Monthly Archives: May 2017

GVM weight compliance for caravans and Trailers

digital-gvm-weight-measurement-caravanWith a crackdown by Roads and Traffic Authorities on vehicle and caravan weights, it is critical that the GVM weight compliance of every trailer or caravan shipped is easily documented for the customer.

Kimberley using Digital technology with easy single reference display

The technology used by Kimberley shows all the weight data using 4 digital sensors on ground pads. The data is transmitted to a remote control pad. By placing the remote control pad near the VIN number and photographing the 2 items, the customer receives the compliance record of the GVM, the drawbar weight and the Tare weight of the unit.
Note the digital display shows the position for each sensor and the value to one decimal place.

GVM, ATM, Drawbar weight and Combined vehicle Mass:

GVM-weight-compliance-caravanGVM is the vehicle’s “gross vehicle mass” calculated by adding the weight that each axle has on the road. For a 4WD, the front axle and rear axle weights are added fo give the GVM. For a trailer or caravan, the GVM is simply the axle loads (both axles for a tandem trailer). The drawbar weight becomes part of the vehicle weight and vehicle GVM.

The other published capacity is “Combined Vehicle Mass”. This adds the caravan axle(s) load, which is called the caravan GVM to the 4WD’s GVM. As you can see, GVM is always a measure taken from the axle weights on the road. This will be all 3 or 4 axle (if tandem) weights on the road.

The road and traffic authorities generally check “Combined Vehicle Mass” by weighing each axle. They DON’T weigh the total caravan weight. They weigh the axles, one at a time. They then add up the axle weight and compare your actual weight with the maximum shown on the compliance plate. If you are over the number on the vehicle compliance plate, they may ask you to make a correction to move on. Can you?

Why the authorities don’t measure the “ATM” weight of the caravan?

Between the main bulk of the caravan and the road is the suspension. The suspension plays a vital role in caravan stability. And within the suspension, the tyres: their loading, rating and performance is critical. An engineering consultant experienced in serious caravan accidents related to the author that in his many years of experience, suspension and tyres were the root cause of the majority of serious accidents. In some cases, the tyres were over loaded to their specification.

This is one of the reasons why the roads and traffic authorities want to weigh the vehicle and the caravan axles. They want to then calculate the tyre loads, check the tyre ratings and ensure they are within specification.

What are the GVM results for this finished unit?

The GVM is 454kgs and 499kgs = 953kgs. The drawbar weight is 172.5kgs (this reduces significantly once the water tanks are filled)

Towball weight is added to vehicle GVM

It is not uncommon to find a caravan within specification but a vehicle over specification.
People load the vehicle with gear to “lighten” the load on the caravan.
Please watch this! Pay attention to the maximum payload of your vehicle.
The towball or drawbar weight adds to the vehicles GVM NOT to the caravan/trailer’s GVM.
For this reason, caravans with heavy towball weights add a lot of weight to the rear axle of the vehicle. In fact, the vehicle’s compliance plate has the maximum rear (and front) axles loading and these numbers are used during checks by the road and traffic authorities.
Note that published “kerb weights” include all fuel tanks full.

Design weight may be far higher than ATM

Some people confuse the ATM with the design loading level of a caravan. For off road applications we increase the “safety factor” of our engineering design considerably.
The Kruiser E Class is designed for a total weight of 3,000kgs whereas the ATM is 2500kgs.

Ballina June 1st 2017