I think one trouble you may have with using the Hoosier Road Race Radial for autocrossing is getting heat into them during the short autocross runs. The DOT autocross compounds are designed to get up to temp very fast. The road race compounds take longer to get to temp but then tend to be a little higher grip then an autocross compound.
BTW Pirelli also makes 13" and 15" slicks. Not sure what they are importing to the US but the 15" slick is being used in the World Challenge B-Spec class based on the press release.
They come in:
H - HARD
M - MEDIUM
S - SOFT
SS - SUPERSOFT
Again not sure what compounds are being built in these sizes and what is being imported into the US. Not sure who is doing the tire service for World Challenge but maybe they can help with the Pirelli slick questions.
C: Nominal section width expressed in mm - 190
D: Nominal external diameter expressed in mm - 580
d: Nominal rim diameter of the rim, expressed in inches - 15
13''
160/530-13
180/530-13
180/560-13
200/540-13
250/575-13
15''
190/580-15
235/580-15
16''
200/600-16
20016
235/580-16
17''
225/625-17
245/620-17
18''
235/625-18
235/645-18
245/645-18
265/645-18
275/645-18
285/645-18
295/680-18
305/645-18
305/660-18
305/680-18
315/675-18
315/680-18
325/650-18
325/705-18
19''
235/645-19
255/650-19
295/680-19
305/690-19
