What's
my Rollout ?
by Al Smyth - Portatree Timing Systems, Inc.
Probably the most unknown drag racing value is rollout.
Some think it is the amount of inches that their car rolls out of
the stage beam (they are partially correct).
When racers inquire about their rollout, we can't provide one
simple answer. Rollout is the time from when the driver initiates
the leave until the car physically leaves the starting line that
starts the Elapsed Time (E.T.) clock. The start of the race can
be initiated by rolling out of the stage beam (stage beam makes
-- light on tree goes out), guard beam breaking (some tracks don't
have a guard beam, but its purpose is to limit rollout length),
or either one happening first. It is important to know this because
if your track is using a different method than another track, your
Reaction Time (RT) will change !!
Rollout consists of 7 variables of which the driver has control
of 5 and track personnel control the other 2. The Track sets up
the height of the beams on the race track and if they are set too
high, the rollout is increased (harder to red light). If they are
set low, the rollout is decreased (easier to red light). The track
also has control of traction. If the track is slippery (tires spin)
then you will have a longer rollout.
The 5 variables that you can control are:
- Weight of Vehicle
- How you stage the car -- shallow or deep
- Clutch / Converter Slippage
- RPM of the leave
- Front Tire Diameter / Air Pressure in the front
tire
When you are practicing with a practice tree whether
it is a table top or the full sized tree, it is important to use
a rollout number that your vehicle can attain. After you practice
and get consistent at that rollout number, you should make the vehicle
work with you -- don't try and compensate to work with the vehicle.
If you have a delay box then you use the delay box
to vary the rollout number so working with the vehicle just got
a whole lot easier, but remember, the rollout is still a variable.
Even with a delay box, you can still red light if you stage too
deep or get too much traction.
Good luck racing and practice daily !!!
TYPICAL ROLLOUTS
Jr. Dragster - Gas Motor |
.40 - .44 Seconds |
Jr. Dragster - Alcohol Motor (sm. front tires) |
.36 - .38 seconds |
Jr. Dragster - Alcohol Motor (lge front tires) |
.31 - .34 seconds |
Motorcycle |
.18 - .22 Seconds |
Pro Stock Bike |
.24 - .28 Seconds |
Pro Stock Car |
.24 - .28 Seconds |
Super Comp Dragster |
.18 - .22 Seconds |
Super Stocker (3200 lbs) |
.30 - .34 Seconds |
Top Fuel -- Dragster / Funny Car |
.28 - .32 Seconds |
Calculation (Estimate Only): Weight of Vehicle / 10,000
3200 lbs / 10,000 = .32 Seconds
This estimate does not work for vehicles that slip clutches excessively.
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