Stock		Street Prepared		Prepared		Modified		Street Touring
AS	.815	ASP	.852	AP	.872	AM	1.000	STS	.783
BS	.812	BSP	.847	BP	.874	BM	.955	STR	.810
CS	.804	CSP	.844	CP	.857	CM	.924	SM	.846
DS	.799	DSP	.819	DP	.853	DM	.900
ES	.786	ESP	.822	EP	.873	EM	.908
FS	.807	FSP	.817	FP	.865	FM	.904
GS	.789
HS	.781							Go Karts
SS	.830							F125	.948

SIR/SCCA uses the PAX index for the Street Tire and Guest classes.

Just find the PAX index value for class of your car, then multiply
the corrected time by the index value. The product is the indexed time.