I'd love to know what kind of tires that folks were running at the last Flag event and how they performed in the morning versus the afternoon.
A couple of data points that I know are
I was running Kumho 710's on a CSP Miata and was over a second slower on Saturday afternoon than Saturday morning.
Brian Peters was also on 710's (CSP Miata) and ran withing .1 second of his morning time. He might be an alien according to some. I believe he had FTD for Saturday.
On Sunday we went to street tires in the afternoon and Dave Lahey ran about the same time in a CS Miata (thanks matt) on Kumho street tires as he did on 710s in a CSP Miata in the morning.
I had timing problems in the afternoon in Matt's car and didn't take the rerun but the stick felt better on the street tires than the 710's I even ran two runs in Dave's 1.6 Miata with some kind of street tire that had fallen off one of Dave's myriad of Miatas so he could have an a/c car to drive from Phoenix to Flag. Even these tires were more fun to drive than the 710s had been on the last couple of runs in the morning. I ran in B group so my last two runs were after the course had been run 4 times by group A and twice by group B. Really rambling here but please put in your $.02. We may end up with a "Afternoon FLAG" spec tire --- LOL

i would have to say that it seems that in the heat, the Flagstaff lot is better on Street Tires (or AWD)! not so sure about the morning, maybe they are quicker then, too? nah, can't be. once that tar starts seeping up out of the asphalt, R tires are toast, and Street Tires Rule! one thing i noticed on Matt's car (and thanks again!), was that they picked up this goo, probably making them stickier than they had been? all conjecture, as i pretty much drove like chit all weekend. well, except for that ONE run in Matt's car. (0.005 quicker than the owner, last run!) btw, Steve, those are BFG Sport something-or-others on the red car. too bad the anemic 1.6 is even worse in the altitude! time to swap on some Azenis!

Brad ran my car with 710s in morning A group. He and Dave were within .016 seconds if I recall.

My first run in the morning B group was over a second off of Brad. Every subsequent run I had was slower. My car has never felt that undriveable. I had trouble putting power down and trying to carry any kind of speed into corners. I basically coasted most of my runs

In the afternoon A group, Brad was 1-2 seconds off his morning times and I think he was getting slower with every run. After my first two runs in the afternoon I went slower and was frustrated. I put my street tires on (205/50/15 azenis) and my third run was about 3.5 seconds faster than my 2nd afternoon run. My 4th run was my top time of day.

FWIW, my 710s were over 2 years old and I have no idea how many runs are on them ~150? Point being my tires were far from optimal.
Here's another thing to consider, last year I had fresh V710s on my (CS) car and the grip on the lot was good. Dave, you and Don both did well in your csp car too.

I think the biggest problem was all the loose gravel being tracked into the skidpad from grid. Anyway, I hope to be able to try out my fresh 710s in Flagstaff next month

i was running 265 bfg kdw's in my awd evo and it was doing great in the morning but after lunch when it was starting to get hott my tires just werent there, i drifted most of the track my last few runs saturday and spun out on a very easy corner late sunday. so i say that pretty much when the tar comes out everyone is screwed lol

yes, but last year we got rain mid-day which cooled things down. no rain this year (yet!), and very little cloud cover. also, even though the Flagstaff guys were wiping off tires just before the start (and thanks for the effort!), and sweeping the start, it made no noticeable difference.

FTD both days last year was neat too! not to blow my own horn or anything... this year, nothing even close to that. different car? different weather? surface? who knows. but the CS car on MX tires was the most fun to drive, that is for sure!

It was like running 4 different events. Sat morning on 710s was OK, once I got through the first left hand turn and the worst of the gravel. Sat afternoon was just plain weird but I managed to turn some times close to my best morning time - but just don't ask me how because I don't know either. The amount of slipping, both controlled and uncontrolled reminded me of my off-road motor cycling days. My tires, especially the fronts, look like scabbed over burn victims. I think I'm going to have to drive them around on the street before the next event to try and scrub some of that gunk off. Still, it was fun. I'm not so good at courses that invite extended use of first gear, so it was good practice.

Sunday I opted for my street tires (Azenis 615) . Being in the first run group was a blessing but the traction went away after my second run. The afternoon was like being on a different course. I changed my lines in most of the turns to draw a long an arc as possible to keep momentum up. Weird thing is that my best time was my last run where I was just trying to conserve momentum, be smooth and tried to knock a couple apex cones down. There's a lesson there, but I'm sure I'll forget it by the next event.

I just went through my accelerometer data. It is difficult to tell due to slight variations between runs, but it looks like the sweepers lost about 5% grip in the afternoon--At least on my Hoosier A3S05s. My tires looked normal after the morning runs, but they were finishing with a tar glaze in the afternoons.

I could not beat the times I ran in the morning (second runs were fastest on both days), although I did get within ~0.05sec on an afternoon run. On Sunday, double apexing the left sweeper at the grid side of the loop seemed to find a little more grip in the afternoon. Presumably from running a 'less abused' line.

Team "PAX Multiplier, don't fail me now!"

I didn't run in the afternoon on Saturday but I'll chip in anyway. I ran Kumho MXs.

I did finish the day with a few hints of tar glaze on the tires. I ran in B group. I do know that I went from almost no oversteer on my first run to nearly cooking the finish on my last run. That could be a combination of me pushing hard and being able to get heat in the fronts and not in the rears.

I'm not quite sure how tar could make street tires faster than R tires. Even if the tar effectively increased the coefficient of friction for a street tire but was slippery enough to cause an R tire to have an effective decrease in its coefficient of friction, in theory the worst that could happen would be that the two would equal each other; and even then, the R tires (at least the 710s and Hoosiers) are basically slicks and provide a larger contact patch.

I'm gonna go with Kevin and say the biggest problem was gravel. R tires pick up more of it and generally don't have any void space in the tread design to hide it; if you roll over some, it is pretty much guaranteed to get on the surface and interfere with the tire contact on the pavement. Street tires, not so much.

Someone correct me if I'm wrong...

The gravel definitely had an effect. Even I was having wheelspin at the start.

However, the course had the same afternoon grip loss on Sunday. They moved the grid to the clean lot up the hill (above Saturday's first left turn), so there was much less gravel on the course. And, instead of having one household broom to clean the course, they brought a leaf blower.

I’ll chime in here but keep in mind that I was on two and half year old Hoosier SO4’s (aka Crap) tires. The morning sessions on both days produced my best times -- check that -- the morning session on Sat and my first run in the morning on Sunday produced my best runs. In the afternoon on Sat I got progressively slower. By the last run I think I could have walked the course faster? My tires were glazed over and had tons on tar and gravel on them. On Sunday I lowered the front end to try and get some much needed grip and even did a few figure eights before the course was setup to scrub off some of the tire crap, but it didn’t help much. My first run was my best and like Saturday I again got progressively slower. Didn’t bother with the afternoon session. Next month I’ll bring the street tires just in case, they seemed to work for everyone else.

It wasn't the gravel that was causing the major issues, but something unique to the lot sealant. I also had gunk on my tires following the afternoon session, but not as bad as those people that ran in the afternoon A group (when the surface was the hottest).

It's probably not a coincidence that I nearly matched my best morning run on my first afternoon run, as the car became more "challenging" with each consecutive run. That said, I don't think I slowed much more than 0.5 sec from my best, even with a passenger. So it doesn't appear that my car/tires fell off as much as some others.

Street tires most likely didn't suffer as much pickup simply because they weren't as sticky to begin with. I'd wager the guys that were heating their tires up more were getting even more gunk on them.

i know my street tires were covered in lot sealant and made them appear to look sticky but when they got out there were slippery as hell. so i think every one pretty much suffered from the lot sealant race or street tires

The Cooper Cobra street tires on my Mg actually didn't work until they got really hot. Afternoon runs and the final pass were about my best times. My question is what air pressure work best for everyone as I was down to 24 psi by Sunday afternoon and Mark came over and told me it looked like I was getting a flat. They did look a little soft.

Guy

I was running RT-615's and I found that I shed 2 seconds off my morning time when things started to warm up. Or was it that all that afternoon wind cleaned off the loose stuff before the last group?