Rear coil springs for a Z4

2003 Z4 3.0

The dealership reported that the bottom couple coils on my springs have rusted through in the past few months. I have yet to jack the car up since buying it so I don't know how bad we're talking about here. It hasn't effected the feel of it from what I can tell.

Rock auto doesn't have anything listed, neither does O'Reilly. Amazon has them for $317, BMW is asking $400 for parts, $200 labor. If it's anything like a Honda, Chevy or Hyundai I can do it myself but are they really so rare? And it looks like they don't have standard coilovers for these?

Also, are there standard upgrades for these? I assume stock parts are good enough performing.

ALSO I just noticed there's a tech tips part of the forum. Does this belong in there? It looks like there's a lot of overlap here.

EDIT i just looked through the "just how good are the really good coilovers" thread and MAN there's a lot to know about this stuff

Eibach, H&R, and ST all make springs for these. I'd certainly take the opportunity to upgrade - my BMWs have generally gotten Eibachs and Bilsteins. Nothing terribly difficult about doing these on a BMW - you should be able to do all four corners in a day.

In reply to 02Pilot :

Just the springs or do the whole coilovers?

Also, are you recommending all four be done at once rather than just the bad axle?

Yes, I'd do all four, springs and struts/shocks, at once. Good savings in combined labor, and a significant handling upgrade. Inspect everything else before you order parts - depending on mileage, you may be due for control arm bushings and (likely) sway bar end links. I also strongly recommend a set of poly rear subframe bushing inserts - these really firm up the rear with essentially no NVH downside.

Rear springs are easy compared to the springs on the front struts-- I recall them being essentially ready to fall out once you release the shock and sway bar.

I'll pile on for doing the sway bar links and bushings while your in there.   

Strut and shock mounts should be given a good look while you're in there-- I replaced the rear shock mounts with ones from Rogue Engineering so that I theoretically don't have to take the interior of my coupe apart again to replace either the shocks or shock mount.  I don't think you have that challenge on the roadster.

I track my coupe, and I actually found one of the OEM front strut mounts torn about a third of the way around before I replaced the OEM setup with adjustable camber plates.    Rear trailing arm bushings didn't last at all, and I'm hoping the spherical bearings from Bimmerworld I replaced them with the last time puts an end to that.

Karacticus said:

Rear springs are easy compared to the springs on the front struts-- I recall them being essentially ready to fall out once you release the shock and sway bar.

I'll pile on for doing the sway bar links and bushings while your in there.   

Strut and shock mounts should be given a good look while you're in there-- I replaced the rear shock mounts with ones from Rogue Engineering so that I theoretically don't have to take the interior of my coupe apart again to replace either the shocks or shock mount.  I don't think you have that challenge on the roadster.

I track my coupe, and I actually found one of the OEM front strut mounts torn about a third of the way around before I replaced the OEM setup with adjustable camber plates.    Rear trailing arm bushings didn't last at all, and I'm hoping the spherical bearings from Bimmerworld I replaced them with the last time puts an end to that.

I'm curious: what, if anything, have you done to the rear subframe mount bushings? Just doing inserts on my 128i (and my 2002, for that matter, though less relevant given the differences in design) made an enormous difference in stability and transitional handling. I would think any improvement would be even more pronounced on the track - I'm interested in your assessment.

The Tech Tips I think is more a place to post "Hey, I have a nifty way to do a thing!" as opposed to questions, so I think you're good there.

I'll just add that you should prepare yourself temporally, financially, emotionally, and spiritually for the possibility that rust bad enough to eat your springs may have done enough damage to the hardware to make these jobs tougher than normal. That probably also means they're even more important to take care of.

In reply to 02Pilot :

Not a thing at this point, though at 110,000+ miles, I do have a rear end clunk under extremely hard track cornering that I now know isn't the rear shock mounts.  Might be rear subframe...

At least the E8x Z4 isn't prone to pulling the subframe mounts out like the Z3s.

In reply to Karacticus :

Seriously, try the inserts. It took maybe an hour total to fit them on my 128i, and they're cheap - one of the best bang for the buck upgrades you can do. Or you could take the truly grassroots approach as I did on my cars before poly inserts were readily available - fill the voids with 3M Window Weld, sometimes with pieces of steel tire cord stuffed in there as well.