Steering wheel wobble at higher speeds

[ryushe]

Recently my '04 Z4 has developed an irritating wobble in the steering wheel at speeds around 65-80 mph. The wobble is more pronounced when coasting at those speeds than under acceleration. Rest of the car seems fine, as in, I don't feel anything else shuddering or vibrating apart from the steering wheel. At low speeds I don't notice anything at all, and steering is as sharp as ever.

Since first noticing the wobble, I've had the wheels rebalanced and the alignment checked, and both came back just fine. Also had the same people check for any movement in or damage to any parts related to the suspension, and can't see anything there either. Wheels themselves are true and fairly new (Michelin PS5s). About half a year ago I replaced most bushings up front for polyurethane versions, so don't suspect anything amiss there.
I also haven't hit any potholes, curbs, or other things that might have damaged something.

The only thing I can imagine would be some sort of play or issue with the steering rack, housing, or pump, but apart from taking the car apart I don't know how to diagnose this. So
I'm a bit out of ideas on what to check for by now, so hopefully someone here might have some suggestions on things I can still have a look at.
Thanks in advance for any suggestions!

 

[perttu]

Did you check this out already: https://z4-forum.com/forum/viewtopic.php?t=100725

 

[WouterZZZZ]

A wobble in the steering wheel mostly means: an issue to look at the front of the Z4. In my case, a 2006 E85 it was a combination of: balancing wheels (not static but with power roll), replacing shocks and replacing both silence blocks. My suggestion is: check the latter.

 

[Mr Tidy]

My current one had a slight wobble above about 50 mph when I got it. After removing wheel spacers, raising the ride height and swapping from 19s to OE 18s I had a 4 wheel alignment done but the guy who did it had to replace both track-rod ends as the threads were seized solid and after that the wobble was gone so they'd be worth checking.

It drove so much better when I got it back - and the steering wheel was no longer off-centre when going straight!

 

[ryushe]

Apologies, apparently I didn't aut subscribe to my own topic

Thanks for all replies, and yes, did check that thread.
In the meantime a local independent specialist has gone over the car and their conclusion is that this is a known issue with the power steering module (i.e. sticky steering). I have no experience with sticky steering, but for those of you that know about the symptoms, does this sound familiar at all?
Next step is to have a check to see if my wheels are true or not.

 

[Mr Tidy]

Well if you have some time to spare here is a link to a thread about sticky steering:- https://z4-forum.com/forum/viewtopic.php?f=2&t=100725&hilit=steering+issues+solved

 

[perttu]

I had very similar sounding symptoms as described in your original post. The problem was corrected by doing the ring adjustment as described in the above thread. The steering adjustment works both ways, if you tighten the ring too much, you’ll get sticky steering. Turn it too much other way, you’ll get loose steering and symptoms you described. There’s no shortcut really, other than experimenting with correct setting. I ended up tightening the ring around 20 mm, which fixed it for me.

 

[Davz]

Have you checked the control arm ball joints? Play in the ball joints can result in wheel wobble.