Reduce tires pressure by increasing wheel temperatures?

[Xwang]

Hi to all, I've read an article which says that in order to reduce the tyres pressure, F1 teams are trying to increase wheels' temperatures (and I suppose the temperature of the air inside the tyre by conduction) using the hot air coming from brakes.
Now, if the ideal gas law is applicable (PV=nRT) and if we consider n and V constant, I can't understand how it is possible to reduce P while increasing T.
Can someone explain me how they do it?
Thank you,
Xwang

[rscsr]

You should link the article in question, because it sounds pretty much like a mixed up journalist.

[1158]

You should link the article in question, because it sounds pretty much like a mixed up journalist.

Yeah pressure increases with an increase in temp

I was wondering if some teams found a way to increase the volume of the air in the tyre. The only way to do that would be get the rim to expand and for that you would want to heat the wheel up. I just don't know if it would be possible to build a wheel that can expand enough to increase the internal volume to an extent that the increase in volume provides a sufficient decrease in tyre pressure.

[mrluke]

I think this is linked to the pressures being enforced by the FIA but without having the temperatures specified, therefore the higher the temp the tyres are when they are checked for compliance, the lower they will fall when they cool back down.

I thought the regs were updated to cover this by placing a limit on the upper limit for tyre blankets.

[Xwang]

This is the article:

"The MERCEDES HAS DISCOVERED BEFORE ALL
The winner is lowered more pressures
Remember the many problems that Mercedes had complained to the brakes during 2014? Then the same team then world champion, traced the causes
- Above all, to throw off - the compatibility problems with KERS. In fact even then the Mercedes was the first who understood that in order to optimize
the best Pirelli tires, it was necessary to make them work at much lower pressures than those who were then only indications. Hence the idea of
utilize heat from brake discs to heat the wheels. The Mercedes was the first to resort to the procedure - initially did not happen - the
warm up the brake discs even on the starting grid with the appropriate hot air blowers. They said it was to have the brakes perfect
efficient and temperature, but in reality this would be enough to make some hard braking carried out in a matter of training. Today in F1 wins who is able to
further lowering the pressure of the tires: Pirelli which imposes increasingly higher values, knowing that in the race they will drop immediately, reaching
so the pressure - for them - optimal. Amid the drivers who sometimes see Grosjean in China, if you have not very efficient cars in this exchange
Heat-wheel disc brakes, so go into crisis and accuse the tire saying that they can not drive because minimum pressures are too high.
And that Haas is still lacking on this technical issue, as demonstrated by the fire that spread from the inside of the wheel, from the basket area.
The "degeneration" of the aerodynamic brake drums is typical only of the current F1. Indycar in the structure that covers the brake discs, serves mainly to
protect them - when they are warmer and therefore more vulnerable - during tire changes. Prototypes in the LMP1 class, the need to travel at least two stints
with a set of tires, and the possibility to dispose of tires specially made for the technical characteristics of each car, drastically reduces the need
to lower the minimum temperatures the inflation."

[rjsa]

No one revoked the ideal gas law. They are (were?) heating the brake disks before the race, before the pressure control - pushing the pre race pressure up artificially. This results in a lower pressure during the race.

[bill shoe]

No one revoked the ideal gas law. They are (were?) heating the brake disks before the race, before the pressure control - pushing the pre race pressure up artificially. This results in a lower pressure during the race.

Ah, so they force the pre-race pressure up via temporary high-temps in the wheels and this allows the actual running pressure, once things have roughly stabilized, to be closer to the pressure minimums set by the FIA/Pirelli. Nice trick, actually. I hadn't heard of this before. The article provided by Xwang has either lost something in translation or was not very clear in the first place.

This probably explains much of the elaborate brake ducting we've seen recently. It has two purposes beyond brake cooling: 1. act as a barrier to prevent brake heat from getting to the wheel where it will cause higher running tire pressures, and 2. channel cool airflow directly against the inside of the wheel to cool the wheel and thus the air inside the tire.

Other creative methods to maintain FIA pressure minimums pre-stint while also allowing lower pressures once things have "settled in"?

[1158]

So what are the FIA/Pirelli doing about pressures for tyres at pitstops? They can check them while they are in the warmers but as the team is running them out to the box it wouldn't be hard to release a small amount of air, though getting the same amount out of each tyre would be very difficult.

Just a random thought.

[hollus]

Would a passive pressure relief valve in the wheel rim be legal?
One could then overheat the wheel on purpose in the formation lap or even during the race to let some air out, then allow the temperatures to go back to normal and the pressures to go down. If the heat comes from the brakes and not from the rubber, it should be OK.
Probably a bitch to control, though. If you over-deflate... plus differences left to right.

[mrluke]

Would a passive pressure relief valve in the wheel rim be legal?
One could then overheat the wheel on purpose in the formation lap or even during the race to let some air out, then allow the temperatures to go back to normal and the pressures to go down. If the heat comes from the brakes and not from the rubber, it should be OK.
Probably a bitch to control, though. If you over-deflate... plus differences left to right.

I think racecar engineering reported into this in some detail where it was happening in Nascar. Suffice to say it didnt go down well when caught.

[erikejw]

"Artificial" cooling of the rim during the race would help tyre pressures too.

Any way of transfer heat away from the air inside the tyres will do hence to cool the rims will help.

Use of really hot air when the tyres are inflated might last a few minutes when the tire pressures are checked prerace.

[Ricdijk]

Could the air for the blown axle also be used for bringing the temp down?

[gandharva]

FIA already investigating, but seems legal so far.

AMUS: https://translate.google.de/translate?s ... edit-text=

http://www.wheels24.co.za/FormulaOne/f1 ... s-20160512

[bill shoe]

Many possible get-around and/or cheat mechanisms. Here's an easy way to enforce the intent of the rule--

Require wheel/tire assemblies that come off the car to sit by themselves in shade at ambient temp for an extended time. At the end of this time the tire pressure needs to still comply with the FIA/Pirelli minimums. This would preclude shenanigans involving either temperature-manipulation or air-mass-release. Downside is that the air inside warm tires cools down pretty slow (rubber is good insulator), so the extended time could be as long as a couple hours. This is OK for qualy on Saturday, but who wants to wait for Red Bull's tires to cool for two hours on Sunday after the race just to determine if they won? Not that I'm saying RB would manipulate anything, of course.

[PlatinumZealot]

Would a passive pressure relief valve in the wheel rim be legal?
One could then overheat the wheel on purpose in the formation lap or even during the race to let some air out, then allow the temperatures to go back to normal and the pressures to go down. If the heat comes from the brakes and not from the rubber, it should be OK.
Probably a bitch to control, though. If you over-deflate... plus differences left to right.

That is a very interesting proposition..
Does anyone remember how easily the rear tyres seemingly dislodged themselves from the wheel on the Renault in the earlier races? It could very well be that the rims are designed to release air until a certain pressure is reached... while the wheel is not spinning. The pessure would drop after the formation lap. The only hole in this theory, is that Pirelli can easily test the tyre pressures when the teams hand back the tyres.