Re: Air pressure and reaction time
[Re: jst19600]
#2286482
04/12/17 05:01 PM
04/12/17 05:01 PM
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Joined: Oct 2003
Posts: 4,013 South Park, Pa.
68LAR
master
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master
Joined: Oct 2003
Posts: 4,013
South Park, Pa.
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Not sure if it affects R/T that much. I thought that the increase in front tire air pressure was to decrease rolling resistance, thus lowering ET.
4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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Re: Air pressure and reaction time
[Re: Locomotion]
#2286541
04/12/17 06:44 PM
04/12/17 06:44 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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It does. I've had to vary it between 50 and 26 lbs. Somebody told me the rough average, but I forgot. But the higher you go, there are diminishing returns - i.e.: 30-35 lbs will make more difference than 35-40 lbs. True.. as the pressure goes up the dia will change less at some point.. I could get a small amount of change inn reaction time.. but not much at all... I changed from 30-50 psi
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Re: Air pressure and reaction time
[Re: MR_P_BODY]
#2286552
04/12/17 07:02 PM
04/12/17 07:02 PM
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Joined: Oct 2003
Posts: 4,013 South Park, Pa.
68LAR
master
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master
Joined: Oct 2003
Posts: 4,013
South Park, Pa.
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It does. I've had to vary it between 50 and 26 lbs. Somebody told me the rough average, but I forgot. But the higher you go, there are diminishing returns - i.e.: 30-35 lbs will make more difference than 35-40 lbs. True.. as the pressure goes up the dia will change less at some point.. I could get a small amount of change inn reaction time.. but not much at all... I changed from 30-50 psi Well, today wasn't wasted. I learned something new...Thanks..I personally can't see the diameter changing more than an 1/4" at best going from recommended psi to 40 or 50 psi, but evidently I'm not getting it.. Thanks for the info. I run my fronts at 40 psi when racing, 32 on the street.
4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
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Re: Air pressure and reaction time
[Re: jst19600]
#2286844
04/13/17 03:29 AM
04/13/17 03:29 AM
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Joined: Jun 2005
Posts: 6,257 gulfport, ms, west mi
rowin4
master
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master
Joined: Jun 2005
Posts: 6,257
gulfport, ms, west mi
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There's a couple of guy's at the track that play the tire pressure game, one runs one front tire so low the starting line guy has backed him off. He claims he can leave as the 3 yellow comes on . I've watched , he does, he also red lights a lot. Another uses his tire pressure pounds to rpm launch 26 pounds =2600 rpm etc. . Just one mans theory but he wins a lot. Go figure. I just run 35 psi, pull the wheels out of the light on launch and red light.
it's ok to butt heads, just don't do it with a butthead
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Re: Air pressure and reaction time
[Re: 66coronet]
#2287183
04/13/17 06:36 PM
04/13/17 06:36 PM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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I was gonna try 20psi on my race car but after lowering it to the 20 I looked at the tires.. I was afraid it would hit the rims on the way back down from the normal wheel stand.. they were low.. also on my car I had 3/4" of stagger on the front end.. the right tire was set back the 3/4" to give me a littler longer time in the lights to slow the reaction time.. I used a 24.5" tall tire and the car reacted very quick.. I was running a 1.19 60' on a normal basis unless the tires were getting old(70-70 passes).. the rear tires were MOST of the time set at 6 7/8 to 7 1/8 psi.. depending on the track.. this pic is with a lower rpm launch and between the rpm and tire psi it started rolling/folding the tires
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Re: Air pressure and reaction time
[Re: DusterKid]
#2287346
04/13/17 11:16 PM
04/13/17 11:16 PM
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Joined: Aug 2003
Posts: 43,230 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,230
Bend,OR USA
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I used a 2x4 (laid with 4" side down) and a square to figure out how much roll out my tires had with X amount of air. I started at 25 psi and went up to 35 psi, in 5 lb increments. There was a bigger difference between 25-30 than 30-35. I forget the exact measurements but there was 3/32" difference with 5 lbs of air change. Also a "race" tire may change differently than a "street" tire. I bought a 10 ft. cloth seemstress tape to check tire circumferences on both my front and rear tires at different tire pressures I shoot for 1/4 inch vareince on the rear tires, inflate as needed to get that
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Air pressure and reaction time
[Re: 68LAR]
#2287736
04/14/17 04:18 PM
04/14/17 04:18 PM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
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It does. I've had to vary it between 50 and 26 lbs. Somebody told me the rough average, but I forgot. But the higher you go, there are diminishing returns - i.e.: 30-35 lbs will make more difference than 35-40 lbs. True.. as the pressure goes up the dia will change less at some point.. I could get a small amount of change inn reaction time.. but not much at all... I changed from 30-50 psi Well, today wasn't wasted. I learned something new...Thanks..I personally can't see the diameter changing more than an 1/4" at best going from recommended psi to 40 or 50 psi, but evidently I'm not getting it.. Thanks for the info. I run my fronts at 40 psi when racing, 32 on the street. I do about the same as I run about 35 on the street and 40 at the track. Does it help any ?? Most likely not much if any. Ron
Last edited by 383man; 04/14/17 04:19 PM.
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Re: Air pressure and reaction time
[Re: dmking]
#2288663
04/16/17 11:28 AM
04/16/17 11:28 AM
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Joined: Jan 2003
Posts: 5,894 Florida
Locomotion
master
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master
Joined: Jan 2003
Posts: 5,894
Florida
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i also was bulbing a lot and someone told me about slowing my car down reaction time wise with air so i went down to 30 in the front and down 2 in the back and boom i'm at .015. it seems to work. i am on regular bias tires . the rear must wind up the sidewall a little bit more before it rotates the tire and lower in the fromt must make the contact patch a little bit longer. Exactly! It does make a difference. There are variables that often make it difficult to see. A major variable is a driver's "margin of error". i.e.: If a driver can consistently stay within a .03 spread in reaction times, than a change in air pressure that should make an .01 difference may not be obvious. But keeping very detailed, long-term records of all variables will help. This includes different tracks, day/night, possible lane differences & more.
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