its actually due to sway. trailer sway is reduced with heavier tow ball weights. we don;t need much ball weight because our speeds are reasonably low. in countries like the USA where speeds are much higher, higher ball weight is required to reduce trailer sway at high speed.
tweake,
Sep 7, 5:56pm
legally you can exceed towbar specs. the only legal spec weight spec you cannot exceed is the trailer coupling.
so legally you can have a 2000kg tow bar and tow 3500kg on it, provided the trailer coupling is rated for 3500kg. many towbars have long lost the plate off them so people have no idea anyway. certainly not a good thing and insurance will kick up a stink but not illegal.
the law is crap, pretty much ignored and rarely enforced anyway.
mrcat1,
Sep 7, 7:08pm
Not exactly right, its to stop the tail end of the tow vehicle from stepping out at high speed from sway supposedly, I have spent a lot of time trying to get my trailers to tow right and one I had to stop swaying at 80kmh, and it was due to too much ball weight, but its got 6 meter drill rig extensions up high that are quite heavy so it comes down to what load is also on the trailer, its not really a hard and fast rule for every trailer.
johotech,
Sep 7, 7:18pm
It's all academic when people take no notice of how it's loaded.
People load the trailer to the max and then have nothing in the back of a ute and then on a wet road the tail wags the dog and it's all on. Quickest way to jack knife.
electromic,
Sep 7, 8:50pm
Seen it many times. I always load the back of the ute up when towing.
never had that, tho have spun out a few times and had to use 4wd to get up the hill. if the rear is being pushed hard enough to push it sideways then you need to check the trailer brakes. if its wagging the dog due to improper trailer loading then loading the ute won't fix that. a lot of people use suv's for towing which have no weight in the rear.
mrcat1,
Sep 10, 9:24pm
How do you think vehicles get jackknifed then? And loading the ball weight up is totally different than ballasting the back of a ute.
tweake,
Sep 10, 10:32pm
they are only jackknifing because trailer is out of control. the trailer goes out of control for other reasons. if trailer is under control then ballast weight makes no difference. you will loose drive are a rear driven tow vehicle far easier than you will ever jackknife.
the other thing is people using ball weight to ballast the rear, thats another discussion.
mrcat1,
Sep 10, 10:53pm
If the back of the tow vehicle is to light and the trailer starts swaying, that's when the trailer will flick the back of the tow vehicle around and jack knife the unit. Why do you think when you use a tractor unit as a pull tractor on a very heavy simple type pull trailer like they used to use to pull export containers around auckland even with tandem drive axles on the back they had to have a ballast block put onto the turntable on the back off the tractor unit, for traction in pulling and also in braking so the heavy trailer didn't push the arse of the tractor around and jack knife the whole unit.
tweake,
Sep 11, 6:46pm
the trailer sway is the real problem, fix that and you don't need ballast in the back. if you load the trailer properly the trailer won't sway.
blaming the tow vehicle loading instead of the dodgy trailer? is this yet another case of bad trailer culture?
mrcat1,
Sep 27, 12:10am
I think you are the one with bad trailer culture, considering I have 8 trailers with some heavy loads on them all the time I do have some understanding of trailers and how they work, sure if you have a badly loaded trailer it will sway and it will cause the tow vehicle to jackknife easily, more so if the tow vehicle is too light in the rear end, but heres one thats going to stuff you, even if the trailer is loaded right and the tow vehicle is either too light total or too light in the arse in certain circumstances the trailer can and will still make the tow vehicle jack knife. Ideally you need the tow vehicle the same or heavier than the trailer to have the most control over the trailer in all circumstances.
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