Ok, I am not so smart when it come to this stuff, so bear with me. I ride my bicycle around my neighborhood frequently. If my tire pressure is low, It requires a lot of extra energy on my part to not only get the bike going, but to also keep it going. Once I pump the tires up, everything becomes much easier. Does this same principle not apply to air pressure while drag racing. Shouldn't you get faster times with the most air pressure possible while still being able to keep traction on the start? I am assuming that there is a fine balance between traction and resistance. Searching for the sweet spot so-to-speek. Thanks

P.S. I am assuming that a 9 sec. car has enough power to overcome the resistance created with lower tire pressure.

 

your theory is somewhat correct bob.
think of it this way. ever see a top fuel dragster do a burnout? fat low pressure tires spin and stand straight up! same thing applies. by lowering the pressure you are allowing the sidewall to twist a bit instead of spinning. hard sidewall breaks traction easily soft underpressure sidewall grabs with the torque and pushes you forward in stead of breaking traction.
granted there has to be a fine line between this so the car doesnt get squirrley going down the track. hence test and tune! the lower pressure also allows for a bigger traction patch on the pavement. its a game many racers play all the time as track conditions constantly change
you should have enough hp to overcome the drag created and the pressures build up quickly in the tires during the race.
there are racers whose cars have so much power they have to bolt the tires to the rims and run tubes to keep from literally ripping the tires from the rim. the bolted tires may be running as little as 5 to 9 lbs of air

 

I know lots of people that have 9,8,6 second cars..............but they are ALL running true slicks(with tubes). The Hoosiers that we're running are drag radials and are not intended to run such a low tire pressure.

 

I keep my drag radials at 20 psi and warm them up well before launching.

 

i havent been able to find any info on the recommended pressures vfor the dr's . any ideas? i hope to be testing next week but its still in the 30's!

 

A co-worker of mine runs the Hoosier DRs on his 750rwhp C6 vette and he contacted Hoosier and they stated that since the tires are still "radials" that they should be run from 18-20psi(no lower).

 

So Steve, if I understand what you are saying, the combination of centrifugal force and the buildup of pressure should reduce the contact patch and reduce drag (friction). Whereas when I am riding my bicycle with low tire pressure, I do not have enough centrifugal force to build up heat thus increasing tire pressure. Sorry for the simplified analogy, but I am trying to get a better understanding of this. And, I think this is making sense to me.

 

you got it bob!
and from what moparburst is saying, because these are radials they shouldnt be run below 18 psi. so ill yield to his info and try the pressures from 222 to 18 if i can ever get to the track.
i ask when i go to price those goodyears i sent to you and see what the techs say

 

I got my Crankshaft Position Sensor in the mail today from where I thew a P0335 code at the strip. Man what a pain to swap out. After about an hour and several cut knuckles later, I decided to get my wife to help me. My hands are just too big. Wy wife is 4'5" and 85 lbs., so while I was having problems with too big hands, she had problems with too short of arms. Anyway, we eventually got it done. I must say.... My wife is quite the trooper. For a little gal, she's a scrapper.

 

I just went out last night and raced(at 18psi) and ran 11.98, 11.95, 11.90.........last pass was with a 1.71 60'.


PS There was a 1950DA

 

Comgrats Mopar.... Very impressive. What RPMs were you launching at?

 

Last pass was about 2200rpms..................the others were 1800-2000. They don't usually prep the track on Friday nights so I launch low for fear of spinning but last night was prepped halfway decent.

 

I think I am going to try around 2200 the next time I go. I was hoping to go today, but we have about 3 inches of global warming on the ground here in middle georgia.

 

mopar, we have to talk about your cooling mod...lol....

 

Rob at needswings wass developing a VERY similar setup to mine a while back and he should be able to make you one. It's nice to make your IATs drop to 45* at the push of a button.

 

LOLZ........

 

Thanks Mike, I need to talk to Rob anyway....a have couple of things I need to buy for the coupe that I know he is developing right now...so, I will ask about this mod as well....nice times...

 

well from what i have seen it wont matter what i launch at! i have 1.7 60 ft times when i ran the c3 with no tune and dr's . so if my 60 ft times are still the same its my top end that is lacking, hopefully the dyno tune and added hp will help that

 

Trust me Steve, you will notice a huge change through 2nd and 3rd with the tune. You will be wishing the track was longer so you could bust into 4th.

 

Mopar, congratulations on the times. I will have to start trying to launch higher RPMs. I am only launching at about 1400. My 60's are good at 1.72 though. I'll try to catch you guys when the track opens back up next month......