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DRR Trophy
Picture of whitey234
posted
What would 5lb pressure difference make in rollout….I haven’t raced my altered for about 3 years and thinking about increasing pressure by about 5lbs..should it slow down RTs or increase them and by approx how much….altered weighs around 1850 with ladder bar rear solid front and ET front runners…small block 383….launch rpm is 4600


Growing old is mandatory, Growing up is optional
 
Posts: 28 | Location: Sydney Australia | Registered: January 05, 2006Reply With QuoteReport This Post
DRR Elite
Picture of 1320racer
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based on your avatar photo, playing with front tire pressure won't do anything for your reaction times.


O'IT!

Offering 1st hand experience and advice based on 3 decades of on track proven performance

"if you guys are so broke dyck you can't buy USA made parts you need to stay the fuc at home that's the bottomline" ----Tim McAmis



 
Posts: 12038 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR Trophy
Picture of whitey234
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That’s an old photo..it now drives out and just Carrys the fronts and drops them down under full power


Growing old is mandatory, Growing up is optional
 
Posts: 28 | Location: Sydney Australia | Registered: January 05, 2006Reply With QuoteReport This Post
DRR Elite
Picture of 1320racer
posted Hide Post
What’s your current front tire pressure and are you transbrake or footbrake launching?


O'IT!

Offering 1st hand experience and advice based on 3 decades of on track proven performance

"if you guys are so broke dyck you can't buy USA made parts you need to stay the fuc at home that's the bottomline" ----Tim McAmis



 
Posts: 12038 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR Trophy
Picture of whitey234
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Transbrake and 30 psi


Growing old is mandatory, Growing up is optional
 
Posts: 28 | Location: Sydney Australia | Registered: January 05, 2006Reply With QuoteReport This Post
DRR Pro
Picture of CURTIS REED
posted Hide Post
Tire pressure changes on my roadster, which is 2000lbs with me in it and 51.5% on the rears, makes almost no difference unless I go so low I worry about them.



____________________________
2017 and 2018 Osage Casinos Tulsa Raceway Park No-Box Champion

2018 Div4 Goodguys Hammer award winner
 
Posts: 2361 | Location: KIEFER, OK. | Registered: August 17, 2007Reply With QuoteReport This Post
DRR S/Pro
Picture of "The Bender"
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I was wondering about this also. I run a 28x4.5 front tire at 35#. I'm going to run some .5 pro tree no box index stuff. I'll need to slow down the leave, I've been running 1.07 in the box when leaving on the top bulb. I plan on lowering the launch RPM, but was also wondering how much tire pressure would change things.....


272" Spitzer
540 Chevy
The Blower Shop XR1
FTI XPM Series Converter
FTI Level 6 Powerglide
3.69@199
.916 60'

2017 Bradenton Heads Up Madness
Open Outlaw Champ

2018 PDRA T/D #5
2019 PDRA T/D #2

2020 Retired From T/D Competition....

2020 Bradenton NMCA Hemi Shootout Winner

2021 getting back into bracket racing........
 
Posts: 2986 | Location: Yes | Registered: July 08, 2009Reply With QuoteReport This Post



DRR Trophy
Picture of whitey234
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Thanks….over here in Australia we don’t get that many times in the year to try things out so it just helps to ask those who have a lot of tracks to get plenty of runs in a year..


Growing old is mandatory, Growing up is optional
 
Posts: 28 | Location: Sydney Australia | Registered: January 05, 2006Reply With QuoteReport This Post
DRR Trophy
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Almost did not bother to replay because Mr. no it all 1290 love to tear up anyone who doesnt agree with him but.. what brand tire do you use . I have used Goodyear-very stiff wall tire almost no change however Hossier and M/T will but not at 30lbs. Have run those at 24-28 and you can fine tune R/T there but try starting line RPM first-works much better 200 RPM is about .01 on my 100 inch W.B. door car that runs 8.80s in 1/4


The difference between ignorance and stupidity. Ignorance is lack of knowledge. Stupidity is the inability to learn. Don't be stupid
 
Posts: 302 | Location: des moines iowa | Registered: January 10, 2020Reply With QuoteReport This Post
DRR Sportsman
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i have played with this some. i normally run around 35 to 40 psi in the front on any given day. i typically have 1080 to 1085 in the box for a long tree. when i 6.0 index race on a .4 tree i have to stiffen my rear shocks some and will go to 50 psi in the front, that combined will be worth about 010 to 015 in react. front tire pressure is probably only worth 4 or 5 thou maybe per 10# of pressure. at least that is what i see on my stuff.

ep
 
Posts: 660 | Location: dodging double wides... | Registered: November 28, 2007Reply With QuoteReport This Post
DRR Elite
Picture of 1320racer
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quote:
Originally posted by vetman:
Almost did not bother to replay because Mr. no it all 1290 love to tear up anyone who doesnt agree with him

You shouldn’t of and Wrong only ass holes like you that only reply to debate my over 3 decades of track proven advice, who think they know yet ain’t done shyt nor have shyt worth talking about.

Let’s us know when you have a car on par with either of these which are 2 of the best on the property where ever we compete and their driver one of the best in the country under 30. This is just the past 3 weeks…



This message has been edited. Last edited by: 1320racer,


O'IT!

Offering 1st hand experience and advice based on 3 decades of on track proven performance

"if you guys are so broke dyck you can't buy USA made parts you need to stay the fuc at home that's the bottomline" ----Tim McAmis



 
Posts: 12038 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR Sportsman
Picture of FootbrakeJim
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Whitey234, are you trying to shorten your R/T, or slow it down? Raising pressure in the fronts should either make your lights quicker, or make no difference at all. Long list of variables involved, but the basic concept is that increasing the tire pressure will make the tire more round, (shorten the footprint / distance between the stage beam and back of the tire). Less FORWARD travel required to clear the beam. As Ed hinted in the first reply to your question, if your front tires clear the beam by traveling vertically, tire pressure will likely make no difference in R/T.


Dan "Jim" Moore
Much too young to feel this damn old!!
 
Posts: 983 | Location: Farmersville, TX  | Registered: December 05, 2002Reply With QuoteReport This Post
DRR Elite
Picture of 1320racer
posted Hide Post
most alterds(center steer) I see bracket racing don't work well. That said, 30 psi is low. My suggestion would be lower the launch rpm to get a competitive reaction time window then raise the front tire pressure to dial it in.


O'IT!

Offering 1st hand experience and advice based on 3 decades of on track proven performance

"if you guys are so broke dyck you can't buy USA made parts you need to stay the fuc at home that's the bottomline" ----Tim McAmis



 
Posts: 12038 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR S/Pro
Picture of Lenny5160
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To make RT slower, you'd need to lower the pressure. I agree with other posters that you might be looking at .010 difference between the low and high in the 'safe' range.

I'd be decreasing launch RPM first. Bringing your rear tire PSI down as far as you are comfortable would likely help more than anything you can do to the fronts.


Tony Leonard
 
Posts: 2944 | Location: Inver Grove Heights, MN | Registered: March 18, 2004Reply With QuoteReport This Post



DRR Trophy
Picture of whitey234
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Thanks for your replies..as it was midnight here with my last post I only just got back on..I’ll try the tire pressures at 30 and go with lowering startline…..last time I raced in Sydney was before the track was ripped up and relaid with new concrete….I was averaging 020 reaction time and that was getting me rounds but with the new surface I have noticed that people are regularly going in the 010 range


Growing old is mandatory, Growing up is optional
 
Posts: 28 | Location: Sydney Australia | Registered: January 05, 2006Reply With QuoteReport This Post
DRR Pro
posted Hide Post
quote:
Originally posted by WHOMPWHOMP:
quote:
Originally posted by pauley:
i have played with this some. i normally run around 35 to 40 psi in the front on any given day. i typically have 1080 to 1085 in the box for a long tree. when i 6.0 index race on a .4 tree i have to stiffen my rear shocks some and will go to 50 psi in the front, that combined will be worth about 010 to 015 in react. front tire pressure is probably only worth 4 or 5 thou maybe per 10# of pressure. at least that is what i see on my stuff.
ep
BUT….you a bad man….
 
Posts: 1082 | Location: USA | Registered: December 04, 2008Reply With QuoteReport This Post
DRR Pro
posted Hide Post
quote:
Originally posted by WHOMPWHOMP:
quote:
Originally posted by WHOMPWHOMP:
quote:
Originally posted by pauley:
i have played with this some. i normally run around 35 to 40 psi in the front on any given day. i typically have 1080 to 1085 in the box for a long tree. when i 6.0 index race on a .4 tree i have to stiffen my rear shocks some and will go to 50 psi in the front, that combined will be worth about 010 to 015 in react. front tire pressure is probably only worth 4 or 5 thou maybe per 10# of pressure. at least that is what i see on my stuff.
ep
BUT….you a bad man….


VERY Bad ….On Jegs Allstars Roster for US Nationals
 
Posts: 1988 | Location: 53056 | Registered: December 30, 2009Reply With QuoteReport This Post
DRR Sportsman
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Very impressive! Congrats on the Jegs All Stars!


BG
 
Posts: 699 | Location: Florence, SC | Registered: August 25, 2019Reply With QuoteReport This Post
DRR Pro
Picture of CURTIS REED
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Congrats EP.



____________________________
2017 and 2018 Osage Casinos Tulsa Raceway Park No-Box Champion

2018 Div4 Goodguys Hammer award winner
 
Posts: 2361 | Location: KIEFER, OK. | Registered: August 17, 2007Reply With QuoteReport This Post
DRR Trophy
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I learned a lesson with changing front tire pressures the hard way. My son and I went to T&T on a Friday night and his RT's were good. Dad got a little concerned with the car hiking the front tires with the new Weld 2.0's and the Hoosiers deforming on landing. So, Saturday morning when he wasn't around, (we have a rule that I don't mess with the car on race day), I went from 32psi to 35 and kind of forgot about it. Well first time shot RED, second time shot RED, first round RED and now he is PO. We were talking at the trailer, and it dawned on me what I had done. He scowled at me and reset the pressure to 32 like we had always run and won the by back (I paid) and a few more rounds. Lessoned learned and the valve stem caps are Loctite now. LOL
 
Posts: 74 | Location: upstate NY | Registered: January 15, 2018Reply With QuoteReport This Post
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