Originally Posted by BimmerRob08
Well let me back up a bit. Originally when I installed my AP BBK I had to run 12mm spacers along with the OEM 18" wheels with the stock Pilot Super Sport Michelin's. Was super smooth up until that day. Every since there has been some degree of vibe's. So with a new set of Michelin's installed on my ARC-8 wheels about a year ago and new AP rotors, road force balanced, it was smooth. Then about this last fall started the steering wheel wobble at cruise and increased vibe under braking. Installed new Bridgstone Potenza's, correct size tires now on the ARC-8's (265/35R18F, 285/35R18 Rears) Road Force balanced again. Did some rotor disc cleaning with race pads to clean up the surface of any pad transfered materail build up and now pretty much smooth under braking but at cruise above 78mph, I still have this slight vibe/steering wheel wobble. Its never smooth like at say 50mph for example once I get it up past 78mph and higher.
A while back I had asked APEX about the wheels but the responce was that maybe I hit something or bent the rim(s). Very, very unlikely but I was running tires two sizes smaller for a while. Now with proper size tires, no spacers, I still got the same damn problem. Right nowmy Potenza's are ony about a month new and barely any miles as I don't DD the M3.
I think I have two seperate issues. One is the AP BBK rotors probebly gained some uneven pad material which I think so far is cleared up but I can't be sure with the steering wheel still manifesting a vibe at 78~80+mph.
Thanks for the clarification. At the speeds you are describing, you can absolutely rule out the rotors being the problem. If it were the rotors, the vibrations would present themselves in the 45-55 mph range and would become amplified upon braking.
What I would say the problem is, first and foremost the technician "Road-Force" balancing the wheels doesn't know what they are doing. Next time they do it, make sure you watch them do it. Often times I have seen guys use the machine without the actual Road-Force drum because they are misinformed about the purpose of the drum.
Second, when the wheel is on the machine, make sure they are using a 5 lug adapter lock, and not a single center hub lock when they are mounting the wheel to the Hunter machine. This will ensure more hubcentricity when the wheel and tire is spinning and tire run-out is measured more accurately by the machine.
Third, while the wheel is spining, make sure the wheel is true. If you looks like its wobbling abnormally when spinning, this is not a good sign and the wheels aren't 100% true. I also recommend you have them pop the tire bead from the wheel, use a lot of tire mounting lube. You wouldn't believe how many times wheel/tire vibrations are caused from lack of lubrication during mounting and the tire doesn't actually properly seat against the wheel until many miles down the road. Remember, the Hunter machine is measuring wheel balance and tire run-out on what it measures. If anything changes, the previous balancing isn't effective anymore.
Lastly, check your lower control arm bushings. If these items are worn (which they shouldn't be), it will be the cause of vibration in the wheel.