Ice causing wheel imbalance
Overnight the temperature fell to 15F. Next day I had bad vibration whenever driving faster than 35 MPH. When I got home checked the wheels. Sure enough, there was ice frozen to the inside of the rim on both rear wheels. The ice was only on the part of the rim that was at the bottom when it froze causing the imbalance. Moved my wife's car outside and the GLA inside for a few hours to melt the ice and eliminate vibration.
Hope this was a fluke due to odd wet/freeze weather conditions, not something that happens every time we get a deep snow.


