Quote:
Originally Posted by kenwelch
Because they changed the wheels (and tires??) your problem should be in another component that rotates at the problem speed. To locate the problem many auto manufactures have recommended using vibration analyzers to solve the difficult to locate NVH (Noise, Vibration, and Harshness) problems. We use the OTC model EVA in my Powertrain Class to measure frequency and intensity. With the data you can then begin to zero in on the problem component.
This is a link to a vibration software site with information and equipment descriptions about how to locate the problem component.
http://www.vibratesoftware.com/
Click on “Diagnostics” on the left side and then scroll down to the “road test” section. This should give you an idea what needs to be done.
Warning: IF the dealer did not test drive with a completely different set of tires and wheels, then your problem could be just your tires and wheels. It is possible to have tire and wheel vibrations that are not corrected by balancing. I have seen tires that were “balanced” by just putting on wheel weights so they look like they were balanced. 
Check out this link about advanced tire balancing and service:
http://www.gsp9700.com/pub/technical/4127T/4127t.cfm
Read the sections regarding “Run-out, Force Variation, and Mounting Error.
Most BMW Service facilities in my area are using this equipment and it is also recommended by many other vehicle manufacturers. Light weight suspensions and sensitive BMW owners that want their vehicle vibration free require better quality service equipment. 
There are also videos showing the equipment being used:
http://www.hunter.com/PUB/product/balancer/index.htm
Just click on the video icons.
Please let us know what happens. |
Thanks for the help.
Dealer has tried 2 completely different set of wheels and tyre, so we can conclude it doesn't come from the wheels...
A National bmw person in charge will come and try the car and then take a decision of changing some parts....we'll see.
I did not know the vibration software, i'll look at it....
Let see what happen...