When you are towing, there are many numbers that you must have on your mind during preparations for the trip, or buying a travel trailer. So, you should know what ďoes GAWR means?
GAWR or Gross Axle Weight Rating is the maximum weight one axle can be loaded with together with its own weight.
It is a manufacturer specification of your towing vehicle, truck, or car, and you must be careful never to exceed it.
Besides knowing what that acronym means, you must understand why it is important. And how and where to use it.
What does GAWR mean?
As I’ve said above, it means Gross Axle Weight Rating and is a manufacturer specification of your vehicle. It is the maximum weight an axle on your vehicle can carry, plus its own weight.
Every vehicle has a GAWR for each of the axles. You can find it on the plate attached to the pillar of the driver’s side doors on trucks and passenger cars, with other information.
Usually, you will see two GAWR numbers, one marked FF or FRT, which is the rating of the front axle, and another marked RR, which is the rating of the rear axle.
It is not a load capacity, i.e. how much cargo you can place in your trunk, it includes the weight of the axle itself and the portion of the vehicle it carries.
When you hear some people say that some vehicle has a 60:40 weight distribution, they mean that of the vehicle’s curb weight, 60% carries the front axle and 40% carries the rear axle.
In the context of the rear axle and towing, GAWR is the weight budget for this portion, cargo capacity, passengers in rear seats, and the hitch weight.
GAWR is a manufacturer’s specification, and it is determined by the construction of chassis and axles, and what loads are they capable of safely carrying. It is a design characteristic of a vehicle.
What is hitch weight?
The hitch or tongue weight is the amount of weight of your trailer that is transferred to the hitch and actually carried by the towing vehicle.
More specifically, it is carried by the rear axle, so it uses its GAWR. The maximum hitch weight a towing vehicle can be loaded with is called Tongue Weight Capacity, or TWC.
The TWC of any vehicle depends on the construction of its rear axle and other parts of the chassis. While the towing capacity and TWC are determined by many different factors, their relation is fixed.
The towing capacity is always ten times the TWC. As a rule of thumb, the safest towing is when the hitch carries 10%-15% of the weight of the towed trailer.
So, when a vehicle is towing its maximum, the portion of that weight that is carried by the rear axle should not exceed 10%.
Measuring the weight of a trailer
Knowing how much your trailer weighs can be very important when setting off for the first time on a trip.
While the manuals and specifications can tell you how much your trailer weighs empty and how much it is allowed to weigh when loaded up to the gills, they don’t tell you how much it weighs with your stuff in it. So, you need to weigh it.
This can be done on the road, there are many truck scales and weigh stations that are visibly marked by road signs. What you need to do is to pull the trailer on it, and weigh it.
Simple as that. But you must be careful to actually unhitch it, otherwise, the reading will lower for the weight carried by the hitch.
Measuring the weight on an axle
When towing, you are the most interested in the rear axle and its GAWR, which you should never exceed. Which could make you wonder how would you know if you have exceeded it or not.
And the answer is by simply weighing it. This is also something you can do at weigh station, and it is a two parts job.
The first thing to do is to weigh your trailer along with your towing vehicle, keeping only its rear wheels on the scale. The front wheels must be off. After you have read the weight, you need to unhitch the trailer and weigh it.
The weight that your rear axle carries is the first number minus the second. It must not be above its GAWR.
Once you measure the trailer weight and actual hitch weight, you can know whether you have hit the desirable setting where 10%-15% of the trailer’s weight is carried by the hitch of the towing vehicle.
But you can also find out whether the trailer is actually too heavy for you to tow with that vehicle.
If the trailer weighs less than 10 times the TWC of your vehicle then it can be unsafe to tow it, even if you distribute the cargo so that you don’t load the hitch above the vehicle’s TWC.
Swaying and jackknifing of the trailer can happen very easily in such a situation. And by playing with cargo distribution in your trailer, you can create it.
If the cargo in it is distributed in a certain manner, even if everything else is within limits, you can exceed the rear axle’s GAWR and/or TWC.
But also, if your vehicle can tow that trailer, you can use cargo distribution to achieve the balance where 10%-15% of its weight is carried by the hitch. So, what is cargo distribution?
In simplest terms, it is how and where you place your cargo. What you should keep in mind is that the closer some object is to towing vehicle, the more of its weight is carried by the hitch. So, by moving cargo around your trailer, you can change it.
Knowing what GAWR means and what it is on your towing vehicle allows you to have the safest possible towing experience. It is the maximum weight an axle can carry and includes all the weights transferred through it.
For towing, the more important is the rear axel GAWR, because one of its components is the weight of a trailer transferred to the hitch.