Whether you’re buying a car to tow your trailer or buying a trailer to pull behind your car, you must first calculate the vehicle’s towing capacity. That way, you can tow it safely without causing premature damage to your car and its components.
Your car’s towing capacity is measured by combining its kerb weight and any payload it has. Once you have that total figure, minus it from the vehicle’s gross combined weight rating. That figure represents the maximum towing weight that you must always stay under. Exceeding that figure will make driving dangerous and cause premature wear.
Calculating your towing capacity isn’t as straightforward as most people hope. So, read through this guide to understand the critical measurements involved and how you can arrive at your final towing capacity figure.
What Measurements Must You Know To Calculate Towing Capacity?
The process of calculating your car’s towing capacity isn’t as straightforward as it seems initially. Unfortunately, knowing the trailer or caravan’s weight by itself isn’t enough.
Instead, you must first collect key weight measurements at different parts, which are the following:
1. Weight On The Car’s Side
One of the most important measurements to know is the weight of the car itself. After all, you can’t tow an object if it weighs much more than the car you drive.
Here, the weight you must measure is known as the ‘kerb weight’. That includes the vehicle’s total weight, including your bodyweight and the car’s fluids like fuel and oil.
The manufacturer will provide you with the vehicle’s kerb weight in its documentation, like the car owner’s manual.
2. Weight On The Trailer’s Side
After you’ve identified the vehicle’s weight, it’s time to determine the weight of the trailer you want to tow.
There are different measurements for this, which are the following:
- Tare mass: This is the weight of the caravan or trailer you want to tow. The weight must only include the trailer’s accessories but exclude any equipment or cargo onboard.
- Trailer payload: Separately, you’ll also need to measure the trailer payload. That’s the total weight of everything in the trailer, like the equipment, baggage, or anything else.
3. Weight At The Point Where The Car Connects To The Trailer
Once you’ve identified the separate weight measurements of your car and trailer, the last thing you need to know is the combined weights when both are put together.
More specifically, you’ll need to know the following:
- Gross trailer mass: When you connect your trailer to your car, its weight is measured differently. The gross trailer mass represents how much that trailer weighs when it’s actually connected to your car. That’s because once it’s connected, a portion of its weight is now shifted to your vehicle.
- Towball weight: This measurement represents how much weight is exerted by the trailer onto your car’s towball (i.e. the point that connects the trailer and the vehicle).
- Payload: Last but not least, the payload is a measurement of everything you’re towing. That includes the weight of the trailer, the equipment, and any passengers inside. On top of that, the payload includes the towball weight mentioned earlier.
As you can see, there are several weight measurements that you must first collect to understand your car’s towing capacity. These figures are crucial to ensure you don’t overburden your vehicle and its engine or put yourself in harm’s way.
How Do You Calculate The Towing Capacity Of Your Car?
The first thing you must understand about your car’s towing capacity is that it’s expressed in several ways.
Your car’s towing capacity is any weight that falls within a few set limits calculated using the figures in the previous section.
Here are the limits that form your car’s towing capacity:
- Gross vehicle weight rating: Firstly, you must understand the maximum weight your vehicle can handle. The weight of your car and anything inside it must stay lower than this rating.
- Aggregate weight rating: As the name suggests, the aggregate weight rating is the maximum weight of the trailer and anything in it. In other words, the trailer’s tare mass and payload weight be higher than this number.
- Gross combined weight rating: This rating represents the maximum limit of your trailer and car’s weight when combined. So, the total of all weight in your car and trailer cannot go higher than whatever this figure is.
- Towball weight: The towball weight is also important to your car’s towing capacity. This weight can differ between car makes and models, so your best bet is to refer to the car owner’s manual or contact the manufacturer directly.
Again, remember that there are a few separate weight measurements involved in arriving at your car’s total towing capacity. It’s never just a single figure that represents the maximum towing weight. Instead, there are limits that take into account the trailer and car’s weights with and without additional passengers or cargo inside.
What Happens If You Exceed Your Car’s Towing Capacity?
As you read earlier, your car’s towing capacity consists of several weight limits. You must stay within those limits at all times, or else you’ll experience the following problems:
- Fines: When you exceed your car’s towing capacity, you’re not just putting yourself in harm’s way. Doing so also puts other road users at risk, and that’s why it’s regulated by law. For example, you could be fined for exceeding your towing capacity.
- Loss of control: Excess weight above your car’s towing capacity can also cause it to lose control on the road. Needless to say, that’s dangerous to you, your passengers, and everyone else on the road. In a worst-case scenario, your trailer might move uncontrollably and pull your car along with it.
- Difficulty stopping: People often forget that your brakes are also affected by the weight you’re towing. So if you exceed your car’s towing capacity, you’ll also have a much more challenging time stopping. That is because your brakes cannot provide enough stopping power.
- Excess wear: Your vehicle is designed to handle a certain degree of wear, especially within its towing capacity. Exceeding that capacity will overburden it with too much wear, causing parts to fail prematurely. One example is your braking system, as the brake pads and rotors might fail sooner than expected.
- Engine damage: Lastly, exceeding your car’s towing capacity will damage the engine. That’s because your engine is forced to work extra hard, well beyond what it can typically handle. That can quickly lead to overheating and wearing out of its internal components.
Overall, exceeding your car’s towing capacity is always a bad idea. You must be careful when performing all the calculations mentioned earlier.
As long as you stay within the maximum weights specified for your vehicle, you’ll be able to tow your trailer or anything else safely and without any worries.
Using your car to tow a trailer or caravan can be incredibly useful, especially if you’re traveling cross country. However, you must first understand the car’s towing capacity before you decide to tow a trailer, especially before investing your money in one.
Your car’s towing capacity doesn’t just boil down to one number. Instead, you must collect several weight measurements for the vehicle, the trailer, and both when they’re connected in the middle at the towball. Exceeding the towing capacity is terrible, as it can lead to fines, dangerous driving conditions, and expensive repairs.