2021 French Grand Prix - Le Castellet, June 18 - 20

[djones]

Why do they raise the pressure when they are worried...

Is it that a tyre with less pressure is structurally softer and has more movement and more 'fatigue'?

[godlameroso]

Why do they raise the pressure when they are worried...

Is it that a tyre with less pressure is structurally softer and has more movement and more 'fatigue'?

With a more inflated tire, the sidewall would deflect a lot less at speed. When the tire spins and stretches the pressure inside the tire lowers even more. If the pressure difference between the inside and outside is too great....

[Just_a_fan]

Why do they raise the pressure when they are worried...

Is it that a tyre with less pressure is structurally softer and has more movement and more 'fatigue'?

As a tyre rotates, the part in contact with the road is flattened - that's what the contact patch is. In order for that flattening to occur, the sidewall has to deflect and there is a lot of hinging at the point where the sidewall and the tread meet. And just like getting a piece of plastic and flexing it back and fore lots of times very quickly will heat up the plastic at the flex, so the tyre sidewall / shoulder will heat up.

At 300kmh, the tyre is rotating approx. 40 times per second (83.33m/s / (pi*0.66m)), so the shoulder flexes 40 times a second too but as it flexes one way and then back to "normal", it actually has 80 distinct movements per second. That's a lot of energy being put into the tyre shoulder. If you increase the pressure in the tyre, this deformation is reduced meaning there is a bit less flexing and thus less heating of the critical shoulder area.

[godlameroso]

The more we think about it, the more it seems like it's just a force Pirelli didn't anticipate going through the tire. Nobody is perfect, but the situation is not hopeless either.

[Zynerji]

Why no solid tyres?

Let the suspension sort the rest out

[zibby43]

The more we think about it, the more it seems like it's just a force Pirelli didn't anticipate going through the tire. Nobody is perfect, but the situation is not hopeless either.

They finally stopped hedging and confirmed RBR and AM were somehow running lower pressures while on the track.

https://www.racefans.net/2021/06/17/bak ... i-confirm/

[langedweil]

The more we think about it, the more it seems like it's just a force Pirelli didn't anticipate going through the tire. Nobody is perfect, but the situation is not hopeless either.

They finally stopped hedging and confirmed RBR and AM were somehow running lower pressures while on the track.

https://www.racefans.net/2021/06/17/bak ... i-confirm/

This story is getting weirder by the minute ..

Pirelli has confirmed the tyre failures which put Max Verstappen and Lance Stroll out of the Azerbaijan Grand Prix occured because their tyres were running at lower pressures than expected.

However the sport’s official tyre supplier stated the teams responsible for both cars had complied with the rules and the starting minimum tyre pressures.
Pirelli announced the result of its investigation into the failures on Tuesday. While denying a problem with its tyres had lead to the failures, it also stated the teams had complied with the rules.

“We didn’t say that the teams made something that is not permitted in the regulation,” said Pirelli’s head of motorsport Mario Isola.

Well, yes you did .. as a pressure below the minimum is not allowed per the rules?

“What happened in Baku is simply that the running conditions expected were different compared to the actual running conditions and that created the failure,” he said.
...
Isola said the updated technical directive for this weekend has been brought in because they do not currently have the ability to check teams’ tyre pressures during races.

“Ideally what we should police, the important parameters to police for the tyres, are the running conditions,” he said. “Running conditions are the running stabilised pressure, the load, the speed, the camber. Obviously some of these parameters are not enforceable simply because we don’t have the tools to do that.”

You know what happened, you know it wasn't your fault eventhough both incidents were perfectly identical, you call two teams by name and explain they were utilizing a pressure (in race) that was too low ... and all of that from monitoring that doesn't exist.

Call me tinfoilheaded, but it's almost becoming awkward ..

Just own up : we had a serious mishap, we RCA'd, we found the RC .. chillex, we've got this. Next GP you'll be fine.

[Augustus]

So, who do you think is going to get pole and who will win? Pole will most probably be for Mercedes (I'd guess Hamilton).

[TimW]

Just a guess: Pirelli based their calculations on dry compressed air, while some teams found out they were better off removing the water separator from their compressors?

It's actually against the technical regs to try and remove moisture.

https://www.fia.com/sites/default/files ... -03-05.pdf

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.

"Intention" is the tricky thing here, because if you compress air it becomes challenging to not remove moisture from the gas. An 8 bar compressor will give dryer air than a 5 bar compressor. Connect the hose to the bottom of the tank an you will get accumulated water.

[djones]

Thank you to the people above that explained the tyre issue technically.

It’s interesting that Redbull are now also getting named by Pirelli. It maybe explains their good speed on the last two ‘street’ tracks and a general ability to do fast laps straight away while it can take Mercedes two warm up laps.

If (if) they are doing something a bit untoward with the tyres and rear wing it stinks of desperation. Basing a title fight on things that can easily be outlawed is destined to fail.

[Marble]

I have seen Pirelli cool down pattern, and I have tried to find it by myself using Gay-Lussac law, but I don't know why, I don't get to same coefficient.

For the front tyre, Pirelli has :
PSIf = (T(°C) - 100) * 0,108 + PSIstartf (PSI and °C)

If we use Gay Lussac (or perfect gaz law) we have (Pascal and Kelvin)

Pstart / T start = P / T

ie

P = (Pstart/Tstart)*T
P = (Pstart/Tstart)*T - Pstart + Pstart
P = (Pstart/Tstart)*T - Pstart*(Tstart/Tstart) + Pstart
P = (Pstart/Tstart)*(T-Tstart) + Pstart

And there we have the same form as the Pirelli formula but using Pascals and Kelvin ie in PSI and °C for the fronts

P = (PSIstart*6895)/(T°start+273)*(T°+273-T°start-273) + Pstart
P = PSIstart*(6895)/(T°start+273)*(T°-T°start) + Pstart

Replacing by numeric numbers for PSIstart and T°start for the fronts I have :

P = 21*6895/373*(T°-100) + Pstart
P = 388,19*(T°-100) + Pstart

And finally transforming into PSI :
PSI = 388,19/6895*(T°-100) + PSIstart
ie
PSI = 0,0563*(T°-100) + PSIstart

Problem is I don't get the same coefficient as Pirelli (0,056 vs 0,108)
Where is my mistake ?

[Just_a_fan]

Problem is I don't get the same coefficient as Pirelli (0,056 vs 0,108)
Where is my mistake ?

Just thinking aloud here: do they account for moisture in the gas in the tyre whereas the ideal gas law wouldn't?

[nzjrs]

“What happened in Baku is simply that the running conditions expected were different compared to the actual running conditions and that created the failure,” he said.
...
Isola said the updated technical directive for this weekend has been brought in because they do not currently have the ability to check teams’ tyre pressures during races.

“Ideally what we should police, the important parameters to police for the tyres, are the running conditions,” he said. “Running conditions are the running stabilised pressure, the load, the speed, the camber. Obviously some of these parameters are not enforceable simply because we don’t have the tools to do that.”

You know what happened, you know it wasn't your fault eventhough both incidents were perfectly identical, you call two teams by name and explain they were utilizing a pressure (in race) that was too low ... and all of that from monitoring that doesn't exist.

I laughed at this too. Pirelli "using the teams live pressure data that isn't trustworthy and doesn't exist we have determined the teams that provides us this data are running the tires under pressure".

Yet Max says the RB pressures from the live data was fine.

Does anyone know of Pirelli got some of the forbidden love tire pressure data from any other teams?

[Wouter]

[El Scorchio]

3 cars spinning already in the first four minutes!

Tyre pressures?....