2018-2020 Tyres Thread

[Rodak]

I don't understand what you are doing here:

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

as (- Pstart + Pstart) = 0

Simpler to say
Pstart/Tstart = Pfinal/Tfinal, so

Pfinal = (Pstart/Tstart)/Tfinal

Temperatures in Kelvin, pressures in whatever you want.

[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 ?

I learned gas law as PV over T (vs P over T). Without me doing any calculations could the inclusion of volume alter your coefficient? I think the answer is no based on yours being a factor of 2 off from Pirelli.

Yeah, that was my thought as well : there is a factor 2 somewhere, but I can't find where it's missing ...
You're right about the volume, but I assumed the volume is pretty much constant to apply Gay-Lussac's law (well, it's not exactly constant, but I can't see a factor 2 between the volumes of hot and cold tyres ...)

[Marble]

I don't understand what you are doing here:

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

as (- Pstart + Pstart) = 0

Simpler to say
Pstart/Tstart = Pfinal/Tfinal, so

Pfinal = (Pstart/Tstart)/Tfinal

Temperatures in Kelvin, pressures in whatever you want.

It's just an artifice to have the same form of formula as Pirelli has ie
Pressure = K*(T-100) + Pressure_start

[godlameroso]

New tires have stiffer sidewalls. This not only allows less pressure, but it also allows teams to run less negative camber. Why? Because the sidewalls have less deflection thus the contact patch moves less and requires less camber to compensate for said deflection.

This is beneficial from an aero stand point as negative camber and toe in both contribute to tire wake. By reducing negative camber at the rear you reduce the tire squirt.

Where teams ran 1.8 degrees of negative camber at the rear, that number can now probably go down to 1.4 or 1.3 degrees with no negative impact on tire behavior but better aero behavior.

[PhillipM]

They were up against the limit before and needed more, I doubt any teams will be dropping much, if any, camber angle.