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Tire pressure thoughts and what do you run? #288124 04/14/09 10:50 AM 04/14/09 10:50 AM
Joined: Jan 2003 Posts: 19,363 Las Vegas Al_Alguire OP I Live Here
Al_Alguire OP I Live Here Joined: Jan 2003 Posts: 19,363 Las Vegas	Just curious what others running big Goodyear or other brands of slicks are running for tire pressures. I run a 2078 Goodyear and have been at 8.5-8.75lbs. The Hemi worked well at that pressure but it was also making about 200 less HP than the current engine. The reason I ask is I was, still am talking to a very good Top Sportsman crewchief after this passed weekends wheelstand escapade and through the course of the conversation he asked me what my tire pressure was. He told me I need to go lower by quite a bit actually. He said when the track was tight, as it was Saturday that they lower their air pressure by as much as 1/2 lb. The reasoning was to help build wheelspeed. He went on to explain that what takes place is the lower pressure causes the center of the tire to cup reducing the contact patch, thus giving the needed wheelspeed instead of dead hooking the car. I went back home Saturday night and watched some video we have of faster cars from behind and I can see what he is referring to, most all of them have the tires slightly cupped. He explained when tracks are not as tight, or do not have a ton of bite that they will up the pressure allowing the tire to have a bigger contact patch. It made sense to me just curious what others take on this is. Any thoughts, ideas? Oh yeah I have had my fill, of this as well. "I am not ashamed to confess I am ignorant of what I do not know." "It's never wrong to do the right thing"

Re: Tire pressure thoughts and what do you run? [Re: Al_Alguire] #288125 04/14/09 11:04 AM 04/14/09 11:04 AM
Joined: Jun 2004 Posts: 1,217 Wellington, FL C cudabunch pro stock
cudabunch pro stock C Joined: Jun 2004 Posts: 1,217 Wellington, FL	Al not that I have big tires, but it sounds like it should work.Then again why not go to a skinny tire like a 10.5 and it would give the same thing?Top fuel tires are always cupped.

Re: Tire pressure thoughts and what do you run? [Re: Al_Alguire] #288126 04/14/09 11:05 AM 04/14/09 11:05 AM
Joined: Feb 2004 Posts: 34,884 S.E. South Dakota ! bigdad Still Posting A Lot
bigdad Still Posting A Lot Joined: Feb 2004 Posts: 34,884 S.E. South Dakota !	http://www.popularmechanics.com/automotive/motorsports/1269381.html Maybe that link will shed some light .. Guess you can try what he suggested and see what it does ? The lips of fools bring them strife, and their mouths invite a beating.Proverbs 18:6

Re: Tire pressure thoughts and what do you run? [Re: Al_Alguire] #288127 04/14/09 11:43 AM 04/14/09 11:43 AM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	I have always gone UP in pressure to get the wheel speed on tight tracks and lower on lesser tracks. When going lower on tight tracks you have a greater issue of tire shake(tires trying to drive over itself) a 1/2 pound can mean aot but all cars act differently

Re: Tire pressure thoughts and what do you run? [Re: MR_P_BODY] #288128 04/14/09 11:45 AM 04/14/09 11:45 AM
Joined: Jan 2003 Posts: 32,394 Q Quicktree I Win
Quicktree I Win Q Joined: Jan 2003 Posts: 32,394	as much as I can

Re: Tire pressure thoughts and what do you run? [Re: Al_Alguire] #288129 04/14/09 12:03 PM 04/14/09 12:03 PM
Joined: Jan 2003 Posts: 19,363 Las Vegas Al_Alguire OP I Live Here
Al_Alguire OP I Live Here Joined: Jan 2003 Posts: 19,363 Las Vegas	I guess one other little tidbit or piece of info that might be useful to others is what type of car and how much power are you putting down. I think this is an iportant detail of the equation. So in that vane I will go first. 2840lb tube car with struts and a 4 link. Engine made 1050 on the dyno but since fuel change I have picked up 2mph+(A-B-A test)so may be a tad more now. "I am not ashamed to confess I am ignorant of what I do not know." "It's never wrong to do the right thing"

Re: Tire pressure thoughts and what do you run? [Re: Al_Alguire] #288130 04/14/09 01:13 PM 04/14/09 01:13 PM
Joined: Nov 2006 Posts: 858 Oklahoma silverfish super stock
silverfish super stock Joined: Nov 2006 Posts: 858 Oklahoma	On my Duster it weighs 2400# with me in it. 17.0 x 33.5 x 16 tires. Last year with a 750hp motor I ran the pressure at 6.5# and it worked fine so I didn't play with it any...just bracket racing. This year I have a 1100hp motor but haven't run the car yet so we'll see. I'm gonna start at 6.5# and go from there.

Post deleted by Defbob [Re: MR_P_BODY] #288131 04/14/09 06:14 PM 04/14/09 06:14 PM
A Anonymous Unregistered
Anonymous Unregistered A

Re: Tire pressure thoughts and what do you run? #288132 04/14/09 06:34 PM 04/14/09 06:34 PM
Joined: Jan 2003 Posts: 3,160 L.I. N.Y. Hemi Street HemiGreg master
HemiGreg master Joined: Jan 2003 Posts: 3,160 L.I. N.Y. Hemi Street	use a good calibrated gauge and check often big slicks can change 1 psi just by the weather getting 5 deg warmer and opposite as night falls. like 9 lbs at rest pressure will go about to 9.6 after the burnout. also check press after the run return road so you know ho the friction coefficient heated the tires top end if you were running too low to start it will get much hoter and squirrley on big end. optimise the patch contact based on the roughness and rubber quality already laid down. good idea to have a crew member check before burnout, after burnout.and walk on the start line rubber with rubber shoes to calibrate the "stickness" and adj appropiatle. eventually it becomes second nature. also remember a 1/2 psi diff side to side will cause drifting and we dont usually want that.a durometer test of the tires daily is best. i would put in a perm optical pyrometer over each rear tire and one of them modern pressure transmitters found on the expensive cars now on each tire. leave NOTHING to chance as the start line is random enough as is

Re: Tire pressure thoughts and what do you run? #288133 04/14/09 07:19 PM 04/14/09 07:19 PM
Joined: Sep 2006 Posts: 3,749 Chowchilla,ca Chassisman master
Chassisman master Joined: Sep 2006 Posts: 3,749 Chowchilla,ca	Quote: Quote: I have always gone UP in pressure to get the wheel speed on tight tracks and lower on lesser tracks. When going lower on tight tracks you have a greater issue of tire shake(tires trying to drive over itself) a 1/2 pound can mean aot but all cars act differently x2....but in some cases lowering can help wheel speed....OR it can cause extreme wading...Al...wish I had a better picture of that rear angle wheelie.....I'd like to see the black tracks. Last edited by Chassisman; 04/14/09 07:20 PM.

Re: Tire pressure thoughts and what do you run? [Re: Chassisman] #288134 04/14/09 07:27 PM 04/14/09 07:27 PM
Joined: Nov 2003 Posts: 6,293 Rock Springs Bob_Coomer master
Bob_Coomer master Joined: Nov 2003 Posts: 6,293 Rock Springs	I ran the largest softest Good Year Tires that is offered for a 15" diameter wheel. Think they were 17x34 IIRC. Anyways On a marginal track, the car picked up from a 1.14-1.16 short times, to consistent 1.07-1.08 short times. This was going from 7-7.5LBS to 5-5.5 lbs. FWIW MPH actually didnt change much (even though I picked up .15 seconds overall), I guess due to spinning and wheel speed. About 143-144mph in the 8th [color:"red"]65 Hemi Belvedere coming soon [/color] [color:"#00FF00"]557" Indy engine 1.07 60ft 144mph in the 8th 2100 lbs package [/color]

Re: Tire pressure thoughts and what do you run? [Re: HemiGreg] #288135 04/14/09 07:29 PM 04/14/09 07:29 PM
Joined: Jan 2003 Posts: 16,925 NC 440Jim I Live Here
440Jim I Live Here Joined: Jan 2003 Posts: 16,925 NC	WOW, bigger league than me. My little tire is about 14 x 32 and I run 11.0 psi with 700ish horsepower at 3190 lbs. But I dead-hook, not wheelspeed (bracket racing). 1993 Daytona, 5.50 at 130mph (1/8) 1.19 sixty ft (PG). Link to 572 B1 - Part 1

Re: Tire pressure thoughts and what do you run? [Re: 440Jim] #288136 04/14/09 07:31 PM 04/14/09 07:31 PM
Joined: Jan 2003 Posts: 4,616 Kissimmee Fl. D dusturbd340W5 master
dusturbd340W5 master D Joined: Jan 2003 Posts: 4,616 Kissimmee Fl.	Quote: WOW, bigger league than me. My little tire is about 14 x 32 and I run 11.0 psi with 700ish horsepower at 3190 lbs. But I dead-hook, not wheelspeed (bracket racing). Yeah me too we have been playing with air pressure the last few weeks 14x32 also and my car likes no less that 8 and no more than 10 70 duster full chassis super pro 416 CNC Indybrock heads 727 w/brake best so far 1.212 60 6.219 in 1/8 at 110.88 9.768 at 137.81 1/4

Re: Tire pressure thoughts and what do you run? [Re: Chassisman] #288137 04/14/09 07:36 PM 04/14/09 07:36 PM
Joined: Sep 2006 Posts: 3,749 Chowchilla,ca Chassisman master
Chassisman master Joined: Sep 2006 Posts: 3,749 Chowchilla,ca	I also just noticed something.....your wheelie bars arent doing you much good at all.....ya...they are keeping it from tail standing BUT...those poor things have absolutely NO leverage to help control the wheelie.You REALLY need longer wheelie bars for that car....yes they are a pain....but you need them to make that thing fly ! And those bars have been on that car for 5 years and arent bent...oh...and it's won A/Gas at the March Meet 2 of the last 3 years...also has won alot of other 7.60 index classes. This shot is with the wheelie bar 1" higher than the first pic !!!!!! The car has a PG also...no fancy clutches to tune...torque multipliers suck at times when it comes to controling the launch...especially in cars with engine set back... Last edited by Chassisman; 04/14/09 07:41 PM.

Re: Tire pressure thoughts and what do you run? [Re: Al_Alguire] #288138 04/14/09 08:51 PM 04/14/09 08:51 PM
Joined: Nov 2005 Posts: 656 Kokomo, IN 540dust mopar
540dust mopar Joined: Nov 2005 Posts: 656 Kokomo, IN	Well, I have a thought,... if you lower pressure the contact patch gets longer. More of a "tangent" if you will area between the track and the tire, you can actually watch that area get longer as you reduce pressure. Not sure what that means and how that and cupping interact. I am like 440Jim, a bracket racer which my thinking is trying to get close to a dead hook to make it the most consistant. I run about 9 lbs in a 14-32W-15 on a 15" wide rim with a heavier much less powered back-halved 4-link car which probably means absolutely nothing in this situation. But thats what I run anyway.... Good Luck

Re: Tire pressure thoughts and what do you run? [Re: HemiGreg] #288139 04/14/09 09:31 PM 04/14/09 09:31 PM
Joined: Nov 2003 Posts: 10,384 Upstate NY Bigcube I Live Here
Bigcube I Live Here Joined: Nov 2003 Posts: 10,384 Upstate NY	Quote: also remember a 1/2 psi diff side to side will cause drifting and we dont usually want that. I will tell you it can cause much worse than a little drifting. I had 1 psi different from one side to the other by accident and when the front end came up it hooked so hard I almost hit the tree. I'm not in the same leage HP wise but I found the launch was much too violent when the pressure was too low. The car still hooked but it wound the tires up like a spring. More pressure really smoothed out the launch. I'm about the same weight as you but 200 less HP. Jim

Re: Tire pressure thoughts and what do you run? [Re: Al_Alguire] #288140 04/14/09 09:33 PM 04/14/09 09:33 PM
Joined: Oct 2004 Posts: 8,165 Left Coast B BobR master
BobR master B Joined: Oct 2004 Posts: 8,165 Left Coast	Quote: Just curious what others running big Goodyear or other brands of slicks are running for tire pressures. I run a 2078 Goodyear and have been at 8.5-8.75lbs. The Hemi worked well at that pressure but it was also making about 200 less HP than the current engine. The reason I ask is I was, still am talking to a very good Top Sportsman crewchief after this passed weekends wheelstand escapade and through the course of the conversation he asked me what my tire pressure was. He told me I need to go lower by quite a bit actually. He said when the track was tight, as it was Saturday that they lower their air pressure by as much as 1/2 lb. The reasoning was to help build wheelspeed. He went on to explain that what takes place is the lower pressure causes the center of the tire to cup reducing the contact patch, thus giving the needed wheelspeed instead of dead hooking the car. I went back home Saturday night and watched some video we have of faster cars from behind and I can see what he is referring to, most all of them have the tires slightly cupped. He explained when tracks are not as tight, or do not have a ton of bite that they will up the pressure allowing the tire to have a bigger contact patch. It made sense to me just curious what others take on this is. Any thoughts, ideas? Oh yeah I have had my fill, of this as well. Al, You may get several different opinions on what the added or subtracted tire pressure actually does. When we run our car your outlined way is exactly how we pursue it. If you get up too high in pressure, though, the tire will quit working. On our deal we use more pressure than you do and I know that several of the competitors in our class do too. Believe me when I say that we are usually looking for more bite. We also find that dead hooking yields the best ET's. You may have to do some chassis work and possibly move some weight around to keep from wheel standing. Also, lower your traction bars to keep the car from getting a lot of rearward momentum.

Re: Tire pressure thoughts and what do you run? [Re: BobR] #288141 04/15/09 01:24 AM 04/15/09 01:24 AM
Joined: Jan 2003 Posts: 19,363 Las Vegas Al_Alguire OP I Live Here
Al_Alguire OP I Live Here Joined: Jan 2003 Posts: 19,363 Las Vegas	Well thanks for the input fellas. Goodyear actually suggested I run 6.5-7lbs with these tires,power and weight. I have not gone below 8.25 as of yet, we have been as high as 10.0. Ron as you know and have seen in person the car still hits the tire plenty hard. Was talking with Gillettes(VG TS team out here)crew chief, he was the one suggesting the change and asking. me what I was running. As for the bars, we can all agree they are pretty much window dressing. They dont do much really. We did collapse the springs fully today and lowered them a bit, will see what that does. I am waiting to take the car to Sarmento to get some new ones whittled up. I am just a number in line right now. "I am not ashamed to confess I am ignorant of what I do not know." "It's never wrong to do the right thing"

Re: Tire pressure thoughts and what do you run? [Re: Al_Alguire] #288142 04/15/09 01:51 PM 04/15/09 01:51 PM
Joined: Sep 2006 Posts: 3,749 Chowchilla,ca Chassisman master
Chassisman master Joined: Sep 2006 Posts: 3,749 Chowchilla,ca	Quote: Well thanks for the input fellas. Goodyear actually suggested I run 6.5-7lbs with these tires,power and weight. I have not gone below 8.25 as of yet, we have been as high as 10.0. Ron as you know and have seen in person the car still hits the tire plenty hard. Was talking with Gillettes(VG TS team out here)crew chief, he was the one suggesting the change and asking. me what I was running. As for the bars, we can all agree they are pretty much window dressing. They dont do much really. We did collapse the springs fully today and lowered them a bit, will see what that does. I am waiting to take the car to Sarmento to get some new ones whittled up. I am just a number in line right now. Well once you get those new longs outback things are gonna change for the better...I might be up there the first weekend in May at the track...but Dragfest is also that weekend and my Fiat will be in Bakersfield....right now it looks like I'm going to Sac and my car is heading to Bako...LOL....and sorry I cant just run up there and throw you a set on...but we are going 18 hours a day right now with no end in sight.

Re: Tire pressure thoughts and what do you run? [Re: Chassisman] #288143 04/15/09 02:24 PM 04/15/09 02:24 PM
Joined: Jan 2003 Posts: 4,573 ...gently down the stream LAR_414 master
LAR_414 master Joined: Jan 2003 Posts: 4,573 ...gently down the stream	Between 19.5 and 22.5 psi on my 28x13.5 ET streets on 10" wheel....with the Auto Trans. I'll probably try 25psi with the stick shift, because I want a little spin coming out of the hole.

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