Section § 393.75: Tires.

Guidance Q&A

Question 3: May tires be filled with materials other than air (e.g., silicone, polyurethane)?

Guidance: Section 393.75 does not prohibit the use of tires filled with material other than air. However, § 393.3 may prohibit the use of such tires under certain circumstances. Some substances used in place of air in tires may not maintain a constant physical state at different temperatures. While these substances are solid at lower temperatures, the increase in temperature from highway use may result in the substance changing from a solid to a liquid. The use of a substance which could undergo such a change in its physical characteristics is not safe, and is not in compliance with § 393.3.