Suggestion for lowering GVM and Rear Axle load when towing a van

[Briar]

I have been looking at options for trying to ensure I stay compliant with weights when towing the van. I have gone over weighbridge at tip a few times. GCM is never an issue, nor is Vans ATM or GTM. It's always the cars GVM and especially rear axle that will get you. When towing the van I always take a second spare for the D4. Just a case if on the blacktop, but I usually carry a full second spare on the roof rack (pioneer) as close to the front as I can.

What I had manufactured at a local fabrication place was modelled of the standard caravan rear tyre carrier that bolts on the rear of the van. I got some D4 wheel nuts and high tensile bolts to suit and when towing van will move the spare tyre that normally sits underneath the D4 behind the axle, to be placed on the tyre carrier on the van. (The vans spare tyre is on a winch system and located underneath the van).

I done done preliminary calculations based on weight of tyre and leverage effects of moving the spare from behind D4's rear axle. The Full tyre's weight is about 32kg. Due to leverage and location this adds about 40kg to rear axle and decreases front axle by 8kg. By placing the 32kg tyre at back of van will lower my van's towball weight by about 12kg which equated to about 20kg removed from rear axle and about 8kg added to FA.

End result (and I accept my figures are very rubbery until I more accurately weigh, is:

Van's ATM increased by 32kg (no big deal as I had over 200 kg available)
Towball load reduced by 12kg, ( not much but will monitor van's towing).
Car GVM (when towing) reduced by 44kg (tyres 32 and ball weight 12).
Car's Rear Axle load reduced by 50-60kg

When need to go offroad in just the car it will be 10 mins to move spare from back of van to back underneath D4. Will see how this solution works.

180250180251

[veebs]

Have you still got your third row seats installed? Bit of weight saving potential there...

[Briar]

Have you still got your third row seats installed? Bit of weight saving potential there...

Nah. Third row is out. Pulled it out when I put Drifta drawers in. Drawer weight is about the same as third row of seats. Even though I have fridge slide as part of drifta setup, I got the option of turning it (as well) into a side by side drawer setup, which is what I've turned it into. Gives me a flat surface at back. Going to experiment with fridge on second row of seats behind passenger which will put it mid axle rather than behind axle as is normal.

[veebs]

Nah. Third row is out. Pulled it out when I put Drifta drawers in. Drawer weight is about the same as third row of seats. Even though I have fridge slide as part of drifta setup, I got the option of turning it (as well) into a side by side drawer setup, which is what I've turned it into. Gives me a flat surface at back. Going to experiment with fridge on second row of seats behind passenger which will put it mid axle rather than behind axle as is normal.

Is that their new '3 in one' setup? I was watching the video on it, looks pretty sweet, but probably more than I need... How have you found the Drifta kit?

[Briar]

Is that their new '3 in one' setup? I was watching the video on it, looks pretty sweet, but probably more than I need... How have you found the Drifta kit?

No, not the 3 in 1. It probably has a name but you could call it a 2 in 1 setup. I had the original setup as fridge slide on left and single drawer on right. The fridge has the "box" that goes over fridge. However, I got it with another drawer that bolts onto the fridge slide. With a lid that goes over the now LHS drawer. So I've gone from single drawer on RHS with Fridge on LHS, to 2 drawers side by side. I'm finding it pretty convenient to have a larger flat surface in the back though.

[Briar]

Is that their new '3 in one' setup? I was watching the video on it, looks pretty sweet, but probably more than I need... How have you found the Drifta kit?

Sorry. I've had the Drifta kit in for 2 1/2 years. So much for getting to WA with the van, stupid Covid. The drawers have been bullet proof. Very well made. Have a few friends also gone Drifta. All very happy. I particularly like the integrated pull out table that can be used as a bench or full size camping table. Also I was especially impressed with the ease of fully sliding out the RHS drawer, so I can easily get to the extra storage underneath. No other drawer system that I found enabled this as easily.

[veebs]

Thanks for the review - I expected they would be good, but glad to hear real world feedback.

[josh.huber]

Those weights calculations look well thought out. I would love you too pull the suspension fuse before moving the weight, then put it back in and do a lap of the block to recheck the weights

[josh.huber]

Just to see if the auto leveling of the air suspension changes any of the weights.

[Pedro_The_Swift]

moving just one wheel is a pretty fine margin of error.. a weeks groceries will be greater...


apart from that[tonguewink]
as an interested van owner--
I have always thought the distance from centre of rear car axle to towball has much greater affect than first realised.
how complicated is the formula you used to work this out?
It should be part of the vehicle, like the tyre placard.

[Xtreme]

Good move to reduce tow ball weight. IMHO the 10% recommended is totally wrong.

From your photo of the tyre mounted on the rear of the van, I'd be concerned about your reduced van departure angle and the possibility of dragging the spare with resultant damage to tyre and/or mount. Had a friend who experienced this on his fifth wheeler.

[veebs]

Good move to reduce tow ball weight. IMHO the 10% recommended is totally wrong.

I'm no expert, but I think it's ok up to a maximum - and that max is a lot less than 350kg a 3.5t trailer would have you believe.

I think the Europeans have a different view - max of ~$150 maybe?

I saw a dual axle brick trailer behind a brick delivery truck (you know the ones, with the little loader chained to the back). Was clearly a lot heavier than a caravan, and certainly won't have been a 10% ball load!

[Briar]

Good move to reduce tow ball weight. IMHO the 10% recommended is totally wrong.

From your photo of the tyre mounted on the rear of the van, I'd be concerned about your reduced van departure angle and the possibility of dragging the spare with resultant damage to tyre and/or mount. Had a friend who experienced this on his fifth wheeler.

hey Rog. I agree about the 10% recommended towball mass as being over emphasised. When fully loaded my van is about 3300 and I run most of the time a ball load of about 270-280 and it tows rock solid so I’m at about 7%. Having a. Enter kitchen and ensuite helps to keep mass centralised. Also my water tanks are either side of the axle so help with centralised mass. My possibly reducing tow ball mass by 12 kg is not much but I will assess if it has any impact on stability as I am well aware of the issues of adding mass at either end of a van. Even though I have ESC on the van, I am not relying on that as a panacea. Thanks for the comment about the height of the tyre. It’s not as much of a problem as you might think. The van is reasonably high with a cruisemaster suspension and the tyre will not hit based on my departure angle clearances. I have no big trips away planned for a couple of months so I’ll have time to measure weights to see what effect moving things around is. I realise the tyre alone is just one thing but weight can creep up in small increments.

[Briar]

moving just one wheel is a pretty fine margin of error.. a weeks groceries will be greater...


apart from that[tonguewink]
as an interested van owner--
I have always thought the distance from centre of rear car axle to towball has much greater affect than first realised.
how complicated is the formula you used to work this out?
It should be part of the vehicle, like the tyre placard.

Hi, I've attached a quick sketch I knocked up on single and double pivot levers (think see-saw's). I assume you're familiar with the Law of Moments so I'm not trying to teach your grandmother to suck eggs here.

My logic is pretty simple. If you have a single pivot see-saw a 100kg mass located 1 metre from the pivot can be balanced by a 33kg mass (approx) 3 metres on the other side on the pivot.

Therefore if we had the same see-saw but attached at 2 pivot points (as per the diagram), the 100 kg load on the RHS will exert exactly the same force on the rear pivot (133kg) and will be compensated by a 33kg upward force on the front pivot.

This is essentially what happens with a vehicle. The tow ball is the load, the rear pivot is the rear axle and the front pivot is the front axle. The increase in rear axle load is "balanced" by the loss of load off the front axle. It all depends on the ratio between the towball and rear axle and the wheelbase distance.

For a D4 with a standard towbar these measurements are:
Rear Axle to tow ball distance = 1.23 metres
Wheelbase = 2.9 metres

Ratio = (1.23/ 2.9) = 0.42

Therefore for a D4 with a 300kg tow ball load, the Rear axle load is:
RAL= 300kg + (300 * 0.42) = 427 kg

Front Axle Load = -127 kg

To put in in simple terms, for every 10 kg increase in tow ball load, the rear axle loading will increase by 13kg and the Front axle load will decrease by 3kg.

Of course you'd need a load cell to accurately measure these loads. You can do the same back of the envelope calculations for your van by measuring the distance from the axle centre you add a load and work out the ratio on the other side of the axle centre to the coupling.

180270

[Phideaux]

I don't know what the 'manufacturer's spec' for towball load is for your LR, but I was under the impression that 100kg was the absolute max one should put on a towball (for an ordinary 'car', as distinct from a dual-wheel truck).

2nd point - the research on van stability (pendulum stuff) (there's some brilliant videos on YouTube, basic research done in a Queensland University, if I recall) is adamant on 'where you put the weight' - ie, as much as possible over the axles, as little as possible out at the ends (which means a lot of spare tyres and gas bottles are in the wrong place). My interpretation of the drawing was that you were putting weight at the extremities, not the centre - which if I've read it right, can be dangerous. The balancing needs to be towards the centre of the see-saw.

If I've read the diagram wrongly, feel free to ignore this post!

[Homestar]

I don't know what the 'manufacturer's spec' for towball load is for your LR, but I was under the impression that 100kg was the absolute max one should put on a towball (for an ordinary 'car', as distinct from a dual-wheel truck).

2nd point - the research on van stability (pendulum stuff) (there's some brilliant videos on YouTube, basic research done in a Queensland University, if I recall) is adamant on 'where you put the weight' - ie, as much as possible over the axles, as little as possible out at the ends (which means a lot of spare tyres and gas bottles are in the wrong place). My interpretation of the drawing was that you were putting weight at the extremities, not the centre - which if I've read it right, can be dangerous. The balancing needs to be towards the centre of the see-saw.

If I've read the diagram wrongly, feel free to ignore this post!

Max towball capacity of most Jap dual cabs is around 300 to 350Kg, not sure on modern LR's but the old RRC is good for 300kg as well - at work we have 3,000Kg trailers with 180Kg nose weights and they are fine, legal - and tow really well. The trailer OEM advises between 4 and 8% of total load for the units we run and we're on 6%. I did struggle with the owner on this as he is an old school '10%' man...

Having said that, it doesn't mean you can't or won't overload a vehicle towing these - we struggle to get the message of GCM, GVM & Axle loadings across to some people that turn up with utes that are dragging their arse already they are so overloaded and they want to stick these on the towball - which we don't allow - it doesn't go down well but with COR rules, we really need to be on the ball when we hire these big heavy trailers out and whacking 180Kg on the back of a loaded ute doesn't make the cut. Don't even start me on the ones that turn up with a 1 tonne ute with 2000Kg towbar and get stroppy with us - we always email every customer that hires these letting them know our expectations around a legal towing vehicle - but most don't read this then just bitch to us when they get here.

I still think there should be a towing license in Australia where you have to pass a test about all of this so those towing understand what they are doing - I think around 90% have no idea other that 'It can tow 3500Kg mate, it's ok' - I need a big facepalm sign I can point to when I get told this...

[Odysseyman]

Disco Ball weight at rear axle:-


To calculate the actual ball weight affect on the rear axle; multiply the ball weight by the (vehicle wheelbase plus the rear overhang) and then divide the answer by the wheelbase.
e.g. Disco:-
w/b 2900mm overhang 1320mm
Total 4220mm
If camper towball weight 240kg


240 x 4.220 = 1013
1013 / 2.900 = 350kg
on the rear axle

[trout1105]

I still think there should be a towing license in Australia where you have to pass a test about all of this so those towing understand what they are doing - I think around 90% have no idea other that 'It can tow 3500Kg mate, it's ok' - I need a big facepalm sign I can point to when I get told this...

I couldn't agree more [thumbsupbig]
It took years for the boating community to eventually require that people have a "Skippers Ticket" which requires them to actally learn how to operate a boat proficiantly and safely why not apply the same idea to people towing trailers, boats and caravans.[thumbsupbig]

[Briar]

Disco Ball weight at rear axle:-To calculate the actual ball weight affect on the rear axle; multiply the ball weight by the (vehicle wheelbase plus the rear overhang) and then divide the answer by the wheelbase. e.g. Disco:-w/b 2900mm overhang 1320mmTotal 4220mmIf camper towball weight 240kg240 x 4.220 = 10131013 / 2.900 = 350kgon the rear axleIf you look at my calculations above, they come out much the same as yours. For a 240kg ball load, my calculation gives a 341kg rear axle load. This is because I measured with a tape measure the "overhang" on my D4, being the distance from centre of rear axle to tow ball. You got 1320mm, I got 1230mm. This accounts for the difference. The main thing is that the longer the overhang, the greater any given tow ball load will have on rear axle for any given wheelbase.

[Macadamia]

get the van setup to use the same wheels offset and stud pattern so they're interchangeable then carry just the two spares that can be used on either car or van instead of a van spare and two car spares. I don't know much about vanlife so not sure how difficult this would be but I know it was an option with the ultimate camper when i looked.

[Xtreme]

get the van setup to use the same wheels offset and stud pattern so they're interchangeable then carry just the two spares that can be used on either car or van instead of a van spare and two car spares. I don't know much about vanlife so not sure how difficult this would be but I know it was an option with the ultimate camper when i looked.
This approach is good in theory however most people will probably replace their tow vehicle without replacing the van and may then end up with a mismatch of wheels/tyre sizes.
I've only ever carried one spare wheel/tyre combination plus a tyre repair kit and, if going really remote, I carry a spare tyre without rim.

[Briar]

get the van setup to use the same wheels offset and stud pattern so they're interchangeable then carry just the two spares that can be used on either car or van instead of a van spare and two car spares. I don't know much about vanlife so not sure how difficult this would be but I know it was an option with the ultimate camper when i looked.

Yes, that would be ideal but hard to do. Seeing I had the D4 first, there was no way I'd be getting 19" wheels on the van with a LR 5 stud pattern. Such a low profile would not be ideal for the van and the cost of getting cruisemaster LR hubs would be cost prohibitive and perhaps not even available. Most off-road and semi-off road vans have 16" wheels nearly all with a Landcruiser stud pattern.

Some who have the money can comprimise with 17" wheels on car and van with same stud pattern, but this would not be an option with the D4.

[Briar]

This approach is good in theory however most people will probably replace their tow vehicle without replacing the van and may then end up with a mismatch of wheels/tyre sizes.
I've only ever carried one spare wheel/tyre combination plus a tyre repair kit and, if going really remote, I carry a spare tyre without rim.

Hey Rog

I'd dearly love to carry just one spare wheel and a spare case, which is what I do whenever towing the van as a minimum on the blacktop. I get paranoid about the cost of possibly having to buy a second 19" tyre (or 18" if running the Moabs) in UpperCumbuctil West for an outrageous price. At least a case can get put on most anywhere on a rim. I have read lots of stuff on this forum and I have concluded that there is just no feasible way for me to break the bead on a D4 rim to change tyres in the scrub. This is why when really remote I just carry a full second spare. I hate lugging the extra weight but don't see any other option.

When I first got my car licence, my Dad who was a mechanic, would not let me travel on a long trip unless I demonstrated to him, not just how to swap a tyre. I had to, (in my old Hillman), crack the bead on the tyre and then using only two tyre levers and a rubber mallet, I had to remove the tube, take the tyre off the rim and then replace the lot. I ended up having to do this a few times, including once on the Strezlecki Track between Arrabury and Innamincka. Hard work but I managed to do it in the Holden Jackaroo. It's just that the D4 beads are so hard to crack I don't see any option except to carry a full second spare when remote.

[Odysseyman]

If you look at my calculations above, they come out much the same as yours. For a 240kg ball load, my calculation gives a 341kg rear axle load. This is because I measured with a tape measure the "overhang" on my D4, being the distance from centre of rear axle to tow ball. You got 1320mm, I got 1230mm. This accounts for the difference. The main thing is that the longer the overhang, the greater any given tow ball load will have on rear axle for any given wheelbase.

it wasn’t my intention to challenge your calculation, it was simply to offer the correct engineering formula. The 240kg ball weight was merely an example.
cheers
David

[Tombie]

Yes, that would be ideal but hard to do. Seeing I had the D4 first, there was no way I'd be getting 19" wheels on the van with a LR 5 stud pattern. Such a low profile would not be ideal for the van and the cost of getting cruisemaster LR hubs would be cost prohibitive and perhaps not even available. Most off-road and semi-off road vans have 16" wheels nearly all with a Landcruiser stud pattern.

Some who have the money can comprimise with 17" wheels on car and van with same stud pattern, but this would not be an option with the D4.

My hybrid and D4 have D4 wheels and tyres [emoji41] in 18s with 265/65-18

[josh.huber]

I wish!! If I measured correctly my D4 wheels will rub on my suspension due to offset. If your keeping both for any period of time I reckon it's a must do modification

[haydent]

Thanks OP for a novel and nice idea to reduce axle weight that im considering doing.
Plz note, if you are removing seats, legally you need to get it re-plated by an engineer.

I just removed the 2x swinging weights 'truck nuts' (harmonic damper) that are at the back bumper. Ill see if there is any noticeable difference and ill be surprised if there is, compared with the roads we drive on.

32kg ! As much as a spare tyre, and it will have greater effect on the rear axle than the spare tyre as its further from the axle, appx 1m so 42kg off the axle (x1.34)

Not sure if all models can do it as easily, 2010 L320 just 4 bolts to separate and remove.

191422

[haydent]

i actually got to test the difference with the weights off, rather than just hypothetical , and they actually account for 47kg of rear axle load on RRS ...