Reading a drag racing time slip

A drag strip has light beams across the track at set distances. Each beam starts or stops a clock when the car passes it. The time slip prints what each clock recorded.

The run starts at the Christmas tree, the starting device between the lanes. You roll in until the pre-stage lights come on. Then you creep forward until the stage lights come on. Staged means your front tires are on the starting line.

On a full tree, the three amber lights flash one after another, five tenths of a second apart, and then the green comes on. On a pro tree, all three ambers flash at once, and the green comes on four tenths of a second later.

Reaction time is the time from the green light until your front tires clear the staging beam. A perfect reaction time is 0.000.

If you leave before the green, the tree shows a red light and your reaction time prints as a negative number. In eliminations, a red light loses the round unless the other driver commits a worse foul, such as crossing the center line.

Reaction time is not part of elapsed time. The elapsed time clock starts when your car leaves the starting line beam. A better reaction time can win the race even when the other car runs a quicker elapsed time. That is called a holeshot win.

The 60 foot time is how long the car takes to cover the first 60 feet. It shows how well the car launched. Time saved at the launch carries through the rest of the run.

The 330 foot time shows how the car pulled after the launch. The 1/8 mile mark is 660 feet, the halfway point of a quarter mile. The slip gives elapsed time and miles per hour there.

The 1,000 foot time comes next. The 1/4 mile mark is 1,320 feet and is the finish line on a quarter mile track. The slip shows the final elapsed time, called ET, and the speed.

Each speed comes from a short trap just before its mark. At the finish line, the speed trap is the final 66 feet.

ET depends on traction and power together. Trap speed depends mostly on power. A strong trap speed with a slow ET points to time lost early in the run.

Look at the 60 foot time first. A slow 60 foot time points to the launch, such as tire spin, too much wheelie or an engine bog. Look at the time between each pair of marks next. A car that is quick to the 1/8 mile but slow from there to the finish is losing power at the top end.

Tuners compare slips from run to run. Write down the weather, the tire pressure and every change you made on the back of each slip. A slip means the most next to a record of what changed.

NHRA Top Fuel and Funny Car race 1,000 feet, not the full quarter mile. NHRA shortened the nitro race distance in 2008 for safety. It has stayed at 1,000 feet since then.

On a nitro slip, the 1,000 foot ET and speed are the final numbers. NHRA Pro Stock and Pro Stock Motorcycle still race the full quarter mile.

In bracket racing, each driver picks a dial-in. That is the ET you predict your car will run. The slower car gets its green light first, ahead by the difference between the two dial-ins. With dial-ins of 14.50 and 15.25, the 15.25 car gets its green light 0.75 second earlier.

The goal is to run as close to your dial-in as you can without going under it. Running quicker than your dial-in is a breakout. If only one car breaks out, that car loses unless the other driver red lights or commits another foul. If both cars break out, the car that broke out by less wins.

In index racing, the class runs to a fixed ET called the index instead of a dial-in. In NHRA classes, NHRA assigns the index. Running quicker than the index is a breakout.