D40 air bags and bent chassis

[grahcom]

Have heard and seen reports and photos of/with D40 chassis can bend if fitted with air bags and on our way caravanning to Cape York a couple of weeks ago we saw a D40 duel cab with a rear tray (not a tub) that had bent chassis. It was travelling south towing a campertrailer, didn't appear to be overloaded, we didn't get a chance to talk inspect the vehicle nor talk with the driver, but others stated the vehicle had bellows type air bags fitted.

This appears to be a fairly common problem for vehicles fitted with bellows type air bags fitted over the top of the axle. ie replacing the bump stops.

We tow 2000kg van with 250kg ball weight and we have PolyAir red bags fitted to our D40 & I fitted them behind the rear axle, so far no problem with chassis, but to stop the bags from bottoming out and causing rough ride over speed bumps, pot holes, corrugations etc. we fitted 1in longer rear shackles, all seems to work fairly well BUT I would not fit air bags to a D40 again, but would use helper springs to aid the rear end when carrying loads.

While those how want a raised vehicle would get a lift kit, I'm happy with the ride and height so when we gat back home will probably try a set of the Ironman Load Plus Helper Springs or a set of Aussie SuperSprings.

cya
Graham

 

[tweak'e]

Ive heard of quiet a few problems with bent, cracked and broken chassis when using air bags. i understand that its the incorrect use of the air bags thats the cause.
they are being pumped up to much which shifts the loading from the springs to the air bags. changes the loading on the chassis to a single point rather than it spread over multiple points. also it puts the loading onto a point thats not designed for loading.

air bags are meant to be spring helpers, not the main spring.

the other thing is where the loading is. double cabs are bad for it because all the weight gets put behind the axle. the further away from the axle it is the more leverage it has. ie it acts like a much larger weight.
put a big deck on, weight at the end of the deck, even worse when they extend the tow ball out and tow a trailer with a lot of forward weight (especially single axle trailer).
they may have 1 ton of load all up (including trailer load on ball), which is what they are rated for, but it will act like 1.5 ton.

 

[manto1975]

2009 Nissan Navara D40 ..
Does anyone know of any chassis builders in Brisbane that can strengthen my chassis as i am going on a couple of trips to the cape and N.T.
I will be towing a 1.6 tonne off road camper, and i will be going off road. The navara has air bags fitted as well, ( not to carry extra weight but to level out the vehicle when towing camper trailer).
I am not saying this will happen to me but i would rather spend the money now and save it happening while on trip and been stuck in the middle of now where.
Any information would be greatly appreciated.
Trevor

2009 D40 Navara, ARB delux winch bull bar, ARB side rails and steps, warn winch, ARB air compressor and air locker, safari snorkel, HID head lights, IPF HID spot lights, ARB rear step and tow bar, Nissan ute liner, ARB 2" old man emu suspension, Polly air bags, 16" alloy wheels with 265x70x16 BF Goodridge AT tyres, Steinburg chip, 2.5" mandrel bent exhaust, bigger intercooler, rhino roof racks, tinted windows, UHF radio, Alpine DVD player with blue tooth, sat nav, reverse camera,

 

[Dion]

2009 Nissan Navara D40 ..
Does anyone know of any chassis builders in Brisbane that can strengthen my chassis as i am going on a couple of trips to the cape and N.T.
I will be towing a 1.6 tonne off road camper, and i will be going off road.
I am not saying this will happen to me but i would rather spend the money now and save it happening while on trip and been stuck in the middle of now where.
Any information would be greatly appreciated.
Trevor

Chassis cracking occurs because people load their trailers incorrectly, overload the tray, and the bending moment through the chassis in front of the rear axle exceeds what the chassis can tolerate. A correctly loaded trailer with the correct ball weight, and an intelligently loaded tray, in the absence of load helper airbags which mask overloading, and you will not need strengthening.

However if you do elect to follow this path, I imagine you intend to strengthen the rails from in front of the rear axle to behind the front 'axle', as within this area is where the moment is greatest?

The key point with reinforcements is to taper, stagger, and radius. Tapering fishplates and radiusing ALL CORNERS reduces stress concentrations, and staggering the ends of reinforcements ensures changes in rigidity along the chassis's length are gradual.

Tapers should be around thirty degrees, and you should plate at least 1.5 rail heights past any joins. Some people will also say stitch welds are better than seal welds as cracks won't propagate but I don't like the idea of water and salt working their way in behind a fishplate.

Remember that the chassis is part of your vehicle's suspension, and off road vehicles are meant to have a flexible chassis.

 

[Red Dog]

2009 Nissan Navara D40 ..
Does anyone know of any chassis builders in Brisbane that can strengthen my chassis as i am going on a couple of trips to the cape and N.T.
I will be towing a 1.6 tonne off road camper, and i will be going off road.
I am not saying this will happen to me but i would rather spend the money now and save it happening while on trip and been stuck in the middle of now where.
Any information would be greatly appreciated.
Trevor

You can try Redland 4X4, they repair the Patrols

 

[filobz]

Grahcom, I fitted the Ironman Load Plus helper springs & for $125 & 20mins to fit them I couldn't be happier.
I tow a 1.8t single axel van & it sits dead level without sway bars. I am lazy, so I don't retension the helper springs when I am not towing or carrying any load, & in my opinion the ride is still better than standard.
Empty, I think the back is about 40mm higher than standard, but since the recall & the new struts, it has leveled out.
Cheers,
Phil