My cars weigh about 2300 with driver, 350 lb/in rear springs, racign beat rear bar (or standard SM rear bar), 1:20 and change my personal record at MSR 1.7 CCW, but 21's are more realistic if everythign is perfect; can race solidly in 1:22s. In endurance trim for the 8 hour, we ran pretty consistent 1:58 at TWS on the 2.9 CCW configuration. Could go faster for sprint or qualifying on shaved tires (we used full tread tires for enduro)