I previously wrote about weighing a fifth wheel camper from the perspective that one would be using a CAT scale which is setup with 3 scales making it easy to get individual axle weights. I forget that I’m a citified-yuppy and am used to living near major highways. I also seem to camp places that I have to take major highways, so finding truck stop/CAT-style scales is easy. My buddy Dave, had a hard time using my directions in getting his setup weighed. So this blog entry is for him. Dave, this one’s for you!
Note, it’s important that you try to do all of these weights at the same time. You want to keep everything the same between each weighing (the same passengers, the same load, as close to the same amount of fuel, etc.). My preference is for the driver to be in the driver’s seat so that you don’t have to add any extra – it just makes the math easier.
When weighing on a single scale, you have to get more weights and then do some math. You still have to do these weights in 2 passes.
Truck and Camper Combined
The first weighing is the truck’s “steer axle” (aka, the front-wheels) on the scale. The important part of this weighing is that your front axle weight doesn’t exceed your truck’s front gross axle weight rating (front GAWR) and against your tire load capacity.
The second weighing is going to give you a total weight of the truck by weighing both of the truck’s axles. You will be able to calculate your rear axle weight by taking the prior weight and subtracting this one. The important parts of this weighing is that you want to compare the calculated rear axle weight against your rear gross axle weight rating (rear GAWR) and against your tire load capacity. Additionally, you want to compare the total weight of the truck against your gross vehicle weight rating (GVWR).
The third weighing is going to be the whole setup – both truck axles and the camper axles. You will be able to calculate the trailer axle weight by subtracting the previous weighing of both truck axles from this weighing. The important part of this weighing is that you don’t exceed your gross combined weight rating (GCWR) and you don’t exceed the axle weight ratings of your camper (for the value that you calculate in this step).
You still cannot figure out the pin weight until you also weigh the truck by itself. So, first go park the camper in the parking lot of the scale house. Now, let’s start the truck-only weightings.
First, weigh the truck’s front wheels (aka steer axle).
Next, weigh with both of the truck’s wheels/axles on the scale. With this weight, you’ll be able to calculate the drive axle by subtracting the previous weight of the truck’s front axle from this one.
Alternatively (and optionally), you can also weigh just the rear axle on the scale. The nice part about this weighing is that it verifies the previous calculation of the rear axle weight.
Crunching the Numbers
Now, once you have all of these numbers, you can figure out a handful of things:
What is the pin weight?
To calculate the pin weight, you’ll subtract the two weights of the truck (loaded and unloaded).
Are you over/under the truck’s gross vehicle weight?
Check the weight of the truck when it was hitched to the truck (2nd weighing above) and compare that against your truck’s GVWR.
Are you over/under the front axle weight rating?
Check the weight of the steer axle in the first weighing against the “Front GAWR” value on your door pillar.
Are you over/under the rear axle weight rating?
Check the weight calculated for the loaded rear axle weight rating (hitched weight of both axles (1st weighing above) minus the hitched weight of just the front axle (2nd weighing above)) and compare that against the “Rear GAWR” value on your door pillar.
Are you over/under your rear tire load capacity?
Check the weight calculated for the loaded rear axle weight rating (hitched weight of both axles (1st weighing above) minus the hitched weight of just the front axle (2nd weighing above)) and compare that against the really hard to read print on the side of the tire (carrying capacity at XX p.s.i.). This one pretty well sucks to read the side of the tire.
Are you over/under the camper’s axle weight rating?
You can calculate what the camper’s axles are carrying by subtracting the gross combined weight from the 3rd weighing minus the truck weight for both axles (the 2nd weighing). You want this to be under the trailer’s axle weight rating – this might be printed on the axle. Otherwise, it’s just easiest to ask on a forum or the manufacturer (smile).
What does my camper weigh?
To figure out what our camper weighs, you need to find the pin weight (see first question in this section above) and add the camper’s axle weight (see the previous question). Add the pin weight with the camper’s axle weight and that is your camper’s total weight.
What is my pin weight percentage?
Take the pin weight (see first question in this section) and divide it by the camper’s total weight (see the previous question) and multiple that result by 100 (to turn it from a decimal into a percentage):
(pin_weight / camper_total_weight) * 100