14:11 - 2017/12/03
Although the earth is one of the purifying agents, it cannot purify the tires.
Question: The earth is one of the purifying agents. Following the example of a shoe's sole that can be purified by walking on the earth, would the same rule apply to car tires?
Answer: The earth cannot purify the tires.[1]
1. Ayatollah Seyyed Ali Sistani ,Question & Answer, Ritual purity & impurity.