rationale behind the 10% rule (7% in Europe)???

[turfclubroad]

I could not find the proper sub forum to start this thread, hence I am posting it here.

I understand that the recommended load distribution is one which results in a tongue weight of 10% of the total gross weight of the trailer. In Europe that number is 7%.

How "hard" is that number, is there a "safety margin" (is there a no go zone), and why is it 10% (and not 7% as in Europe)?

Thx Wiebe

[Nuvite-F]

Hi, Wiebe,

For reasons of stability in the yaw axis you want to have the center of gravity of the trailer forward of the axle.

(If the center of gravity of the trailer were aft of the axle the trailer would try to sit on its rear end, and you would have to pull the tongue down to get it on the hitch ball.)

So far as I know the figure of 10% of the trailer weight on the tongue is just a rule of thumb to make sure the CG is far enough forward of the axle for stability. There is nothing wrong with 20% if it doesn't result in imbalance of the tow vehicle which can't be corrected by the weight distributing hitch.

I don't know why they specify 7% in Europe. I was just up at the Airstream factory and saw a couple of European models on the assembly line. I was surprised to see that they use surge brakes (activated by force on the tongue) as opposed to tow vehicle mounted brake controllers like we use in the US. Maybe the surge brakes are the reason for wanting a lower tongue weight.

Best regards,
Nuvi

[markdoane]

I'd be suprised if the tongue weight in Europe is 7%. I thought it was more like 3-4%, a maximum 100 Kg.

[remcolent]

Max tongue weight on a single axle trailor is 50 KG ( 110 pound ) pound overhere.
On tandem axle trailors it is max 10 % of the total trailor weight.
But 95% ov the cars overhere have a max alowed tongue weight of 75 KG ( 160 pound)
The axles of a european trailor are almost in the middle of the trailor.
All trailors up til 3500kg (7700 pound) have surge brakes.
Most airstreams inported to Europe have been refited with european exles and surge brakes.