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Old 08-09-2002, 09:43 PM   #1
Scooby Newbie
Member#: 16736
Join Date: Mar 2002
Location: Vallejo, CA
2002 WRX Sedan

Question Does tire pressure matter in 1/4 mile

I know our car is AWD and gets good traction, but is it better to lower the tire pressure to get a better time? What should be the PSI for best time?
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Old 08-09-2002, 10:48 PM   #2
Sordid Philosopher
Scooby Specialist
Member#: 16854
Join Date: Mar 2002
Location: East Bay - CA
2003 WRX Sedan


I ran my best 1/4 miles with 40 lbs PSI on the stock 16" wheels. I got that from another i-club member and it worked for me too.

Good Luck.
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Old 08-10-2002, 02:11 PM   #3
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Member#: 8335
Join Date: Jul 2001
Chapter/Region: MWSOC
Location: www.indianaimpreza.com
96 Impreza L 2.2t
99 Impreza L Wagon


its a trade off you see,

Lower pressure improves traction on the line, but adds rolling resistance down track.

Higher pressure may take a little traction away, but decreases rolling resistance.

with my skill level and lack of consistency on the launch, I haven't been able to decide which is better, but I have heard everything from 25 to 40 psi.

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Old 08-10-2002, 02:35 PM   #4
Scooby Newbie
Member#: 10794
Join Date: Oct 2001
Location: Aylmer, QC, Canada
2002 Impreza WRX
13.47 @ 98.98MPH


40PSI here
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Old 08-10-2002, 10:55 PM   #5
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Member#: 14141
Join Date: Jan 2002
Location: [email protected] @ 5800 ft on 13T
2002 Impreza WRX

Default higher is better

I've found pressures above 35 psi are best for a stock setup. I have run both 35 and 40 and not found a lot of difference, but dropping to 26 psi cost me nearly a full second.

I think for the big power guys the traction gained at the starting line is more important than the increased rolling resistance, as they have the power to pull the increased rolling drag.

For those of us making near stock power we lose more to increased rolling resistance, as we can only spin the tires for a couple feet off the line, so gain very little ET by increasing the off the line traction.

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Old 08-12-2002, 02:14 AM   #6
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Member#: 18123
Join Date: Apr 2002
2013 Evolution X GSR


I'm 13.8 almost no matter what I do, but since the front dif is open and prone to wheelspin, I like 30 front/ 40 rear on the 1320 track. I can virtually guarantee 1.8s like that.
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Old 08-12-2002, 02:55 AM   #7
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Member#: 14141
Join Date: Jan 2002
Location: [email protected] @ 5800 ft on 13T
2002 Impreza WRX

Default Very interesting observation


Interesting observation. I have not juggled tire pressures front / rear yet, all my runs were equal pressure all around.

Lower front certainly makes sense and is worth a few passes to check out. Controlling front wheel spin is one issue I plan on addressing as I sort things out.

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Old 08-12-2002, 07:58 AM   #8
Kevin Thomas
Street Racing Instructor
Member#: 110
Join Date: Jul 1999
Location: 1997 OBS, 1996 SVX, 1988 RX
1989 1989 XT6

Default What works!

25psi front, 40psi in the rear

This is what worked for my OBS Wagon the best. Here's why!

1) I experienced really bad and severe wheel hop due to high tire pressures in the front tires. I was forced to reduce tire pressure,

2) Traction improved with reduced tire pressures in front. I believe the auto/AWD has a 90/10 torque split. With a torque split like that, you want good traction up front or else time is lost for that fraction of a second trying to get traction. The wheel hop bouncing the tires off the ground was another reason traction was lost as well.

The rear tires where put to 40psi because it prevents the weight from shifting to the rear. Had it been say, 25psi or so, you would see the weight compress the rear tire. The stiffer the rear, the better it helps prevent weight from shifting to it. Shorter sidewalls and spring spacers would help too but isn't necessary. Oh yeah, and the 40psi helps with rolling resistance as well.
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Old 08-14-2002, 05:36 AM   #9
Easy Street WRX
Default things to think about

there are alot of factors that should be considered , here are some that might help

sidewall integrity of tire, soft, slick style sidewall, lower pressure works better

weight of car

hp delivered to wheels

stick or auto, auto preloads, stickshifts snaps

size of tire,

compound, suspension, track condition, etc,

what best works for me is testing different psi and seeing how the car reacts, just try do change one thing at a atime and see if it works better, keep every other variable the same and just change psi by a few pounds. Once you feel the neck snapping launch you'll know. ali
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