I think the tyre rolling over respectively the surface "crumpling" together at too low pressures isn't modelled yet, which makes low pressure tyres too effective.

Quote from pasibrzuch :

And the point of this thread was: what/how much/in which way, must be changed to make LFS closer to realit, in the tyre pressure case.

Once again, anybody knows the tyre pressures used in motorsports?
It should be a good base for discussion.

Well..i think you cant generalise that, as there is so a hugh variety of different cars, tracks, strategies, wheterconditions where tyre pressure does a hugh difference in laptimes. I´m pretty shure that a f1 cars tyre pressure is above of an f3000´s tyre presure couse of the different forces on the tyres, as an example.

Quote from cpachmann :

Well..i think you cant generalise that, as there is so a hugh variety of different cars, tracks, strategies, wheterconditions where tyre pressure does a hugh difference in laptimes. I´m pretty shure that a f1 cars tyre pressure is above of an f3000´s tyre presure couse of the different forces on the tyres, as an example.

Sure, someone could say that his wr set is realistic because that pressure is used in offroad
I expected answer about similar conditions and car type rather.

Except fuel consumption, I'm worrying about acceleration.
+0,5bar won't give you additional kick at long straight, but +2,5 will

Quote from Hyperactive :

Only speed limit you are obeying while racing is the pit speed limit. Only time when you don't use full throttle is through turns. With more grip (less pressures within reason) you can brake later and start accelerating earlier.

Try with equations:
P1 = power needed to drive 200mph with p-1 pressures
P2 = power needed to drive 202mph with p+1 pressures

now P1 = P2
prove me wrong

At WOT, you will have the same fuel flow and therefore the same fuel burn rate with low pressure tires compared to high pressure tires, this is true. You will get to a higher top speed with higher pressure tires because of less rolling resistance.

However, MPG is Miles per gallon, not time per gallon. You will go more miles in a given time frame with higher pressure tires because you are going faster and therefore you will have better MPG.

Oh, and it is your responsibility to prove yourself right. It is not my responsibility to prove you wrong. Take some personal initiative and either do the thinking or do the work. For example, I could say "The universe is not infinite; prove me wrong". Kind of silly, don't you think

I think tire pressures in LFS used to get your optimum lap times are too low at the moment. You have to put the pressure low to get the tire temps up on the road tires. The race slicks might be close to the right zone. I think the cars feel better with higher pressure, but you lose a lot of grip.

Quote from AndroidXP :

I think the tyre rolling over respectively the surface "crumpling" together at too low pressures isn't modelled yet, which makes low pressure tyres too effective.

I was thinking along the same lines. IRL you will put a psi or two higher pressures for a short qual run (1-2 laps) because you want the tyres to be at their optimum pressure right away on your first flying lap - and in a 20 lap race for example you are a few psi lower because you don't want to be fast for 2 laps and then fade off - you want them to reach optimum well into the race rather than at the start.

In LFS it seems you put way lower pressures for a qual(hotlap) run - and then pump them up for long races, which is opposite to real life imo.

I think LFS tyres have a much larger operational window with regards to the optimum tyre pressure than you have in real life.

Quote from danowat :

instead of trying to be a wise-ass, just say so

i think you are confused. its not me that rating other people's posts as useless or calling them wise-asses.

Quote from Hallen :

At WOT, you will have the same fuel flow and therefore the same fuel burn rate with low pressure tires compared to high pressure tires, this is true. You will get to a higher top speed with higher pressure tires because of less rolling resistance.

However, MPG is Miles per gallon, not time per gallon. You will go more miles in a given time frame with higher pressure tires because you are going faster and therefore you will have better MPG.

Oh, and it is your responsibility to prove yourself right. It is not my responsibility to prove you wrong. Take some personal initiative and either do the thinking or do the work. For example, I could say "The universe is not infinite; prove me wrong". Kind of silly, don't you think

I think tire pressures in LFS used to get your optimum lap times are too low at the moment. You have to put the pressure low to get the tire temps up on the road tires. The race slicks might be close to the right zone. I think the cars feel better with higher pressure, but you lose a lot of grip.

I've done more than enough to explain why what and when. If you still need prove I need to go into equations and stuff. Then you say that it was that and that because the chosen values were pointing to that direction already. Then we go into differential equations and ask me to use just numbers because it's easier that way.

You just said all that has been said already. I have proved "my theory" and I am not interested going into equations. I have not said anything about whether or not LFS has this or not. Nor I'm really interested about it before I get some actual proof, just "some laps around some track" isn't even near enough when you are trying to measure 5% differences I just explained how it works in real life within certain parametres (small speed differences, small pressure differences that are within the area where tire pressure plays the major part of rolling resistance and grip, racing conditions and simple engine models where you don't have ECU's controlling and deviating the fuel flows).

Quote from Hyperactive :

Only speed limit you are obeying while racing is the pit speed limit. Only time when you don't use full throttle is through turns. With more grip (less pressures within reason) you can brake later and start accelerating earlier.

Quote from Hallen :

However, MPG is Miles per gallon, not time per gallon. You will go more miles in a given time frame with higher pressure tires because you are going faster and therefore you will have better MPG.

Hyper - what Eric says here is the key. MPG, not TPG. In fact, you've created yourself a void to fill because what you said proves this fact further:

"With less pressure you can brake later and start accerlating earlier".

Since what Eric said is true - "Less distance travelled at WOT for X seconds due to rolling resistance, yet same fuel consumption rate per unit of time" and also what you said is true:

You're going to burn EVEN MORE gas by braking later and accelerating earlier, thus you've compounded the effect Hallen (and others) highlighted clearly.

Plain and simple, it takes more effort to overcome energy losses in lower pressure tires. That energy only comes from buring fuel. Allowing later braking points, earlier throttle points merely allows you to burn even more fuel no matter how you look at it. With a given line around the track, it will always take more fuel to go faster (big generality / possibly some exceptions I know, assuming everything else is static obviously)

I think Dan's experiment is proof enough this works in LFS too. For the readout, perhaps it's simply a rounding issue. He only missed .25 laps over 11 - that's not a lot, and a longer stint would probably show a numerical difference in consumption.

mpn89 I don't know how you drive but your comment is backwards and should be the other way around. A lower pressured tyre will increase rolling resistance, resistance creates heat, thus bringing the tyre up to temperature quicker.

Another problem with testing road tires in LFS is that the sidewalls do not break down. In autocross and track-days almost everyone puts their pressures up to 40-45 PSI cold to prevent sidewall deflection,which is done in LFS but Deflection causes the plys in the tire to rub against each other breaking the plys down, which from what I understand is not done in LFS.

I am not understanding this correctly I think. I was always under the impression that for maximum top speed you wanted at little rolling resistance as possible. From physics class I can say that resistance prevents things from accellerating. I realize in limited traction envoirments that you want as much resistance as possible to keep glued to the track, but with a pure top speed run you would want as little as possible because at near top speed you are not really using that much traction as your not accelerating that fast for the most part and you would want as little rolling resistance as possible?

thanks Jeff for making that a big clearer =)

http://www.lfsforum.net/showthread.php?p=279904#post279904
And
http://www.lfsforum.net/showthread.php?p=279919#post279919

Quote from Hyperactive :

http://www.lfsforum.net/showthread.php?p=279904#post279904

Thanky Hyperactive, for a second there I thought I was going insane =P

Quote from Hyperactive :

More rolling resistance doesn't itself increase the fuel consumption.

I guess I keyed in on this statement. In a way, I think I can see what you are saying, but that is like saying that aerodynamic drag by itself does not increase fuel consumption. If you have wind blowing over a car that is not moving, then no, drag does not increase fuel consumption. But, like tire pressure, it is part of the overall system and does affect fuel mileage in the racing environment.

Quote from Hyperactive :

I've done more than enough to explain why what and when. .

Yeah, you did... in that other thread. I did not know about that and the way you worded things here, did not make it nearly as clear as to what you were saying.

I just get bugged when people say "prove me wrong". Like the believer saying that UFO's exist because nobody can prove they don't exist. Proving the negative is usually harder than the positive. Also, I believe the responsibility lies on yourself to make yourself clear and to prove your point, which obviously you did in that other thread.

The math would not have helped me much anyway, it has been too many years since I did calculus. :dunce:

Quote from Hallen :

I just get bugged when people say "prove me wrong". Like the believer saying that UFO's exist because nobody can prove they don't exist. Proving the negative is usually harder than the positive. Also, I believe the responsibility lies on yourself to make yourself clear and to prove your point, which obviously you did in that other thread.

The math would not have helped me much anyway, it has been too many years since I did calculus. :dunce:

Some things I could have said better and I could have left off that "prove me wrong" part too, but the simple equations were meant to, kind of, help to understand the logic behind the idea . It was meant to be a challenge, just to see if anyone would _really_ disagree

It was meant as personal insult!!!

Hyper; I saw the other thread now also. I understand better what you're trying to say, but I think you contradicted yourself in this thread unintentionally.

Quote from tristancliffe :

[...]

I've set my AIs off in FOXs at blackwood. They have no experience in XFGs so I thought the FOX would be best for them

I'll post results here in about 2 hours or so

Quote from Viper93 :

mpn89 I don't know how you drive but your comment is backwards and should be the other way around. A lower pressured tyre will increase rolling resistance, resistance creates heat, thus bringing the tyre up to temperature quicker.

But it will be at the wrong pressure and will heat up at the wrong places.

Tyres are designed to reach their optimum shape and work most efficiently within a certain (narrow) pressure envelope, outside of it they won't work good. A tyre at the optimum pressure can be worked harder than a tyre at the wrong pressure because you get the most out of it.

When the ambient and track temperature is lower, do you run higher pressures or lower pressures? You run higher pressures because the tyre needs to reach it's optimum pressure. Same goes for a short qual-run - a slightly higher pressure than used for a race means you'll reach your optimum for your first flying lap. If you run the same pressure for the race you'll be fast for the first few laps but then fade off.

In LFS the pressure envelope seems way too large - if you were to run low pressures for qual IRL you'd end up overheating the tyre shoulders and never been at the optimum pressure = never at the fast pressure. And for a race IRL the pace drops if you have high pressures because the center overheats too much.

Quote :

And for a race IRL the pace drops if you have high pressures because the center overheats too much.

Once centrifugal (yes I know the force is just inertia etc blah blah) tire deformation is modelled, this will probably be the same way.

AI 1 - 59 laps
AI 2 - 59 laps
AI 3 - 60 laps

AI 4 - 52 laps
AI 5 - 50 laps
AI 6 - 51 laps

AI 1,2,3 had maximum pressure, AI 4,5,6 had minimum.

AI 1,2,3 had 1.7% per lap usage
AI 4,5,6 had 1.9% per lap usage

It's not that much but there is an effect on the fuel usage.

Now, let's everyone give 1 euro for somebody to do that test IRL

BTW, how about laptimes of AI?

They ranged from 1:10.95 with high pressures to 1:13.77 with low pressures.

Another test, not sure how conclusive it is, but its a fun way to waste a few hours...........

Fern Bay Club, XFG, 100% fuel

Maximum PSI

Best lap : 56.08 seconds
Total laps : 183.5 laps
Distance : 183.5 miles
Time : 2:52:33.27
Average lap : 56.40 seconds
Fuel consumption : 18.51 mpg
F12 per lap guide : 0.5% per lap

Minimum PSI

Best lap : 56.08 seconds
Total laps : 163 laps
Distance : 163 miles
Time : 2:34:23.24
Average lap : 57.12 seconds
Fuel consumption : 16.44 mpg
F12 per lap guide : 0.6% per lap

Only thing I really learnt is that the AI is COMPLETELY STUPID, and don't learn anything, they make the same mistakes over, and over, and over for 160 laps

They can't understand tyre heat, tyre wear, damage, and quite possibly the S2 suspension etc, so don't expect much. I think they were modelled after Kev.

Quote from tristancliffe :

I think they were modelled after Kev.

Quote from mpn89 :

But it will be at the wrong pressure and will heat up at the wrong places.

Tyres are designed to reach their optimum shape and work most efficiently within a certain (narrow) pressure envelope, outside of it they won't work good. A tyre at the optimum pressure can be worked harder than a tyre at the wrong pressure because you get the most out of it.

When the ambient and track temperature is lower, do you run higher pressures or lower pressures? You run higher pressures because the tyre needs to reach it's optimum pressure. Same goes for a short qual-run - a slightly higher pressure than used for a race means you'll reach your optimum for your first flying lap. If you run the same pressure for the race you'll be fast for the first few laps but then fade off.

In LFS the pressure envelope seems way too large - if you were to run low pressures for qual IRL you'd end up overheating the tyre shoulders and never been at the optimum pressure = never at the fast pressure. And for a race IRL the pace drops if you have high pressures because the center overheats too much.

I still don't see this. Less pressure you will have more grip, more grip you will have more heat, heating the tires faster. You cannot go too low because of cupping and sidewall flex, but still.

I understand that because you don't have a ton of time during a quali session to bring up tire temp, you will not have time to bring the ambient temperature of the air inside the tire up, but surely a cold tire a optimum pressure would have less traction than a tyre at optimum temperature. I have always shot for proper temperatures and never worried what my pressures were, for a race I always had to up my pressure to reduce tyre temps compaired to a quali setup.

I am not arguing, this is how I understand this and I want to know why you think the oposite, your reasoning doesn't make sense to me, anyone else help me?

In real life you use camber to control across the tyre temps, and drive to keep the tyres within temperature parameters. You use the pressure to control the shape (and damping/springing) of the tyre.

Thus, Avon (or Goodyear, or Michelin, or Bridgestone) tell you the range of allowed/safe tyre pressures, which might be +-5psi. You then use the rest of the setup and your own driving to look after the tyres and get the most from them.