Wis. Stat. § 346.58: Special speed restrictions for certain vehicles.

(1) In this section:

(a) “Metal tire” means a tire the surface of which in contact with the highway is wholly or partially of metal or other hard, nonresilient material.

(b) “Solid rubber tire” means a tire made of rubber but not inflated with compressed air.

(2) In addition to complying with other speed restrictions imposed by law, no person may drive any vehicle equipped with metal tires or solid rubber tires at a speed in excess of 15 miles per hour. This subsection does not apply to operation of a bicycle.