*These rules are also in effect for AMSOIL USAC/CRA, USAC West Coast, and Sands Chevrolet USAC SouthWest Sprint Cars for 2018. USAC TECHNICAL UPDATE – TB2018-NAT001 NATIONAL SERIES Date: JANUARY 1, 2018 ALL NATIONAL SERIES -Digital bleeders are allowed. Air may not be introduced to the tire. Bleeders may not be controlled remotely. -Full containment seats mandatory beginning May 1, 2018. Beginning in 2019 all seats must meet SFI 39.2 specifications. Silver Crown Series -Tire options for events in 2018 remain the same as 2017 National Sprint -Suspension adjustments by the driver from the cockpit will not be permitted. -Front axle tethers will be mandatory beginning May 1, 2018. -Hoosier will make 94/14.0 available in RD12 compound