Thread: air suspension question

Hi WardH,

Nice explanation and diagrams! But I'm still unsure of some of the things you're saying:

If you measure the angle from the point of view of the outer CV joint (at the front), it still increases wear on the outer ring as the wheel drops (as the ring is circular), regardless of any pre-existing angle in the horizontal plane. The point may be that this regularly happens when cornering or off-road, but these happen at low speed. Continuous running at open-road speeds will take their toll. When mine went (towing a caravan to the Pilbara and back at 240mm height), it was only noticeable as a slight 'click' when at extreme articulation.

[edit] Of course, I can't say definitively that in this instance running at off-road height caused the CV failure. But it was this event that made me consider an alternative to permanently fitting shortened height sensor rods, to reduce the possibility of it happening again.

Regarding fuel consumption, I can only say that when I run my EAS car around at normal height, and then do the same day-to-day travel at off-road height (via the use of shortened HS rods), the trip computer registers the fuel consumption as having increased by 0.2 to 0.5 l/100 - I know the trip computer is lousy at absolute values, but for a relative comparison I have no reason to doubt it. I can't see why a lifted coiler would be any different? Now consider why the consumption has increased. No doubt some of it could be attributed to air resistance. But around town I wouldn't have thought this would be a major contributor. I suspect that a slight increase in the drag within the CV joints also plays a part.

You're saying that you measure a 4cm frontal offset for the front CV-to-diff. I don't see anything like that on mine at normal height (I haven't mesured it at off-road height). Are you sure that the coil lift itself hasn't contributed to this?

Cheers,

Gordon

Sorry, just thought I should point out:

We're only talking small increases in risk here. If I had a coil D3, I wouldn't hesitate fitting longer coils. The std height coil D3 isn't really adequate for any serious off-road travel.

If I was in the lucky position to choose between a lifted coiler and an EAS car, I'd take the EAS car, not because of any slight decrease in wear, but well, because of the air + TR. It makes it that much more versitile.

Cheers,

Gordon

G'Day Gordon how's things in the west?

You would think I could find better things to do than measure my D3 but thats what happens when you mix retirement and owning a Land Rover.

Had I had the option I would have preferred an EAS vehicle also, but there was none available at the time and looking at what we required the coiler fitted the bill in many ways.

The geometry of the vehicle is quite interesting and during taking the measurements several thing were noted. In the case of the rear suspension the 2 lower arm pivots (near the diff) are at very different heights. This can be seen when looking at it from the front and the first thing you think is "thats going to hit the ground first trip off road"

The effect of lowering the vehicle or when the suspension is compressed is to increase the length of the wheel base, we are not talking huge amounts but over the full range of the suspension travel it would be several mm, so the measured 28mm axle off set at 240mm height is going to increase when at normal height in a EAS or standard coiler. You can also see this when looking at the spring through the wheel arch, it has a pronounced rear leaning angle.

The front spring also has this rear lean but is nowhere near as pronounced and the 2 lower diff side suspension arm pivots appear to be about the same height (I have not measured them)
Where the shock absorber is pivoted/bolted to the bottom arm it is at a slight angle indicating that the wheel under load will also move rearwards. This on a standard height coiler or EAS at standard setting would shorten the 40mm off set that I measured, but if compared to the rear suspension only slightly, but could account for why yours is different.

On the coiler one major short coming is the amount of articulation travel on the front suspension with very little droop and upward travel even under heavy compression. If you jack the whole front end up with both wheels off the ground it looks pretty good the wheels hang down quite well, I did this to see if this put undue stress on the CVs but the shocks limit the travel before this happens. If you then take out the lower shock bolts and lift the front end again the wheels drop even further before binding the CVs so there is room for error but in my view it also means you will never see long travel shocks for coilers as the geometry as it stands will not allow it.

The main problem for the lack of front articulation and why you do not get the same droop that you think you should get when you lift the whole front up is the very strong anti roll bar, as you apply pressure to one wheel say over a large hump or rock and we all like to see that wheel travel up into the wheel arch, the bar is also then applying upward pressure to the opp wheel. (oh how I miss my old disco! not realy) And this is where the EAS via its valveing can replicate a beam axle.

The rear articulation is quite acceptable the anti roll bar is set up quite differently and allows more twisting, the shocks still limit travel well before the point where the CVs are nearing the outer ring

Anyhow because of limited articulation (unless totaly air born and dropped wheels pull the stops out of the shocks Gee I guess some people will do that) I am not worried unduly about my CVs. Rear CVs have over 14000 Ks in lifted height no problems or wear detectable yet. fronts have about 2000Ks. Front and rear lifts were done at different times.

The increase in fuel consumpsion still haven't noticed any and I dont think it would be caused by the slight angle increase on CVs, that being the case extra fuel used means energy burnt, =friction=heat=quickly stuffed CVs. The amount you are indicating via your computer is within the range of averages that I work out when filling up, I dont have a computer. so maybe it has not become apparent yet, Any increase is more likely drag.

Cheers

Howard.