It continues to amaze me the number of people who have no idea what their trailer actually weighs. Recently I saw an individual post a number that had to be less than 50% of the real world trailer weight, but many people aren't sure how to go about getting an accurate weight or actually believe fictious published weights. I had an acquaintance ask me to describe my process for determining the weight and balance of a trailer. While the graphic depicts a small "fifth wheel" style trailer, the same process works for bumper pull trailers as well.
Truck scales are commonly available at truck stops, gravel companies, city dumps, or other places that deal in truck load lots. Some states leave some of their highway scales enabled when the enforcement function is closed - Oregon is one example. A scale that is long enough for all axles at same time will be used for our example. You'll want to talk to the scale operator about your needs since you'll need to record multiple weights during each of two passes across the scales.
Start by loading the tow vehicle and trailer as normal for a trip, i.e. full fuel, water if boondocking, food, clothing, folding chairs, etc.
| ● | Drive the front axle of the tow vehicle onto the scale and record the weight as | A | = | __________ |
| ● | Drive onto the scale until both tow vehicle axles are on the scale and record as | A+B | = | __________ |
| ● | Drive onto the scale until all axles are on the scale and record as | A+B+C | = | __________ |
Park and detach the trailer and then return the tow vehicle to the scale for two more weights:
| ● | Drive the front axle of the tow vehicle onto the scale and record the weight as | Awo | = | __________ |
| ● | Drive onto the scale until both tow vehicle axles are on the scale and record as | Awo+Bwo | = | __________ |
| ● | (A+B+C) minus (A+B) = C (also known as trailer Total Axle Weight) | ___________ |
| ● | (A+B) minus (Awo+Bwo) = Tongue Weight | ___________ |
| ● | Total Axle Weight + Tongue Weight = Actual Trailer Weight | ___________ |
It looks complex but it’s actually quite simple. This will work for single axle trailers or for multi axle trailers IF you (1) don’t want to know the individual axle weights or (2) are willing to assume the axle load is spread evenly between the axles in which case you’ll divide the trailer total axle weight by the number of axles to get the average weight per axle.
Most sources recommend the tongue weight should be 10-15% of the actual trailer weight for standard trailers and 18-25% percent for fifth wheel style trailers.
On shorter scales such as state DOT scales, it may be necessary to weigh each axle individually. It will make it somewhat easier since you won't have to calculate the "C" number - just read it directly from the scale IF the tow vehicle axles are off the scale.
Why do you need the "A" measurement by itself?
ReplyDeleteBy getting just a front axle weight in each sequence you can determine how much weight you're shifting from the front axle to the rear axle when you hitch the trailer.
DeleteJohn, I am embarrassed to admit we have never weighed our trailer. We do know that our 6 cylinder truck is adequate, but a beefier tow vehicle would be a lot better.
ReplyDeleteThanks for making it so easy to understand.
A lot of people haven't weighed their trailer. For me, the benefits are knowing the tongue weight balance is correct and that the tires are not overloaded.
DeleteThank you, John, for this very helpful post! We've also never weighed and need to remedy this soon.
ReplyDeleteWill be saving this great information!
Glad it is helpful and is encouraging people to get an accurate weight. Almost everyone I talk to is surprised at how much heavier the trailer is than they expect it to be. It's good info to help with tire decisions.
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