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 Post subject: Air pressure
 Post Posted: Sat May 27, 2006 12:52 pm 
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I have 32/14 goodyears on my car and have been using 7 psi. Footbraking. I now will be using the transbrake and it seems the tires are folding up on launch. What pressure do you guys like. The car weighs 3,250 with me in it. No tubes and screwed to the rims.
Thanks Greg


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 Post Posted: Sat May 27, 2006 3:08 pm 
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Greg that seems a little low for a thin sidewall tire and that much weight. If memory serves on my Studebaker I ran somewhere near 10lbs HOT. The last set of tires I bought for that car were the "stiff" sidewall tires and I ran those down at 7 or 8 psig, I memory serves.

On my Camaro I run 6psig now and have been as low as 5 during testing but that car is suppose to be near 2300lbs wet.

My suggestion is to go up a pound each race then stop and back down when you see your sort times start to fall off. The tire will let you know when it has too much air in it! A word of caution though, be ready to add some time in the box when you add air as it will make the car leave quicker.

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 Post Posted: Sat May 27, 2006 4:27 pm 
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In general, optimum tire pressure is related to the size of the tire and the weight on the tire. Bigger tires or lighter cars need less pressure and smaller tires or heavier cars need more pressure.

The tires are really part of your suspension too. The pressure needs to be tuned with the shocks, springs, weight and 4-link or ladder bar settings.

On my Camaro I run them at 6.25# to 6.5#. It is ~2350# and 14.5W-32 Hoosiers. On a very light altered they might only be 4.5#, on a heavy high HP car maybe as much as 8#.

Video tape your car at launch to see what is happening to the tire. That will help you tune the car to the tire and the tire to the car.

Rick


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 Post Posted: Sun May 28, 2006 1:50 am 
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Thanks guys, I will slowly sneak up on it and see what happens. Our friday nite t@t track is not properly prepared. I will have to take it on race nite for a proper test.
Greg


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 Post Posted: Sun May 28, 2006 2:02 pm 
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I usually run like 12.5-13.0 cold but I dropped them to 11.5 cold and it helped a little seems to hook up on motor pretty well. My tires are
31x13.5 and my total weight id 2720 with 1058 on the rear..

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 Post Posted: Tue May 30, 2006 4:05 pm 
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in my 2750 lbs car, i run 7 lbs. tires ar 15x15x33 hoosier do5's. car runs 9.0's in the qrt.

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 Post Posted: Wed May 31, 2006 12:27 am 
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This is all good advice. I do agree with Ken, It sounds like your pressure is low for a the weight of your car. The heavier cars do like a lot more pressure, I run a stiff sidewall slick because mine is a stick-car and I only run 4.5 - 5 lbs in mine. My car weigh a little over 2200 lbs. I like the Mickey Thompsons better than anything else I've ever run. When I ran goodyears, I couldn't get any tech advice from goodyear. M/T people were very helpful.

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 Post Posted: Wed May 31, 2006 7:02 am 
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chuck, your response to tech help was good info. if the manufacturer is willing to give you tech advice that is a big help and is very important in my book. tony.

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 Post Posted: Wed May 31, 2006 6:42 pm 
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AS of now 7.5 P.S.I. seems to work pretty well with those stiff sidewall goodyears..on the wagon... =; =;

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 Post Posted: Wed May 31, 2006 7:51 pm 
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Tray, are your goodyears 32/14. Mine are D1984 , I think I am correct that mine are stiffwall as well. Next time out I will increase mine and see what happens. =;


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 Post Posted: Wed May 31, 2006 8:45 pm 
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yep,,same ones.... =;

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 Post Posted: Fri Jun 02, 2006 1:01 am 
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It's always been my experiance that an under inflated tire is cold in the center and hotter on the outsides and over inflated is hotter in the center and cooler on the outsides. A pyrometer is best way to check but a cotton glove right after the burnout is close. Watch out they do get warm. It's not uncomon to get 2 to 3 hundred degrees.

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 Post Posted: Sun Jun 04, 2006 10:57 am 
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Did some footbrake testing fri. nite. They had scraped the track and it was kinda slick, but I went up to 9lbs. of air before the 60 fell off. The track closed at 10 and I run out of time. Somewhere between 8 and 9 will prob. work. I still may have to move the instant center though, it is hitting the tires really hard even off the footbrake. I will take it back on race nite next time to get better track conditions. It still went 6.10@ 113 with a 1.35 60. =;


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 Post Posted: Sun Jun 04, 2006 8:17 pm 
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traysvega wrote:
AS of now 7.5 P.S.I. seems to work pretty well with those stiff sidewall goodyears..on the wagon... =; =;


Tray, regular sidewalls may get you that 1.29 60' timeyour looking for :-k

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