RSA 266:48: Tire Requirements.

It shall be unlawful to drive a motor vehicle or trailer upon the ways unless such motor vehicle or trailer is equipped with tires in safe operating condition in accordance with requirements established by the director. No tire mounted on a motor vehicle or trailer shall be deemed to be in safe operating condition unless it meets the visual and tread depth requirements set forth in this subdivision. A spare tire shall not be deemed to be a "tire mounted on a motor vehicle or trailer" for the purposes of this subdivision.