[Homeless Junkie]

I ran my tires at 30 psi at the beginning of every session last weekend. I check before I go out on track every time. Seems to work well.

[TrackClub]

Originally Posted by TheRealJA105

In your experience, if you air them back down to 28psi when they are still warm, how much lower do the pressures stay in the next session? If I can gain more time I'm all about it! Perhaps I should just try something new and see if I improve, get worse, or no difference at all?

I see where we missed each other

I do NOT lower them to 28 after each run, but rather to 36 which is about the top hot temp i like (and maybe even less based on actual wear).

So if i come in first run and they are at say 38 i lower to 36. If i come in after a second run and they are 36 i leave them. But most often they will continue to climb past the 36 mark for the first 2 or 3 runs and require bleeding down to 36. Then they usually settle on 35/36 hot for the rest of the day (once the ambient temps stop increasing). Hope this clarifies. Cheers!

[TheRealJA105]

Got ya, but I wonder how many psi you have already dropped with a good cool down lap? Do you ever check the DIC right at the end of your hot laps? That's what I'm going to try to remember to do.

Most times I don't even go right back to my pit and continue to drive around for more cooling after the cool down lap because the brakes and wheels are still so hot.

[TrackClub]

Originally Posted by TheRealJA105

Got ya, but I wonder how many psi you have already dropped with a good cool down lap? Do you ever check the DIC right at the end of your hot laps? That's what I'm going to try to remember to do.

Most times I don't even go right back to my pit and continue to drive around for more cooling after the cool down lap because the brakes and wheels are still so hot.

I mostly ignore DIC as it seems somewhat unreliable vs my gauge. Surely the tires will cool down some on an in lap and so much more the reason to bleed them if they show over 36 (or whatever works on a given day and track). So, I pit, leave the car running and check/bleed the pressures, THEN leave the hood ajar and drive around (paddock/access road) to speed up cooling of motor, brakes etc. Then park and open hood fully. So just like you, but in a different order

[Snakebt6]

Originally Posted by TheRealJA105

Got ya, but I wonder how many psi you have already dropped with a good cool down lap? Do you ever check the DIC right at the end of your hot laps? That's what I'm going to try to remember to do.

Most times I don't even go right back to my pit and continue to drive around for more cooling after the cool down lap because the brakes and wheels are still so hot.

Look at my readings on the previous page to give you an idea.

Pressures were pretty close on my gauge to what the car was showing as well when I pitted.

[Norm Peterson]

Originally Posted by TheRealJA105

Got ya, but I wonder how many psi you have already dropped with a good cool down lap? Do you ever check the DIC right at the end of your hot laps? That's what I'm going to try to remember to do.

Most times I don't even go right back to my pit and continue to drive around for more cooling after the cool down lap because the brakes and wheels are still so hot.

I do much the same, and even if I put off checking tire pressures following session #1 they're never down to the warmish pressure that they started session #1 at. I've checked pressures within 15 minutes of my next session and they're still not all the way back down.

Tire tread surface temperature cools off far more rapidly than does the rubber temperature on the inside, and the air inside necessarily cools off more slowly than that. Meaning that the inflation pressure really isn't dropping as fast as a probe type tire pyrometer might suggest even though that's the better measure for tread temperature.

Rubber just isn't a very good conductor of heat, and aluminum wheels are going to be gaining heat from hot brake components for a while before they're cool enough to help pull heat out of the air inside the tire (instead of potentially pushing heat into that air).


Norm

[TheRealJA105]

Originally Posted by Snakebt6

Look at my readings on the previous page to give you an idea.

Pressures were pretty close on my gauge to what the car was showing as well when I pitted.

Thanks, I do wish i had the PDR for this stuff.

about .5-1.5 psi

Maybe I've been leaving time on the table by not bleeding between sessions, but I'm still skeptical because my first session is never the fastest. (Yes more practice, more seat time in same day, blah blah I understand why i get faster during a day)

[TrackClub]

Originally Posted by TheRealJA105

Thanks, I do wish i had the PDR for this stuff.

about .5-1.5 psi

Maybe I've been leaving time on the table by not bleeding between sessions, but I'm still skeptical because my first session is never the fastest. (Yes more practice, more seat time in same day, blah blah I understand why i get faster during a day)

Given your times on G3s (which make good sense given your skill and car mods), your Hoosier times should give ya a better delta imo. So perhaps there is pace to be gained by better tire management afterall. And maybe on both tires. Worth a try. Could be a nice surprise

[TheRealJA105]

Originally Posted by Norm Peterson

I do much the same, and even if I put off checking tire pressures following session #1 they're never down to the warmish pressure that they started session #1 at. I've checked pressures within 15 minutes of my next session and they're still not all the way back down.

Tire tread surface temperature cools off far more rapidly than does the rubber temperature on the inside, and the air inside necessarily cools off more slowly than that. Meaning that the inflation pressure really isn't dropping as fast as a probe type tire pyrometer might suggest even though that's the better measure for tread temperature.

Rubber just isn't a very good conductor of heat, and aluminum wheels are going to be gaining heat from hot brake components for a while before they're cool enough to help pull heat out of the air inside the tire (instead of potentially pushing heat into that air).


Norm

I agree with everything you said and that's my main reason for not bleeding between sessions, because you aren't getting cooled back down to cold pressure which is the simplest and best controlled set point. Ambient change should be accounted for and I am going to try to pay more attention to.

[TheRealJA105]

Originally Posted by TrackClub

Given your times on G3s (which make good sense given your skill and car mods), your Hoosier times should give ya a better delta imo. So perhaps there is pace to be gained by better tire management afterall. And maybe on both tires. Worth a try. Could be a nice surprise

Definitely worth a try!

I have some PZero scrubs btw not freshy Hoosiers.

[Norm Peterson]

Originally Posted by TheRealJA105

I agree with everything you said and that's my main reason for not bleeding between sessions, because you aren't getting cooled back down to cold pressure which is the simplest and best controlled set point. Ambient change should be accounted for and I am going to try to pay more attention to.

The way I see it, 1st session is kind of a throw-away session no matter where you start. Tire pressures are going to be either too low in the early laps or too high toward the end. This might be more of an issue on cooler days. So I've been trying a "little of each" approach for session 1, where I start my pressures about half as much below target as I expect to gain in pressure rise. If I expect to gain 6 psi and my target was 36, I'd most likely start out at 33.

That does put the pressures at the end of session 1 up above my target pressure. But at least I can bleed back down to maybe a psi or two below my target pressure depending on how long I put off doing so, and I'd rather bleed down from hot or at least 'warm' than from closer to 'cold' because that's where the conditions of the day are putting them. I'm still apt to be a psi or two past target by the end of session 2, so I usually make another adjustment, this time paying closer attention to whether it was the right side tires or the left side tires that gained more pressure.

Since I've had more best lap times of the day in session 2 than in any other session, that hasn't been a bad approach. But I may need to rethink the post-session 2 bleeding..


Norm

[TrackClub]

Good thoughts Norm. No matter what strategy one uses: tire pressure matters and every single pro team pays extremely close attention to it.

[Badmojo]

Yes, you are probably not driving hard enough. If that is the case, then focus on fundamentals. Keep the cold starting pressure at 28 PSI and adjust as needed during the day if pressures rise. Also verify your tire pressure gauge is accurate. TPMS is ok as an indicator, but you need an accurate hand held gauge. One of my TPMS is 1.5-2.0 PSI off. The tires handle dramatically different at 36 vs. 38 PSI. Don't go over 37 PSI hot.

Originally Posted by Snakebt6

When I was at Daytona last my tires never reached the targeted pressure per the performance supplement. 35-37psi. Temps were also shown in the green and normal. I believe I started at 30 PSI in all.

I'm assuming because I was not driving hard enough to build up enough pressure in them.

I'm going back Thursday. Is it that important to be at the targeted pressure as opposed to 34 or 35 psi?

I'm going to start with 32 psi this time and air down if I go over 37 but just curious if a pound or two lower makes a difference to what I'm feeling at a big open fast track like Daytona.

FYI on the other hand at the Firm I had no issue hitting the targeted pressures and "warm" temps.

Just curious how much I should focus on the tire pressures if I'm not reaching the targets at a place like Daytona.

Thanks

[Snakebt6]

Thanks,

I check with both yes.

I was 36 in the front and 38 in the back in the pits after each session. The Cosworth app showed the same when I got home and reviewed the data. (on the previous page.) Next time I go out ill make sure I'm no more then 37. I'm about 1/4" above the winged foot on the wear marks on both front and rear at those pressures.

Heres my 2nd session. Last lap starting at 13:50 was my fastest. It was fun but lots of traffic.