Years ago a friend had a car that usually only got driven on weekends. Old bias ply tires would usually thump and vibrate for first few minutes until tires got warm and round again. One day it was worse than normal and car shook bad. He figured he had a tire separation or threw a wheel weight and prepared to spend some coin taking it in to tire store. Just on a hunch we popped the hubcaps. Mud dobbers has built huge adobe hut inside! knocked it out and problem went away...cost ZERO cents.