LAD questions:

[ss2115]

Does anyone know if the LAD system is supposed to always run in a pressurised state so that its always lifting the rear suspension a bit, or should it only be activated when the springs are compressed by a heavy load and it compensates the natural ride height of the springs only?

The reason to ask is that I've adjusted the rod to the regulator on the rear roll bar to get some more ride height and reduce the rear wheel camber, but I have only gained 10mm and the system won't pump up any further. The switch at adjustment is still slightly over on the "increase height" side but it doesn't rise any further. Putting heavy weights in the load area drops the height without any compensation.

This indicates that the rear springs are probably sagged and the LAD has been compensating all this time but now is at its maximum.

I'd also like to know what most people's ride height is for the back suspension with standard LAD suspension. Mine doesn't seem to equate with the Bently book at all (much higher at 560mm), and my friendly BMW mechanic measured mine against an exact same 525i Touring and its 545mm - closer but still higher than Bently.
My front ride height measures 570mm and now with the extra 10mm adjustment of the LAD, my rears are also 570mm.

I'm wondering if Australian spec cars had higher ride heights due to the rougher roads than europe - perhaps a Sth Africa Spec or something?

This all started because a wheel alignment showed excessive rear wheel camber (no adjustment) and rapid wearing of the inside edges of the rear tyres.
We cannot find anything wrong with the bushes or anything, so we wondered if the LAD had gone out of adjustment and the rear wheels were splaying.

Any comments or advice would be welcome.
Also - is it possible to get new bombs (Nitrogen spheres) still? These won't be effecting the ride height, but will effect the ride quality - mines quite hard at the rear.

[shogun]

the system runs always when engine is on, it pumps the fluid to the rear axle to the regulating valve, and there are 2 valves inside, a minimum and a max. pressure valve.
min pressure p = 30 bar The overpressure valve limts the max. pressure to p = 130 bar and opens at 130 Bar.
Here the complete system described by me, German with drawings, also some English, use google
http://www.7-forum.com/forum/24/komponenten-niveauregulierung-edc-deren-lage-84467.html
and here I copied something:
and I recently posted this:

LAD bleeding + correct adjustment information

The ride height is adjusted to a predefined height (distance from the edge of the rim to the edge of the wheel well) with the pre-defined weight in the trunk. Both values can be found in the Bentley Repair Manual and they are also mentioned on this board.

Here is a trick from my own experience that should make the job easier. You should loosen the lever on the stabilizer so you can change the adjustment. If you move the lever forward, in the driving direction, you also move the lever on the control valve forward and the result should be an increase in ride height, in reverse, moving the lever backwards, should result in a decrease of the ride height. First thing to do after a repair is to remove all the air from the system. You should raise the car with the wheels hanging free and the engine running, move the lever fully in the ‘UP’ direction and let it sit for 5 to 10 minutes. You should repeat this perhaps 2 to 4 days. Driving also aids in the removing of the air. The air collects at the top of the shock absorber which then in turn is removed by the previous procedure on the car lift. The only way I can tell, in my opinion, that all the air is gone is by repeating the above procedure, It took 4 days before I felt the car was stable again in cornering and driving, and I did not have sudden changes in characteristics. After a few days you can adjust the ride height. The lever on the control valve has in the center ( ‘0’) position, vertical, a small dead zone in the ride height control between raising and lowering the rear. You should check the center position carefully. One should slowly move the lever a little in the direction to raise the rear and listen carefully for the sound of flowing hydraulic oil. Small movements of the lever cause large changes. The trick is to adjust the ride height (with the prerequisite extra weight in the trunk) exactly at the point where you can hear the hydraulic fluid flow. You probably will need a few tries to get this right but you try to get the ride height correct at the onset of the hydraulic fluid noise. Now carefully tighten the lever without moving it relative to the stabilizer bar. Now check the ride height once more without the weight in the trunk, it should not have changed Note: Theory and real world are two different entities and there is no sure method to remove the air. I removed the air 5 times on the same day and re-adjusted the ride height , then I would find the car the next morning sunk uneven again. the abnormal drive characteristics disappeared at the same time the pentosin level stabilized. Note: The car stood lower in the right, but the left side would also sink over night, as measured with a ruler. When the car started the rear would pump back up, but the pentosin level would be permanently a little lower unrelated to the control valve and the new bombs. Mainly the right side maintained a lot of air in the shock absorber. I have a special test corner and the car would go soft in the rear, something that never happened with the old shock absorber. But luckily now the right shock is okay.



how to repair the valve http://www.bimmerboard.com/forums/posts/538359
http://www.bryanborough.com/750iL/LADRegulatingValve/index.htm
http://www.bryanborough.com/750iL/LADRegulatingValve/P1010322.htm

The bombs are still available from the dealer or online shops, I should have 2 new ones made by Meyle still on stock.

37211132043 Meyle Self-Leveling Accumulator Sphere/Air Cell; Left/Right; For Self-Leveling Suspension System
2 per car. List price $230.00, normal net price$141.99, special sale price $134.89, at Autohaus Arizona. That is the cheapest I could find.
Normally they sell around 160-200$.
If you want my ones made by Meyle, $140.00/piece plus actual shipping from Japan to AUS, should be cheaper than from AutohausAZ from USA, as they select not the cheapest and slowest shipping methods.
I already paid for shipping to here and import duty, so that is the best price I can offer. If you pay by paypal, add the paypal cost, otherwise I make a loss.

Febi also produces them.

[ss2115]

Hi Shogun - nice to hear from you again.
I didn't break into or crack any lines, so I have no reason to suspect any air in the system.
Also, its never sunk overnight.
I believe its all working correctly as it should.

The problem is that I seem to have reached a maximum (130bar you say) and the ride height is only just making it to correct height with nothing left in reserve for heavy loads.
eg: adjusting the valve manually allows it to sink and also to rise quite well. However, we started at 560mm and can only go to 570mm maximum height even if the valve is held over to go up and the engine held at 2000rpm for several minutes.

I'm also asking for ride height specifications because mine seems to be higher than the Bently manual (it says 526mm at the back, which would have my car very low at the back and higher at the front). At 560mm high ride height at the back, the sills are very parallel with the road - now at 570mm its only slightly perceptively higher at the back. But the LAD running at full pressure all the time with the valve always "on" to retain this ride height cannot be correct .

Plus my rear wheel camber is quite pronounced, which indicates the rear needs to be higher as well. There are no camber adjusters fitted on my model. The rear bushes are fine. The dog bones look a little ratty where the excess rubber goes over the metal, but the actual inserts are fine. I'm not sure if the dog bones effect camber anyway - do they?