Hokay, rare occasion when I ask for help - but it was bound to happen
Without questioning the infinite wisdom of the LFS tire physics model - can someone please answer the following questions (with proof hopefully).
LFS tires are "preheated" already when we exit the pits to let's say 15°C below their "optimum" operating temperature. The color of everything in that stage is dark blue (surface, tire walls, pressure inside the tire). As we go out and do a lap or two the temperatures of the thread ofcourse go up and over the tire's life span they can go to the red zone and then slowly go back to brownish and green and in the end back to blue - when they usually pop. Now, the inside of the tire (the area where the air is) also changes color - goes to blue-ish/green or green during a normal race, but can go to brown/red if you just do a burnout - my understanding is that this color represents the pressure inside the tire (and not the air temperature inside the tire - cause that would be pretty useless).
Question number 1: (by Jonesy) "like, say I put 200kPa in a tire, warm it up to 120degs would give me the same amount of psi in a tire as if I put 180kPa and warm it to 120degs?"
With my limited knowledge of thermodynamics I kinda used a simplified politropic equation to calculate the following example: We have a tire with 200 kPa @ 25°C, we warm it up to 90°C and get 240 kPa in it (these kinda numbers are usually correct in "other sims", I cannot say for real life because I never actually measured a pressure after the tire has been driven/races - but it's safe to say the pressure goes up - the problems come up when we ask by "how much"). We have a second tire with the cold pressure of 220 kPa @ 25°C and we warm it up also to 90°C - how much will the pressure rise? The method I used for this (not taking into consideration how the tire actually produces heat and ignoring the volume etc) is a simple politropic function that states
T2/T1 = (p2/p1)^(n-1/n)
T's - are temperatures in Kelvins
p's - pressures in kPa
n - politropic exponent (not sure about the proper english term)
From the first case (200 kPa @ 25°C -> 240 kPa @ 90°C) I got the n being 12.238 (which is wierd because n is usually from 1-1.4, 1.4 being kappa). But let's go forward anyway, that n was used for the second case to get the p2 or the hot pressure of the tire. The resulting p2 equaled 272 kPa (from 220 kPa @ 25°C to 272 kPa @ 90°C). So the answer to Jonesy's question was: you would get a higher resulting pressure in the first case (the higher cold pressure).
Now back to the LFS realm. One thing I've noticed in LFS is (if the inside colouring is actually the pressure) the lower cold pressure you put into a tire - the higher resulting hot pressure you will get. This is kind of opposite to the example I calculated above - but I think it is correct (and my whole calculation was an EPIC FAIL) because it takes into consideration of how the tire actually produces heat.
Tristan (as you are probably going to be the first one to reply cause ur such a forum fanboy ) - correct me if I'm wrong: as I understand it, the tires' ability to produce heat depends on it's ability to deform - no deformation no heat. Ofcourse the actual friction and sliding (slip angles) of the thread help this quite a bit - but in LFS not as much. Why not as much? The example I can provide is if you take a MRT out on any track, put 150 kPa cold pressure in all the tires (cold in this case is already preheated but who cares) - drive some laps and notice that the color inside the tire (pressure area) remains blue or even goes darker towards black - surface temperature also remains blue or barely greenish. Now cut the cold pressure in half say 70-80 kPa and do some laps. Resulting temperatures and pressures are both higher, inside of the tire is green, sidewalls are green, surface temps are green.
So if my understanding was correct.. When a tire has a lot of cold pressure and is just rock hard, it cannot deform and produce temperature. But then again - if you put in lower cold pressures and you get a higher hot pressure because of it. On the other hand, the overinflated tire should be prone to sliding much more and the surface temperatures should actually be higher, shouldn't they? Just to get back to MRT example for a sec - the cold pressure that you leave the pits with actually drops even more as you are driving and the air is cooling the tire - I would expect it to at least remain constant, but I guess the rate of cooling is higher than the rate with which it can produce temps? That's kinda the question number 2
Finally, question number 3/suggestion: (maybe move this post into Improvement suggestions section - I've only put it here because it will get more views ) Can we please get a pressure reading added into the F9 menu - so just a number inside the color of the "air" that will tell us the exact value of the pressure as the tire goes through it's temperature/life cycle? I don't think this would be such a huge deal to add, especially if we consider real life where we could test this very easily - just inflate a tire - drive - connect the pressure gauge after 2 laps. There are even pressure sensors in newer cars that monitor pressures in real time and report to the driver (for all the people who were about to say "Can u see tire pressures in real cars while driving?" - yes you can.)
P.S. One more thing. The F9 menu inside a FZR looks normal (tire load above tire temp in numbers above the thread temps in color) but in FO8 and BF1 the temperatures in numbers are overlayed on the thread temps in color making the colours and the numbers hard to read - this might just be due to the fact that tire profiles in openwheelers are larger than in GTR's but maybe it can be fixed somehow? If it's too much hassle then forget about it.
Without questioning the infinite wisdom of the LFS tire physics model - can someone please answer the following questions (with proof hopefully).
LFS tires are "preheated" already when we exit the pits to let's say 15°C below their "optimum" operating temperature. The color of everything in that stage is dark blue (surface, tire walls, pressure inside the tire). As we go out and do a lap or two the temperatures of the thread ofcourse go up and over the tire's life span they can go to the red zone and then slowly go back to brownish and green and in the end back to blue - when they usually pop. Now, the inside of the tire (the area where the air is) also changes color - goes to blue-ish/green or green during a normal race, but can go to brown/red if you just do a burnout - my understanding is that this color represents the pressure inside the tire (and not the air temperature inside the tire - cause that would be pretty useless).
Question number 1: (by Jonesy) "like, say I put 200kPa in a tire, warm it up to 120degs would give me the same amount of psi in a tire as if I put 180kPa and warm it to 120degs?"
With my limited knowledge of thermodynamics I kinda used a simplified politropic equation to calculate the following example: We have a tire with 200 kPa @ 25°C, we warm it up to 90°C and get 240 kPa in it (these kinda numbers are usually correct in "other sims", I cannot say for real life because I never actually measured a pressure after the tire has been driven/races - but it's safe to say the pressure goes up - the problems come up when we ask by "how much"). We have a second tire with the cold pressure of 220 kPa @ 25°C and we warm it up also to 90°C - how much will the pressure rise? The method I used for this (not taking into consideration how the tire actually produces heat and ignoring the volume etc) is a simple politropic function that states
T2/T1 = (p2/p1)^(n-1/n)
T's - are temperatures in Kelvins
p's - pressures in kPa
n - politropic exponent (not sure about the proper english term)
From the first case (200 kPa @ 25°C -> 240 kPa @ 90°C) I got the n being 12.238 (which is wierd because n is usually from 1-1.4, 1.4 being kappa). But let's go forward anyway, that n was used for the second case to get the p2 or the hot pressure of the tire. The resulting p2 equaled 272 kPa (from 220 kPa @ 25°C to 272 kPa @ 90°C). So the answer to Jonesy's question was: you would get a higher resulting pressure in the first case (the higher cold pressure).
Now back to the LFS realm. One thing I've noticed in LFS is (if the inside colouring is actually the pressure) the lower cold pressure you put into a tire - the higher resulting hot pressure you will get. This is kind of opposite to the example I calculated above - but I think it is correct (and my whole calculation was an EPIC FAIL) because it takes into consideration of how the tire actually produces heat.
Tristan (as you are probably going to be the first one to reply cause ur such a forum fanboy ) - correct me if I'm wrong: as I understand it, the tires' ability to produce heat depends on it's ability to deform - no deformation no heat. Ofcourse the actual friction and sliding (slip angles) of the thread help this quite a bit - but in LFS not as much. Why not as much? The example I can provide is if you take a MRT out on any track, put 150 kPa cold pressure in all the tires (cold in this case is already preheated but who cares) - drive some laps and notice that the color inside the tire (pressure area) remains blue or even goes darker towards black - surface temperature also remains blue or barely greenish. Now cut the cold pressure in half say 70-80 kPa and do some laps. Resulting temperatures and pressures are both higher, inside of the tire is green, sidewalls are green, surface temps are green.
So if my understanding was correct.. When a tire has a lot of cold pressure and is just rock hard, it cannot deform and produce temperature. But then again - if you put in lower cold pressures and you get a higher hot pressure because of it. On the other hand, the overinflated tire should be prone to sliding much more and the surface temperatures should actually be higher, shouldn't they? Just to get back to MRT example for a sec - the cold pressure that you leave the pits with actually drops even more as you are driving and the air is cooling the tire - I would expect it to at least remain constant, but I guess the rate of cooling is higher than the rate with which it can produce temps? That's kinda the question number 2
Finally, question number 3/suggestion: (maybe move this post into Improvement suggestions section - I've only put it here because it will get more views ) Can we please get a pressure reading added into the F9 menu - so just a number inside the color of the "air" that will tell us the exact value of the pressure as the tire goes through it's temperature/life cycle? I don't think this would be such a huge deal to add, especially if we consider real life where we could test this very easily - just inflate a tire - drive - connect the pressure gauge after 2 laps. There are even pressure sensors in newer cars that monitor pressures in real time and report to the driver (for all the people who were about to say "Can u see tire pressures in real cars while driving?" - yes you can.)
P.S. One more thing. The F9 menu inside a FZR looks normal (tire load above tire temp in numbers above the thread temps in color) but in FO8 and BF1 the temperatures in numbers are overlayed on the thread temps in color making the colours and the numbers hard to read - this might just be due to the fact that tire profiles in openwheelers are larger than in GTR's but maybe it can be fixed somehow? If it's too much hassle then forget about it.