TKOGTO

I did.

Used them for the 1st time last week @ WGI (on stock wheels). On day 1 in the low 60s and overcast, psi got to 42 after ~20mins on the front left, 39 everywhere else (started @ 29 in front, 30 in rear). At these levels the grip level declined dramatically. On day 2 at ~67-68 F*, it took less than 15min for the tires to become greasy to the point of being dangerous. PSIs did not get as high and in each instance there was only 1 hour between runs. When sessions were 90-120 mins apart, the PSIs still increased 9-13 but took longer to get there.

Is this common for the NT01s?

I did not experience nearly as much psi increase with R888s and only on the hottest of days (90+F*, high humidity) did they materially give up grip during a session.

blkbrd69

If you have any moisture in tire pressures will increase much more than normal. Tire shop getting carried away with lube can cause this as well as portable pumps.

Try purging with dry air or better nitrogen. 10 psi is normal, I have to start at 1psi below low pressure warning with tires warm. They tend to go up a few psi just driving to the staging lanes and idling.

davidfarmer

I agree with above, tire pressure is determined by gas laws not tire compound. Drain and vacuum your tires if your shop installs them wet, and refill a few times with nitrogen or dry air

FASTFATBOY

If you're building over 5-6 psi a session, lower the start pressures until you get into that window.

jlutherva

I use nitrogen and my tires go up 4 psi in mild weather. Another alternative to reducing moisture is to ask the tire shop to use hairspray rather that the soap solution. OK, maybe it's not hairspray; it is labeled specifically for mounting tires, but sure as heck smells like hairspray.
Cheers,
Jim

bj1888

It doesn't help that you had low starting temps to begin with. The amount of air required to hit 29 psi at 60 degrees is a lot more than what's required to get 29 psi at 80+ degrees ambient temperature. When it's cooler, you're going to need to move your cold pressure down to compensate for air density changes.

TKOGTO

Got it.

Thanks guys.

Mordeth

Terry, is that you? If so, I have video/data from that session and can post/send it if you want. I was in the blue C6Z, also on NT01. You passed me at the beginning of the session around lap 2 or 3. You were definitely faster than me. Then I passed you around lap 4 once my tires warmed up and you got squirmy. I think your tires were already hot/high pressure when you went out, and by the 3rd or 4th lap I bet those tires were at 40+psi. We were running laps around 2:09. After I passed you, you kept up for 1 lap then I didn't see you anymore.

Here is what I do and am able to manage the NT01 pretty well. I realize that there are more variables at play here but this is what works for me.

Target hot: 37psi

1st session: Start both right tires at 29 psi and both left at 28psi. End of session I look at them on the DIC on the out-lap/pit-in. Once I get into the garage I adjust them all to 35psi (they are all around 36-37 psi usually) so I take out 2-3 psi. I go to 35 psi after the first session as I know the day will get warmer and the track will get hot.

Sessions 2-4: After each session I immediately check psi on the DIC during pit-in and with my tire pressure sensor in garage. Anything over 37 is taken down to that level. I usually have to adjust 1-2psi for each session. I think this is the critical step. Continually adjusting the pressure down to the target immediately following each session. I can usually get them to all be at 37psi HOT by the end of the day.

When I go home and get up the next morning, the right tires are around 24psi cold and the left around 22psi cold. Theoretically, this could be my starting psi at the beginning of the day. But I don't like going out with pressure that low so I work my way down, always targeting 37psi, which for me works good for these tires.

TKOGTO

Yes, Anthony it is. First off, thanks again for your help with the cracked rotor. No way DeWayne or I were getting that caliper off without you doing all the heavy lifting.

Second, WTF were they doing putting you in Novice to start? You were quicker than 50% of the guys in the ADV group even if you include the Kohr Autosports Mustangs and the Elan prototypes that didn't crash ruining a session each day. I can't imagine how fast you would be going @ the end of the back straight in that C7 Z06 in your avatar if you're hitting close to 160mph in your C6 Z.

Third, as suggested above, there must have been a moisture issue in my tires for them to have acted as they did. They were new and the local Town Fair Tire that mounts them is not exactly a race shop. They're good guys and they don't scratch the wheels but they're not thinking about keeping the moisture level to a minimum. I will hit Costco before my next track day with the Vette (@ WGI w/ SCDA in July if you're interested) to get the nitrogen service. I will also follow your advice re: setting psi's before and after, adjusting for the nitrogen.

With the R888s and even MPSS', I have noticed excellent grip right up to 36-37. At 38, each started to go away. At 39, it was not possible to approach a personal best. In the 2nd to last lap we ran together, the AH (Comp Mode) kicked in hard on the entry to T7. I had been over driving that entry for 2 days so I just thought I did it again trying to keep pace with you. When it happened again in T6, T7 and T8 of the next lap, I knew the tires were toast.

PM me your email address and I will send you the SW trace thru T8 from several different laps. You can see the huge increase in angle needed to take the same line at the same speed once the tires went away.

Mordeth

I will be at the SCDA event @ the Glen in July! So I will see you then Terry! I will PM you my email.

Also, with Nitrogen, it does work but as soon as you add back in regular air the benefit is mostly lost. But certainly worth a shot!

crimlwC6

I start NT01s at 24 to 26 cold and race then in 25 minute races.