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PSI for track days

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staynhome29

Ready to race!
So I was experimenting with psi for my weekend track day as I got a lot of useful information from some pretty competitive FWD racers.

They basically said to run a slightly higher psi in the rear and less in the front so that the rear loses grip and the front gains grip. This induces some lift induced oversteer (a tad) but nonethless some controllable oversteer.

When my buddy was behind me, he thought I was about to spin as my rear would come loose but my fronts kept pulling me forward.

I beat my personal best lap time by 1.8 seconds and the car rotates so much better.

I ran 31 > 36 cold psi on starspecs 225/45/17.

FYI
 
Deaks2

Deaks2

Ready to race!
Good tip. It's also important to re-adjust your pressures between track runs in order to avoid cooking your tires.
 
Gunkata

Gunkata

Drag Race Newbie
31 seems a tad low in the front, but it sounds like it worked well. I'd rather have some oversteer than under. I will have to try this for my track day on saturday. Thanks for posting.
 
RacingManiac

RacingManiac

Drag Race Newbie
The front PSI is sorta a compromise between steering feel/reaction vs outright grip. Lower PSI(to a point) will give you more grip(bigger patch)....but the trade off is obviously transient response....
 
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staynhome29

Ready to race!
RacingManiac said:
The front PSI is sorta a compromise between steering feel/reaction vs outright grip. Lower PSI(to a point) will give you more grip(bigger patch)....but the trade off is obviously transient response....
Click to expand...

The starspecs have pretty stiff sidwalls so you can get away with slightly lower psI.

More important than the cold psi is the hot psi. Usually I never do a cool down lap and just book it in so I can measure the psi when the tire is still really hot. Have to constantly adjust to maintain that correct psi throughout the day.

I do have a big RSB so that coupled with the psi really helped rotate the car better.

Let me know if it works.
 
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PandaGTI

Go Kart Champion
I've never done this cause I'm just too lazy... But try chalking the tires to see at what psi do you start to get roll over on the side walls... That will give a better idea of what psi to run at cause it's different for each tire.

At 31 psi your side walls may have gotten really hot making the tires feel greasy
 
Gunkata

Gunkata

Drag Race Newbie
xHeartcoreboyx said:
I miss the star specs from my previous car, noisy mofos though!
Click to expand...

lol - YES. so noisy I had to sell mine immediately. I couldn't handle it for DD, absolutely ridiculous. Dedicated track tires, sure, street driving - hell no for me.
 
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carsfeverguy

Go Kart Champion
Hey guys,
I'm on Hankooks Ventus v12s 18/225s
Did a track day on Mosport in July. Have one coming up end of August.

My cold psi at the begining of the day was 35PSI all around.
After the session, it got to around 40.

Driver side front seems to have a lot more roll marks on it...
Also, traction seemed to get lower as the session progressed...

So, How do I avoid tire roll, presumably from lower psi and overdriving, and avoid the greassy feeling of overinflated tires?


Should I have a stagered front to back as well as side to side psi's?

Like lets say Warm PSI's

FL: 35 FR: 33 RL: 38 RR: 38


Mosport has a lot of High speed and hard righthanders.. but also a very treacherous left turn 2.
 
RacingManiac

RacingManiac

Drag Race Newbie
Mosport is definitely an asymmetric setup track. Turn 1, 3, 8 are all really fast right hander, 5a/b is a right leads to a longest "straight", and turn 10 leads into the fast(momentum critical) turn 1-3. So yeah, left side grip and balance is very important....

If you have the front tire roll over a lot, then you need to run higher PSI as you really don't want to be cornering on your sidewall. Add more rear PSI if you have to tune understeer out...

As far as decreasing grip, aside from PSI change, the tolerance for heat build up for road tire is not that high....up to some point you just have to have them cool down....
 
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PandaGTI

Go Kart Champion
Best way to figure out PSI is to chalk the side walls and figure out what is the lowest pressure you can run before the side wall rolls over by watching the chalk rub off...
 
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staynhome29

Ready to race!
PandaGTI said:
Best way to figure out PSI is to chalk the side walls and figure out what is the lowest pressure you can run before the side wall rolls over by watching the chalk rub off...
Click to expand...

I've gone as low as 29 psi cold on a70degree day and I was good. No rollover on star specs.

I'm close to the edge though by a few millimeters.

Also try apexing a tad early, trail brake mid turn and then hammer throttle. Rotates the car easier that way.

I'm glad we have more track junkies on this forum.


Now if only we can beat the civics and s2000 on the track....
 
RacingManiac

RacingManiac

Drag Race Newbie
Went down to 30 PSI cold on my stock Pirelli(yes I am still using that...) for autoX today, was definitely too low, the tire rolled over and was plowing like a snow plow...:D

33PSI is the limit then....
 
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