How far overweight are you? GVM and Tare weights explained

Author: Rob Burton   Date Posted:4 March 2016 

GVM and Tare weights Explained

For the purposes of this article we are going to use the company 2015 Dual Cab Isuzu D-Max as an example so all weights etc. apply only to this vehicle and are for information only.
When setting up your new 4x4 or work ute there are many things you need to consider such as tub or tray, tool boxes or a service body, what type of bulbar and if you are going to fit a winch? But one of the most important things is "How much does your vehicleReally weigh and how much weight can it Actually carry?" To calculate how much load you can put onto your vehicle you will need to know your TARE weight and your GVM.

So your max vehicle weight is known as the GVM (Gross Vehicle Mass) and this is theMaximum your vehicle can weigh on its own without a trailer etc. This includes the vehicle PLUS driver, any passengers, accessories and anything else that wasn’t fitted or in the vehicle when it rolled off the factory floor.

The GVM can usually be found on either the manufacturer's ID/VIN Plate (Photo below) or the ADR (Australian Design Rules) import plate which are both under the bonnet usually on the fire wall or in the case of the D-Max on the leading edge of the engine bay. The GVM for the D-Max is 2950kg with a TARE weight of 1925kg but this weight is not on any maker’s plates or even in the owner’s manual I had to find this on Isuzu’s website.
BUT this weight is the ‘Dry’ weight i.e. what it weighed when the vehicle rolled off the factory floor without any accessories, passengers etc. and so the only way to know what your vehicle weighs now with all your non factory accessories (remember they don’t come from factory with a canopy or a bull bar etc. these are fitted by the dealer or your aftermarket supplier such as us at KPD4x4 or Cammo Offroad etc.)  is to take the vehicle to a public weighbridge and weigh the thing.

Down here in Melbourne we are lucky enough to have 9 such weighbridges within 50 km of the city plus many metal recyclers (scrap yards) have weighbridges so they can calculate the weight of your scrap. But these services are generally not free and in the case of one company it will cost you $30 for this service. To find out where your nearest one is just put Public Weighbridge into Google.

As you can see by the photo above the company D-Max is not as it was from the factory but we haven’t exactly gone overboard with the accessories. We have fitted a TJM Fiberglass Canopy, a Dobinsons Deluxe Steel Bullbar with one of our Carbon 12K winches, a 20” LED Light Bar and a set of Wispbar Roof rack bars. All this plus the driver adds to the Tare weight which is now 2265kg. So to calculate what we can carry we need to minus the new Tare from the GVM giving us 658kg load capacity not the 1025kg as it came from the factory and as advertised!

A Spring upgrade is most suitable for vehicles with higher than standard constant load. EFS Leaf springs offer increased load carrying upto the GVMor as part of a GVM upgrade kit
EFS Multi-Leaf Springs are made from high quality Japanese grade SUP9 & SUP9A Alloyed Carbon spring steel. 
Designed as a comfort Leaf Spring that incorporates special features , to give the driver a comfortable ride on road & increased control off road with increased articulation & clearance. Available in 30mm to 80mm raised heights with a load increase of 100kg to 700kg over factory springs.
So what can we do to help you with all this?
If you are still within your GVM but are carrying so much load that the rear of the vehicle sags down then you have a couple of options, if the load is constant such as a service body or toolboxes etc. you may want to do a spring upgrade to carry the load better. If you have varying weights e.g. you carry tool boxes during the week or have a slide on camper or rooftop tent, then you may want to add a set of load assist air bags from Boss or Thor (links below). With these you can fine tune the pressures and heights independently on both sides so if you have more weight on one side you can get the vehicle back to level.

Your last option would be a set of Super Springs (link below to a video explaining how these work), these are an add on leaf spring with roller brackets at each end that helps support the load and the more weight you add the more they come into play.
All of these options you better weight carrying UPTO the GVM of the vehicle, if when you go to the weighbridge you are unlucky enough to be over the GVM of your vehicle then your options are firstly to lose some weight if possible or if you have something like a service body you may need to look at an engineered GVM upgrade using either heavier rate springs or a combination of springs and airbags which when done correctly and signed off by a qualified automotive engineer can legally increase your GVM.

The final thing to cover is GCM(Gross Combined Mass) this is the combined mass of the vehicle and the mass of any trailer being towed. This is where people often come unstuck because in the case of the D-Max the GVM is 2950kg the Max towed mass is 3500kg (braked) but the GCM is 5950kg which is 500kg LESS than the 6450kg total of 2950kg GVM + 3500kg Towed Mass!
Boss or Thor Load Assist kits are more suited to varying loads and offer the user the ability to fine tune the ride height to suit the load by varying the pressures in the bags independently side to side. Another added bonus is you only need high pressures in the bags when you are carrying heavy loads. This means a more comfortable ride when unloaded.
Confused? Worried you might be overweight? Take the vehicle to your nearest public weighbridge and get it weighed, do some research online or in your owner’s manual for the Tare weight and compare these figures with the GVM placard. After that use the link below to get in touch with us here at KPD4x4 the suspension upgrade specialists and we can give you some options and quotes to safely carry the extra load.



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