Be best to find out throught he
www.usacracing.com website, It's there in PDF form somewhere.
Straight from the Rulebook. If they are changing, I'd call USAC
NOTE IT SAYS 2013 RULEBOOK
SPRINT CAR SERIES
2013 Rule Book
4
313
Tires
A.
Hoosier HT2, HTW (same as HT2), hard F55 and DT3 are the only approved Right rear tires; LR, RF and LF are open.
The HTW is a west coast tire that is identical to HT2
B.
Any solvents or chemicals applied in any way to a tire that alter the chemical makeup of the compound or have the
effect of altering tire durometer or construction is prohibited. Any tire can be confiscated at any time. Tire found to
deviate from the original factory specifications, the maximum penalty is a one year suspension from competition and
loss of all points earned for the season