Reduce tires pressure by increasing wheel temperatures?

[nevill3]

On Sky Sports F1 grid walk today, Paul Hembrey from Pirelli stated that there will be live, constant monitoring of the tyre pressures from either the next race or the one after IIRC. This will ensure that all the teams comply with the higher minimum settings imposed by Pirelli for safety reasons.

[erikejw]

Red Bull covered their wheel rims today before the start.
If they were at ambient temperature I wonder wht they felt the nees to do that ;) Quite clever to preheat them and put hot air(or nitrogen) into the tyres.

They might be in breach of 12.8.3 that stipulates that the every tire should have a "single fixed internal gas volume".

They are possibly in breach of the fixed volume. When they manipulate the temperature they manipulate the volume at the same time. The volume is linearilly correlated to the temperature as of the gas law pV=nRT.

FIA and Pirelli need to stipulate a pressure and a temperature in the rules instead of only pressure otherwise some teams will have a huge benefit or get rid of the pressure rule altogether.

[erikejw]

Assuming appropriate load capacity.... Does lowering the tire pressure decrease tire temps ? Why/How?

Brian

In theory yes but effectively no.
The total kinetic/heat energy in a gas is very low and the heat transfer between the tire and the air inside it is very low and slow.

A fluid transfer or a solid material transfers much more energy. Compare swimming in 4C water, you'll die in minutes and walking outside when it is 4C. Same temperature but the exchange of heat energy is very different.

2 psi lower tire pressure is explained by roughly 9 %(depending on target psi) higher temperature when the pressure is measured compared to ambient temp so about 27 degrees difference starting from 300 Kelvin.

[bill shoe]

On Sky Sports F1 grid walk today, Paul Hembrey from Pirelli stated that there will be live, constant monitoring of the tyre pressures from either the next race or the one after IIRC. This will ensure that all the teams comply with the higher minimum settings imposed by Pirelli for safety reasons.

I don't think this addresses the (rumored) problem. First, it's unlikely this info will be made public anymore than the not-quite-live tire pressure info the FIA has now. Second, in all likelihood all teams already do comply with the minimum pressures, including the two rumored trickster teams (I won't say cheater teams, cause I don't know what they are doing). The issue is that despite all the teams doing tricks with hot pre-race wheels, etc., these two trickster teams have running tire pressures that are ~ 2 psi lower than all the other teams.

FYI the load carrying capacity of a tire depends on the contained mass of the air (or of whatever gas is used). So then load carrying capacity is a function of volume (the tire's toroid shape) and pressure. Pressure itself is only an accurate proxy for load capacity if the volume is constant and temp is constant, i.e. ambient "cold" tire temps.

[bill shoe]

Here's another idea for how the tire pressure rules could be circumvented.--

Steam has a very large volume relative to the equivalent mass of dry air and water. So maybe the trickster team puts really hot steam in the tires and then somehow controls or manipulates the temp so it cools off right after the start of the race. This would condense the steam into water and greatly reduce pressure...

[1158]

From the regs:

12.7 Treatment of tyres:

12.7.1 Tyres may only be inflated with air or nitrogen.

12.7.2 Any process the intent of which is to reduce the amount of moisture in the tyre and/or in its inflation gas is forbidden.

12.7.3 The only permitted type of tyre heating devices are blankets which use resistive heating elements. The heating elements may only act upon the outer tyre surface.

To me 12.7.3 rules out heating the wheel up because that would also heat the tyre.

[Fulcrum]

From the regs:

12.7 Treatment of tyres:

12.7.1 Tyres may only be inflated with air or nitrogen.

12.7.2 Any process the intent of which is to reduce the amount of moisture in the tyre and/or in its inflation gas is forbidden.

12.7.3 The only permitted type of tyre heating devices are blankets which use resistive heating elements. The heating elements may only act upon the outer tyre surface.

To me 12.7.3 rules out heating the wheel up because that would also heat the tyre.

Is there a formal definition for 'air' in the technical regulations?

If this is open to interpretation, i.e. anything that's breathable vs. fixed constituents, that's a loophole for sure. Not sure whether it can be exploited though.

[Tommy Cookers]

Singapore 'air' at 32deg C usually contains 4% water vapour ie 4% of the air pressure comes from water vapour
(Abu Dhabi 'air' at 32deg C usually contains 0.1% water vapour)

with natural humidity up to 11% of inflation pressure with 'air' at 52deg C could come from water vapour, and about 26% with 'air' at 72 deg C

some tyre or wheel treatment (or ingredient - absorbed by tyre fitting lubricant ?) could absorb this water vapour
eg absorbing water will lower the inflation pressure accordingly (eg after official measurement)

or a water-emitting ingredient could supply water vapour to hot air pre-measurement, later condensing as the air is cooled, so lowering the pressure
(as another post has said)

[erikejw]

"Any process the intent of which is to reduce the amount of moisture in the tyre and/or in its inflation gas is forbidden."

Hence it is fine to increase the moisture.

"No valves, bleeds or permeable membranes are permitted other than to inflate or deflate the tyre whilst the car is stationary."

The key word is stationary. So it is ok to use those technologies at the grid before the start and during a pitstop(after the tyre is fitted and before the car moves, it seems marginal during a pitstop).

Other techniques than those mentioned is then allowed during racing.

They need to rephrase that part to something like:
It is forbidden to inflate or deflate the tire(after the initial inflation of the tire) directly or indirectly.

[hollus]

Stationary... If it is to be taken literally, and this is getting into conspiracy theory land, one could build a passive relief valve that only works above a certain pressure and when under certrifugal force...

[nevill3]

Pirelli have got their way and will be introducing the live monitoring, but I presume it will require a change in the regulations before any penalties can be applied if teams are found to be running lower pressures during the race. As it says in the article on here Pirelli will need to establish what a safe "running" pressure is and when it should be measured.

An extended safety car stint would reduce the tyre temperatures so causing a fall in the pressures, so I presume the teams will have some input as to when or if in race penalties could be applied.

[rjsa]

Pirelli have got their way and will be introducing the live monitoring, but I presume it will require a change in the regulations before any penalties can be applied if teams are found to be running lower pressures during the race. As it says in the article on here Pirelli will need to establish what a safe "running" pressure is and when it should be measured.

An extended safety car stint would reduce the tyre temperatures so causing a fall in the pressures, so I presume the teams will have some input as to when or if in race penalties could be applied.

They can pass anything, anytime, under "safety".

[Edax]

From the regs:

12.7 Treatment of tyres:

12.7.1 Tyres may only be inflated with air or nitrogen.

12.7.2 Any process the intent of which is to reduce the amount of moisture in the tyre and/or in its inflation gas is forbidden.

12.7.3 The only permitted type of tyre heating devices are blankets which use resistive heating elements. The heating elements may only act upon the outer tyre surface.

To me 12.7.3 rules out heating the wheel up because that would also heat the tyre.

Interesting they only speak about moisture reduction.

Theoretically you could cover the rim with an thermal activated oxygen getter (a compound which starts to oxidize at a prescribed temperature). As the oxygen is consumed and converted to solid oxide, the pressure drops.

The rim only heats up during the formation lap, as the brakes get heated so the tire would still be in spec with only the blankets on, but have a lower pressure once the wheel is at racing temperatures.

[zac510]

Motorsport.com have an article today about hollow spoked wheel rims:
http://www.motorsport.com/f1/news/tech- ... ck-740986/

but to be honest I don't understand some parts of it, in particular these two paragraphs seem contradictory:

My illustration of the Mercedes wheel rim above shows how hollow spokes are designed to intersect with the wheel rim itself, thus creating an enlarged but still fixed, internal gas volume.

In motion, the internal gas volume is likely to change, which in turn has an effect on the pressures, temperatures, spring rate and shape of the tyre.

[hollus]

I also didn't understand what he means, and I'd really like to.
As an aside: No surprises there, but isn't it a bit disingenuous of the rule makers to suggest that something made of rubber and subjected to changing temperature, changing downforce, changing lateral forces and tremendous, changing centrifugal forces could ever hold a constant internal volume?