the world of caravanning. Here, the weights are presented in two groups, Essential Weights and Other Weights. The Essential group covers those weights extremely important for safety and legal reasons. The Other Weights group covers items used generally for guidance and planning purposes. Further, Matching Weights shows the combinations of weights that must be taken in to consideration when buying a caravan or tow car.
Essential Weights for the Tow Car.
Maximum Trailer Weight. The maximum weight of a caravan or trailer the car may tow as specified by the manufacturer. It is an offence to tow more than the stated limit.
Maximum Towball Weight. The maximum weight that may be applied to the car towball. Is an important safety limit specified by the vehicle manufacturer. If the towball weight is too high, braking, steering and roadholding will be seriously impaired because excess weight on the rear will tend to lift the front wheels off the ground.
Gross Vehicle Weight *. The absolute maximum the car and all that it carries may weigh.
Gross Train Mass*. The maximum permitted total combined weight of the laden car and laden caravan.
* Not available for many cars although now required under European law. Currently these are seldom, if ever, checked by authorities.
Essential Weights for the Caravan.
Maximum Technically Permissible Laden Mass (MTPLM). The absolute maximum the caravan may weigh as specified by the manufacturer. The caravan plus everything carried in- and outside must not exceed the MTPLM. It is an offence to tow a caravan weighing more than the MTPLM. Was previously known as the Gross Vehicle Weight.
Hitch or Towball Weight, Maximum and Minimum. The weight of the caravan pressing down on the car towing hook.
A maximum limit prevents overloading and possible damage to the A frame. A minimum weight, if stated, is given to make sure the tail doesn?t shake the dog, so to speak. The hitch weight plays a critical role in stability and is best checked before each trip using a either a special, but cheap, weighing scale or a combination of bathroom scales and a suitable piece of wood.
If a recommended hitch weight is unknown or, more likely, was never specified by the manufacturer a commonly used guide figure is 7% of the actual caravan weight. An optimal towing weight is found only by trial and error. The hitch weight is ?adjusted? by placing items of suitable weight in front or behind the axle, keeping the heaviest items close to the axle.
85% weight ratio. The laden weight of the caravan as a percentage of the laden weight of the towing vehicle considered to be acceptable for towing. Is an advisory figure recommended by most caravan organisations. The purpose is to give a guideline caravan weight for safe towing by inexperienced drivers but many caravanners with years of experience stick with this figure.
Mass in Running Order (MRO or MIRO). The empty weight of the caravan as delivered when new but excluding dealer fitted equipment and extras such as gas cylinders, bike rack and sparewheel carrier. Is used when calculating the user payload. Manufacturers have been known to be somewhat negligent with this figure in the past, omitting to include items such as the refrigerator and heater. May be called Unladen Weight on older caravans.
Caravan User Payload. Found by subtracting the MRO from the MTPLM. Is the total amount of equipment, clothing. food etc the user can put in, or on, the caravan
Caravan Personnel Effects Payload. A standard allowance for the weight of personnel items such as clothes bedding, food, crockery and cooking utensils. The standard is based on the number of beds and caravan length, the intention is to make for easier comparisons. Is part of the User Payload.
Caravan Essential Habitation Equipment. Similar to Personnel Effects Payload but for water and gas, is part of the User Payload
Caravan Optional Equipment. Items such as sparewheel, bike rack, stabiliser and battery fitted by the dealer or owner, is also part of the User Payload.
Kerbweight. The basic empty weight of the car in running order. The kerbweight includes the sparewheel, jack, battery and all necessary fluids plus a tank full of petrol, but not the towbar. Recent changes to European regulations require kerbweight to include 75 kg for the driver and his luggage. Some manufacturers are stating the revised kerbweight in their 2004 brochures.
When choosing a car or caravan it is necessary for legal and safety reasons to check the weights of one do not exceed limitations of the other. For drivers with a group B license only there are extra limitations to be considered. The points to check:
1. For group B + E license holders the actual weight of the caravan when laden must not be more than the Maximum Towing Weight of the tow vehicle.
2. In addition, for group B license holders, for caravans weighing more than 750 kg the MTPLM must not be more than the car kerbweight and the total weight of the car and caravan together must not be more than 3500 kg.
3. Hitch, or towball weight must not be more than the maximum specified for the caravan, car or towbar manufacturer.
4. The total combined weight of the car and caravan including all payload and passengers must not exceed the car gross train mass.
Actual weight of your caravan. Caravan weights have rightly become an important safety issue and are now regularly being checked by the police. Best way to know the exact weight of a caravan is to visit a local weigh bridge, pay the small fee and have it checked.
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Posted 19 March 2007 - 02:31 PM