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Re: 2018-2020 Tyre Thread
Posted: 23 Jun 2021, 20:55
by 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.
Re: 2018-2020 Tyre Thread
Posted: 25 Jun 2021, 12:47
by Marble
subcritical71 wrote: ↑23 Jun 2021, 20:35
Marble wrote: ↑18 Jun 2021, 09:25
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 ...)
Re: 2018-2020 Tyre Thread
Posted: 25 Jun 2021, 12:49
by Marble
Rodak wrote: ↑23 Jun 2021, 20:55
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
Re: 2018-2020 Tyre Thread
Posted: 07 Jul 2021, 15:40
by 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.
Re: 2018-2020 Tyre Thread
Posted: 07 Jul 2021, 17:49
by PhillipM
They were up against the limit before and needed more, I doubt any teams will be dropping much, if any, camber angle.