Farkles, Gear & Accessories > Trailers & Towing

Tongue weights

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Dragonstaff:
A question for the brains trust.

What sort of tongue weight is recommended for an ST1300, no pillion, and a driver weight of 64 or so kg? Trailer gross is 185kg, but unlikely to actually get to that much.

Brock:
I believe the towball weight should be about 10% of the trailer weight.

I could be wrong but.

So rounding up the trailer weight to 200Kg, you could expect 20Kg.

When the trailer is loaded, you could use a stick to support the tongue at towbar height on some bathroom scales to see actual..
take a ride to see how it feels, too much weight and the bike will feel bad,  too little and the trailer will want to sway all over the place.

StinkyPete:
As a long time caravanner, 10% is the generaly accepted ball weight.
If your ball weight is too low,  the trailer can develop a resonant sway, which will increase until you crash, which won't take long on a bike.   :eek
Accelerating hard can pull you out of a sway.

Williamson:
In my view, the 10% rule is only a guide, but also the maximum mass that should be placed on the tow ball.  It is somewhere to start and then through a little bit of trial and error ... 


--- Quote from: Brock on February 20, 2022, 05:05:35 AM --- ... take a ride to see how it feels, too much weight and the bike will feel bad, too little and the trailer will want to sway all over the place.

--- End quote ---

... shuffle the load inside the trailer, you'll likely find a sweet spot.


--- Quote from: StinkyPete on February 20, 2022, 06:24:50 AM ---... If your ball weight is too low, the trailer can develop a resonant sway, which will increase until you crash, which won't take long on a bike. 
--- End quote ---

Yes, that could be a very, VERY bad outcome.  However in my experience (with the CB1300 and Classic trailer), an alert rider will feel the trailer starting to sway way earlier than a driver towing a caravan.  I put this down to the inherent instability of a two wheeled tow vehicle when compared to a four wheeled vehicle, and most riders being very much "in one" with their motorcycle and will pick up anything out of the ordinary very quickly.

Tyre pressures can also have an impact on sway.  Before you start shuffling your load around inside the trailer to eliminate sway (if any), make sure you have these as per the manufacturer specs.

You also need to be aware that too much mass on the tow ball can induce a bending moment at the point where the vertical supports (on a Classic tow hitch) join the horizontal bars (I have some pics which I'll post, if I find 'em).  On the underside of the horizontal bars there is a longitudinal plate with a number of holes to attach the vertical supports.  When possible select the holes closest to the the tow ball, but this may also have an bearing on the tow ball height, so a bit more trial and error may be needed on this point.

Dragonstaff:
As I am going away this weekend, for the first trip with the trailer, I loaded it up today with everything I am taking, and did the 70km round trip into town to fuel up. I weighed the loaded trailer on a pair of bathroom scales I got from the local op shop, and weighed the tongue with a spring balance from my local BCF store. The loaded trailer was 125kg and the tongue was around 11.5kg at tow-bar height, so just under 10%.

I didn't feel it at all. Even on the 8 km of freshly graded dirt between me and the black stuff, the only way I knew it was there was to look in the mirrors. No pushing on the downhill slopes, and no swaying even over the loose(er) ridge in the middle. It was the same on the sealed roads, no problems. I am now quite happy to do my 800km round trip for my weekend away.

Thanks everyone above for your help and insights.

I might get a few pics on my run and do a ride report next week. Might.

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