I bought the car last month. 2010 BMW 328i. Everything that is not drive train related is stock bmw components. So it has a cheaper coilover kit on it and the rear driver suspension has sagged from where it should be or the passenger side rear has become higher than it should be. Theres about a half inch difference between the two. I replaced the shocks yesterday because they needed it and while in there I compared the coilover settings from both sides and they are within millimeters of each other if not exactly the same setting.
Making assumptions that the spring has sagged on the driver side. Is there something I am ignorant of that I should look at? Do I just replace both rear springs? If I replace the springs do I get stock ride height springs or lowering springs?
If you like the (non-sagged) height and rate, just get a replacement set of generic race springs. Eibach makes decent ones in just about every rate and length. There will hopefully be some numbers on the springs that tell you what they SHOULD be. If not, you can figure it from free length (of the unsagged one), the number of coils and the wire diameter.
That's assuming they're a cylindrical spring and not tapered. No matter what, I would not assume stock geometry springs would fit.
It's also possible the car is bent, or the upper spring perch has shifted. Get some pics and I might be able to tell more.
You'll have to determine the OD or ID of the coilover springs, the stock springs will not work.
With actual quality springs (Eibach, Swift, Hyperco) the numbers printed on the spring will give you all the numbers you need. Length, diameter, rate, or the part number to look them up. Pull the numbers from the other rear spring and buy two new ones.
I don't know about the cheap stuff with off brand springs.
Ok thanks. That gives me a starting point. I wish I had taken pics yesterday when I had it all apart, I remember the coils had writing all over them so hopefully that's the info I seek.
I'd make sure you had accurate measurements side to side. A few mm is 3-4 in my mind, and that's 1/8". If the springs are pretty far inboard from the hub, it'll be a decent amount at the wheel.
And if the surface isn't perfectly flat, that's an easy half inch right there.
Unless they're really awful springs, it's doubtful one has failed that badly. Maxspeedingrods notwithstanding.
I'd get the measurements perfect side to side, measuring the lower spring perch to an easily repeatable reference point on each side. Even on an uneven surface, you probably won't be off more than an 1/8 at the wheel.
If it's cheap coil overs there are often multiple adjustment points also - body height and perch height. Make sure you investigate both.
Did you measure the springs when you did the shocks?
In reply to ГУЛАГ мальчик УР следующий :
Bad metallurgy can lead to spring sag. So can coil bind - it basically hammers the spring flat.
The latter leaves characteristic marks on the springs. see those little pencil-like marks where the coils have touched? You'll be able to feel coil bind too, as it'll feel like a hard impact.
If the springs have sagged, the free length will have decreased. Measuring the bad side against the good side will tell you.
In reply to TravisTheHuman :
Ok. it was the perch height that I looked at yesterday and the body height that prompted me to look in the first place. I can slide my index finger between the top of the tire and the fender on the passenger side and it touches both sides of my highly calibrated 1/2 inch wide finger but the left doesn't allow any finger in there at all.
In reply to dean1484 :
I didn't because the springs and shocks were separate and I wore myself out getting the first shock installed so the only thing I did regarding the springs was check the perches to see if they were off from each other. They didn't appear to be but I did not measure them either.
In reply to Keith Tanner :
The springs looked in good shape. When I'm driving there is no apparent bind or bottoming at all even on the side thats lower. So I'll need to remove them to measure them against each other? I'm liable to take the lazy way out and take the info from one of the springs and buy two better quality units and replace them honestly.
Was the car corner weighted?
The left side may be heavier enough from the right side that simply adjusting the springs to the same perch height will cause uneven ride height.
Does BMW still stick a gigantic battery in the left rear corner of the trunk?
In reply to Pete. (l33t FS) :
The battery is in the passenger side rear corner which is the higher sitting side. I like how you think though.
I've seen alot of cars with cheap coil overs with side to side ride height issues, like the lift not even sliding under the drivers side. Are any of the factory spring pads still in place or did the coil over kit eliminate those? Can't remember on the e9x but many bmw's have different thickness spring pads you can use to even things out.
Looks like the rear "coilover" on that car is the typical set up used on BMWs where the spring sits in a pocket on the trailing arm at the bottom, and the car body forms the upper spring perch.
Same as my E30 and E36.
The height adjustment is a threaded collar "stool" and the perch is the ride height adjustment.
I've got $5 to the OP that says either the collars are not set the same side to side, or one side has the rubber donut used for NVH missing. I'll Zelle the money if one spring has fatigued so much it dropped the ride height.
In reply to ГУЛАГ мальчик УР следующий :
I found the issue and it was way more simple than I was making it. There was never a problem .
Whenever I noticed the issue it was always on my driveway with the parking brake on because my driveway is angled up. I parked the car in my garage which is flat and I didn't engage the parking brake. Before I jacked it up and removed the wheel I had the big brain idea to measure the distance from the ground to the fender edge on both sides using the center of the wheel as the center point to get an accurate copy . Passenger side 24 7/8 inches. Drivers side drum roll please. 24 7/8 inches. Perfect and i measured 3 times to be sure.
I packed everything away and backed the car out and parked it and when I engaged the parking brake I felt the right rear rise up as it rolled slightly into engagement. So yeah. Sitting with the parking brake engaged on a hill causes that.
PROBLEM SOLVED. Thanks for your input and everyone else. You can keep your fiver.
So now you have to figure out why the left side brake doesn't work? 
Ride height always always always has to be measured on a flat, level surface.
In reply to gunner (Forum Supporter) :
Sweet! I love those kinds of fixes....
In reply to ГУЛАГ мальчик УР следующий :
They're the best kind.
