[Roman N52B25]

Hello,

I am struggling with this problem quite a long time and I wasted probably all the ideas I could have. I guess here will be some experienced people for sure that could give me some tips. I really done the best I can so that I dont't get obvious reactions such "did you try to balance the tyres...?"

I am experiencing steering wheel wobble/vibration at higher speeds like after 85-90km/h. The car has the version with hydraulic steering, not the electronic one.
The car was on it's original dampers, arms etc that were shot. I experienced some vibration then already, so I thought if all the rubber bushings are shot, I will replace it and it should help.
I already had wheels road balanced and it did vibrate on the winter ones (16") as well as with the summer ones (17")...

If I let the wheel on straight line, it vibrates back and forth. Sometimes more, sometimes less. But I can definitely feel the vibrations in my hands when driving. It seems that bad roads amplify the vibration. Sometimes the steering wheel does not vibrate at all, but it's mostly on short, random road sections.

-I changed all the suspension arms, ball joints, dampers. All installed on cleaned surfaces, torqued to specs as it should be. I went everything through and marked the torqued ones - nothing was left without tightening. I tightened all the bushings in compressed state as it should be done.
-Steering rack was okay without play, I relubricated the pinion and put new tie rods with new tie rod ends.
-I did the geometry after all that, everything has been set to its specs.
-I did measure the hub and disc runout with gauge and made the mating surface rust-free and as flat as it goes without machinery, then I put new rotors, pads, bushings and sliding pins into calipers, all working as it should be, nothing stuck here.
-All wheels torqued step by step to 30-60-90-110 nm so that the wheel sits flush and centered. The brake rotors were bed in slowly and correctly, I drove extra just to bed them in.
-I tried to experiment with the tyre pressure all the way from 2 bar to 2.5 bar front and no change in vibration could be spotted. The higher pressure would only result in harsher vibrations.
-I did resurface the mating surface of wheels that goes to hub so there is no high/low spots caused by rust/oxidation.
-I did let the tyre shop road balance all the wheels once more and they said we could try to mount new front tyres if new tyre with another tread pattern would help. Got new dunlop sportmaxx rt2 in the front, mounted and road force balanced all was well under the limit as the machine showed. It seemed that the vibrations were a little bit less harsh but today, is's same as before.
-the car has no runflat tyres mounted as that would be the first thing I would go after...

As I was slowly running out of ideas, by luck I found out that the front subframe bolts were not as tight as they should be (probably from when I did the oil pan gasket), I tightened them to 110 nM as supposed from bmw and added thread locker. It did not help either.



So now the most important question. Did I overlook something? Had someone from you guys had same problem and solved it? Every single hint would help here.

Thank you

[lordnikon]

Check this thread:

https://www.e90post.com/forums/showthread.php?t=674537

[Roman N52B25]

Originally Posted by lordnikon

Check this thread:

https://www.e90post.com/forums/showthread.php?t=674537

Thanks for this one. I went through it and the only thing that would apply to me are the hubs, engine mounts and drive shaft with its bearing/guibo. The problem is that all the things that are mentioned there I already changed for new parts from oem manufacturers. I think that the old bushings could mask and absorb the vibrations and after I changed all those things, the new, stiff bushings are transfering all the vibrations to the steering wheel.
I checked the calipers already and already rebuilt them 2 years ago completely (piston, seals, rubber bushings etc.) with that went all new rotors and pads to prepared hubs. I will check today the driveshaft but l don't think it's cracked or loose. I had it on my E46 before and I'm pretty confident I would recognize shot shaft bearing/guibo.

[E91 Hoarder]

[Roman N52B25]

Originally Posted by E91 Hoarder

I'll definitely check this one. But the steering was sharp and crisp, no dead spot, no play to the sides and no play in bushings. But this one I left without check as this was the last thing I would guess. Thanks for this hint

[Roman N52B25]

So the problem is solved for now. I can not say exactly what had final effect becauseI did more things at once.

1) Hubs - sanded down to 0.01mm flatness tolerance and cleared them from rust
2) Rotors - cleared all the contact surfaces
3) All checked after mounting - I installed the rotors, evenly tightened with bolts and washers, sanded the little imperfections on rotors so that I get again runout as low as possible
4)Scraped the imperfections on rim to hub contact surfaces, checked for flatness.
5) Tightened the sliding bushing a bit on steering rack. I only turned the cap for like a 1/8 of a turn

There is very slight play in the steering shaft, not in the u-joint itself. It could be the coupler or where it connects to the steering rack. I checked only the bolts - all tight. I guess that there can be a bit play because it's telescopic shaft and there has to be at least a little space for the parts to slide.
But after I did all this I went for a test drive and with summer tyres the vibration is not there anymore. With the winter tyres it persists but it's noticeably weaker vibration in comparison to before. I guess this is the point where I stop throwing more time/money at it as in winter I'm really not going over 100km/h.