e39 self levelling suspension

[Scamp's Walker]

Have just had an aftermarket towbar and bypass towing electrics fitted for towing a trailer and the car is behaving strangely. One indie says that I need a towing/trailer relay to pair up with the self levelling suspension (SLS) and all will be well, then an amendment to the OBC to educate it for when the trailer is attached. Another says having a towbar fitted and towing a heavy trailer will make no difference and a third says he can manually set the car up so that it realises it is towing. The third scenario will be a permanent version of what the intelligent BMW OE electric kit does once the trailer electrics are connected and the trailer attached, I think it involves resetting the height of the rear suspension!). The dedicated wiring kit for the car is £150 ish plus two to three hours labour apparently.

Am I being sold a line here? Has anyone else had this or understand any of it?

[SJobson]

I don't see why it will make a difference - the self levelling uses sensors on the front and rear suspension to set the ride height. Whether you have a heavy trailer attached is irrelevant.

[bramley]

I agree with SJobson. OP has your SLS warning light come on or something? If so perhaps the towbar fitters have spliced some wiring they shouldn't have? I only say that as a mate with an Isuzu pickup recently had a towbar fitted and the fitter sent a current down the wrong wire which illuminated the engine warning light.

I'm sure the SLS system is entirely self sufficient and needs no fiddling with, regardless of the load placed on the car.

Is there any reference to towing in the manual? (haven't got mine to hand)

[Scamp's Walker]

Thanks guys, sounds like I am being told a few porkies. Car is ultra sensitive to bumps etc when the trailer is attached, made the wife and kids feel seasick! Car is due for an Inspection 2 so will be checked out anyway as the other option may be worn bushes or something of that ilk as car is approaching 100k but just thought I would canvas personal experience as I havn't a clue what they were talking about!

[SJobson]

The rear subframe bushes on Tourings usually need replacing before 100k; my car was on 126k when I bought it and I had them done straight away. That could be the cause of your problem - or maybe one of the airbags is leaking a bit, or the dampers are just tired...

[Crombers]

My bushes were entirely knacked by 66k, diagnosed by the ruddy great whack of the subframe banging off the boot floor. That said I've had both air springs and reservoirs replaced as well by 70k.

Air Suspension - Brilliant when it works!

Unless your car is sagging in any way without anything attached I'd be thinking along the lines of the ride height sensors.

[Pork_n_Beem]

Have tow bar on mine fitted, no problem suspension is brilliant and after 203k miles have replaced just dampers and one air spring.

self level is adjusted by sensors on front and rear wheels