Front tire size question

Old 08-14-2009, 11:06 AM
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Drtmod5
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Default Front tire size question

What affect does changing front tire height have on your run? In other words what #'s will change? Thanks, Dave
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Old 08-14-2009, 12:54 PM
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FullTimeRacing
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I have it in my mind that a TALLER tire will slow your reaction time.

Do to longer roll out.
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Old 08-14-2009, 02:04 PM
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DirkaDirka
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Ok how does the front tire size effect the times? I am only asking cuz I dont know and I wanna learn as much as I can for when I build my car for the track.
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Old 08-14-2009, 03:50 PM
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curtisreed
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Taller tire will slow reaction times and give quicker et's as said because of more roll out. Basically you get a longer run before you break the beams so you are already moving more at the start of the clocks. Or with the taller tire you can roll in deeper so that you are further down the track and slightly ahead of the other guy at the start.

All of this is small amounts though, you are not going to pick up a couple of tenths with a 2 inch taller tire. This is one of the reasons the Top Fuel guys went back the the 17 inch tires from the short airplane tires years back. Going to a shorter tire is just the reverse of all of this.

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Old 08-14-2009, 03:50 PM
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More rollout will make the car ET and 60' slightly quicker because you have a "running start" , so to speak. Reaction times will be slower all else being equal because you have a longer distance to go before leaving the beams. This is why it is critical to stage the car exactly the same every time when bracket racing.

So if you have a DONK you better leave on the top bulb.


I got treed on that one. ops:
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Old 08-14-2009, 04:09 PM
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DirkaDirka
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Ok what do you guys mean by roll out? Sorry I am a lil lost at the moment but not quite there yet. Also what does e.t. stand fer? What I am getting from this is that a taller tire will basically cause you to hesitate on the start. Sorry guys I am trying to learn. I dont know much about the track. Also what do you mean with breaking the beams?
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Old 08-14-2009, 05:07 PM
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fla1976
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Roll out is the amount of time that it takes to break the beams. The bigger the tire the longer it is going to take for it to leave the beams. The beams are the sensors that are used to prestage and stage the car. When you roll forward the tire breaks the beam and the top amber light is illuminated. As you roll forward the second beam is the broken and the second amber light is lit. If you barely break the second beam then you have to roll further to unbreak the beam. A larger tire will remain in the beam longer so it appears the you haven't moved yet , but you are actually leaving already. Hope this is clear as it is easier to say than to type, especially if you a "pecker typer". ops: Oh yeah, ET is short for elapsed time or the time it takes to run the length of the track. RT is you reaction time, or how long it takes you to leave after the light turns green. RT does not affect the ET. The clock doesn't start until the front tires are out of the beams.
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Old 08-14-2009, 05:17 PM
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Originally Posted by DirkaDirka
Ok what do you guys mean by roll out? Sorry I am a lil lost at the moment but not quite there yet. Also what does e.t. stand fer? What I am getting from this is that a taller tire will basically cause you to hesitate on the start. Sorry guys I am trying to learn. I dont know much about the track. Also what do you mean with breaking the beams?
OK Dirka I'll try to help. If you took two pieces of string ran them parallel to each other say a 1/2 inch high and a 1/2 inch apart to simulate two beams of light. Now if you took a dime and stand it on edge it would just touch both pieces of string or both beams of light. Now if you took a quarter and did the same it would touch both strings or beams of light longer. Hence short tire vs taller tire. Taller tire stays in the beams longer fools the timing system a little where as you are moving a little and it can't tell till you move enough to clear the back string or light as it be.
ET is elapsed time or how long it takes to run the 1/8th or 1/4 mile. Sorry so long . Hope this helps.
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Old 08-14-2009, 05:17 PM
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DirkaDirka
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OK I think I get it now. SO bigger tires will affect yer reaction time but not yer E.T. Except make yer E.T. a hair faster. So shorter tires are better on the front. Thanks alot for the info. Its alright to be a pecker typer. U sed to be one. Now I just got to quit looking at the keyboard when I type. LOL
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Old 08-14-2009, 05:21 PM
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BEAST477
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Shorter tires are better on cars that react slower. If your car reacts quick you have a better chance of turning on the RED bulb more often.
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