Experience whobbling in back end when going 70 mph. Is sporadic. Not caused by the road, or windy conditions. 30,000 miles on car.
Tire inflation correct? No obvious misshapen tread or sidewalls? No bent rim? No play in wheel bearings? These things should be checked first.
You could try switching the tires front to back and see if it is different.
you might be mistaken in front or rear so swapping tires might not give you any more info
Make sure your lug nuts are tight.
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