If there's difficulty balancing a tire and the dynamic balancing machine requires more and more weights around the rim, suspect something may be inside the tire. It could be an emergency liquid flat repair, excessive compressor liquid, or something inside the tire causing this problem.
The tire must be dismounted to verify this condition. Unbalanced tires cause a vibration that increases with vehicle speed. They also wear and become cupped.
Tire Pressure Monitoring Systems
Today's vehicles contain (TPMS) Tire Pressure Monitoring Systems. They may be direct or indirect. An indirect system uses wheel speed sensors to calculate tire pressure. An indirect system uses wheel speed sensors to calculate tire pressure. A tire with low air pressure has a lower profile and spins faster than a properly inflated tire.