Harry7239

I was wondering how to determine my vehicle's rollout? Is there a formula? I know it depends on how I stage, my tire pressure, and probably the car's 60' time.

mackeyred96

Harry, I borrowed this from aniother web site.

" Rollout is the distance that your tire has to travel to exit the starting line. The starting line beams are about an inch or two off the ground. If you measure your tire width that far above the ground, you will find that it is about 11-14", depending on your tire height. Let's say it is twelve inches. This means that your car has to roll forward an entire foot before the reaction timer stops. This has two effects: 1) You must react before you see the green-light, and 2) Your car effectively has a rolling start of one foot before the reaction timer stops, and the ET timer begins."

Harry7239

yeah what i'm thinking of is regarding a practice tree, which would be a number like .350 for my car. I think that would be the time it takes for my car to travel the rollout and activate the beams.

ralph

Harrison, you have to compare you actual lights at the track to the practice tree. If you're avg a .050 light at the track, but your avg on the practice tree is .010, you probably need to add .040 to the roll out assumption on the practice tree. There are two components to you reaction time....your personal reaction time (the time it take you to react to the light) and your cars reaction time (the time it takes your car to roll out of the beems after you hit the throttle). You can determine your reaction time by stting the practice tree to a protree with zero roll out. Take 50 or so hits and see what your avg is. For most people it's between .180-.220. The vehicles roll out is dependent on a bunch of things like power level, converter, tire size, staging depth, etc.

However for what you're trying to do, comparing track R/Ts to practice R/Ts is the best way to determine rollout. If possible, you should find a confortable spot on the tree first. Something you can hit repeatedly. Then try to adjust the rollout (car and/or staging) to get good R/Ts using that spot on the tree.

Peter Biondo will tell you that the only purpose of the top 2 yellows is to distract you and you should completely ignor them and react only to last yellow. Then adjust your car to get good R/Ts. But that is easier said then done....at least for me

Harry7239

I found what I feel is the correct rollout for my car at .350. When I shallow stage, this is exactly how I run. I realize how I had that -.075 redlight, I actually was anticipating the 3rd amber as opposed to waiting for it to appear (which I originally thought). What I might do (since I live 1 mile from the track) is go test on friday and double check my r/t's then hopefully go rounds on saturday.

Thanks for the help guys, I think I have it sorted out!

jamiejamison

If you have a digital camcorder you can record the rear of the car and tree at the same time. Then count frames from the time your brake lights go out until the green light is on. Count the frames, 30 frames per second and do the math. Example: 11 frames times 1/30 = .367 rollout.
JamieJ

geekracer

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