GVM, GCM and Tow – Know the basics

How to get the most out of them and how to increase them

Whether you are packing up and hitting the road or carrying proverbial elephants to work each day, there are three things that you need to be mindful of in order to avoid the legal headache of being deemed over-weight on the road.

The GVM, GCM and Tow Capacity of your vehicle are not a guideline but the law. Non-compliance with these weight restrictions can lead to your insurance and registrations cancelled, third party litigation and possible criminal negligence charges in the very worst-case scenarios. In the event of even a minor accident, if your vehicle is proven to over-loaded, you can face some very serious consequences.

So how can we be sure we are fulfilling our legal requirements when carrying and towing? Firstly, it is important to understand what these weight categories are, and how that affects us in a practical sense.

GVM – Gross Vehicle Mass or the total weight that is allowed for your vehicle

When estimating weights required, this needs to include the maximum seats (passengers at 68kg), all inclusions on the vehicle such as bull bars, winches, etc., all tanks full of water, fuel, etc. and all belongings.

The legal GVM is set by the manufacturer and can often be capped by the manufacturer. This means that you cannot increase this without Federal Compliance or a Second Stage Manufacturer’s Compliance. A capped GVM is a very good indication that the vehicle is at the peak of it’s performance already and it is not wise to exceed this.

Tow Capacity

Tow capacity is a pretty simple aspect to travel. What is often complicated is getting a true value of the weight you are towing. Many people forget to combine all the inclusions in the weight of what they are towing and simply look at the “dry weight” listed by the manufacturer. It is important to be realistic about what you are towing so you don’t get caught out by the real weight of it.

Tow or Vertical Ball Weight

An often-overlooked aspect to GVM calculations is tow or vertical ball weight. An approximate allowance of 10% of the weight of what you are towing needs to be included in your GVM as ball weight. This often puts people well over their legal GVM because it can be upwards of 200kgs that has not been accounted for.

GCM – Gross Combined Mass or the total weight of putting it all together

Now to GCM – the most misunderstood and ignored weight restriction in Australia. To keep GCM simple, remember that it is GVM (including ball weight) + Tow Capacity that equals GCM. Everything that is on the road needs to be included your GCM calculations.

If your head is spinning with the numbers, take a look at this Quick Checklist to help guide you. It won’t include everything but at least you can start with the basics and add things as you build your own vehicle’s scenario.