Leaf springs and Air bag suspension.

DUSTYRHODES · Veteran Member

Leaf springs and Air bag suspension.

rockylizard · Guru

Gday...

Firstly welcome to the forum

You will find that it is almost universal that utes - HiLux, Colorado, Ranger, Mazda, Isuzu, Narara etc should not have airbags fitted and used for carrying heavy loads/caravan towball weight. I am sure others will provide similar responses to you.

This site will give you considerable evidence of the damage it ultimately causes to utes fitted with airbags.

https://www.google.com.au/search?q=air+baqs+in+utilities&biw=1366&bih=643&source=lnms&tbm=isch&sa=X&ei=laqsVNfLCIG0mwW1s4CYCg&ved=0CAYQ_AUoAQ#tbm=isch&q=broken+chassis+in+utes

Cheers - John

exa41 · Guru

Hi DR , Yep , I friends boss fitted air bags to a falcon ute ,broke the chassis both sides with over weight and pressure.

ken thomas · Guru

I put ironman helper springs on my ranger and lifted it up 50mm and the van sits level, the ride is still good
Ken

Gundog · Guru

Sorry Rocklizard that link has little reality to the use of Airbags.

That is more about overlading the tub, the real question which has been answered before on this forum how much do you or intend to load into you tub/vehicle before hooking up your caravan.

Using my Ranger as an example

TOWING LIMITS 3T with load levelling kit, without 1.8T

GROSS VEHICLE MASS = 2.9T

GROSS COMBINED MASS = 5.5T

So Dusty your starting point is how heavy is your vehicle with a full tank of fuel and the normal number of passenger.

Lets use some rubbery figures (I'm yet to weigh mine as I am still doing some fit out before retirement) kerb weight of the vehicle + fuel + partner as ready to start loading the tub is 1.95T

2.9 - 1.95 = 0.950kg

we add the tow ball weight which is 10% of the caravan weight 2.5t van = 250kg

950kg available - the 250kg tow ball weight that leaves us with 700kg to put in the tub.

Lets recap GVM 2.9T + Tow weight 2.5T = GCM 5.4T

So when you massage the numbers even more if you went to a 3T caravan with 300kg ball weight

1.95T +300kg = 2.25T

2.25T + 3T = 5.25T in this case you would only have 250kg available to load in the tub.

Rather than say Air bags are not suitable you need to start at the very beginning and get you weights right for your vehicle to ensure you stay within your GCM .

A WDH is essential + drive to the conditions.

At the end of the day check with your insurance company and vehicle manufacture prior to fitting load sharing accessories and above all else before commencing your travels have individual weighbridge dockets for Tug Van and combination, because if you do have to make a claim that your proof your not overloaded

DUSTYRHODES · Veteran Member

Thanks all, geez they must making chasis rails out of tin these days. I remember having 'pump up shockers' probably Monroe, on my old Holden 40 years ago.

Perhaps they need some plating.

Thanks Gundog,
I weighed the vehicle (Dmax) with the Van connected and got these figures at each axle.

Front......... 1098 kg
Rear axle... 1288 kg... without the van 1048 kg, so the Van is throwing 240 kg onto the ball, about what the dealer said.
Van............ 998 kg... If I add 240 kg to this (from the rear axle of the Dmax) then that gives the correct weight (approx) for the Van at 1240 kgs.
Total........... 3,384 kg.

I'm not looking to pump the Air bags up to a rediculous pressure, just add a bit of help. (maybe famous last words)

WDH. ?? not sure what this is. Weight Distribution H........ ?

Can't use 'Ride Levellers' as our Van is an Off Roader and uses the Trig Off Road coupling, so too much movement.

I'm an ex long distance Truckie and always drive to the conditions. I like to drive. hehe.

Ken, I did look at the helper springs in BCF a week ago, thought at the time they might be the easy and cheapest way out. Good to know that they work as they should.

Of course I will be adding new shockers soon, as the originals have been very good but struggle on the back with the extra weight. Nearly 5 years old now, almost Seasick.

Cheers Dusty.

-- Edited by DUSTYRHODES on Wednesday 7th of January 2015 06:14:47 PM

PeterD · Guru

Gundog wrote:
Sorry Rocklizard that link has little reality to the use of Airbags.

That is more about overlading the tub, the real question which has been answered before on this forum how much do you or intend to load into you tub/vehicle before hooking up your caravan.

The trouble is the two are interrelated. People see that the back end drops too low. The thing that causes the rear end to drop too low is because the rear suspension is overloaded. They then jack the rear end with air bags. With the ute in its overloaded state gets the chassis hammered by the air bags.

Another thing that causes the overload is the badly distributed load. Twin cab utes are designed to be loaded evenly over their length, this includes passengers in the rear seats. Also some believe that these utes are rated to carry about one tonne and you can put this load in the tub. That is far from the truth. Out of this one tonne you have to subtract the weight of all the accessories you load onto the truck (including probably 100 kg of canopy,) the weight of the fuel and passengers. In addition they don't use WDH but they only make allowance for the ball weight which is not sufficient. When you couple a van to the ball you remove weight from the front wheels (can be up to half the ball weight) in turn this weight is transferred to the rear axle. If your tug is too far down at the rear you have loaded too much weight at the rear (this applies to all vehicles.)

If the rear of your vehicle drops too low then you should consider using WDH and reducing the load. This will prevent the overloading of the rear axle.

The following diagram will demonstrate the amount of extra load that is carried by the rear axle when WDH.

HR WDH display.jpg

Baz421 · Guru

DUSTYRHODES wrote:

I don't want to be bounced around by heavy springs when the van is not used, and a pair of adjustable Air bags is my favored solution but ARB say they won't fit them to a vehicle with leaf springs because of some owners putting so much pressure in them that the bag was carrying all the weight and the chassis had been bent. ?
Has anyone fitted air bags to an Isuzu or Rodeo or to any vehicle with leaf spring rear suspension. ?
Cheers, DR.

I see you have had some advice DR.

We have LC79 series ute and ARB et al, often say this because some at ARB and others are worried about lawsuits, unfortunately.

We have uprated suspension and shocks and upgraded GVM to 3,700kg vice 3,300kg.

We have a pod on the tray almost permanently and use all of our GVM and almost all of our GCM when fully loaded tug and van. I'm ex mechanic and could see some signs of sag in springs when fully loaded so 4 years ago added Firestone airbags, not the cheapies.

I only add about 5-10psi normally and sometimes 15 psi as the load sharing with the springs. We also have the HD REECE (imported one from USA) weight dist hitch. All works very well.

Problems arise and I've personally seen 2 guys with 90psi in well tub dual cab utes. These are the chassis that fail and for good reason it seems.

The quality of the steel, Aussie versus imported, is such that many sell chassis based on Aussie made steel. I've seen imported brake cylinders (cast ones) that were porous when some in the NT wanted to buy cheap rather than genuine Tojo parts. I would suggest that some chassis are the same, ie made to a minimum spec.

I wrote some info on minimum specs on another thread I'll see if I can find it. Basically it's about a product manufactured to a price rather than quality.

Hope this helps you.

Cheers Baz

See this thread DR - http://thegreynomads.activeboard.com/t59238487/my-44-kva-generator/

-- Edited by Baz421 on Wednesday 7th of January 2015 10:09:28 PM

Brenda and Alan · Guru

PeterD the example you have shown shows that the advertising for these WDH from hyman reese seems to pluck their figures out of the air. The caravan shown is heavier at the rear in an uncoupled condition so how in the world could it impose any ball weight on the tow bar as shown . Further this van becomes 40Kgm lighter at the rear and 40 Kgm heavier at the front when its coupled to a vehicle ( ie weight unchanged) but magically imposes 360 Kgm on the rear axle and the tow vehicle becomes a total a of 220 Kgm heavier overall. This is just total garbage and absolutely no justification to use a WDH.

Now the poster was asking about air bags on leaf sprung vehicles. The fact remains that they are designed to carry the load on the rear axle to the chassis AT the spring hangers NOT at a

point half way between and this is why they cause chassis to crack or bend when they are used to compensate for over loading.

Alan

-- Edited by Brenda and Alan on Thursday 8th of January 2015 10:30:10 PM

-- Edited by Brenda and Alan on Thursday 8th of January 2015 10:37:57 PM

Delta18 · Guru

DUSTYRHODES wrote:

WDH. ?? not sure what this is. Weight Distribution H........ ?

Can't use 'Ride Levellers' as our Van is an Off Roader and uses the Trig Off Road coupling, so too much movement.

Cheers Dusty.

-- Edited by DUSTYRHODES on Wednesday 7th of January 2015 06:14:47 PM

WDH = Weight Distribution Hitch. Probably similar to what you call Ride Levellers.

It is there to transfer some of the ball weight onto the car front wheels.

Your statement about not being able to use the WDH is not really correct. They are most use on the highway to assist with stability at highway speeds.

For the low percentage of time your van would spend Off Road in situations that would make your Treg Hitch work as it is designed to, you would remove the WDH.

At walking speed it does nothing.

Aus-Kiwi · Guru

Some common sense.. Unfortunatly not very common..

mr glassies · Guru

hey dusty look at sax 3 stage suspension
i had it fitted to the colorado and its the best setup you could ask for it rides just like standard empty and weight rate is picked up as you load more in the vehicle mine is virtually standard picks up at about 250 kgs on the 2nd stage and then more for the 3rd but i haven't loaded it up that far yet . i have even stopped using the wdh its that good ute sites dead level used to drop 65 mls with 240 kgs on the ball now 15 ml would pull it up wort every cent i paid

dibs

PeterD · Guru

Brenda and Alan wrote:
PeterD the example you have shown shows that the advertising for these WDH from hyman reese seems to pluck their figures out of the air. The caravan shown is heavier at the rear in an uncoupled condition so how in the world could it impose any ball weight on the tow bar as shown . Further this van becomes 40Kgm lighter at the rear and 40 Kgm heavier at the front when its coupled to a vehicle ( ie weight unchanged) but magically imposes 360 Kgm on the rear axle and the tow vehicle becomes a total a of 220 Kgm heavier overall. This is just total garbage and absolutely no justification to use a WDH.

Is it Brenda or Alan who composed this badly written prose?

1. For starters the diagram is not an advert for HR. It's a table of results recorded by Tom Olthoff (or one of his colleges) at a caravan show many years ago when he was technical editor of Caravan World. Nothing was plucked out of the air. The table was part of an article on WDH penned by Tom and published in Caravan world. Of late Hayman Reese have recommenced these demonstrations at shows. Keep an eye out for one of them when you go to a show.

2. The group axle weight of the van in the first two conditions is the same. The van was not equipped with load bearing suspension. The change of weight between the front and rear axles is the result you expect when you change the trim of that van when you lower the front end. It also demonstrates why you have to de-rate the tyre and axle loadings when they are used in an axle group that does not incorporate load sharing suspension.

3. You obviously did not read and understand the sentence in my previous message: "When you couple a van to the ball you remove weight from the front wheels (can be up to half the ball weight) in turn this weight is transferred to the rear axle." You also did not twig to the fact that the extra 140 kg "magically imposed on the rear axle" comes about from by the front axle now being 140 kg lighter. If you understand the principle of levers you would understand what is going on. If you remove weight from the front wheels it must go somewhere, it does not disappear.

4. This is not "just total garbage and absolutely no justification to use a WDH." There is no smoke and mirrors involved, nothing has been plucked out of the air. The figures have simply been noted at a demonstration. To those that understand first year high school physics the results are perfectly logical. I believe it is a good practical demonstration of why WDH should be used, particularly if you are going to have a fair sort of load in the tug. If you have a heavily laden tug and no WDH then there is an extremely good chance you have an overloaded rear axle.

In addition, you missed something else. When the WDH is applied the van appears to become 60 kg heavier and the tug 60 kg lighter. This also can be explained with the theory of levers.

Oh, and by the way, I agreed with your bit that I snipped from the quote.

Gundog · Guru

mr glassies wrote:
hey dusty look at sax 3 stage suspension
i had it fitted to the colorado and its the best setup you could ask for it rides just like standard empty and weight rate is picked up as you load more in the vehicle mine is virtually standard picks up at about 250 kgs on the 2nd stage and then more for the 3rd but i haven't loaded it up that far yet . i have even stopped using the wdh its that good ute sites dead level used to drop 65 mls with 240 kgs on the ball now 15 ml would pull it up wort every cent i paid

dibs

After looking at their web site I make the conclusion that the Sax 3 stage suspension in not the answer for towing, it cannot distribute the load evenly across the tug and towed vehicle.

Sax is just another type of helper spring, like all helper springs it prevents the suspension from flattening out.

There is no reason why except for off road use not to use a Weight Distribution Hitch, if you bother to actually read my earlier post about load calculation and others about weight distribution there would be no need for helper springs in Utes, however I do concede that Cruisers etc do not suffer from overloading like utes because the mentality of some people will just load the tub or tray until its full with no disregard for weight.

I neglected to mention in my earlier post the weight distribution within the van is just as important as the towing vehicle.

For the off roaders there is an adaptor plate for some of the treg style hitches that allow you to use a WDH for normal travel.

Radar · Guru

Hi DR.

My first question DR is did you not hear enough crap on the road while you were driving?

Then to the others HR is a product sold by marketing to make money whether it works or not in all situations.

But for the love of me I can not see how a HR hitch can put weight of the back wheels onto the front wheels alone.

Maybe by using stressed bars attached from the A frame to a hitch you may achieve this.

Now the man asked will leaf springs work with air bags? Yes they will and transfer some weight to the front at the sometime. Transports was using this idea until outlawed back in the eighties to help with overloading axles.

Yes I have seen 2 bent crew cabs, one using air bags and one not, both been towing heavy trailers. Both broken near the spring hanger between the cab and ute. Not bent but cracked chassis.

A very good friend was the transport maintance man loaded up the crew cab ute tools, batteries, starter, motors and list goes on had helper springs then added air bags and often for good measure would drop the van on. If there was a ute that should of broke it was this one, he ran a max of 25 with the van but mostly 15 to 18 pound going to 2 to 4 hundred kilo meters to fix a broken down transport.

If you ask The Air Bag Man Company he tell you they work also because he has a product to sell. Ralph

Ps. Sorry this is long winded. You know truck drivers like to talk.

Woody n Sue · Guru

Well after all that I'm even more convinced that a 5th wheeler is the only way to go don't have any of these WMD,s whoops I mean WDH's to deal with, it hitches on top of the rear axel and the weight distribution is just great, every time, no need to worry about where to put that extra slab of ale, crate of wine or cheap purchase of bulk food, no need for air bags either rides a treat control is a dream, safer than a gazell in a zoo full of lions.

PeterD · Guru

Radar wrote:
1. Then to the others HR is a product sold by marketing to make money whether it works or not in all situations.
2. But for the love of me I can not see how a HR hitch can put weight of the back wheels onto the front wheels alone.
3. Maybe by using stressed bars attached from the A frame to a hitch you may achieve this.
4. Now the man asked will leaf springs work with air bags? Yes they will and transfer some weight to the front at the sometime.

1. Yes there are shonks in the caravan business. The biggest problem with these people is they sell the wrong model of equipment. You see small vans with the HR 600 bars when they most likely should have the HR mini-hitch. On the other hand you see too many larger vans that just have the shepherd crook toys.

2. The WDH does not do their job alone. They are part of a system. I have not seen the wheelbarrow analogy espoused for a while so here it is again. If you have a wheel barrow in front of you and you push down on the handles you will remove some of the down force (weight) on the front wheel. If you put enough force on the handles you will remove so much down force on the front wheel that the wheel will rise off the ground (luckily caravans don't go that far.) In the same manner hitching a van to a tug has the same lever action.. Applying the WDH is like extending the handles of the barrow. Whilst the first bloke is pushing down on the handles a second one pulls up on the extended handles. The second bloke can exert enough force to counteract the effect of the first one upsetting the weight distribution within the wheelbarrow.

The lift on the WDH bars comes about by the spring action pulling down on the drawbar of the van. You will notice in the table I posted above that the vans axle group is 60 kg heavier when the it was before the WDH was applied. If you add the tugs wheel weights together with the 220 kg ball weight you will see that the tug is also 60 kg lighter. This all works as a team with the forces added by the WDH rearranging the way the load is distributed amongst the axles.

3. Maybe you are attempting to describe WDH.

4. Many respondents have come on these forums and have argued that strengthening the tugs rear suspension will restore the weight back onto the front axle. None of them have been able to satisfactorily explain how this is so in mathematical or mechanical terms.

PeterD · Guru

Woody n Sue wrote:
Well after all that I'm even more convinced that a 5th wheeler is the only way to go don't have any of these WMD,s whoops I mean WDH's to deal with, it hitches on top of the rear axel and the weight distribution is just great, every time,

This is a great way to go. There are many of us that think that for anything over about 6 meters in length you are very much safer with a 5th wheeler than a wobbly. The problem is there are too many thinking of the overly large Yankee units when 5th wheelers are mentioned. There are many reasonably sized locally manufactured units available. They are not much dearer than one of the great gin palaces you see behind twin cab utes but with the extra cost you often achieve a better lounge/dining area.

I can but dream. I spent my cash before suitable utes and the smaller 5th wheelers came on the market.

Woody n Sue · Guru

Well yes PeterD those big yank tanks are awfully big maust be a gas at the servo filling up each day anyway me thinks some of them are just compensating for a smaller problem they have but I digress, our 24ft trailblazer and patrol are plenty big enough for us .

Gundog · Guru

In the tow ball thread I commented that I have read my load distribution hitch fitting instructions.

Paragraph 10: states

If towing across a steep incline such as a driveway or boat ramp, it is recommended that the spring bars are disconnected beforehand to prevent risk of damage to the load distribution hitch and/or vehicle chassis.

-- Edited by Gundog on Saturday 10th of January 2015 05:51:46 PM

Baz421 · Guru

Ian found this for air pressure and load. I thought I read ages ago 1psi = 60 lbs but maybe this is more accurate.

Expert Reply:

Other than saying that the air bags need to be kept between 5 and 100 psi, Firestone does not offer much in the way of specifics. The instructions mention that as a general rule of thumb, 1 psi will support approximately 40 lbs of load.

cheers Baz

-- Edited by Baz421 on Saturday 10th of January 2015 09:00:51 PM

Baz421 · Guru

Woody n Sue wrote:
Well after all that I'm even more convinced that a 5th wheeler is the only way to go don't have any of these WMD,s whoops I mean WDH's to deal with, it hitches on top of the rear axel and the weight distribution is just great, every time, no need to worry about where to put that extra slab of ale, crate of wine or cheap purchase of bulk food, no need for air bags either rides a treat control is a dream, safer than a gazell in a zoo full of lions.

You can still overload the rear axle my friend,,, quite easily.

-- Edited by Baz421 on Saturday 10th of January 2015 09:06:19 PM

mr glassies · Guru

Gundog wrote:
mr glassies wrote:
hey dusty look at sax 3 stage suspension
i had it fitted to the colorado and its the best setup you could ask for it rides just like standard empty and weight rate is picked up as you load more in the vehicle mine is virtually standard picks up at about 250 kgs on the 2nd stage and then more for the 3rd but i haven't loaded it up that far yet . i have even stopped using the wdh its that good ute sites dead level used to drop 65 mls with 240 kgs on the ball now 15 ml would pull it up wort every cent i paid

dibs
After looking at their web site I make the conclusion that the Sax 3 stage suspension in not the answer for towing, it cannot distribute the load evenly across the tug and towed vehicle.
Sax is just another type of helper spring, like all helper springs it prevents the suspension from flattening out.
There is no reason why except for off road use not to use a Weight Distribution Hitch, if you bother to actually read my earlier post about load calculation and others about weight distribution there would be no need for helper springs in Utes, however I do concede that Cruisers etc do not suffer from overloading like utes because the mentality of some people will just load the tub or tray until its full with no disregard for weight.
I neglected to mention in my earlier post the weight distribution within the van is just as important as the towing vehicle.
For the off roaders there is an adaptor plate for some of the treg style hitches that allow you to use a WDH for normal travel.

hmmmm don't know what the difference between a ford and a holden is but id love to see full pay load including the van on the back at its correct ball weight . i stated it went down 65 mill with 240 kgs on the ball and that was with no pay load in the tub just a fews cloths as were only doing small runs till the business sells. like tha add and from experience having them installed it rides like standard on the main spring up to 250 kgs it picks up the more weight put in the tug and the 3rd picks up the final weight .

as for helper springs being not the answer i dunno about that and maybe i should take the helper springs of my trucks . sorry i didn't and don't bother to read all the posts on this site . as for your comment about not needing helper springs i can tell you from experience if i had to level the tug and van with a wdh id do some serious damage to the tow bar or its connection to the tug chassis or the draw bar of the van .how many tug and vans do you see with the front wheels just touching the road by having a sax system installed front coils/shokes rear springs/shokes it has greatly improved the handling of both the weight including side sway from pushed air from bigger trucks and x winds . (now I'm going tone told wdh will stop side sway) yes i dosnt transfer the weight to the front but it helps the rear stand up to the extra weight on the tow bar keeping all 4 wheels in good contact with the road

1 of your comments / however I do concede that Cruisers etc do not suffer from overloading like utes because the mentality of some people will just load the tub or tray until its full with no disregard for weight. does this mean cruiser drivers have a different mental state than most other people .

I neglected to mention in my earlier post the weight distribution within the van is just as important as the towing vehicle. you can't get more dedicated to weight loading than having your own drawbar scale . which i do.

dibs