Our Weighbridge Results: How We Worked Out Our GVM, GTM and GCM
One of the first things we did when we got our caravan was get it weighed. We went down to a weighbridge where we could weigh the caravan and the car, so we could get a better understanding of how close we were to our weight limitations.
There’s the legal side of it, and there’s also the way the caravan will tow. If you’re not getting too close to those limitations, you’ll find that towing will be a lot better and you’ll probably be more economical. The big thing, though, is that you’re going to be legal on the road. So here are our real numbers, what each one means, and the one mistake to avoid when you add them up.
– For caravan scales and all your caravan gear: Caravan RV Camping
– For tow hitches and towing gear: VicOffroad
– For the rest of your camping kit: Snowys
How We Weighed the Car and Caravan
We’ve got a full step-by-step guide on how to weigh your caravan at a weighbridge, so here’s just the short version of what we did on the day.
Tim was in the car, we had full fuel, and all the gear we would normally take with us was loaded in. That gave us a pretty good representation of what the car would weigh when we’re actually travelling. Then we recorded these weights:
- Front axle of the car only on the weighbridge, caravan connected.
- The whole car on the weighbridge, caravan connected. Then the same again with the caravan unhitched. The difference between those two is, theoretically, your tow ball weight.
- Caravan wheels only on the weighbridge, car off it. This is your GTM, the gross trailer mass.
- The caravan on its own, wheels and jockey wheel both on the weighbridge. This is your ATM, the aggregate trailer mass.
- Jockey wheel only on the weighbridge, to double check the tow ball weight.
The weight at the jockey wheel and the weight at the tow ball will be a little bit out. Look, it’s only really going to be out by a few kilos, but it’s close enough to get an understanding of how close we are to our weight limitations.
Our GVM: 2820kg Against a 3200kg Limit
Our rear axle came in at 1660kg. That 1660 includes the tow ball downforce, because the caravan is connected, so that’s the total weight that is on the car. Our front axle came in at 1160kg.
Add those two together and you get your GVM, the gross vehicle mass, for your vehicle. For us that came out at 2820kg. Our vehicle’s GVM limitation is 3200kg, so we’re quite a bit under the legal limit for our tow vehicle, which is good.
Our GTM: 2520kg Against a 2765kg Limit
For the caravan, we weighed the caravan wheels only, which equates to the gross trailer mass. That’s just the weight going on the wheels of the caravan, not what’s on the hitch.
It came in at 2520kg. This van’s legal limitation is 2765kg, so we’ve come in at well over 200 kilos less than what we can legally weigh the van up to.
How to Work Out GCM Without Doubling Up
Your tow vehicle also has a limit on its gross combination mass, the GCM. That’s the weight of the caravan and the weight of the vehicle added together, and this is where it’s easy to get it wrong.
You add the GVM (worked out from the front and rear axle while connected to the caravan) to the gross trailer mass. You don’t want to add in the aggregate trailer mass. If you add in that total, you’re actually doubling up on your tow ball mass, because the tow ball mass is already being counted in the weight of the car.
- GVM, car connected to the van: 2820kg
- Plus GTM, caravan wheels only: 2520kg
- Equals GCM: 5340kg
That’s well underneath the limitation for our car. If you’d like to run your own numbers, our caravan weights guide and calculator walks through each one.
What We’re Fixing Next: Getting the Van Sitting Level
All in all, we were pretty happy with the weights. We’re not close to any of the legal limitations of either the tow vehicle or the caravan, which gives us a bit of room to move if we need to add a few more things or take a little more luggage. Plus we’re not overstressing the car or the caravan by loading them up to their limits.
The next thing we have to do is get the van sitting level. At the moment the front of the van is ever so slightly too high. It should be level or just leaning forward a little bit. So Tim will do some measurements, work out how much lower our tow hitch needs to be, and get a new tow hitch that sits slightly lower. Then we should have a van sitting just right on the road. (If you want the why behind this, we’ve written about how towing level changes your tow ball weight.)
Weighbridge or Scales?
A weighbridge will only be so accurate. They’re usually accurate within 10 to 20kg. The good thing for us is we weren’t really close to our limits, so we were pretty happy using the weighbridge method.
If you are getting pretty close to your weight limitations, getting a set of scales would be a good idea. You can weigh your vehicle and your caravan at home, they’re accurate down to the kilogram, and you can re-measure again and again. The other option is to get a company to come in and take all the measurements for you with their scales.
👉If you’re close to your limits and want to weigh at home, have a look at this Camec 1500kg drive on weight scale from Caravan RV Camping!
Our Thoughts
It’s really good to get an understanding of how close your total combination, both your vehicle and your caravan, is to your limitations, and whether you need to make any adjustments. Being well underweight is always going to be better if you can. It might also make you rethink how much stuff you need to take with you, because you could be surprised how quickly those weights add up.
Have you weighed your rig yet, and which limit did you end up closest to? We’d love to hear in the comments.
Related reading
👉We’ve put weight checks like these into our caravan maintenance schedule, so you know what to check and when. Have a bit of a look at it here.
