mmitev

This questions is a bit of an overkill, but maybe someone here has some insight.. AFAIK, there are at least 3 types of rear air springs for the E61, at least they have different numbers on Real OEM:
1) Standard
2) Sport-Settings
3) M-Sport
4) M5? (have not checked, but not really interested, as presumably very hard)
5) Alpina B5T? (don't know where to check..? but am interested, as Alpina usually modifies suspension components pretty well)

What are the exact technical differences between all those? Is it only spring rate that differs, by how much, and does this spring rate depend on the ride height? I.e. standard air springs become crashy at lower ride height, and M-sport become wallowy at higher ride height?


The reason I am asking is:
On my car I have installed the Koni FSD shocks, the H&R anti-roll bars, and an additional strut brace. Now I want to change the springs with progressive ones, at the front most probably Eibach Pro-Kit, as they are recommended for the Koni FSDs.

I have an unconfirmed information from several sources that the factory "sport-settings" springs are a piece of c**p, and are basically just hard without much sophistication or versatility. So I want better springs, ideally progressive. Front end is easy, but the back end

Depending on the info on the above types of air springs, it might be easier to decide.

phelix

I think the sport and M sport are one and the same - see http://bmwfans.info/parts/catalog/E6...and_ctrl_unit/

I have an early E61 sport and was generally happy with the ride except for the tendency of the rear end to wallow after dips and humps. Fitted FSDs and am very pleased - seems like the right shock for the car. Stiffer anti roll bars are the only other thing I would consider but usually there's so much stuff in the car cornering is done at a rate where the body roll isn't an issue.

mmitev

I will have to admit you are right, so option 2) and 3) in my list are the same thing.

After adding the FSD shocks, the anti-roll-bars and the strut brace (and spacers though their effect is tiny), the stability and sportyness of the car has improved (I am really happy with those mods) so much that I think I can afford a little more comfort from the springs, at least over slight road imperfections. Hence the plan for progressive front springs.

That leaves the question whether the Alpina B5T air springs are different (and how so) from the M-sport ones?

And whether putting standard air springs in the rear will be madness? How soft are they at -30mm ride height than stock? How will this "softness" play out in combination with FSD and the thick ARB?

Seipäänreikä

Hello
When I lowered my x-Drive I didn´t notice any difference with the springs. There´s a huge difference with the shocks so they "hide" the changes with the air suspension. I think the softness/hardness is the same when its stock or -30mm lowered and it all depends of your Koni`s and the other mods.