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View Full Version : What is it with hard/soft tyres in GT3 after patch 4.0?



Max Torque
12-02-2018, 09:56
Hey guys, I noticed that past patch 4.0 hard tyres seem not to be the best option even on higher track temperatures any more. I observed that on Imola, track temperature was 38 or 43C, but the car (488) was quite nervous on the rear. I asked in chat as I heard something about tyres being a subject to changes in patch 4.0. So they suggested softs, I tried it and it worked just fine. So what are the new "rules" for tyres? How hot needs the track to be for hards to be the better option? What beyond track temparature has to be considered?

Boneboys
12-02-2018, 10:01
Lk here, maybe this post is relevant...

http://forum.projectcarsgame.com/showthread.php?53613-GT3-car-balancing&p=1474685&viewfull=1#post1474685

CoproManiac
12-02-2018, 11:07
Not quite sure, but I had the same problem you had, also on Imola.
Prior to Patch 4.0 hards were to be used if the track temp was around 20 degrees or more. When Patch 4.0 was released, I did a 13 lap race on Monza on a 38 degrees track and my left tyres stayed around 90 degrees all the time, while my right tyres stayed around 75 degrees C.
http://forum.projectcarsgame.com/showthread.php?60829-PC-Patch-4-0-Discussion-thread&p=1472872&viewfull=1#post1472872

I'm not sure what the exact threshold is.

pferreirag60
12-02-2018, 12:00
I feel the same, but in my tests around nordschleife, with a track temp of 38c and Air temp of 25c, after 1 lap, the rear tires (Ferrari enzo- hard tires) after 85c they feel like driving in ice, not yet in red colour, but yellow at 85 and feel like Ice, even in third gear it looses traction badly. Sometimes i think that even at 75c the hard tires have no traction.

I tried the softs in Texas with the track variant, also with the Enzo, i think 42c on track, and I could mantain the tires almost at 85 maybe less, for 40 minutes without loosing to much traction, sometimes had to slow just a bit so i could had less temp, but after i could again push the car. So with an Ai 100:100 i could lap 0.700s faster than them.

KANETAKER
12-02-2018, 13:19
Question: If I increase the air pressure on the soft tires could I prevent them from overheating? Or do I have to use hard tires even if that means having less grip and being slower in lap times?

DozUK
12-02-2018, 13:36
Question: If I increase the air pressure on the soft tires could I prevent them from overheating? Or do I have to use hard tires even if that means having less grip and being slower in lap times?

If you increase the pressure you will slow down the overheating (Although not necessarily eradicate it) as there won't be as bigger patch of tyre in contact with the track however you will lose grip for exactly the same reason.

The hard compound doesn't always equate to slower lap times like you expect from F1 on tv. My advice is to have a track day on the track in same conditions and run 10 consistent laps in soft and again in hard compound and compare the results. You may be surprised by your findings, you may even get addicted to data analysis :)

OddTimer
12-02-2018, 13:37
Question: If I increase the air pressure on the soft tires could I prevent them from overheating? Or do I have to use hard tires even if that means having less grip and being slower in lap times?

based on York's video, overheating has to do with track temperature, tire compound and your driving style. Pressures can help a little bit, but not like PC1.

doing some racing at Monza. I've got better results on hards when track is at and above 40C, below that I am using softs, but more tests are required!

Max Torque
12-02-2018, 14:31
based on York's video, overheating has to do with track temperature, tire compound and your driving style. Pressures can help a little bit, but not like PC1.

doing some racing at Monza. I've got better results on hards when track is at and above 40C, below that I am using softs, but more tests are required!
Ok, prepatch car was undriveable under said conditions on softs.

KANETAKER
12-02-2018, 14:47
For now I have been doing a lot of races in Daytona Road with the Porsche 911 GT3, and what I have noticed is that despite being set the race in spring or summer (and with heat in the environment and asphalt), I have less grip with hard tires unlike how it was before patch 4.0 in which only soft tires were used if the race was set in Winter or at night. In contrast to using soft tires I have better grip, but instead after a few laps I do not know why I lose some grip in turn 4, and it gets worse when I tackle the "bus stop chicane" ... Because of this I no longer achieve I can even match my personal record of 1:45 high in race with the Porsche GT3 made with hard tires before the patch 1.4, now my best time is 1:46 high using soft tires.

I would have to carry out tests but using hard tires, but there is the problem that in the first laps they do not get warm enough to have a good grip, and although later the performance improves but I can not attack the track so hard at the start of the curves (as well as in curve 4 and in the "Bus Stop Chicane") because I notice that the car wants to go spinning (oversteer, less grip), even with TC activated.

MaXyM
12-02-2018, 16:14
I'm really confused with those tires.
Being initially convincing (after patch3) about their realistic behaviour, right now those tires are close to what I think is proper. The only one thing I think is a bit off: a wear, especially in higher temps.
Yesterday we did 1h race (GT3@BrandsHatch) with 35*C-40*C of track temp. Soft tires was performing very well reaching about 105*C-110C while pushing hard and lasted for a whole race without need to change, because final wear was about 50%.

Is such little wear proper?

Rodders
12-02-2018, 16:15
Initial use of the new soft and hard dynamics I'm finding softs better only for a few laps if the temp is roughly 70F or above but for the race hards still best - more consistent - unless the track temp is 70 or under. The softs lose lateral grip badly when they heat up too much which leads to understeer or oversteer depending - and usually when you don't expect it so hards still seem to be a safer bet for the race. A few races now I've done qualy on softs and the race on hards. Depends on the car and track too. It's good to have softs more useable now and having a decision to make on race compound.

As you say KANE, the hards are worse for the first few laps but then they settle into running temp and pressure and are more consistent for use during a race. I had 2 races where the other 2 drivers up front stuck with softs for the race and after a few laps I could see they were struggling where I wasn't and I went on to win comfortably. Track temp was between 70-80F in both instances.

In PCars 1 getting tyres at the right temp was most important, in PCars 2 it's all about the pressure. You will only make a small diff to temps by lowering or increasing tyre pressure; unlikely enough to stop a tyre going from overheated or too cool to optimal - pressure on the other hand is vital. A few PSI over optimal and the tyres lose a huge amount of grip. It's like being on a severally overheated tyre and it's much easier to get tyres at optimal pressure for any given race conditions.

In fact in general I'll lower the pressure on a tyre for a hot track and raise it for a cold track to keep pressure optimal.

Rodders
12-02-2018, 16:16
I'm really confused with those tires.
Being initially convincing (after patch3) about their realistic behaviour, right now those tires are close to what I think is proper. The only one thing I think is a bit off: a wear, especially in higher temps.
Yesterday we did 1h race (GT3@BrandsHatch) with 35*C-40*C of track temp. Soft tires was performing very well reaching about 105*C-110C while pushing hard and lasted for a whole race without need to change, because final wear was about 50%.

Is such little wear proper?

I agree wear seems too low atm, especially on softs. Tyre wear is barely a concern anymore.

Max Torque
12-02-2018, 17:23
Initial use of the new soft and hard dynamics I'm finding softs better only for a few laps if the temp is roughly 70F or above but for the race hards still best - more consistent - unless the track temp is 70 or under. The softs lose lateral grip badly when they heat up too much which leads to understeer or oversteer depending - and usually when you don't expect it so hards still seem to be a safer bet for the race. A few races now I've done qualy on softs and the race on hards. Depends on the car and track too. It's good to have softs more useable now and having a decision to make on race compound.

As you say KANE, the hards are worse for the first few laps but then they settle into running temp and pressure and are more consistent for use during a race. I had 2 races where the other 2 drivers up front stuck with softs for the race and after a few laps I could see they were struggling where I wasn't and I went on to win comfortably. Track temp was between 70-80F in both instances.

In PCars 1 getting tyres at the right temp was most important, in PCars 2 it's all about the pressure. You will only make a small diff to temps by lowering or increasing tyre pressure; unlikely enough to stop a tyre going from overheated or too cool to optimal - pressure on the other hand is vital. A few PSI over optimal and the tyres lose a huge amount of grip. It's like being on a severally overheated tyre and it's much easier to get tyres at optimal pressure for any given race conditions.

In fact in general I'll lower the pressure on a tyre for a hot track and raise it for a cold track to keep pressure optimal.
Even with track temperatures above 40C I had massive difficulties to get the hards to temp although I only had lowest pressure value applied. I even chose softs for 48C track temperature and it still worked. Only disdvantage I noticed is that the soft seem to perform perfectly just below 100C and then start to lose a lot of grip, but on the other hand it was pretty easy to get the temps back to the 90-100C area.

sylekta
12-02-2018, 18:32
I agree wear seems too low atm, especially on softs. Tyre wear is barely a concern anymore.

I think that matches real life, a set of tyres usually goes 2 fuel stints as they cant change tyres and fuel at the same time, so they change tyres when its a driver change.
Maybe thats hards though, so hards can last 2 fuel tanks and softs should be at the end of their life after 1 fuel tank

Nighttiger
13-02-2018, 09:41
As a rule of thumb, you run softs on track temps below 25C and hards above 25C. The main contributor to tyre temperature is the compound, track temps and driving style. Pressures are not mainly used for temps like in Pcars 1.

Do you know if your pressures where correct? In Pcars 2 it is not only about the temperature because most tyres have a wide working range. Apart from the temperature you should get your hot pressures right as they determine the contact patch with the road and thus your grip. In the garage sub forum there is a sticky with the go to hot tyre pressure per car class. Go check that out. Drive 6-10 laps, look at the telemetry screen and check the pressures. Adjust the cold pressures to get the right hot pressures. You will see, it makes a huge difference!

Renoldo1990
13-02-2018, 09:59
. Adjust the cold pressures to get the right hot pressures.

Mainly you have to adjust the brake ducts if you want to get the hot pressures right.
The brake temperatures have an much bigger impact on the hot-pressures because it heats the tyres from inside.

Nighttiger
13-02-2018, 10:33
Mainly you have to adjust the brake ducts if you want to get the hot pressures right.
The brake temperatures have an much bigger impact on the hot-pressures because it heats the tyres from inside.

In this scenario I assume the brake ducts and brake temps are sorted

bazzalaar
13-02-2018, 18:00
If you increase the pressure you will slow down the overheating (Although not necessarily eradicate it) as there won't be as bigger patch of tyre in contact with the track however you will lose grip for exactly the same reason.

That's not right, if this actually works in the game then it goes against what happens in real life. In theory what you've suggested would make the tyre temps rise too quickly and your tyres would over heat even faster...
As tyres get hot, the pressure increases within them and there is an optimal point where temps meet pressure. So by your logic, increasing the pressures to the point of reducing the contact patch (over inflation) would go against real life. Imagine the Hot working tyre temperature for GT3 is 26 degrees, you want to try to maintain that throughout a race distance. Increasing the pressure would force the tyres to over heat and reduce longevity of the tyre. The only scenario I can understand your way working, would be if you had initially under inflated the tyre and the sidewalls are doing too much work. or maybe for qualifying, if you were driving a car that took too long to bring the tyre temps up gently, you'd fire enough pressure in to the tyre to be within a coupe of PSI of hot working pressures so that they would come in faster, but they wouldn't last as long.

David Wright
13-02-2018, 18:12
That's not right, if this actually works in the game then it goes against what happens in real life.

In real life, increasing tyre pressure makes the tyre stiffer. Making the tyre stiffer means the tread and sidewall deform less at the tyre rolls along. Reducing the deformation reduces the rolling resistance and the heat generated by the deformation. Less heat generated means the tyre runs cooler.

bazzalaar
13-02-2018, 18:42
In real life, increasing tyre pressure makes the tyre stiffer. Making the tyre stiffer means the tread and sidewall deform less at the tyre rolls along. Reducing the deformation reduces the rolling resistance and the heat generated by the deformation. Less heat generated means the tyre runs cooler.

I can understand what you're saying. but that's wrong. I've got a lot of experience in real life with track and race cars. I can't understand this logic, unless you're already running very low tyre pressures...

I'll try to make my reasoning for this simple. During qualifying you set your fastest lap, at the end of that lap the tyre pressures are 26 psi. What ever is happening to the tyre at that point in regards to pressure, temperature, flex, is working optimally to produce the grip for you to set your fastest lap. Therefore that is the optimal temp and pressure to make the tyre work. The longer you drive the more the temp will increase as will the pressure and you'll lose grip. You cannot say increasing pressure will stiffen the tyre and run cooler. increasing the pressure will push you beyond the optimal point, the tyres will over heat faster and you'll lose grip quicker.

hkraft300
13-02-2018, 19:20
I can understand what you're saying. but that's wrong. I've got a lot of experience in real life with track and race cars. I can't understand this logic, unless you're already running very low tyre pressures...

I'll try to make my reasoning for this simple. During qualifying you set your fastest lap, at the end of that lap the tyre pressures are 26 degrees.

You'd want to get your units right before ranting on someone else's logic.
Doesn't say great things about your track and race car experience.

Fight-Test
13-02-2018, 20:05
Is it possible that the conversation is being derailed by not differentiating between Core temps and Tire surface temps? Isn't it true that raising core pressure will increase core temp but because it can decrease tire contact surface, the tire surface temp would decrease?

bazzalaar
13-02-2018, 20:22
You'd want to get your units right before ranting on someone else's logic.
Doesn't say great things about your track and race car experience.

Thanks for the heads up, post edited! Don't think my experience on track and that of typing a sentence and making a mistake are really the same thing, but hey ho.
I don't mean to come across as ranting, it's hard to understand context through written words sometimes. I'm trying to point out my understanding of what was being said.

The message as I understood it, is that, if you can reduce the rolling resistance of a tyre, through increase in pressure, you can reduce tyre temps. My experience of it in real life (despite my ability to correctly check my units of measure) is that it doesn't quite work like that.

bazzalaar
13-02-2018, 20:30
Is it possible that the conversation is being derailed by not differentiating between Core temps and Tire surface temps? Isn't it true that raising core pressure will increase core temp but because it can decrease tire contact surface, the tire surface temp would decrease?

It's all relative. Increasing core pressure will increase core temp, but that heat will pass through the tyre carcass. If you increase tyre pressure and reduce surface area you would decrease the consistency of the temperatures across the tyre, depending on which bits are in contact with the track. But you'd find that the patch in contact with the track would be doing far more work, because it isn't spreading the load across the tyre, it will over heat.

If you're struggling with tyre wear, you need to identify the temperatures across the tyre and compare them. Inside shoulder, centre and outside shoulder. If you’re getting too much heat through the centre of the tyre you need to reduce pressures. If the shoulders of the tyre are hotter than the centre, increase pressure. If the temp is even apart from one of the shoulders, try altering the camber settings to adjust the contact patch area. e.g. if the tyre temp is showing significantly higher on the inside shoulder than the middle and outside. Give the car more positive camber. Bigger contact area, spreading the load, wear and temperature.

hkraft300
13-02-2018, 21:03
Isn't it true that raising core pressure will increase core temp but because it can decrease tire contact surface, the tire surface temp would decrease?

Yes, this can reduce contact surface/ pliability. The load remains the same (the mass of the car, downforce etc), so that smaller contact patch actually gets hotter, because there's less of it having to do the same amount of work. The hotter patch heats the tire, pressure goes up, smaller contact patch, more scrubbing/ sliding... you end up with "less tire" therefore less grip.
Again, it's all relative. At that stage, we're already way over-pressurised.
Although there are advantages such as low rolling resistance at tracks like Le Mans. You have a lot of track to cool the tires.

On a side note: One of Schumacher's Ferrari's (F2002?) Used refrigerant gas in its tires instead of air to maintain stable tire behaviour!


Thanks for the heads up, post edited! Don't think my experience on track and that of typing a sentence and making a mistake are really the same thing, but hey ho.
I don't mean to come across as ranting, it's hard to understand context through written words sometimes.

It'll prevent someone misunderstanding you.
There's no such thing as bad students, only bad teachers!

bazzalaar
13-02-2018, 21:10
It'll prevent someone misunderstanding you.
There's no such thing as bad students, only bad teachers!

Very true!

You're correct about the gas. I think most high profile race series use it these days. It's nitrogen they use.

hkraft300
13-02-2018, 21:15
Very true!

You're correct about the gas. I think most high profile race series use it these days. It's nitrogen they use.

Refrigerant gas is very different to air. That got banned from F1, and I believe nobody else has thought to or been able to use it.

Air is ~80% nitrogen. Maybe they use straight nitrogen for it's dryness? I'd think it makes bugger all difference TBH.

bazzalaar
13-02-2018, 21:21
in the technical regs it just says "Teams are allowed to inflate tyres with air or Nitrogen"

Sampo
13-02-2018, 22:33
I don't know if it will help, but you can see what the memory mapped data from the game says about different parts of the tyre. I've read that there might be some outdated data in there, but this is what the game spits out atm.
http://forum.projectcarsgame.com/showthread.php?60868-Anyone-interested-in-a-PC-program-that-shows-most-memory-mapped-stats

Schnizz58
13-02-2018, 22:46
Maybe they use straight nitrogen for it's dryness?
That's exactly right. It's not the nitrogen per se but rather the fact that it contains no water vapor. It's the water vapor that causes the pressure to go up and down with temperature. At least that's what I was told.

morpwr
13-02-2018, 22:59
Refrigerant gas is very different to air. That got banned from F1, and I believe nobody else has thought to or been able to use it.

Air is ~80% nitrogen. Maybe they use straight nitrogen for it's dryness? I'd think it makes bugger all difference TBH.

They do use it for dryness and less variables. It actually does help quite a bit in a race car passenger car its a waste. I actually worked on a nitrogen dryer because we found tanks of nitrogen varied greatly in moisture content. Unfortunately for the guy that owned the car and at the time worked for a major commercial drier company nascar wouldn't allow it in the pits. But it did work very well for managing tire growth and keeping things consistent.

jan.ringas
14-02-2018, 14:17
I'm really confused with those tires.
Being initially convincing (after patch3) about their realistic behaviour, right now those tires are close to what I think is proper. The only one thing I think is a bit off: a wear, especially in higher temps.
Yesterday we did 1h race (GT3@BrandsHatch) with 35*C-40*C of track temp. Soft tires was performing very well reaching about 105*C-110C while pushing hard and lasted for a whole race without need to change, because final wear was about 50%.

Is such little wear proper?

I think current GT3 cars do have such low tire wear.

Here in germany we have the "ADAC GT Masters", a GT3 series with two 60 minute races per weekend. There has to be taken one mandatory pitstop in each race, but only to switch drivers (there are two drivers sharing each car).
Tire changes are not intended, unless there are climate changes (i.e. dry->wet or wet->dry) or a tire has been damaged and if nothing special happens, the tires do hold up for the whole distance of 60 minutes in that series.

So I'd guess that the low tire wear in PC2 is indeed correct (at least for the GT3 cars).

Lawndarts
16-02-2018, 14:06
To simplify all this and ground it in reality. The goal is to get tires to a sustained optimal operating temperature and stay there as much as possible. Any changes and adjustments are simply to achieve that. There is core temps and surface temps but they arent really monitored because a driver can feel it very clearly, with pressure being the only exception. The only part that is sometimes measured is surface temps of the tire accross the full width of the tread, but scrub patterns tend to show this prior to needing temp readings.

As we arent pro drivers, but do have pro driver tools in PC2, one of the leading indicators is looking at your surface temps accross all 3 areas of a tire, inner, mid, and outer. This is especially important after youve reached optimal temp because too much camber for instance, can artificially effect uneven heating. So caster, toe, and camber need to be appropriate for the track you are on. As you watch the telemetry, and the tires naturally cool in a straight, you need to look for how and what parts of the tire heat up through the turns. If its nice and even then youve got the front setup about as good as its going to get.

The problem most people have, that makes it a tough topic to discuss here is whether your driving the car well enough to reach optimum temps. Some drivers scrub their tires a lot with over steer, spiking temps, others who strive to be smooth dont work them hard enough, and the oddity with either is they could both be putting in the same lap times. This in-turn reveals both could be doing a lot more to improve their times but how each can improve is very different. But I digress.

In short, just pay attention to sustaining temps through the twisties, with the understanding they will fluctuate but should never exceed the optimal range. Also, your better off dealing with cooler tires than over heating them in any instances. The telemetry screen and basic alignment knowledge is really all you need. Race engineers joke that tires are voodoo black magic but they arent hard to figure out.

hkraft300
16-02-2018, 19:15
PC2 tires have a fairly broad operating range for temps and pressures. For hard tires you're looking at >70℃ and soft <90℃ tire temps. Pressures for GT and prototypes anywhere between 1.6-1.9 bar as per Ringley's sticky post.

So tweak and see which gets you the best performance. Obviously when you tune your tires to either extreme you have little room to play. For example, 1.9 bar pressures at Spa is good for a clean lap but a little mistake or heat of battle might shoot the tires beyond its happy range and you're screwed. Work to your abilities and circumstances. Getting the tires switched on will probably net you the best gains in tuning terms.

tommysalami
16-02-2018, 19:20
PC2 tires have a fairly broad operating range for temps and pressures. For hard tires you're looking at >70℃ and soft <90℃ tire temps. Pressures for GT and prototypes anywhere between 1.6-1.9 bar as per Ringley's sticky post.

So tweak and see which gets you the best performance. Obviously when you tune your tires to either extreme you have little room to play. For example, 1.9 bar pressures at Spa is good for a clean lap but a little mistake or heat of battle might shoot the tires beyond its happy range and you're screwed. Work to your abilities and circumstances. Getting the tires switched on will probably net you the best gains in tuning terms.

You mean 70 and 90 F right?

Max Torque
16-02-2018, 19:59
You mean 70 and 90 F right?
No, Celsius.

tommysalami
17-02-2018, 00:55
No, Celsius.

Oh you're right, I was thinking track temps. duh, should have paid more attention

Max Torque
05-04-2018, 16:02
- The weather sync among players have been fixed already?, and when you join a dedicated server and you have some different weather too to others that are already in for a while?

- Have softs gone back to previous patches so hards are usable again?
I am digging this out again. Did I miss something? Are hard tyres broke now since 4.0? I drove 3 laps Nurburgring Combined with hards and 29C and indeed the car was 10-15 seconds slower than in time trial (with fuel for 3 laps indeed...). I even spun out in the fast left hander at Schwedenkreuz were I usually only lift very gently. I still do not have a clear rule which track temp is the border between softs and hards.

Schnizz58
05-04-2018, 16:24
I am digging this out again. Did I miss something? Are hard tyres broke now since 4.0? I drove 3 laps Nurburgring Combined with hards and 29C and indeed the car was 10-15 seconds slower than in time trial (with fuel for 3 laps indeed...). I even spun out in the fast left hander at Schwedenkreuz were I usually only lift very gently. I still do not have a clear rule which track temp is the border between softs and hards.

I didn't think hards were changed in patch 4 but I could be wrong. They definitely improved the working range for softs. I'm not sure where the crossover point is either but I've run softs when temps were > 30C and they didn't melt over the course of a 30 minute race. I guess try both and see which one works better for you.

demand34
05-04-2018, 19:47
I am digging this out again. Did I miss something? Are hard tyres broke now since 4.0? I drove 3 laps Nurburgring Combined with hards and 29C and indeed the car was 10-15 seconds slower than in time trial (with fuel for 3 laps indeed...). I even spun out in the fast left hander at Schwedenkreuz were I usually only lift very gently. I still do not have a clear rule which track temp is the border between softs and hards.hard tyres are useless since patch 4 unless you are on a 40C upwards temp at dubai or Algarve

hkraft300
06-04-2018, 05:57
hard tyres are useless since patch 4 unless you are on a 40C upwards temp at dubai or Algarve

Over 30℃ at Nurb GP, Silverstone, Spa, Road America, Sonoma, Red Bull is borderline, Indy Road... >40℃ Bathurst, even Monza, Bugatti, Daytona... you'll need hard tires in GT cars. So no, not entirely useless.

Soft tires might do you well for qualifying and a short Sprint race. Try running the 911 R on soft tires on a warm track and tell me your tires aren't cooked :rolleyes:

rich1e I
06-04-2018, 10:51
Hard tyres aren't completely useless, I'd still prefer them over softs, but i'm going to try soft tyres in a 20 - 25 minutes race and see what happens as I really haven't used them much.

belaki
06-04-2018, 13:04
That's exactly right. It's not the nitrogen per se but rather the fact that it contains no water vapor. It's the water vapor that causes the pressure to go up and down with temperature. At least that's what I was told.

By definition all compressed gases will expand\contract with changes in temperature. The resistance to expansion\contraction will be impacted by the heat capacity of the gas in question. If water vapor is present this becomes part of the calculation. Compressed nitrogen will have zero water vapor (if you understand how it is made you'd understand why), and nitrogen has roughly 5% greater heat capacity at 175 degrees F than air. In other words, the amount of heat required to cause a measureable rise in temperature at a given temperature and pressure is slightly higher for nitrogen than air - thus nitrogen will be slower to rise in pressure as carcass temperature rises. The vast majority (if not all) of major professional racing teams use nitrogen, and I would assume the PC2 tire model is based on nitrogen instead of air.