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How does front tire size affect reaction time

Posted By: moparguy7074

How does front tire size affect reaction time - 06/18/13 10:56 AM

Just like the subject says, how is reaction time affected by a change in front tire size? I have 25's on my car now, how would 26's change it? What about 27's? I'm running a trans brake btw, launching at 3400, and I always have to wait when I see the bottom yellow or else I go red.

Any help would be appreciated, cause my lights have been all over the place.
Posted By: Just-a-dart

Re: How does front tire size affect reaction time - 06/18/13 01:16 PM

If you shallow stage the taller tire takes longer to roll out of the 2nd beam (starting line), but you are limited by what fits.

Do you have a adjustable slow switch for your T-brake?
Posted By: MR_P_BODY

Re: How does front tire size affect reaction time - 06/18/13 01:36 PM

A taller tire spends more time in the lights... if
you lower the air pressure it can help fine tune your
RT... lowering your RPM will help also.. but if your
RT is all over the place then you need to practice on
a tree
Posted By: Crizila

Re: How does front tire size affect reaction time - 06/18/13 03:25 PM

Looking at tire size ( diameter )only, smaller = faster reaction time and larger = slower. IMO, the human factor makes it a moot point. Keep in mind that's coming from someone that went red .003 in the first round last Saturday night.
Posted By: Duster3105

Re: How does front tire size affect reaction time - 06/18/13 04:36 PM

Brian,
I can tell you I ran 28" tall tires and with my RA and getting older I needed to do something as my lights were getting extremely slow. I tried rolling in a little more and that helped some, tire pressure adjustments helped some.

I went to a M/T 26" tall and found my air pressure "Sweet Spot" to be at 40psi with my RA and age my lights are way better than they have been in the last 2 years and still foot-brake'n Just an FYI

You pretty much know my set-up, 4:56 gear, very good converter, Duster @ 2970# w/ my old butt in it.

Rick.....
Posted By: moparguy7074

Re: How does front tire size affect reaction time - 06/18/13 04:43 PM

Thanks everyone for all the replies! Getting used to this transbrake isn't easy after footbraking forever!!!
Posted By: cudasteve68

Re: How does front tire size affect reaction time - 06/18/13 05:12 PM

Quote:

A taller tire spends more time in the lights... if
you lower the air pressure it can help fine tune your
RT... lowering your RPM will help also.. but if your
RT is all over the place then you need to practice on
a tree




That is why alot of Super Stock & Stockers run big tall azz front tires. Gives them more roll out, or a running head start before tripping the timers. Some of the fast ones even run offset front tires for the same result. All Profession heads up clsses run offset front tires. Some Super Stock & Stockers run up 1.0" of stagger
Posted By: Cab_Burge

Re: How does front tire size affect reaction time - 06/18/13 09:36 PM

Quote:

Just like the subject says, how is reaction time affected by a change in front tire size? I have 25's on my car now, how would 26's change it? What about 27's? I'm running a trans brake btw, launching at 3400, and I always have to wait when I see the bottom yellow or else I go red.

Any help would be appreciated, cause my lights have been all over the place.


Have someone carefully video the front tires when you launch to see if the car lifts the tires out of the beams or rolls them through the beams If it is rolling them through then the 2 inch taller tire may slow the reaction time down a tiny bit while slowing the measured 60 ft times down also I used a set of 22 inch tall 135x15 Sr on my old Duster when I ran it in S/ST back in the early 1990s when NHRA division 7 used the 4/10 Pro tree in S/ST, I had a 727 with a early slow reacting transbrake Those tires help maybe .02 or .03 on the reation time, not enough to help when your cutting .06 or slower with them on I would work on making you and the car consistent first on the reaction times and then look at making any mechanical changes to make the car slower or faster on the reaction times, like changing the front tire size, front tire pressues, the starting line stall RPM and so on Back in the day I had a set of the Stahl 31 inch tall tires on my 1963 M.W. Belevdere, they got old and weather cracked so I switch to a set of the Moroso 29 inch tall tires, I did redlight a lot less with the taller tires I would cut .003 to .015 in time trails and now and then cut a .498 or .499 in eliminations, espcially the first or last round After switching to the 29 inch tires I cut a lot more .498 and worst lights BTW, I carry 24, 26 and 27 3/4 inch tall tires in the trailer now to use as needed
Posted By: Duner

Re: How does front tire size affect reaction time - 06/18/13 09:46 PM

I'm still trying to figure out when to let go of the button myself!

Of course, having both of our race tracks go belly-up isn't helping the seat time very much.
Posted By: MR_P_BODY

Re: How does front tire size affect reaction time - 06/18/13 10:29 PM

Quote:

Quote:

A taller tire spends more time in the lights... if
you lower the air pressure it can help fine tune your
RT... lowering your RPM will help also.. but if your
RT is all over the place then you need to practice on
a tree




That is why alot of Super Stock & Stockers run big tall azz front tires. Gives them more roll out, or a running head start before tripping the timers. Some of the fast ones even run offset front tires for the same result. All Profession heads up clsses run offset front tires. Some Super Stock & Stockers run up 1.0" of stagger




I run 3/4" stagger to the front of my car to help
make a longer roll out... but my tires are short
Posted By: His and Her 69's

Re: How does front tire size affect reaction time - 06/19/13 05:41 AM

Brian, I talked to Bob Frazee when I had my car cause I was like you are now. 1 day I was deadly and then the next time I was really late so it was all over the place. His advice was practice a LOT and when you get a consistant R/T then start working on getting the car in the zone you want. You have to be like a robot first, same thing every pass. Once you get that sweet spot you NEVER change what you do, you change the car, tire pressure, roll in a touch more, etc.

Some people when they change to a brake are killer on the tree, and some are not without practice. Burns was Great when he installed a brake in his camero.
David
Posted By: bigdad

Re: How does front tire size affect reaction time - 06/19/13 07:24 AM

If your track allows a transbrake in the No E class like mine


Get a adjustable button ...


I suggest

http://www.biondoracing.com/product/TERM.html


I have one, it works as described







Posted By: gregsdart

Re: How does front tire size affect reaction time - 06/19/13 12:20 PM

Think in terms of what you have to do to tune the car to YOU. The mind wants to do what it wants, and that is to leave exactly when that yellow you are looking at comes on. Tune to it. Delayed release button, stagger, bigger tires, less launch rpm, they all help. The problem is, the transbrake made your VEHICLE reaction time much better, which is what you have to change. If the class you race in allows the slow release button, I would start there.
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