timmay77

Looking into replacing the rear air springs in hopes to freshen up the rear suspension. (Please don't bring up removing the SLS system, I want to retain it.)


Does anyone know the difference between the Euro M5 touring air springs and the US 535xi air springs? Different part numbers. I am wondering if they are "stiffer".


M5 - 37122283615


535xi - 37126765602

RIHI

I think the difference lies in the M5 is RWD and the XI is AWD, maybe an altogether different air spring.

I'm with you. I love the SLS system and wouldn't think of removing from my car.

timmay77

Since the M5 is RWD and has adjustable dampening shocks in what would be considered a "sport" suspension, do you think the air spring would be "stiffer"?


I sent an email to Arnott, whom makes a replacement air spring for the 535xiT. They did tell me that the air spring DOES where out and will become "bouncy". A new unit will stiffen up the suspension. Then again, they may just have been trying to sell me on parts......

jcolley

Someone please correct me if I'm wrong, but this is highly pertinent to my interest.

The purpose of the air spring on any E61 is not to provide damping, but to correct ride height due to load. The E61 M5 has EDC dampers where as the non-M E61 has non-EDC dampers. The purpose of the dampers is...well...to dampen motion. The notion that air springs make things spongy is just silly to me as an engineer. Does the air inside become old and lose its firmness? Silliness.

I have discovered in the last few months that BMW has taken to renumbering parts common on multiple platforms on various reasons unknown.

The only reason I can see the air spring being different (since it's purpose is to be a variable length spring) is if the mounting points of the EDC dampers are further apart and the spring perches different from the E61 M to the Non-M.

Conversely, the entire rear suspension cradle is different from the non-M to the M. Luckily, the part number for the E61 M rear cradle is identical to the E60 M5 6MT cradle. No idea what is different between the 6MT and SMG cars cradles though, since the EDC dampers between the SMG and 6MT are have the same part number.

On that note, I have a *really* silly amount of M parts if anyone is looking to experiment.

Edit: Didn't realize you were over here too Timmay, good to see you.

timmay77

I wasn't suggestion the air inside becomes old and loses firmness. I was suggesting that the rubber air spring loses it's firmness and gives more creating the sponginess. I see it all the time at work. We use air bladders, pretty much the same design as an air spring, to lift 3,000lb pallets of product. After a few years, these bladders wear out, they are rubber after all. The side walls weaken and give out, not allowing the bladder to lift the pallet high enough to clear the chains they are riding on. The bladder doesn't "blow out" it just loses it's original form, due to the rubber wearing out, causing an issue. I am no engineer, just a dumb mechanic, but I do not see why our air springs would be any different? They are made of rubber. Rubber wears. With the same amount of pressure to lift the rear of the car, it will hold the rear up. Of course. But given a load (bump in the road) if the sides are weak, it will give out more than a new OEM unit, causing the extra suspension travel........


Thoughts?

tenaciousjeebs

Hi, not sure if anyone on this thread is still active on this site, but I'm wondering if you ever figured out if M5 air springs are compatible with the 535xi? I have the 2010 535i xDrive and I'm trying to figure out suspension options. The air springs are indeed different parts numbers, but the subframes look almost identical with the exception of some stop washers and the guide rods, and the "left/right swing parts" ie part of the wheel suspension where the air springs sit are the same across each platform.

neilv

I looked into it before; there are 3 air springs, standard & X-drive, sport & M-sport and M5.

Sport & M-sport are 15mm lower than the standard & x-drive so im sure its shorter and may be able to handle more pressure while maintaining that height. The M5 is so uncommon its hard to know but im sure its even further along those lines.

tenaciousjeebs

That is hugely helpful, thank you! I'm very interested in getting rid of the SLS system and replacing the air springs with coil springs (I know there are many reasons to keep them, but there are far too many failure points in the system for my liking), and it sounds like installing any aftermarket coil springs meant for the M5 would need shorter/stiffer shocks. As far as I can tell, the swing arms on the 535i xDrive and the M5 are exactly the same part, at least according to real OEM, and I'm assuming that therefore the coil springs should seat exactly the same.

amesser325

The E61 M5 only came with airbags in the rear from factory. I think there are a few aftermarket kits that use coil springs but I'd spend a good bit of time on spring rates. I used an ISC kit years ago (kept the rear bags) and ended up buying another set of like 6k springs for the front since the as-shipped coils were horribly mismatched with the rear and it has a garbage buckboard ride. Once matched F - R it rode much better.

For what it's worth, the non-M and M knuckles only differ in the upper front ball joint socket. Pretty much everything else is the same, swing arm included. I'm an ABS issue away from finishing my E61 M5 build and used a mish mash of E60 M5 and E61 535xiT parts, and had no parts interchange issues.

tenaciousjeebs

Dude, THANK YOU! Does that mean that I’m likely able to use coil springs from the e61 M5 coilover kit (with air bag delete) on my 535i xDrive? Also, did you end up replacing your bags or will you keep them?