Rear tire air pressure

BIZMANRACING · 07-16-2008, 11:07 AM

this feels like a really stupid question. what should air pressure be in the rear tires?

i know all cars are different, some like higher than lower and that the type of car matters, as does weight. but, my question is for me and my car.

its a 9.6 full body camaro weights 3050 with me in it, i got 8 lbs in my big tire car. my 60 ft times however have no reason to them. i've been at low as 1.31 for the first run of the day and i've had 1.31 as the last run of the day. unfortunally i've also had a few 1.35 and some 1.37. this as we know is death at the finish line. your either holding a ton, or you hope that your oppounet had like a .110 r/t since you don't have a pray of running the number.

bobby · 07-16-2008, 04:43 PM

Quote:

Originally Posted by BIZMANRACING

this feels like a really stupid question. what should air pressure be in the rear tires?

i know all cars are different, some like higher than lower and that the type of car matters, as does weight. but, my question is for me and my car.

its a 9.6 full body camaro weights 3050 with me in it, i got 8 lbs in my big tire car. my 60 ft times however have no reason to them. i've been at low as 1.31 for the first run of the day and i've had 1.31 as the last run of the day. unfortunally i've also had a few 1.35 and some 1.37. this as we know is death at the finish line. your either holding a ton, or you hope that your oppounet had like a .110 r/t since you don't have a pray of running the number.

I have 28x11.5 on the back of my Firebird and run between 10 1/2 to 11. This is a footbrake car. When I ran 28x9, I ran 11.5 to 12. I use M/T bias ply's.

BIZMANRACING · 07-17-2008, 10:09 AM

thanks bobby

but, thats not what i mean by big tire. i ran those pounds also when i had the smaller tire.

no my question was for door slammers weighting 3000 lbs with 32X14.0X15 i got 8lbs. some folks say i should have less, but the car weights so much.

your thoughts?????????

bobby · 07-17-2008, 11:09 AM

OH, they are big for me, LOL. My brother runs something like a 14x32 and runs 9, I think. I usually don't check his tires. His wife does that for him. He also runs a footbrake car and M/T tires.

Dave Goob Cook · 07-17-2008, 11:11 AM

You are close, given the variances of tire gauges at low pressures, you could run anywhere from 6 1/2 to 8 1/2 and be "correct"....it also matters whether it is a stiff sidewall, the front/rear weight balance, and how much it gets up on the rear tires for the launch.

If you aren't wadding the tires on the launch, they leave a full footprint, and wear even across the tread section, you have it right.

Sounds like you are having a hot track / tire compound issue to me.

I ease up on the burnouts when the track is hot, as well as running a "medium-hard" (Goodyear D-4A) compound for that purpose.
When the track temps exceed 110-120 degrees, I do a dragster type burnout and roll to the line.

BIZMANRACING · 07-17-2008, 03:27 PM

hi dave

no i don't have the corage to do a dragters type buntout. with no line lock at all, i'm not sure it would clean off the tires enough and "hook" on the hit. sometimes i'll do a shorter burn out and roll forward. its just those 60 fts not being consistant enough for my liking. just was wondering if pressure helped one way or the other.

as for the foot print yea i know about that one to. seems smooth right across, its about time to rotate them i got about 20 runs on them now, time to flip them over

Joe Sprint Bros · 07-21-2008, 12:59 PM

Don't forget to measure the rollout while you're rotating them.Joe.

BIZMANRACING · 07-21-2008, 02:18 PM

Why ?????

mrolds · 07-22-2008, 12:12 AM

I ran 8-10.5 on my 14.5 x 32's on my 3200# 65 442 clone running as quick as 9.90.
If you think you're 60's are inconsistent , try radial slicks! On a poorly prepped track my 30 x10.5 radials will 60' Either 1.50 or 1.80 ,& not much in between. Now on a decent track they'll be 1.50 all day!

SlickVic · 07-22-2008, 11:15 AM

Carlos, the tires can be a differen't circumfrence even though they are the same size so measuring the rollout of each tire will tell ou this. Also in a 2500 lb car and 2700 lb car i run 6.5 to 7.0 In a 3100lbs car We run 7.5. You need to run as high as pressure as you can w/o spinning or being inconsistent. So i would start out around 7.5 and go up from there. And it does depend on the gauge, but i use two of the 80$ jegs gauges and both of them read exactly the same.

07-16-2008, 11:07 AM	#1
BIZMANRACING Junior Member Join Date: Oct 2004 Location: east brunswick, new jersey Posts: 62 Likes: 0 Liked 0 Times in 0 Posts	Rear tire air pressure this feels like a really stupid question. what should air pressure be in the rear tires? i know all cars are different, some like higher than lower and that the type of car matters, as does weight. but, my question is for me and my car. its a 9.6 full body camaro weights 3050 with me in it, i got 8 lbs in my big tire car. my 60 ft times however have no reason to them. i've been at low as 1.31 for the first run of the day and i've had 1.31 as the last run of the day. unfortunally i've also had a few 1.35 and some 1.37. this as we know is death at the finish line. your either holding a ton, or you hope that your oppounet had like a .110 r/t since you don't have a pray of running the number. __________________ S/ST 1739 Carlos Mendes

07-17-2008, 10:09 AM	#3
BIZMANRACING Junior Member Join Date: Oct 2004 Location: east brunswick, new jersey Posts: 62 Likes: 0 Liked 0 Times in 0 Posts	Re: Rear tire air pressure thanks bobby but, thats not what i mean by big tire. i ran those pounds also when i had the smaller tire. no my question was for door slammers weighting 3000 lbs with 32X14.0X15 i got 8lbs. some folks say i should have less, but the car weights so much. your thoughts????????? __________________ S/ST 1739 Carlos Mendes

07-17-2008, 11:09 AM	#4
bobby Member Join Date: Jun 2008 Location: League City, Texas Posts: 243 Likes: 0 Liked 0 Times in 0 Posts	Re: Rear tire air pressure OH, they are big for me, LOL. My brother runs something like a 14x32 and runs 9, I think. I usually don't check his tires. His wife does that for him. He also runs a footbrake car and M/T tires.

07-17-2008, 11:11 AM	#5
Dave Goob Cook Member Join Date: Dec 2006 Location: Indy Posts: 422 Likes: 0 Liked 0 Times in 0 Posts	Re: Rear tire air pressure You are close, given the variances of tire gauges at low pressures, you could run anywhere from 6 1/2 to 8 1/2 and be "correct"....it also matters whether it is a stiff sidewall, the front/rear weight balance, and how much it gets up on the rear tires for the launch. If you aren't wadding the tires on the launch, they leave a full footprint, and wear even across the tread section, you have it right. Sounds like you are having a hot track / tire compound issue to me. I ease up on the burnouts when the track is hot, as well as running a "medium-hard" (Goodyear D-4A) compound for that purpose. When the track temps exceed 110-120 degrees, I do a dragster type burnout and roll to the line.

07-17-2008, 03:27 PM	#6
BIZMANRACING Junior Member Join Date: Oct 2004 Location: east brunswick, new jersey Posts: 62 Likes: 0 Liked 0 Times in 0 Posts	Re: Rear tire air pressure hi dave no i don't have the corage to do a dragters type buntout. with no line lock at all, i'm not sure it would clean off the tires enough and "hook" on the hit. sometimes i'll do a shorter burn out and roll forward. its just those 60 fts not being consistant enough for my liking. just was wondering if pressure helped one way or the other. as for the foot print yea i know about that one to. seems smooth right across, its about time to rotate them i got about 20 runs on them now, time to flip them over __________________ S/ST 1739 Carlos Mendes

07-21-2008, 12:59 PM	#7
Joe Sprint Bros Junior Member Join Date: Nov 2004 Location: Virginia, USA Posts: 46 Likes: 0 Liked 0 Times in 0 Posts	Re: Rear tire air pressure Don't forget to measure the rollout while you're rotating them.Joe.

07-21-2008, 02:18 PM	#8
BIZMANRACING Junior Member Join Date: Oct 2004 Location: east brunswick, new jersey Posts: 62 Likes: 0 Liked 0 Times in 0 Posts	Re: Rear tire air pressure Why ????? __________________ S/ST 1739 Carlos Mendes

07-22-2008, 12:12 AM	#9
mrolds Junior Member Join Date: Feb 2008 Location: Le Claire, IA Posts: 29 Likes: 0 Liked 0 Times in 0 Posts	Re: Rear tire air pressure I ran 8-10.5 on my 14.5 x 32's on my 3200# 65 442 clone running as quick as 9.90. If you think you're 60's are inconsistent , try radial slicks! On a poorly prepped track my 30 x10.5 radials will 60' Either 1.50 or 1.80 ,& not much in between. Now on a decent track they'll be 1.50 all day! __________________ Jeff Smith S/ST- Pro/ET 5102 Creating the streetable S/ST Olds

07-22-2008, 11:15 AM	#10
SlickVic Junior Member Join Date: Jan 2006 Location: Maryland Posts: 81 Likes: 0 Liked 0 Times in 0 Posts	Re: Rear tire air pressure Carlos, the tires can be a differen't circumfrence even though they are the same size so measuring the rollout of each tire will tell ou this. Also in a 2500 lb car and 2700 lb car i run 6.5 to 7.0 In a 3100lbs car We run 7.5. You need to run as high as pressure as you can w/o spinning or being inconsistent. So i would start out around 7.5 and go up from there. And it does depend on the gauge, but i use two of the 80$ jegs gauges and both of them read exactly the same. __________________ 87 Cavalier, 92 Corvette, 72 Nova, 68 Firebird