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Tire Pressure Help!!!

**Broadcasted** | THURSDAY | Practice @ 6pm | Qualifying @ 9pm | Race @ 9:15pm (EST)
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MattMiles44
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Tire Pressure Help!!!

Post by MattMiles44 » Tue Mar 26, 2019 3:33 pm

Hey guys. I'm still totally lost when it comes to setting up tire pressure. The chassis I'm alright with, I have a pretty good understanding of spring rate and cambers. It's tire pressures where I'm lost.

I understand that low pressure means more grip and more heat buildup, and high pressure means less grip and less heat buildup. But I get confused when the track temp changes. I run 22 PSI all around, after about 8-10 laps I see temps reach 200-210 F (outer 170 F) and the rear reaches nearly 230 F on a 100 F - 105 F track. I've moved the PSI around, did 20 PSI in the front and 24 in the rear. Same amount of laps and same track temp, got the same pressures. 

Am I not doing enough laps for accurate data? Also, what tire temp should I be aiming for? I'm not asking for everyone's tire pressures, I understand it really depends on many different factors. As a moto guy, tire pressures are much different (obviously) and i'm just having issues understanding what I'm looking for when testing tire pressures and what temps I should be aiming for.

Last question, if a track cools down from 105 F to 90 F, should I lower pressure or raise pressure?

All answers or links are appreciated. I lowered tire pressures for Watkins Glen and it dropped almost a full second for my pace, but I haven't the slightest clue why that was  :oops: :cry:
 
Thanks guys  :mrgreen:
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Re: Tire Pressure Help!!!

Post by DeamingPie » Tue Mar 26, 2019 4:05 pm

While I cannot answer the tire dynamics that iRacing uses, I can tell you all last season my pressures were set at 19 PSI all around, and it hasn't changed at all this season. I have noticed that if you set the PSI higher, the operating temp of the tire will come up quicker but grip will suffer mid race.

Don't take this as gospel, but it seems that the lower the PSI the lower the tire temps will be, even though you are creating more of a contact patch. The only race I ran into severe grip problems was Tsukuba. This could also be a cause of running too high camber as well.
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Rem Ambruosi
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Re: Tire Pressure Help!!!

Post by Rem Ambruosi » Wed Mar 27, 2019 4:07 am

Hi , I feel out the track, and as its afternoon for Rd Atlanta, it was morning for Watkins, so i will pick a few psi levels.and after a few prac runs, I will pick the best, even if the best is still a little loose, then I don't change it for prac, qualify or the race. 

When one psi setting is good at lets say 70-80F, we all know it might not be so great at 90-100F, you need to pick a psi that your comfortable with for the time of day, as you cannot go into the pits and keep changing psi every time it jumps up by 10F if your racing.
Its a hard call, doing at least 10 prac laps per psi set ups takes time, but its time worth doing.
I like running the same psi all round.
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Re: Tire Pressure Help!!!

Post by TRG » Wed Mar 27, 2019 8:55 am

When you say you pick the best pressure, how does one decide what the best is?
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Rem Ambruosi
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Re: Tire Pressure Help!!!

Post by Rem Ambruosi » Wed Mar 27, 2019 9:36 am

TRG wrote: When you say you pick the best pressure, how does one decide what the best is?
Testing, Testing , Testing  ,and its all about how it feels for the individual driver, Erik says he uses 19psi, it works for him, but that might not be any good for you, I don't use 19psi
I really go by what time of the day it is, in my view air temps also play a part in deciding pressures, so its all about testing in the same condition as race conditions , usually pressures between the 19psi-22psi, I feel anything under or over is a bit of a waste of time, but  hey that's just my opinion.
I use a different psi for morning, afternoon , late afternoon and night, mostly due to different air temps.
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Re: Tire Pressure Help!!!

Post by TRG » Wed Mar 27, 2019 9:45 am

Makes sense. Thanks Rem.

I was curious if there was any analytical way to sort it out based on hot pressures, temps, or other telemetry. Scientific methods are always easier in my mind.
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Rem Ambruosi
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Re: Tire Pressure Help!!!

Post by Rem Ambruosi » Wed Mar 27, 2019 9:57 am

TRG wrote: Makes sense. Thanks Rem.

I was curious if there was any analytical way to sort it out based on hot pressures, temps, or other telemetry. Scientific methods are always easier in my mind.
I'm on the other end of the scale, I use the KISS method  (Keep It Simple Stupid) lol
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MattMiles44
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Re: Tire Pressure Help!!!

Post by MattMiles44 » Wed Mar 27, 2019 1:33 pm

Thanks guys, just gotta keep trying to feel it out. think I found my pressures for tomorrow, just hope tread won't fall off after a few laps. Good luck tomorrow!
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Re: Tire Pressure Help!!!

Post by TRG » Wed Mar 27, 2019 1:36 pm

I can't wait for iracing to implement different compounds....
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Re: Tire Pressure Help!!!

Post by SharkV » Wed Mar 27, 2019 4:08 pm

TRG wrote: I can't wait for iracing to implement different compounds....
I think Only F1 and  Indy has different compounds 
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Re: Tire Pressure Help!!!

Post by crich88848 » Wed Mar 27, 2019 6:55 pm

SharkV wrote:
TRG wrote: I can't wait for iracing to implement different compounds....
I think Only F1 and  Indy has different compounds 
Danny.. we don't use that four letter word. Might cause Paul to relapse.
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Re: Tire Pressure Help!!!

Post by paulwildridge » Thu Mar 28, 2019 8:15 am

WE SHOULD RACE INDYCAR NEXT SEASON!!!!!!!
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Re: Tire Pressure Help!!!

Post by TheGreatC81 » Thu Apr 04, 2019 10:36 am

Ok, I'm confused. I was told several times that until the new tire model comes out, we should run the lowest pressure we can. Is that not the case with the Radical? I'm used to GT cars.
I usually look for an operating pressure of around 21.5 psi. To get there I have the Radical at 16-16.5 psi all around. It takes a couple laps to get up to temp and pressure, but once there it feels pretty good. (To me anyway, but what do I know?) 
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