Tire diameter effect on rollout and reaction time improvements

[dvw]

This was touched on in another thread. So rather than clog that one up a here is a new thread. In my years of drag racing it's been a focus of quick consistent reaction times. What does that entail? Three items. The car the driver, and where you stage. Practice for the driver to be consistant is #1 in my book. The closer you can group your R/T the better chance of winning. If you are .000, .100, .050? That's not going to get you far. If you are . .040,.060, .050 or .000, -.020, -.010. Then you can work with that. How? Now we're at the 2nd item. The car itself. Many different theories. The one in this discussion is rollout. Many believe front air pressure. Myself? I don't buy it. With the link provided you will see how little even 2" of diameter changes rollout. I'm pretty sure changing the rollout to equal 2" of diameter by changing air pressure is imposible. With properly located beams a 28" tire will move 13.09" before breaking the beam. A change from 26" to 28" results in a 1/2" change in rollout. What is a 1/2" worth? Depends on how far the car moves in the first 1/2". Plenty of ways to change the car to speed or slow the cars R/T. I think for the majority of us mortals R/T is way more driver and staging than car. Your thoughts?
Doug
Wallace Racing - Roll Out

 

[RemCharger]

I have to agree. Walking around the staging lanes you see a lot of people fretting about tire pressures.. 1 guy will walk around checking tires 3 times before he's up. It might just be common human nature to always blame the equipment, instead of the driver( who couldn't actually be the problem??! Lol)
It's like skeet shooting,, with a moving target. Another thing of note is different trees/computers/ and bulb types. We went to a new system last year and it took a bit to try and adjust. But once you're there, you're there.

Oh, and I check the front tire pressure in the spring, and maybe once or twice during the season. Maybe.

 

[RemCharger]

 

[Curiousyellow71]

We have a local track that one lane seems to be .007 quicker on the reaction time then the other. Never noticed that at another track?
I've also wondered the effect of reaction time difference from up out of the lights when the transbrakes released, vs rolling through.The car should be going forward at the same time, but it seems to me that tire diameter may even have less effect up out of the lights then rolling forward. We really never experienced what tire size changes can do because top bulbing a .500 full tree in super pro is different then trying to cut lights on the .400 pro tree or trying to get the car to leave consistently w the footbrake. Footbraking we frankly were winging it and not consistent enough to know what any kind of change would do.Lol

 

[GTX JOHN]

Consist positioning in where you are staged in
the lights is Vital so as to be at the same place every
time. I stage shallow and therefore at the same
position every time. No bouncing or guessing where
you are. I adjust other variables that I can control
accurately a couple (not all are) starting line RPM and where I leave
on the tree.

MY .02 = For Free!

 

[khryslerkid]

Ever been to a track and all of a sudden everyone seems to be red lighting?

 

[fullmetaljacket]

At events where I was chasing or being chased and actually came home with trophies, I would stage my 28" Moroso Drag Specials shallow gauged by a couple of minute bumps right after the bottom bulb was flicked on. Pressure was more or less at 34 Lbs. This was a while ways back when the car would cut consistent 1.65's all day long, but somehow ET fairly well. Car was in the money 95% of the time.
Later on during those late evenings, a different type of staging was in affect. LOL.

 

[fourgearsavoy]

I always looked at rollout as something that was just part of the package that you deal with what you have and work on your procedure instead. I have too many other things to be concerned about in staging a stick car.

 

[padam]

I might try blinders this year.

 

[fullmetaljacket]

I might try blinders this year.

I bet staging a stick car must be the closest to floating in space. Because of their violent and sudden leaves, perhaps it's safe to stage deep?

 

[NSS Guy]

Just a thought, rear tire psi has more of impact on RT. Especially bias tires with soft sidewalls, lots of motion going on before the car actually moves. Same thing with front shocks being tight or loose on extension

 

[67MPRFAN]

I'll admit, I definitely need more seat time

 

[padam]

I bet staging a stick car must be the closest to floating in space. Because of their violent and sudden leaves, perhaps it's safe to stage deep?

No I stage shallow. I am still gonred leaving on the last yellow, but I believe I am anticipating the light.
That’s why I think blinders would help.

 

[dvw]

Good responses. Since I'm a bottom bulb racer thats my focus. Not sure I'm good enough to say one lane could be .007 different from the other. All my runs are logged. When comparing R/T at the beginning of last year it was surprising that my average over the previous 4 years was better in one lane. During this span the data was from 13 different tracks. So it wasn't the track. It was me. Not sure why but I focused on my weak lane this year. It was my better lane. I agree with Jim. Rear pressure with bias slicks can change R/T. If you watch the tree count down? My bet is your R/T high to low is greater than those who stare at the bottom only. However iy takes better concentration not having a heads up on the tree starting down. Changing to the bottom you may be slower until you gain concentration. I challenge those who go red to try the same on a .500 pro tree. My bet is you will find you are cheating watching bulbs. Talking red not, - .00X. As for a blinder. What happens at night when you can see the glow of the first 2 bulbs?
Doug

 

[LemonWedge]

I changed tire size last year halfway through the year. I went back and do the math on the before & after. My times did move in the direction the theory says they should by .013. Now, was that completely due to the change, or just coincidental, or maybe some semblance of both??? I’ll never know for sure, but the math didn’t lie, and perception can be reality.
I’ll tell you this much. I was frustrated enough with it all that I went a whole new direction and invested in a transbrake and adjustable button just to get a better handle on things. We’ll see how that goes. Today’s adjustable brake buttons are a tool that are hard to argue with. I realize that in the OP’s world of NSS racing, they’re not applicable. I run almost exclusively NHRA Pro ET though…. So if you can’t beat em, join em.
With all that said, I agree with most everything Doug brings up above. And totally agree that the best process is to find a spot you can be consistent at, then keep yourself there and adjust the car to suit that spot.

 

[dvw]

I have to believe that a trans brake with a good button would be a beneifit. Many events we run against trans brake cars. Also a fair amount of stick cars. There are some really good drivers running all three options. We can hold our own pretty decent.
Doug

 

[padam]

I know on a practice tree I react a lot faster to a full tree than a pro tree, even if I concentrate on the bottom bulb. Habits and peripheral vision I guess.

I tried a couple times to use a blinder last year, but couldn’t get it set up right.

Edit;
I do have to ad, that after I started concentrating on the bottom bulb only last year, my red lights went way down.

 

[fourgearsavoy]

My procedure starts at the second bulb. Get on the 2 step and my left leg starts to move when the bottom bulb comes on. It's amazing how much time it takes to get the stick car moving from staged to green. It's amazing how some racers like Larry(Battlestar) can be so consistent by leaving old school just mashing the gas and letting it fly on the bottom bulb .

 

[dvw]

I know on a practice tree I react a lot faster to a full tree than a pro tree, even if I concentrate on the bottom bulb. Habits and peripheral vision I guess.

I tried a couple times to use a blinder last year, but couldn’t get it set up right.

Edit;
I do have to ad, that after I started concentrating on the bottom bulb only last year, my red lights went way down.

Exactly, anticipation. When you [practice enogh you will be within .01 or less on either tree.
Doug

 

[33 IMP]

Front tire pressure is not gonna mean ship to rollout. Ten pounds more pressure means what, 1/4"? Less?
My experience is that front tire height needs to change by two inches or more to have a substantial effect.
I was running two different cars, a footbrake car with a fairly poor 60ft, that I was still redlighting against a full tree. I've tried changing my "cue" on the light. Doesn't work for me. I'd slow from .489 to .689 or worse.
25" changed to 29" helped. So did rear tire pressure, and starting line rpm.
Other car was a big tire (bias) transbrake car against a pro tree that couldnt go red. (At least with ME driving, it couldnt! Lol). Ran 22.5 tires that helped, ran as much air in the rears that would still dead hook, that helped more.