Airbag, suspensions and trailers.

Hi everyone,
how to correctly level off car + trailer?

I recently towed my new custom off-road trailer (1.0T or so) and I found the hitch too low on the ground which doesn't help on soft sand or when good clearance is required.

I suspect the trailer was not correctly loaded or, even worse, not properly designed, anyway I have to solve the problem. I already inverted the tow-bar tongue of my LC78 2012 but the trailer is still not perfectly aligned. Car and trailer have same tyres.

I wold like to ask your suggestions about suspensions, airbags, springs. The LC is fitted with standard suspensions.

Thanks in advance for all your comments.
Nick
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Reply By: Notso - Wednesday, Jan 23, 2013 at 19:39

Wednesday, Jan 23, 2013 at 19:39
You can get hitches with a larger goose neck on em.
AnswerID: 503233

Follow Up By: nick DG - Wednesday, Jan 23, 2013 at 19:46

Wednesday, Jan 23, 2013 at 19:46
yes, the trailer will rise but not the hitch from the ground
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FollowupID: 779880

Reply By: Rockape - Wednesday, Jan 23, 2013 at 20:19

Wednesday, Jan 23, 2013 at 20:19
My thoughts only,

I hate airbags. Trucks and commercial trailers have proper airbags entirely different to the lets get it level ones you place under a light weight. The guy who bought my Troopy put them in because the back sat down a little when loaded with gear and a big camper trailer. I just shook my head and said to him, you are placing a lot of load on the chassis where it wasn't designed to have.

Mate do your self a favour and install heavier springs and shocks to match. As you know there are heaps of places out there that will set you right on spring rates.

if you want to do a little research contact Dobinsons, Kings, or lovells and they will give you the good oil on what you need. Best to put her on a weighbridge and see what load is on that ball when the trailer is on and loaded.

Rant over,
RA.
AnswerID: 503240

Follow Up By: olcoolone - Wednesday, Jan 23, 2013 at 20:34

Wednesday, Jan 23, 2013 at 20:34
Spot on....... there is no excuse for not doing it right the first time.
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FollowupID: 779887

Follow Up By: Member - Rosco from way back - Wednesday, Jan 23, 2013 at 21:42

Wednesday, Jan 23, 2013 at 21:42
x2

Couldn't agree more re the bags and leaf spring setup.
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FollowupID: 779896

Follow Up By: Aussi Traveller - Thursday, Jan 24, 2013 at 00:34

Thursday, Jan 24, 2013 at 00:34
Just to add, Airbags are not a load leveling device, they are for support not for lifting.

Phil
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FollowupID: 779915

Follow Up By: Member - PJR (NSW) - Thursday, Jan 24, 2013 at 09:13

Thursday, Jan 24, 2013 at 09:13
When we towed all I did was load the van so that, with a bit of strain, I could lift the towball onto the car. 100 lbs at max. The main aim was to minimise any change to the car's suspension and balance as much as I could.

As I see it, putting any weight on the towbar puts that weight mainly on the car's rear axle. Just lifting the body away from the axle (air bags) does not move any weight to the front of the car. That is definitely an imbalance in my mind. Thus upsetting the "balance" and road handling dynamics of the car. This to me is dangerous and unacceptable. If the towing vehicle (tug as some call it yuk!) is out of balance then surely that is dangerous. Heavier springs and shocks would help but very little, if any, of that weight is transferred to the front axle.

I am yet to see a device that would transfer half of say 200 kgs onto the front axle of a car. This would mean an imbalance in my mind. Level rider type springs may move some forward but not enough in my mind.

Our set up was always level, in balance and easy to drive. Even at 80 MPH plus (130K+ and yes, totally illegal). Load the van properly and all this "band aid" stuff is not necessary.

Phil
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FollowupID: 779925

Reply By: Tim HJ61 (WA) - Wednesday, Jan 23, 2013 at 20:45

Wednesday, Jan 23, 2013 at 20:45
Before you do anything, can you measure the drawbar height without the trailer and then with the trailer.

If there is not much difference, then it would seem pointless to spend money replacing your current springs.

I'm thinking a 1.0T trailer should not load up the LC so much that it's tail goes droopy.

If you add air bags when you don't need them then you are raising the rear of the vehicle above standard height which 'might' impact on your handling - tail up, front down.

If the trailer was custom built to match the LC, why not take it back to the manufacturer and have a chat about options. They may have mismeasured something and need to lift the hitch on the trailer.

The other possibility is that you've really loaded up the rear of the LC with very valuable and important 'stuff', and the LC has reached it's load limit before the addition of the camper. In this case, upgrading spring capacity is clearly in order.

Tim
AnswerID: 503244

Reply By: splits - Thursday, Jan 24, 2013 at 11:58

Thursday, Jan 24, 2013 at 11:58
Nick

There are a couple of ways to look at this problem. The first is the weight of the car. Is it under GVM? Don't forget the maximum weight should be reduced for off road and sandy surfaces. Cars are not designed to carry their maximum weight in the worst conditions they are likely to encounter for extended periods. That is why parts like chassis, wheel studs and axle housings break.

If the weight is ok but the car is still too low at the rear then you have a weight distribution problem. The answer is to redistribute it correctly, not, as Phil said, turn to a band aid solution like changing the suspension design. We all know that will lift the rear but do you know what it may have done to the overall handling of the car. You can never change anything on a car with out affecting something else so it is not a bad idea to know what you are doing..

What is the tow ball weight on the trailer? It may be poorly designed but the axle would have to be down near the tail lights for a 1 ton trailer to overload the back of a 78 series.

If all is ok there then you can either alter the tow bar or put a step in the trailer draw bar.

If you start fiddling with the tow bar then contact the bar manufacturer first. Any alterations will have an effect on leverage, flexing, stress etc so, in the interests of safety and reliability, they should be consulted. It should be remembered that the weight on it is static weight only. It will increase considerably as the rear of the car bounces up and down or drops suddenly into depressions or wash-outs in the road.

Before you do anything, take the time to read this article.http://www.caravanandmotorhomebooks.com/pdf/vehicle_dynamics_complete.pdf
Note what stiffening suspensions on one end and not the other will do. Read what he said about trailer ball weights. In thread 67469 on this site, someone mentions running his 1.5 ton camper successfully at 25 kg. In one of the very recent magazines from 4wd Action, someone had a large camper trailer custom built to have 50 kg on the ball. All of this ties in with the information in this article.
AnswerID: 503281

Follow Up By: Member - PJR (NSW) - Thursday, Jan 24, 2013 at 16:06

Thursday, Jan 24, 2013 at 16:06
Which Phil are you talking about Nick.

I do not like "band aid" solutions that just level the vehicles and not balance the loads.

Phil
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FollowupID: 779935

Follow Up By: splits - Saturday, Jan 26, 2013 at 09:53

Saturday, Jan 26, 2013 at 09:53
Phil

Please read carefully what I wrote and note the punctuation marks. I said "not turn to a band aid solution" but added the words "as Phil said" between two commas to acknowledge that you had already said not to use that method

By the way, I am Splits not Nick. Nick is the person who asked the question in the first place. I was addressing my reply to him so I started with his name.
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FollowupID: 780061

Follow Up By: Member - PJR (NSW) - Saturday, Jan 26, 2013 at 10:14

Saturday, Jan 26, 2013 at 10:14
Hi Splitz (sorry about the "Nick")

No argument from me. We both know what you are saying now.

Cheers

Phil

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FollowupID: 780064

Reply By: Batt's - Thursday, Jan 24, 2013 at 12:22

Thursday, Jan 24, 2013 at 12:22
I'm not sure what your rear suspension is independent or solid axel but my patrol has poly air bags inside the standard coils just pump them up when required which raises the rear about 40mm before you add weight then just let them down to 4 or 5 psi when not using them the car sits back down to standard height. Make sure the trailer is sitting level with the car ,not at a big angle it will tow a lot better. I suggest talking to a 4wd accessories outlet you don't need to spend a fortune. Also using a set of bathroom scales and some timber to spread the weight over the scales & while the trailer in on the car lower the jocky wheel to get the towball weight so you don't exceed the manufactures recomended weight
AnswerID: 503282

Reply By: The Bantam - Thursday, Jan 24, 2013 at 18:07

Thursday, Jan 24, 2013 at 18:07
Lets step back to some basic issues.

What exactly is dragging?

If the hitch is in the Australian standard height range and the drawbar is flat and straight, particularly if the hitch is mounted on the top of the drawbar, it is more or less unavoidable that the drawbar and hitch will have clearance problems.

These days it is more or less de-rigour for off road trailers to have the hitch mounted between the drawbar rails to a plate welded to the bottom of the rails, giving 2, 3 or 4 inches extra ground clearance over the on-road trailer.

Most trailers also mount the drawbar below the chasis, which is far from helpfull.

There are some...um...inventive..designes that do not have a conventional flat drawbar for this reason

NOW
for proper dynamics the line of the trailer chasis should be level or slightly down at the front...never up at the front, on a flat level surface......how does the rig sit?

If its all sitting the way it should on flat level ground and there is an appropraite amount of ball weight, there may be "nothing wrong"

If this is a landcruser station waggon, they have a reputation for dragging their bums at the best of times, this is why they are so often lifted and people almost always relocate the spare wheel.

Now remember too most non commercial 4WD stationwaggons ( because they are marketed as SUVs are low slug, softly suspended and by the time you put 4 large people a bag of clothes each, a tent and a slab of beer they are over their GVM.....mostly ya get somethig like 600 kg over curb weight

SO....now...exactly what is the problem?
What is dragging and when?

cheers
AnswerID: 503300

Reply By: nick DG - Thursday, Jan 24, 2013 at 22:32

Thursday, Jan 24, 2013 at 22:32
Thank you so much,
I found all your comments very helpful. The Vehicle Dynamics doc is very interesting.

I am currently overseas and when I will back home in the next few weeks I want take couple of pix and measures.

I will post again everything as" Airbag, suspensions and trailers part 2" and I will be very pleased if you have a look again and comment.

Cheers,
Nick

AnswerID: 503311

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