[HR9121]

Throttle stop racing is heads up index racing sometimes referred to as .90 racing and there are 3 classes in both sanctioning bodies 8.90, 9.90 and 10.90. In NHRA they are super comp super rod and super street. In IHRA they are quick rod super rod and hot rod. 8.90 and 9.90 run on 4 tenths pro tree where as 10.90 runs 5 tenths tree. Dragsters are only allowed in the 8.90 categori es and 10.90 is allocated to full bodied door cars. Throttle stops are used to slow the cars down as m any are much faster than the indexes and are slowed a predetermined amount as early in the run as possible to allow the car as much mph as possible on top end. Not everyone uses the stops there are a few who still use ballast to get the desired et. Hope this helps.