Tire pressures and temperatures at the track

[ayao]

Sorry to intrude here -- I'm a 1M guy over at 1addicts but follow some of the threads here as it seems there's a larger tracking population here. I wanted to run some of the numbers by forum folk here to see if I could glean any useful advice.

My first HDPE of the year was with HOD at Thunderhill in the intermediate run group (for the first time.)

Big O Tires was out there with a crew of people offering free nitrogen flushes in addition to tire pressure measurements/adjustments and pyrometer readings. I stopped by immediately after each track session primarily because I've been recently obsessed with the idea of camber plates and whether I need them for the car.

Relevant info is as follows:
-staggered 245/40/18 - 265/40/18 on OEM M3 18" wheels on factory PS2s
-35 psi cold all around
-tires have maybe 7,500 miles and 3 HPDEs on them
-stock suspension
-starting ambient temps were 60F warming up to 80F as the day progressed
-20-25 minute sessions, counterclockwise direction
-MDM mode
-RBF600 fluid and PFC08 pads

Session #1
LF temp (outer/middle/inner) - 98/102/101; 40 psi
RF temp (inner/middle/outer) - 103/102/104; 41 psi
LR temp (out/mid/inn) - 97/95/96; 40 psi
RR temp (inn/mid/out) - 96/97/100; 40 psi
-tires were purged with nitrogen and pressures adjusted to 34 psi front / 30 psi rear

Session #2
LF (out/mid/inn) - 130/128/125; 36 psi
RF (inn/mid/out) - 128/132/134; 37 psi
LR (out/mid/inn) - 122/126/129; 33 psi
RR (inn/mid/out) - 128/128/125; 33 psi

Session #3
LF (out/mid/inn) - 128/130/128; 37 psi
RF (inn/mid/out) - 134/143/142; 37 psi
LR (out/mid/inn) - 125/129/132; 33 psi
RR (inn/mid/out) - 134/133/133; 33 psi
-front tire pressures reduced to 35 psi

Session #4
LF (out/mid/inn) - 149/152/152; 37 psi
RF (inn/mid/out) - 155/162/157; 36 psi
LR (out/mid/inn) - 142/150/152; 34 psi
RR (inn/mid/out) - 152/151/149; 34 psi
-front tires pressures reduced to 35 psi

I didn't bother getting measurements after the 5th session. Session #1, the tires felt great. With each subsequent session the tires felt progressively greasy and slippery. Session #4 just felt like a disaster. (Session #5 was salvaged by dialing back the pace and paying more attention to smoothness and consistency.)

I'm trying to reason through the data and don't have enough experience to draw even broad-brushstroke conclusions about car setup or driving deficiencies.

My analysis of the data:
1. right-sided temperatures are higher than the left, since we were driving the track in a counter-clockwise direction
2. no problems with RR camber given relatively even temperature distribution
3. LR inner temps are higher than outer temps given the direction the track was driven -- (is a 10 degree temp difference significant or acceptable given the track configuration?)
4. Tire pressures seem more consistent with nitrogen

My conclusions are that I need to burn through these PS2s. (Incidentally, tire pressures the following morning were about 28 psi cold.) They're great on the street but no good for the track. After that I'm hoping that AD08s in the same stock sizes will be a reasonable next step. My impression is that camber plates won't offer very much at this point.

I'd greatly appreciate any insight the track warriors on the forum have to offer.

[chili cheese]

I won't comment on the specifics of each tire's temp and the track you ran.

However, your conclusion is correct. The PS2s are not for track duty. Even with camber plates, they will get greasy after a few laps. The AD08 is a nice double duty street/track tire. Many people are having good luck with them in this regard. Adding camber plates with the AD08s will help things further.

Good luck!

[Richard@M-World]

Here is a document which may help you get a basic understanding of adjusting alignment and pressure to control tire temperatures.

http://www.tirerack.com/tires/tirete...nd_Feeding.pdf

Tire temperatures change rapidly as you go through different sections of the track; therefore there is a very limited window to get a meaningful measurement of tire temperatures. You should be doing multiple, consistent HOT laps (measure using lap times), and then immediately go into the hot pit to take measurements. If you cooled down for even half a lap, the temperature data would not be very useful.

On a properly driven 1M/M3 with stock suspension, you should be seeing much higher temperatures on the outer edge of each tire. Your temperatures are very even across the width of each tire which makes me wonder if you waited too long to get your measurements.

[Raucky2000]

^Ditto on the tire temps, but a good start to taking notes and keeping track for next time.

[ayao]

Originally Posted by Richard@M-World

Here is a document which may help you get a basic understanding of adjusting alignment and pressure to control tire temperatures.

http://www.tirerack.com/tires/tirete...nd_Feeding.pdf

Tire temperatures change rapidly as you go through different sections of the track; therefore there is a very limited window to get a meaningful measurement of tire temperatures. You should be doing multiple, consistent HOT laps (measure using lap times), and then immediately go into the hot pit to take measurements. If you cooled down for even half a lap, the temperature data would not be very useful.

On a properly driven 1M/M3 with stock suspension, you should be seeing much higher temperatures on the outer edge of each tire. Your temperatures are very even across the width of each tire which makes me wonder if you waited too long to get your measurements.

Thanks for the link. Much of it is not as intuitive as I'd like -- still lots to learn.
From your description of proper tire temperature checks it is apparent that I waited much too long to obtain the temperature data. I generally did at least half a cooldown lap in addition to some waiting in line to get measurements taken. One of the guys said that he likes to see even temps across the tire. Is this an accurate statement?

In any event I'm likely getting a little ahead of myself trying to analyze this data when I should probably be focusing on smooth inputs and enjoying myself on the track.

[Porschefile]

Originally Posted by Richard@M-World

On a properly driven 1M/M3 with stock suspension, you should be seeing much higher temperatures on the outer edge of each tire. Your temperatures are very even across the width of each tire which makes me wonder if you waited too long to get your measurements.

For sure! and the outside edges will be gone in 1-2 days unless you're running less than 9/10 or so.

[Richbot]

+1, if you're doing a cooldown lap the temps are pretty much useless. If I want good temp data I come in during a hot lap and make sure the crew knows I'm coming, and have them start with the most critical (outside) tires first

[Richard@M-World]

Originally Posted by ayao

Thanks for the link. Much of it is not as intuitive as I'd like -- still lots to learn.
From your description of proper tire temperature checks it is apparent that I waited much too long to obtain the temperature data. I generally did at least half a cooldown lap in addition to some waiting in line to get measurements taken. One of the guys said that he likes to see even temps across the tire. Is this an accurate statement?

In any event I'm likely getting a little ahead of myself trying to analyze this data when I should probably be focusing on smooth inputs and enjoying myself on the track.

Yes. Typically a 10 degree F difference across the tire is considered optimal.

If you are serious about this, what you need is a contact pyrometer (the device in the middle).

But if you are new to the race track... just enjoy driving

[admranger]

Originally Posted by Richbot

+1, if you're doing a cooldown lap the temps are pretty much useless. If I want good temp data I come in during a hot lap and make sure the crew knows I'm coming, and have them start with the most critical (outside) tires first

As usual, I'm in agreement with Richbot. Tire temps after a cooldown lap are pretty useless, especially if you use an infrared pyrometer. Probe type are best (I had the Longacre one that recorded the four tires w/o having to write anything down...team owner/wife liked it).

BTW: NASA's online magazine has a great article on tire temps and a downloadable spreadsheet that does some nice calcs to help you determine what to do to get the temps where they need to be. www.nasaproracing.com You might have to be a member to get it, but from what I've seen so far it is worth the cost of membership. Very nicely done.

I'll concur that the PS2's suck ass on the track. They spit me off track for my first time ever as a student/instructor. They got hot and then they were gonzo w/o the hint of a squeak, squeal, or squawk. Just went from traction to no traction. Nice. Good thing they were almost gone b/c they went off the car as soon as some new RE11's showed up at Costco. You can't beat the RE11 for a dual duty tire, except they cost a bit...

Be smooth. Be fast. Be safe.

[bigjae1976]

I don't think tire temps are useful in the HPDE format.

If the main concern is tire life (aka how fast will I ruin my tires), I take tread depth readings before and after the event and then I take hot pressures after coming off track.

But why did you continue to run the rear temps lower throughout the day. I would have went with 34psi all around from the start. Maybe 34fr/33rr if you have MDM on or a twitchy right foot.

Originally Posted by admranger

BTW: NASA's online magazine has a great article on tire temps and a downloadable spreadsheet that does some nice calcs to help you determine what to do to get the temps where they need to be. www.nasaproracing.com You might have to be a member to get it, but from what I've seen so far it is worth the cost of membership. Very nicely done.

Hmm...that would be awesome so I'm not showing up to the track guessing and then running the latter half of my sessions with NT01s being overinflated and somewhat more skittish. The Hankook RS3s really spoiled me. They did really well from 35psi - 42psi, very little difference in grip.

[ayao]

Originally Posted by bigjae1976

I don't think tire temps are useful in the HPDE format.

If the main concern is tire life (aka how fast will I ruin my tires), I take tread depth readings before and after the event and then I take hot pressures after coming off track.

But why did you continue to run the rear temps lower throughout the day. I would have went with 34psi all around from the start. Maybe 34fr/33rr if you have MDM on or a twitchy right foot.

I think my general concern (possibly unfounded) is tire temps pointing to camber issues leading to accelerated tire wear.

The tire guy convinced me that it would be reasonable to run the rear temps lower than the fronts to decrease understeer. It generally made sense to me. However, I am not convinced that I felt an iota of difference; any benefits may have been obscured by the ensuing greasy slip-and-slide feeling.

[bigjae1976]

If tire life is a concern, I think most will find that around -2.5 camber in the front with a sticky street tire will be close to optimal. I'm at -2.2 camber which I think is my optimal #.

[admranger]

Originally Posted by bigjae1976

If tire life is a concern, I think most will find that around -2.5 camber in the front with a sticky street tire will be close to optimal. I'm at -2.2 camber which I think is my optimal #.

I assume you are lowered or have camber plates? I'd love to get 2.2 neg camber, but I'm no where near that in stock form w/the pins pulled and the struts slammed as far in as they'll go.

[ayao]

Originally Posted by bigjae1976

If tire life is a concern, I think most will find that around -2.5 camber in the front with a sticky street tire will be close to optimal. I'm at -2.2 camber which I think is my optimal #.

Are you switching camber settings for the track or just leaving it as is for street and track?

[bigjae1976]

I have GC plates with dinan springs so I'm at the OEM ZCP height. I would get the Vorshlag plates if you can, they are better built.

Yes, I have my camber plates and tie rods marked. I put on track tires and brake pads at the track. So it takes another 3 minutes or so to change the camber and toe. I think Paradocs just adjusts one tie rod but he's if you are really lazy. That causes your wheel to be off center for one setting. I adjust both sides so my wheel is always centered...because I'm like that.

[admranger]

Depending on how much camber you are adding, you *can* set it up so that when you move the struts in towards the center for the track day, you get just the perfect toe for the track too (zero toe). Slap them back for the street settings and you have toe-in for the street which helps make the car more 'driveable' in every day situations. Take some time with a set of Longacre toe plates and your iPhone smartlevel app and you can find a happy medium.