Rear suspension uneven before and after shock/spring replace

[Manny G.]

Hey everyone,

So I've been scratching my head over this one for a bit.. a while back, I noticed that the rear driver side sits about 1/2" (13mm) lower than the rear passenger side. I changed a set of Koni shocks that the PO had installed for a set of Bilstein sports. Still uneven. I replaced the gold Quickor? Korman? brand springs for a nice NOS set of Eibachs... still uneven in the rear.

I've tried to adjust the perches on the rear shock... its most noticeable on the lowest perch. If I set it to the highest one, .. the unevenness slightly adjusts but not much.

Any ideas of what I should check next?

[autox320]

Hey everyone,

So I've been scratching my head over this one for a bit.. a while back, I noticed that the rear driver side sits about 1/2" (13mm) lower than the rear passenger side. I changed a set of Koni shocks that the PO had installed for a set of Bilstein sports. Still uneven. I replaced the gold Quickor? Korman? brand springs for a nice NOS set of Eibachs... still uneven in the rear.

I've tried to adjust the perches on the rear shock... its most noticeable on the lowest perch. If I set it to the highest one, .. the unevenness slightly adjusts but not much.

Any ideas of what I should check next?

? tried adding another isolator where the spring sits; this should add stack height to the spring raising the body on the low side, or remove the isolator for the higher side lowering it

other than that have you measured camber on each rear side? if excessive camber at near the same height the trail arm could be bent

[mxl556]

I owned two e21's and both were the same. I do not know why, I was never able to fix it, but I did not try too hard. What I have learned is that the front suspension or even it's alignment will affect the rear. On my current e21 I have replaced most of the suspension and it did not change anything. The only suspension parts I have not replaced are rear trailing arm bushings and front subframe. However, my front alignment is out of spec (caster) so I blame it on that. Could also be body sag in the rear (towers).
If I were you, I'd get an alignment with the printout and see. You should align it after shock change anyway.

Max

[epmedia]

Is a rear anti-sway bar installed?

[Manny G.]

? tried adding another isolator where the spring sits; this should add stack height to the spring raising the body on the low side, or remove the isolator for the higher side lowering it

other than that have you measured camber on each rear side? if excessive camber at near the same height the trail arm could be bent

I havent measured the camber, but it recently had an alignment and everything seemed fine. Ill have to dig up the alignment sheet from my documents for the car to see what spec the rears were, ... a bent trail arm does not seem far fetched possibility to me right now

I owned two e21's and both were the same. I do not know why, I was never able to fix it, but I did not try too hard. What I have learned is that the front suspension or even it's alignment will affect the rear. On my current e21 I have replaced most of the suspension and it did not change anything. The only suspension parts I have not replaced are rear trailing arm bushings and front subframe. However, my front alignment is out of spec (caster) so I blame it on that. Could also be body sag in the rear (towers).
If I were you, I'd get an alignment with the printout and see. You should align it after shock change anyway.

Max

your reply definitely has me suspecting rear trailing arms now. I'm going to take a look at the printout a little later today and see.. but funny you mention front suspension, I'm having issues getting it to the ride height I would expect for Eibach springs. It seems like it is still at least 1" too high

Is a rear anti-sway bar installed?

Why yes, I do... could that be causing it?

[epmedia]

Why yes, I do... could that be causing it?

Possibly, if bent or bushing improper or if adjustable.

[mxl556]

Considering the condition and low mileage of your car, it's highly unlikely that it is anything but tired/aged rubber. I would suspect trailing arm bushings, left side would see more wear and would sit lower. How is the tire wear, if driver's side rear inside wears more than the passenger side, it is excessive toe out which is caused by worn bushings. Also, I would check subframe bushings, they are very easy to replace on the e21.

I know that my car has the same issue and I know that the trailing arm bushings are definitely due for replacement, everything else has been replaced. Just have to get to it someday.
Even though some may say that trailing arm bushings do not affect the ride height, I have seen a significant change in ride height in my old e30 when I replaced trailing arm bushings.

Max

[autox320]

Considering the condition and low mileage of your car, it's highly unlikely that it is anything but tired/aged rubber. I would suspect trailing arm bushings, left side would see more wear and would sit lower. How is the tire wear, if driver's side rear inside wears more than the passenger side, it is excessive toe out which is caused by worn bushings. Also, I would check subframe bushings, they are very easy to replace on the e21.

I know that my car has the same issue and I know that the trailing arm bushings are definitely due for replacement, everything else has been replaced. Just have to get to it someday.
Even though some may say that trailing arm bushings do not affect the ride height, I have seen a significant change in ride height in my old e30 when I replaced trailing arm bushings.

Max

Agree with Max and if not replaced trail arm bushes in awhile would suspect them. If worn can make the trial arm out of plane and will show up as ride height change.

When measuring camber in the rear a bent trail arm will be several degrees off from side to side at near the same height. Like -2deg on one side and up to -6deg on the other. Like say would suspect bushes first then bent arms since bushings affect camber.

Swaybar being connected "could" if the links are in extension bind lifting one side of the rear. Should never happen if adjustable links cause take out any extension preload. Even so I'd think the swaybar would have to be seriously stiff to change ride height even in bind. In other words least likely scenario to suspect a swaybar IMO. Best way to find out is disconnect one side taking it out of the equation see if makes a difference.

If the front is tall it can also be the bumpstops not trimmed. Most common on bilstein HD's and not sports due to length of the bumpstops. Sometimes when using sports though depending on spring length it will be on the stops at ride height. Some think they "settle" over time, but what actually happens is the stops at the sit position get crushed enough to eventually let the car rest where it should. If somehow remove the front struts to trim look into trimming at least one knuckle off the stops. These are internal to the strut insert after edge hammering off the bottom silver cap.

[320iAman]

It could be several items including the rear axle carrier and its rubber mounts, if you want go after it you'll need to check every component and measure each one, how much is it out of level ? Could measure left side of the bumper and then right side for comparison as a start, measure the rear axle carrier left side and right side and compare there,this would help isolate where the shortness and tallness is, measuring the bumpers and elsewhere and compare them. Measure on a flat level surface or close too it. A torpedo level with magnets will show slope or not. A drawing with front and back, left and right measurements of the car and on the side view left and right side and underneath in few places will show a good deal useful information. Who said it would be easy,,,lol.

A Chassis or frame shop would do the same thing and more except measure heights with laser level precision.


Randy