The bracing part on the G20 is the only vehicle in the entire BMW range EVER that has a 1 piece constructed part, and it’s also a Flat pressed part. I presume that It would therefor need to be made of a high strength material to function as a long term structurally functional component, especially if the vehicle was involved in a collision. It is well known that ‘mass’ reduces resonance, or indeed softer materials e.g. lead would have a much lower natural frequency to that of a
HSS (high strength steel).
After my last post I decided to check all models to confirm that no other models use a similar strut bracing. The new model 8 series is the only car that initially looks close, but when we zoom in, it’s made from three separate parts, which would reduce the chances of resonance amplification.
So, All other BMW vehicles up to the 3 series G20 (inc. F30, E90, E46, G30, etc...) all utilise tubular pipe/bars, which will have a totally different/lower tone acoustic dynamic to single skin pressed plates.
I don’t know why they’ve decided now to change this age old design, since there’s no real weight saving advantage, and these braces are normally hidden by covering trims anyway.
I did however mention earlier the possibility that the hub bearings may have an influence on these cars too.
We stripped the brake discs off again to further examine the hubs, and although there’s no apparent tolerance in the axis there appears to be something strange when the bearing is rotated quickly in opposing directions..., both sides appear to be similar in function meaning they are from my experience just not smooth enough.
We’ve ordered 2x SKF hubs which should arrive this week, as there’s little point ordering from BMW if they are supplying from the same manufacturer as already used during construction.
Once we’ve modified the strut brace, fitted the front wheel hub bearings and fitted the F30 Damping washers (as shown by part ‘20’ on the previous post part diagram), then we’ll see if the majority of the noise is gone.
There’s always going to be some road noise on rough terrain, but if we can make our cars as good as the F30 that we moved from, then I’ll be very pleased.
So, if this all works, it’s a troubleshooting job for me at BMW
