Polyairbags query

[Fvandenboom Junior Member Find all posts View Profile Close Fvandenboom]

2016 GXL I recently had standard shockers & springs replaced with TJM kit & polyairbags. I have never used airbags before and am puzzled about my experience here. Here are some heights for u to consider - heights are from ground to top of wheel arch passing thru wheel center.
(1) no load in rear, 5 p.s.i - height 960mm
(2) less than 100kg in back of prado, 240 kg on towbar from camper trailer, 30 p.s.i. - height 935mm
(3) same as (2) with 5 p s.i - height 920mm

i thought the whole point of air bags is to get back end close to normal unloaded height. I don't see them doing much. Is it possible the wrong thing has been unstalled? Would appreciate yr insights. thnx. Frank

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

The bags take some of the load but dont actually lift because they are not longer than the spring, if that makes sense. The capacity of the bags is huge with a diameter of around 100mm and a pressure of say 30psi equates to a load capacity of 300kg ish. I have been meaning to do some testing with Whitey to determine their actual assistance. But it will depend a lot on the spring / bag combination.

Say 10psi and then height with no drawbar load, 50kg, 100kg, etc up to 250kg. Then repeat with 15psi and 20psi etc. I started but ran out of interest and my scales aren't accurate enough.

As long as they fitted the longer bags to suit the lift they should be ok. Where are you measuring from and to? Usual method is from the lower lip of the rim vertically to guard. Adjusted for 17" wheelsvso the numbers line up with the database. Guessing younare measuring from the ground so you have a 40mm lift? Should still have been the longer bags.

[Fvandenboom Junior Member Find all posts View Profile Close Fvandenboom]

I'll be talking to TJM about it this week but i hope i don't get fobbed off because I'm not technically strong on this stuff. I was led to believe that the airbags would solve the sag problem often experienced when towing a van or camper. They actually make very little difference.

[Leethal Advanced Member Find all posts View Profile Close Leethal]

In my opinion that 240 kg ball load is substantial, don't forget that weight is behind the vehicle and as such will have a greater effect on ride height than 240 kg carried in the back of the Prado. Lifting/carrying 240 kg that is a metre or so behind the axle will test your suspension set-up, do you know what load rating springs you have?
Are you inflating the bags before hitching the camper on? That is the correct way to inflate air bags. increase pressure then load up the vehicle.

I think you need TJM to confirm what parts have been fitted, the part numbers should have been listed on your invoice (if only for the TJM store's stock control) the case might be that you are asking the air bags to do ALL the load carrying, air bags should be used to assist the springs not be the main load bearer.

Lee

[Fvandenboom Junior Member Find all posts View Profile Close Fvandenboom]

Thnx Lee. I am inflating the bags before applying the load. TJM did not include any part numbers or codes on my invoice - clearly I have been naive in not picking that up. I am seeing them on fri with my Kamper. I was upfront with these weights when getting quotes so hope this doesn't become difficult. My camper is a Kimberley Kamper - they are notorious for being heavy at the hitch and there are plenty of Prados dealing with weights well above 250kgs.
I get yr point that the bags are there to support the springs but i was led to believe they would contribute more to leveling the back end. I will let u know the outcome later in the week.

[rascal Member Find all posts View Profile Close rascal]

FVandenboom, I have a bilstein/dobinsons combo from Zordo (quick plug for John Zordo. His awesome reputation is thoroughly deserved) and coilrite airbags in the back of my 2013 V6, which I use when towing my 2400kg trailer (ball weight is 180kg)

I originally went with C327 coils which are 35% stiffer than factory, but found it too harsh when unloaded, (and didnt even need my airbags when towing above trailer)
I have now changed to C325 coils which are only 5% stiffer than factory and find this perfect.
When hooking up the loaded trailer, the rear of the car sags about 30mm. Jacking up the trailer and putting 28psi in the bags (almost full pressure) made it sit at pre-load level again once I let the jack down. So my airbags match almost perfectly my load. Though this is only 200kg (180 + 20 odd in rear of car) whereas yours is 350kg, which is 75% more.. I'd suggest you'll need heavier springs to carry the load.

[404pug Avid PP Poster! Find all posts View Profile Close 404pug]

Intersting Rascal. I too swapped 327 Dobinsons for 325 but for a slightly different reason. Mine is a GX so is about 100kg lighter than a GXL so I found that it sat a bit high as well as being a little harsh when empty (which is most of the time) .When combined with Whitey's revealed Iron man shocks the combination of ride and handling is great. I will keep the 327s because they were sensational on a heavily laden desert trip recently and will be used again. I had airbags in my 120 but my preference is actually heavier springs for heavier loads