Weight Distribution Hitches - Necessary?

[Dion]

I would argue with a ball download that big, the pathfinder would be sitting very low in the rear, unless in-spring airbags were installed.

Hey Tony, those WDHs are a terrible band aid solution to an avoidable problem and put colossal bending moments through the tow bar, you sure you can't rearrange your set up to avoid needing one?

 

[Old.Tony]

I don't know how to avoid it, other than bolting 200Kg of something onto the front of the car to balance the load at the rear. Thankfully as the trailer masses pass 2T they start to back off the required ball weight - I've seen 3T vans with 230Kg ball weight requirements. Double axles help considerably, too - that's probably why.

If there's a way to avoid the WDH I'd be interested in it. Sooner rather than later, actually, because I'm going to be buying the new WDH tomorrow afternoon.

 

[Dion]

Well they aren't exactly overnight fixes, they're a function of how little engineering goes into trailer manufacture, but there's some stuff you can implement. More plies on your van tyres, experimenting with increasing van tyre pressure (both with the aim of increasing lateral tyre spring rate), centralising the mass of carried items and fluids etc low and centered around the axle group (reduce van's moment of inertia about z-axis (vertical) and x-axis (longitudinal), minimise distance on tow vehicle from rear axle to tow ball (WDHs usually increase this dimension), increase draw bar length (maximise vehicle's lever arm over the van)... Then everything else is impossible with the current van, like moving the axle group aft, and the ultimate, a fifth wheel setup....

 

[Dion]

I'm also not a believer in the minimum ball weight theory - that is a rule of thumb that masks what is actually going on. It's entirely possible to get the ball weight spot on what is requested (especially with a short drawbar) but still have sway issues. With a huge mass at the rear or the caravan like a water tank, and another bigger mass right up front to get the ball weight on the money like fuel, generator, waste tank, gas bottles, take your pick, a trailer quickly becomes a unit which has the moment of inertia to completely dominate the tow vehicle, esp. with the long rear overhang of a ute, long tow tongue, short drawbar combo that is common. The usual solution: use a massive ball load to artificially increase the vehicle's control, partly by shifting the mass onto the tow vehicle itself, and then rectify the subsequent axle load issues with a wdh that redistributes the loads across the axle groups

I know shorter drawbars are preferable off highway and I'm sure that is important for how you personally use your van, but a wdh in that same scenario (off highway) is a whole other issue - driving over grade changes is worse again.

 

[Dion]

And sorry for completely hijacking your thread John.

 

[Old.Tony]

As you can see on my rig, I've got a VERY long drawbar and the axles are set quite a way back. The water tanks sit in front of the axle group but with independent suspension and no solid surface that allows me to easily work underneath, I can't start looking at moving the water tanks further back. I would also like to bolt an additional tank under the rear.

I bit the bullet today and purchased a new Hayman Reese 275Kg WDH that doesn't have the silly knuckles.

I find that they do help, significantly. The van is generally quite stable behind the car, except when large trucks come alongside as you'd expect.

However, on loose surfaces without the WDH the steering on my car is far too light (because of the ball weight), hence the WDH and my desire to retain it. All of the advice I've ever received about the tow hitch is that the ball weight should be 10% of the towed mass - and on our single axle van, that was important because it was bloody unstable otherwise.

This double-axle van of ours is different - it's much more solid on the road. Once I can spend some time shifting weight under it, I will probably give it a try, reducing the ball weight to say 30-50Kg and taking it for a drive.

 

[phil300]

Hi Old Tony

WDH dont do much for sway control but do alot to putting weight back
to front wheels.

For sway control you need one or two of these

http://www.lets-getaway.com/swaycontrol.htm

cheers Phil

 

[JASON-D40]

nissan state that a wdh not be used with a genuine towbar.

with all the different sizes and layouts of vans available today, id say its necessary to use a wdh with a van over 1500kg.

they are there to distribute the weight back to the tow vehicle to maintain level towing. Once again not every towball height or coupling height is the same.
Having a level towing setup will make a considerable difference to sway etc.

vans are getting heavier as people demands for basic essentials continues to grow.

wdh are not advisable to be fitted for offroad or reversing applications, however if using for offroad I strongly recommend lowering a link or two on the chains.

from my experience if there is enough ball weight that a wdh is required, I can only see positive results from using one.

Tony, I would be interested to see how a van your size with a towball weight that light tows. From my experience in the industry, I have sent caravans the size of yours back to the manufacturer with ball weights of under 50kg, that light a ball weight is considered dangerous.

I remember towing a new van back from a a transport depot 15km up the pacific motorway, at 70kph I was taking up 2 lanes. Got back to the dealership and lifted a 20ft external caravan of the towball. Popped the ball weight scale machine under it and it was 28kg. Worst van I have ever towed.

 

[BravoBrad]

I've got one of the Hayman Reese units. Are they necessary? not always.. Are they worth it..Yerp.

Just remember to keep the grease up to it.

 

[Dion]

Once I can spend some time shifting weight under it, I will probably give it a try, reducing the ball weight to say 30-50Kg and taking it for a drive.

Not that light. How much does the van weigh?

 

[gazza414]

nissan state that a wdh not be used with a genuine towbar.

with all the different sizes and layouts of vans available today, id say its necessary to use a wdh with a van over 1500kg.

they are there to distribute the weight back to the tow vehicle to maintain level towing. Once again not every towball height or coupling height is the same.
Having a level towing setup will make a considerable difference to sway etc.

vans are getting heavier as people demands for basic essentials continues to grow.

wdh are not advisable to be fitted for offroad or reversing applications, however if using for offroad I strongly recommend lowering a link or two on the chains.

from my experience if there is enough ball weight that a wdh is required, I can only see positive results from using one.

Tony, I would be interested to see how a van your size with a towball weight that light tows. From my experience in the industry, I have sent caravans the size of yours back to the manufacturer with ball weights of under 50kg, that light a ball weight is considered dangerous.

I remember towing a new van back from a a transport depot 15km up the pacific motorway, at 70kph I was taking up 2 lanes. Got back to the dealership and lifted a 20ft external caravan of the towball. Popped the ball weight scale machine under it and it was 28kg. Worst van I have ever towed.

here are a few pics of my bike trailer hitched up on the Landcruiser..ball weight around 400kg..tows beautifully..approx 10% trailer weight..Landcruiser has airbags and upgraded springs .I have both the 550lbs and 750lbs bars and the adjustable height tow hitch...this goes off road

as to why Nissan state what you mention would require a technical response from Nissan....,,tow bar design ?...dunno

 

[gazza414]

As you can see on my rig, I've got a VERY long drawbar and the axles are set quite a way back. The water tanks sit in front of the axle group but with independent suspension and no solid surface that allows me to easily work underneath, I can't start looking at moving the water tanks further back. I would also like to bolt an additional tank under the rear.

I bit the bullet today and purchased a new Hayman Reese 275Kg WDH that doesn't have the silly knuckles.

I find that they do help, significantly. The van is generally quite stable behind the car, except when large trucks come alongside as you'd expect.

However, on loose surfaces without the WDH the steering on my car is far too light (because of the ball weight), hence the WDH and my desire to retain it. All of the advice I've ever received about the tow hitch is that the ball weight should be 10% of the towed mass - and on our single axle van, that was important because it was bloody unstable otherwise.

This double-axle van of ours is different - it's much more solid on the road. Once I can spend some time shifting weight under it, I will probably give it a try, reducing the ball weight to say 30-50Kg and taking it for a drive.

Does your caravan have truly independent suspension or load sharing coupled axles ?

 

[JASON-D40]

Hi Gazza,

Not sure to the reasons why Nissan state that, but its on the sticker inside my door.
Might be another one of these don't recommend it because they don't sell one.
Might also have something to do with a precaution with the earlier towbar/ chassis issues

Got me buggered anyway, just thought with a vehicle with a rated towball capacity of 300kg, a WDH would be necessary.

 

[Old.Tony]

Not that light. How much does the van weigh?

My current van weighs 1.8T. With its current weight, it does sit exceptionally well on the road.

 

[Old.Tony]

Does your caravan have truly independent suspension or load sharing coupled axles ?

Truly independent suspension. Both axles terminate on trailing swingarms with independent leaf springs and shock absorbers. The springs are not connected by a rocker or other load-sharing device.

 

[Old.Tony]

Hi Gazza,

Not sure to the reasons why Nissan state that, but its on the sticker inside my door.
Might be another one of these don't recommend it because they don't sell one.
Might also have something to do with a precaution with the earlier towbar/ chassis issues

Got me buggered anyway, just thought with a vehicle with a rated towball capacity of 300kg, a WDH would be necessary.

The older "Nissan" hitches are made by Hayman Reece, but like the ARB/Nissan bull bars, they're different to the ones made with their own stickers on them. These older hitches don't have enough mounting bolts to withstand the torsion imparted by the WDH.

 

[tweak'e]

theres a few posts about those early bars breaking with just normal loads.

 

[Dion]

Gazza,

4T trailer? Must be a nice track setup - multiple bikes or just lots of tools?

Tony,

Somewhere north of 100kg but south of 180kg would be my target for experimenting. What air pressure do you run in your trailer tyres, and what carcass construction are they? Looking at the photo of your caravan - what I'm talking about is a longer draw bar.

This article (which is pro-WDH) covers reducing the polar moment of inertia.

 

[gazza414]

Hi Gazza,

Not sure to the reasons why Nissan state that, but its on the sticker inside my door.
Might be another one of these don't recommend it because they don't sell one.
Might also have something to do with a precaution with the earlier towbar/ chassis issues

Got me buggered anyway, just thought with a vehicle with a rated towball capacity of 300kg, a WDH would be necessary.

A friend with a D40 asked me the same question only a few weeks ago . I'm not familiar with the d40 chassis so I could only assume it was due to the lack of integrity of the C section of the chassis which the tow bar is mounted to.
When I fitted mine to the d22 I added xtra bolts and larger chassis washers to aid the load. It does look flimsy but as stated it would be of interest to hear the official technical line from Nissan as to why.

 

[Old.Tony]

Tony,

Somewhere north of 100kg but south of 180kg would be my target for experimenting. What air pressure do you run in your trailer tyres, and what carcass construction are they? Looking at the photo of your caravan - what I'm talking about is a longer draw bar.

This article (which is pro-WDH) covers reducing the polar moment of inertia.

I'll have a good read of that document later on, I've breezed through it just now and it's typically full of good info - Collyn Rivers is someone whose advice I not only trust but rely on considerably.

Our van is a centre-kitchen model, with the fridge located over the front axle, sink in the middle and stove at the rear. In front of the axle group is the bed, behind is the shower/toilet and a bench seat.

I probably store too much stuff in the front boot - it's something I'll be changing, because I'm sick of the mess, but I think once I add the extra water tank under the rear I'll probably have a ball weight somewhere in the region you're talking about anyway.