Weighing Travel and Fifth Wheel Trailersby Carl Lundquist
Published with the express permission of the author.
Tow vehicle tow capacity and trailer weight is one of the most important factors in the handling and safe operation of any trailer – travel trailer or fifth wheel. The only real way that one can find the weight of a trailer is to weigh it on a scale.
The first thing is to find a public scale. You can find them in contractor’s rental yards, truck plazas, and the yellow pages of your phone book. Try to schedule your weighing for a quiet time of day. Take a helper along with you, he/she can really speed things up by doing the driving while you position the trailer.
When you get ready to weigh, tell the weigh-master that you will need a number of weights -- 3 for a travel trailer, 5 for a fifth wheel trailer. Tell him also that you do not need certified weights.
The first weighing will be with the entire rig, trailer and tow vehicle on the scale. This will get you the combined vehicle weight. Call this weight A.
Now move the tow vehicle so that its rear axle is barely but completely off the scale but the trailer hitch jack is still over the scale. Signal the weigh-master to take that weight. This second weight will be the weight of the trailer weight less the hitch (tongue, pin) weight. (The hitch weight will be still carried by the tow vehicle.) Call this weight B.
Now without moving the rig, uncouple the hitch and use the jack to lift the trailer off the ball or hitch plate. (If you have a weight distributing travel trailer hitch, you need not release the spingbars, their weight will be trivial and evenly split between truck and trailer.) Now weigh the trailer. This will be the actual trailer weight since the hitch weight is no longer supported by the tow vehicle. Call this weight C.
Hitch up, pay your weighing fee, get your weigh sheet, and leave.
OK, so now you can do your calculations.
A = combined vehicle weight. Compare this with tow vehicle GCVWR.
C = trailer weight. Compare this with trailer GVWR.
C - B = hitch (tongue, pin) weight. It should be no less than 10% of trailer weight for a conventionally hitched trailer like a travel trailer for trailer stability. It should not exceed the weight ratings of your ball, ball mount, or receiver.
A - C = tow vehicle weight. It should be compared to your truck’s GVWR.
For Fifith Wheel Trailers Only
If you are weighing a travel trailer with a weight distributing hitch system, the hitch weight will be distributed equally to both front and rear axles and individual axle weights are not usually of much interest. However, on a big 5th wheel trailer, the impact of hitch weight on the rear axle of the truck may well be of concern. So you should take another pair of weights before you take the A weight above.
As you pull onto the scale take a weight with just the front wheels of the truck on the scale. Call this weight D: it is the weight on the front axle. Now move the rear wheels of the truck on the scale and take the weight with both the front an rear axles on the scale. Call this weight E: it is the weight of the front plus the rear axle weights.
Now more calculations:
D = front axle weight. Compare this with the truck’s GAWR for the front axle.
E – D = rear axle weight. Compare this with the truck GAWR for the rear axle.
© 2006 Carl D. Lundquist