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One reason why ‘add more towball mass’ isn’t always the right answer

Got trailer sway? Add more towball mass. Oh, still swaying? Well, add more!

Here’s the problem with that advice. You can end up with a trailer that’s got an ‘ideal’ towball mass, whatever that is, and yet it is fundamentally unstable. And the reason is because you may have heavy weights at either end of the trailer. There’s a huge difference in towing stability between these two:

It’s entirely possible to have a trailer with a lighter towball mass be more stable that one with a higher towball mass, if the trailer with the lighter mass has the bulk of its weight located over the axles.

Some people grasp this intuitively, and good for them. They can go back to calculating moments and explaining the difference between momentum and inertia to lesser mortals. Or maybe just using my towing weights calculator.

For the vast majority of people to whom physics doesn’t come naturally I have, after reading lots of comments, made this video to explain. And not just because I found a way to have 48 bottles of beer and 2 bottles of wine written off against tax.

Don’t just hook up and hope.

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  • by Russ Whitley
    Posted 22 September 2021 07:22 0Likes

    Robert, it’s all very well to talk about where to load caravan weight and I applaud your simplification of the subject. But when looking ata caravan layout people presented with a set of difficult issues. Firstly the location for storage is typically under bed at front, in a front boot or tunnel, in a fridge, not placed over axles or in a rear bathroom. Added to this are external storage boxes, front and rear bars and generator boxes with jerry cans etc and no place to put them centrally. Things like the case of beer typically goes under the bed for example. Is there any information to assist with those sort of issues?

    • Avatar photo
      by Robert Pepper
      Posted 22 September 2021 09:05 0Likes

      Hi Russ – yes, agreed, and I do acknowledge that caravan owners cannot easily move weights around for the reasons you describe and more. So this is an awareness exercise; if you can’t shift weight then be aware of the effects. Also, I’m trying to get van makers to care, and finally there are things you can do. Losing one of two spare wheels, carrying the fridge (and beer) in the towcar, not using multiple, heavy gas bottles. I do plan to do more on this later.

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