Superkarts! USA confirms tire change for X30 Junior. Class structure updates for the 2019 season at Pro Tour and ProKart Challenge levels. Superkarts! USA confirms tire change for X30 Junior. Class structure updates for the 2019 season at Pro Tour and ProKart Challenge levels. Bas Kaligis / Wednesday, January 23, 2019 0 11259 Article rating: 5.0 The 2019 racing season is officially underway for the Superkarts! USA program, as their track team hosted the first major event of the calendar year, launching the second year of the SKUSA Winter Series in Florida. Following the upcoming series finale in February at the AMR Homestead-Miami Motorplex presented by MG Tires, all of SKUSA’s attention will turn to the tenth season of the SKUSA Pro Tour and their growing ProKart Challenge programs for 2019. Read more