what for use what tire?

R1- short races?
R2-races longer than R1
R3- races longer than R2
R4- races longer than R3
R5- do they exist?

ROAD_SUPER -what? when you have super fast race?
ROAD_NORMAL
hYBRID - mix of rally?
KNOBBLY -rally?

please explain me

Well different cars have different tyres available depending on what is most suitable. For example road cars only have the "road" tyres, and racing cars only have the race tyres:

UF1/XFG/XRG: Road Normal, Hybrid, Knobbly
XRT/FXO/RB4/FZ5/LX4/LX6: Road Normal, Road Super, Hybrid, Knobbly
MRT/FBM/FOX: R1/R2/R3
All others: R2/R3/R4

Road Super is just a slightly softer (thus faster but lasts a shorter time) version of the Road Normal. Hybrids are a mix of road and rally, and knobbly is for rally.

R1s can be used for races in the MRT and FBM but probably only qualifying in the FOX, you'll want R2s for FOX races. Increasing the number increases the hardness (R5 doesn't exist, R4 is the hardest) and depending on the car and the length. You can run R2/R2 sometimes in an XRR GT3 for example, but on some tracks you'll need an R4/R3 on an FXR. The limiting factor tends to be the achievable tyre temperature and the amount of grip rather than tyre duration. In F1 for example you could feasibly use Super Soft tyres and Hard tyres at the same track, whereas in LFS the difference between the compounds is much larger. Putting R2/R2 on an FXR will mean they overheat incredibly quickly losing you all their grip, whereas putting R3/R3 on an FBM means they will never heat up and you won't have any grip either!

rule of thumb for any car with R-tires:

If the tires are still blue after some fast laps in the F9 display, choose a lower number.

If they get yellow/red, choose a higher number.

And if the right rubber compund seems to be between two types, i.e too hot for R2 and too cold for R3, you can use tyre pressure to "fine tune" it. Lowering the tyre pressure will make the tyre generate more heat. So hot tyres can be fixed by increasing the tyre pressure, and too cold tyres can be fixed by lowering the pressure.

Quote from Skagen :

And if the right rubber compund seems to be between two types, i.e too hot for R2 and too cold for R3, you can use tyre pressure to "fine tune" it. Lowering the tyre pressure will make the tyre generate more heat. So hot tyres can be fixed by increasing the tyre pressure, and too cold tyres can be fixed by lowering the pressure.

I think that's not absolutely true. Because ,in some cases, if you lower the pressure, the car -because of the more grip- will slide less (both during acceleration and steering) and generally will go more steadily. As a result the tires will last more.

The rule of thumb mentioned above is the best overall choice imo.

Generally higher pressures will actually make the tyre more resistant to wear, making them last longer - despite the fact higher pressures reduces grip. This off course when using the same compund. If you switch compund as you alter the tyre pressure, the story will be different.

Quote from truepiece :

I think that's not absolutely true. Because ,in some cases, if you lower the pressure, the car -because of the more grip- will slide less (both during acceleration and steering) and generally will go more steadily. As a result the tires will last more.

The rule of thumb mentioned above is the best overall choice imo.

it depends if you are considering internal or surface temperature.

Quote from Bmxtwins :

it depends if you are considering internal or surface temperature.

Hm, like a total temperature.

But the surface is importart too. Blue inside and green surface is way better than green inside and red surface.

So if I could chose only one of the two as the most important, I would go with surface.

That depends, obviously it's the tyre surface that's in contact with the road. If you follow F1 or V8SC fore example, you'll find that pressures are very critical for tyre life and even single-lap performance. Internal temperature determines how much pressure is gained from cold temps, and under/overpressure can cause very significant wear and handling issues. Not to mention there should be some effect as to how much and how quickly surface temperatures drop between corners (with slicks anyways).