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Farkles, Gear & Accessories => Trailers & Towing => Topic started by: Dragonstaff on February 19, 2022, 07:35:59 PM

Title: Tongue weights
Post by: Dragonstaff on February 19, 2022, 07:35:59 PM
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.
Title: Re: Tongue weights
Post by: Brock on February 20, 2022, 05:05:35 AM
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.
Title: Re: Tongue weights
Post by: StinkyPete on February 20, 2022, 06:24:50 AM
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.
Title: Re: Tongue weights
Post by: Williamson on February 20, 2022, 08:53:51 AM
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 ... 

... 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.

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

... 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. 

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.
Title: Re: Tongue weights
Post by: Dragonstaff on March 07, 2022, 07:01:57 PM
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.
Title: Re: Tongue weights
Post by: Williamson on March 07, 2022, 07:14:30 PM
.... loaded trailer was 125kg and the tongue was around 11.5kg at tow-bar height, so just under 10%.

 :thumbs

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

If there's no pics, it didn't happen.
Title: Re: Tongue weights
Post by: NTRebel on March 07, 2022, 07:21:00 PM
Got to agree no pics you never left home. :Stirpot :Stirpot
Title: Re: Tongue weights
Post by: Dragonstaff on March 16, 2022, 09:44:57 PM
The trip went well. The trailer ended up at 130 kg or so, with about 12 kg on the towbar. I only knew it was there when I looked in the mirrors, unless the road was really rough when I felt it bounce a couple of times. I might take the pre-load on the shockers down a notch. (It runs a pair of coil-over motorcycle shocks as suspension).

And just for NTRebel:
Title: Re: Tongue weights
Post by: StinkyPete on March 17, 2022, 05:37:36 AM
That's a great looking rig, and I'm pleased it towed well for you    ++