I didn't study this deeply, but I believe the higher pressure in tires lower the friction with road, i.e. less grip, less work for tire, less heat, and faster top speed at straight.
But also with less grip maybe you are sliding more around, that's the source of additional heat with higher pressure?
At least I know LFS works like this, put higher pressure into tire, and as long as you don't micro-slide, the temp of tire will be lower. Although start to be more aggressive and slide here and there, and you can warm up the tires to/beyond temp of lower pressure tires.
I wonder how good the real race drivers are with controlling those micro-slides, in LFS it's easy to save a replay and analyze afterwards where you are losing grip and how much, but in real life you can't do that in such direct and exact way.

Quote from Ped7g :

I wonder how good the real race drivers are with controlling those micro-slides

Your inbuilt gyro in your inner ear is very sensitive and real race drivers would be tuned into it even more, I'd say that it is much easier for a rl race driver to detect and correct micro slides than it for a sim racer with his butt on an office chair listening for tyre scrub sound or visual cues Most quick sim racers are good at predicting when oversteer is likely to happen and correcting before they actually detect it

Quote from Hallen :

I don't know why this is for sure, but from practical experience in standard cars and from spending time in the paddock with race cars, typically, high pressure=a hotter tire in a shorter time. Lower pressures=a tire that takes longer to heat up and get "to pressure and temperature".

One explanation I've seen for that is that your tyres are just an extention of your cars suspension and having a higher pressure is equivelalent to having stiffer suspension which equals the tyres tacking more load thus working harder (pushed into the road surface) with heat being the by product of work. I've read that autocross drivers use higher pressures than race drivers as their runs are very short and want to get heat into there tyres fast - higher pressures would also make their cars more responsive.

I've also read that tyres are a significant part of the total body roll in a road car. I'd be curious to analyse just how much LFS tyres play in body roll in LFS and how that compares to RL. Also I would be curious to investigate contact patch behaviour under different pressures. In LFS you get the distinct impression that lower pressure equals more grip, where in RL it would seem that the situation is not so straight forward.

Quote :

On the one side, we have an ex karter (world rotax max champion) who believes the following: High pressure= higher volume of air molecules, therefore more molecules banging into each other, therefore more friction... and therefore, more immediate temperature throught the tyre. All this means the tyre comes on more quickly, but may not last as long.

The other arguement in the team is from a single seater race engineer who says: Lower pressures mean more "roll"/"flex" which creates more friction in side walls etc. This allows the tyre to generate heat quickly and therefore, comes on quickly. Higher pressures allow less roll/flex and therefore, slightly longer to come in but more stability (pronlonged life).

The reply from the karter... Softer temps generates side wall heat and mainly surface temperature which is not what cause a tyre to work, as you need core tyre temp to work, not only surface heat.

Who the hell knows?

Just about any tyre/race engineer.

The heat generated by roll, flex and movement of the tyre is what heats the ''inner core''. This isnt just pressure related as its a critical aspect of tyre design in the design of the carcass.

A higher pressure/over pressured tyre will flex less, so heat less. However the higher pressure tyre will likely overheat the tyre surface and underheat the carcass or ''inner core'' due to increase slide/slip, thus reducing its grip even more.

Best, Maz

Quote from Mazar :

JA higher pressure/over pressured tyre will flex less, so heat less. However the higher pressure tyre will likely overheat the tyre surface and underheat the carcass or ''inner core'' due to increase slide/slip, thus reducing its grip even more.

Could you get away running a higher pressure with say a very soft compound of rubber than normal. That's the grey area for me were I can see it may be possible to turn common practise on its head Soft compound with grooved tyres might still generate heat in a beificial way if the rubber treads are flexing enough to heat the tyre evenly, and in F1 they probably don't want the tyre walls heating alot as that would effect the feel of the car too much.

Quote from Mazar :

Just about any tyre/race engineer.

The heat generated by roll, flex and movement of the tyre is what heats the ''inner core''. This isnt just pressure related as its a critical aspect of tyre design in the design of the carcass.

A higher pressure/over pressured tyre will flex less, so heat less. However the higher pressure tyre will likely overheat the tyre surface and underheat the carcass or ''inner core'' due to increase slide/slip, thus reducing its grip even more.

Best, Maz

In LFS, although lower pressures definitely do increase sidewall and internal temperatures, it also seems to cause the tire surface to heat up more quickly and stay hot longer. It is like the inner tire temperature radiates heat to the tread.

I do notice that when running R3's at higher pressures, that the surface temperature goes up and will go into the red zone, but the rest of the tire stays in the blue zone. But again, if you lower the pressures, generally you will end up with over heated tire surfaces pretty quickly. I will have to do some testing on this stuff to see if a happy compromise can be made.

Maybe it is just that the lower pressure tires are doing more work because of the higher grip levels. But it makes a lower tire pressure almost unusable in long races even with harder tires. The lower pressures will reduce your lap times a tad, but the heat generated will force you slow down quite early in a race.

Quote from southamptonfc :

2 things.

Normally lower tryre pressure means the rubber flexes more easily and so generates more heat.

However, IF higher tyre pressures give less grip, they will slide more and generate more heat.

So who knows??

My thoughts also. Iv seen such a wide range of pressures used in LFS by people and its probably the most important setting to adjust grip levels to your driving style and longevity of the tyre.

As a general rule I try to set them as high as possible whilst providing enough grip in crucial parts of the respective track. This way you can race more consistently. For Qualyfying I use the lowest setting possible until the drag of the tyre or the overheating scuppers your overall hotlap time.

With reference to the impact of the amount of air in the tyre affecting temperatures etc. Things to consiser are:

a) All mass will absorb thermal energy from any other mass with which it comes in to contact, (in the direction that the thermal gradient created by the temperature difference between the two masses dictates).
b) The rate at which the energy transfer occurs is dependant on the thermal gradient between, and the thermal properties of, the two masses.
c) The amount of total thermal energy transfered is related to the specific heat capacity of the mass and the absolute amount of mass.
d) Gases absorb thermal energy in two ways:

i) Convection (movement of molecules)
ii) Conduction (Kinetic Energy transfer between molecules)

Both of those mechanisms are affected by the total amount of gas molecules and their density. ie pressure of the gas. Lowering the pressure of a gas will reduce both it's ability to absorb and to transfer thermal energy. Taken to the extreme, a gas with zero pressure (ie a vacuum) will not absorb or transfer any heat at all.

Quote from BenjiMC :

+1. I am pretty sure he was either mis quoted or mistaken.

I agree, sometimes writers change the quotes thinking they are correcting their misheard mistake, when in reality they heard right.

Quote from legoflamb :

I agree, sometimes writers change the quotes thinking they are correcting their misheard mistake, when in reality they heard right.

Nope. Absolutely not. For qualy and short runs real race cars will generally go out with higher pressures in the tires than they will for long regular race stints.

There is an optimal pressure where the tire works best. When you are doing something like qualifying, especially in F1, you will do an out lap, hot lap, and in lap. The tires won't have time to get enough heat to come up to pressure if you ran at a lower pressure. They therefore start at a higher pressure to make sure the tires are optimal for that one lap.

Longer stints will start with lower pressure because more heat will ultimately be generated so in order for the tire to be at optimal pressure for the majority of the stint, they start with lower pressures that will take a few laps to build up to the right pressure.

I don't know exactly what this means as far as tire temperatures, both internal and surface, but that is basically what is done for the pressures.

The biggest discrepency I can detect with LFS tyres vs rl tyres at the moment is that the range of usable pressures is too large thus allowing larger extremes than you would see in rl.

I'm willing to bet that the tyre contact patch does not distort correctly under low pressure high loads in LFS. In rl you have a minimum recommended pressure, if you go below that pressure there would be reduced grip levels caused by undesirable contact patch distortions, this doesn't seem to happen enough at low pressures in LFS. Irl once the sidewall begins to roll under the rim it will start to have a negative impact on grip levels as it will have the effect of lifting the edges of the contact patch.

So while lower pressure should equal more grip that should only be true within the recommended range, once outside that range tyre grip I suspect should actually drop away sudenly and dramatically.

As a consequence you see all drivers using lower pressures no matter what their driving style, where as in rl if you have a more aggressive style you would more likely be running higher pressures than another driver that is smoother.

Quote from Hallen :

Nope. Absolutely not. For qualy and short runs real race cars will generally go out with higher pressures in the tires than they will for long regular race stints.

There is an optimal pressure where the tire works best. When you are doing something like qualifying, especially in F1, you will do an out lap, hot lap, and in lap. The tires won't have time to get enough heat to come up to pressure if you ran at a lower pressure. They therefore start at a higher pressure to make sure the tires are optimal for that one lap.

Longer stints will start with lower pressure because more heat will ultimately be generated so in order for the tire to be at optimal pressure for the majority of the stint, they start with lower pressures that will take a few laps to build up to the right pressure.

I don't know exactly what this means as far as tire temperatures, both internal and surface, but that is basically what is done for the pressures.

Quote from Official Formula 1 Website (paragraph 14) :

“We issue a safe range of pressures for our tyres and the teams must keep within this range, but there is still good scope for drivers to dial-in to get their preferred response. In basic terms a higher pressure within the safe limits we give will provide more stability, whilst a lower pressure means the tyre heats up slower, but it also degrades less, and is less sensitive to bumps.”

The statement on the official website that I was referring to was "whilst a lower pressure means the tyre heats up slower".

The quote was not talking about what air pressures work best with what tires, nor was the optimal situation mentioned in the aforementioned paragraph. The paragraph states how tires perform "in basic terms."

I agree that the lower the tire pressure, longer time is needed for optimal tire pressure to be reached.

However, I am no expert in this field. If new information comes across my path, from an expert in said field, or data that can be trusted to be true, proving the contrary to what I have read elsewhere, I will agree with the statement quoted from The Official Formula 1 interview.

Quote from Glenn67 :

....

I'm fairly certain that what you mention does happen in LFS, however like you said it might not be or might be too dramatic. There is really only one way to tell, and that would be to try using lower tire pressures in real life and compare. Even then you can't be completely sure.

Quote from xaotik :

You do realise that what you are describing is friction and friction, right?

:smileyrai
I don't know why, but that really made me laugh!