TRAILER BALANCE

Part 5 - Trailer Balance Spreadsheet

What happened to Parts 1 to 4?  They explain the theory behind this spreadsheet and they were moved elsewhere to stop scaring visitors!  If you would like to read them, they’re here.

Below you can download an Excel spreadsheet that will calculate the hitch weight of your trailer design, working from data that you provide.

But please note that the spreadsheet cannot estimate the weight of your trailer - you have to do that for yourself! However it will let you work with just actual dimensions and weights expressed as a percentage of the total trailer weight.

The spreadsheet allows the following weights:

  • a main body weight;
  • a tongue weight;
  • an axle weight (ie, wheels, axle, suspension, etc);
  • up to three extra weights for galley weights, etc, which can be at any position.

To make it easier to do initial estimating, the spreadsheet uses a 'basic trailer weight' - this is the total of the body, tongue and axle weights (but does not include any of the extra weights). The tongue and axle weights are input as percentages of the basic trailer weight and, if you don't have any better data, you can use these default values which are already in the spreadsheet:

These percentages are suggestions - satisfy yourself that they are appropriate before you use them.

You can use from zero to three extra weights. In the diagram above, extra weight 1 is representing weight in the galley, extra weight 2 is representing a tongue box and extra weight 3 is not shown - the possibility to use a third extra weight has been included because if it isn't someone is bound to ask for it! For each one, you need the extra weight in pounds and its distance from the rear of the trailer in inches.

The diagram above shows where the measurements are taken from.  If you prefer to use metric units (eg, kg and cm or mm), you can use the spreadsheet just as it is, but you may want to alter the number of decimal places in some cells.

Excel trailer balance spreadsheet (in a Zip file)

Download

View spreadsheet as .pdf file

View

To make your own version of this spreadsheet in different software, view and save this .pdf file containing formulae for all calculated cells
View

Part 6 - Trailer Axle Position 'Rules of Thumb'

Are all those numbers above just unnecessarily complicated? You just want an answer, not to have to take an exam? Here are some really simple 'rules of thumb' that you can apply:

Axle Position, % of body length
(C/A in diagram above)		 Reasons to pick this value:

40% (eg, 38" from back for 8ft body)

 A reasonable compromise value for an average teardrop.

45% (eg, 43" from back for 8ft body)

 Tongue box.
Light or no galley.
Minimum safe hitch weight wanted.

35% (eg, 34" from back for 8ft body)

 Well-equipped/heavy galley.
Long tongue.
Heavier hitch weight wanted.

Please remember that picking the right axle position does not mean that the trailer can be loaded without any thought - how it is loaded will determine the hitch weight, as much as where the axle is.

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