Steering wheel vibration

[SlowIam]

I have a 2018 6GT with 37k miles on it. I love the car for its practicality, but there is a strange vibration from the steering wheel that is driving me crazy. It has been confirmed by multiple dealers who have since replaced thrust arms, brake rotors, pads, installed the friction discs as per the TSBs and put on new BMW star tires along with alignment and wheel balancing. The problem still exists and the answer I now get is that it is road vibration. The vibration needs some heat in the system to manifest and does not happen always. When I do 50 mile trips at freeway speeds, it happens all the time. It is a slight buzzing sensation ( high frequency ) at speeds above 70mph on part throttle. At no freeway speeds, it’s still there but the dealer will not acknowledge that. I suspect a driveline issue but the dealer refuse to look at this. BMW NA paid for the repairs as this is a CPO expect for the tires. To me, having owned 5 BMWs before this, it is not a normal vibration. Any ideas on what to do next would greatly help.

[craigy85]

Have you had the alloys checked to ensure they're not buckled / warped?

[Gilgorm]

Rims could be warped as stated. But the tire installer should have noticed it, unless they kept installing wheel weights until the problem was corrected.
Has anyone checked your motor mounts and shocks. Both could cause vibrations if worn prematurely.
The good news is you have new pads and rotors.
Good luck.

[SlowIam]

I did question the techs on the rims. Everything is within tolerances. I do have 759i 20 inch wheels on my G30 that I could swap and try out. But I am not sure if these would fit the 6GT with the slightly different offset and the aspect ratio. We did not check the motor mounts, that would be next. On the topic of shocks, isn't the front end a bit floaty/bouncy on these cars? I see this especially when reversing out of my garage where there is a slight step. The front goes up and down like it is a Lincoln (only once though, no secondary oscillations). Also, why would the vibration(the primary issue) due to this only occur at around 65-70 mph when the engine is spinning at 1500 rpm? This issue has me puzzled :P

[RoderickW]

Did the car ever in it´s lifetime changed rims?
If could be that the wrong spacers are used between the axle and the rim.
A lot of the Rims, aftermarket or not, have different diameters from the axle to the inner dimension of the rim.
If could be that all spacers were stuck on the Axle and never have been replaced by the correct ones. This could cause the Rims to "wander" a bit on the axle by 1mm or less, and this is only noticable on speeds from 100 to 140Km/h ish, because the frequency of the rolling tires is then perfect to resonate, and therefore feels quite strong.
I had that same issue on my F06

Normally the F06/12/13 has 72.6mm spacers, but depending on the size of the rim the outer diameter varies quite a bit.

For example some rings are 72.6mm inner/78.1 outer, or 72.6mm/76,9mm outer.
You could check this, it´s quite cheap to install the correct ones, and maybe it helps in your case!

In addition to prevent the wheel to wander a bit on the axle, you can install friction discs between your wheels and the axle, when you mount them. This shouls also prevent the wheels to wander on your Axle. BMW offeres many types of these discs to prevent most vibrations coming from the wheels and axles. The part number for your 6Gt should be: 31108053073, but please check it if it´s compatible.

I hope these both solutions help, in any case these are quite cheap fixes, so worth the try.