Steering suddenly shifts when going over a rise

[110reef]

My car has been doing this for a while, but has been more frequent of late. Occasionally, when going over a rise, making the car get lighter in apparent weight, the steering will suddenly shift a bit. This is very disconcerting at best and may be dangerous at worst. What suspension component would cause this? I have changed many of the components out over time, including struts and control arms, but not all such as tie rods. Any insight would be welcome.

[Turbohugh]

Strut mounts?
Are you the original owner?
Confirm the parts in your strut washer stack, especially the 'gasket' [metal shim]
Inspect the mount for any cracking or damage.
[Feeling like a broken record] : My struts were missing the metal 'gasket' shim and I had about 2mm of lateral play in the mounts leaving a unsettling feeling [along with a steering wheel shimmy] that went away once I replaced the mounts and all the washers correctly [realOEM has a diagram of the correct stack configuration].

[110reef]

Turbo - thanks for your response. I am not the original owner, but have owned it for the past 90,000 miles. Yes, I have replaced the strut mounts. Took me several times to get them right as you say. They caused memory steer when I had them wrong - after I turned right the car would pull right and after I turned left the car would pull left. There is no steering shimmy, just the occasional unsettling change of direction.

[Turbohugh]

Hmm.. My e36 is my first BMW so I'm not a veteran of the 3 series but you may want to just go over every bolt and confirm its correctly torqued.
Just thought of this as well, check your sway bar end links on all 4 wheels. I had a broken end link in the rear that made the front feel wierd until I figured out what was going on.

Have you had your alignment checked?

[110reef]

I recently did have my alignment checked, and it was doing it.

However I have since hit a curb at 45 which broke both my drivers side wheels, broke a strut, set off the side airbag and broke my windshield, so a pretty good hit. I replaced the wheels, and the affected strut, and intend to get it aligned again, but this issue has gotten worse. So before I get it aligned, I was hoping to fix whatever is broken under there first.

[Turbohugh]

Well, with that hit I'd say you may be looking at control arm ball joint and tie rod replacements. I wonder if your rack or subframe have any damage.
YMMV but it seems like when these parts degrade [and having consistent quality is important] its hard to figure out 'what the single issue is' however careful inspection of everything is going to be necessary unless you're willing to just replace everything.
Maybe start going over every bolt one at a time making sure its to spec.?
That's how I tracked down my ball joint issues .I ended up replacing nearly everything but I'm glad I did.

[DatTugrut]

Mine does this slightly. In my case it's going to be a front end refresh.

Mainly control arms- the ball joints/bushing are getting worn out.
Endlinks, Inner, and Outer tie rods.
Strut mounts if I want to really tear into it.

Check the wheels for play. Side to side, top to bottom. You can often feel it by this alone when the parts are worn out enough. I wouldn't suggest driving the car much, if at all after that point.


Oh, this could also very well be your rtabs. You'll mainly feel the looseness in the chassy like the back end of the car is "sliding out". However, if the front is bad enough to warrant replacement parts chances are the rtabs are worn as well.

[Pyropete82]

+1 to turbo comment on sub frame damage. Get new sway links too. I have a vert as well, bump steer was an obvious issue when tie rods and links were blown out.
Go coilovers with pillow ball mounts, no more strut mount to worry bout. Get the m3 suspension though so you can change the sway bar orientation to the dampers rather than control arm.
The only disadvantage to this setup is nvh increasing
If your strut geometry has changed due to the crash you'll need to be able to change your camber easily to compensate for bent metals

[110reef]

Just to add closure to this thread, at the top of the struts in the center of the strut mount there is a bearing. When putting the struts back together, this bearing was in a bind. If the strut mount on top of the strut does not spin freely, then you get the memory steer. So it is important to get the washers back on exactly right and make sure the mount spins freely before reinstalling the strut in the car.