Tire pressure?

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I'm a top 500 tuner, but I have brought most of my knowledge from FM3 to FM4, even my tire pressures. I know we have a new tire model and was wondering if anyone has found a difference in tire pressures.

I still run 29f and 28r for most rwd cars. I haven't benchmarked other pressures in FM4 yet, so any answers are welcome.
 
Well, the only difference I noted was that in FM3 all my cars basically had the same tire pressure and it ran good enough, where in FM4 you really need to test drive and tune the pressures for each vehicle for maximum performance.
 
I'm no top tuner, but in FM3, I thought it was found the best PSI for grip was 32 psi when heated up. I started FM4 doing the same. Then I found SlaveMunkey's tuning calculator. It's been worked on by a lot of Forza tuners, over several editions of Forza. So I figured he has a good idea of the physics of the game. Anyhow, his tuning calculator figures peak grip is at 32.5 psi. So now I aim for between 32 and 32.5 psi after 3 laps. The guidelines in the tuning section on tire pressure, say it's best for handling if the front is slightly higher than the rear.
 
I have a question too, I have my measurements in metric so I have kw, km etc but my pressures are in bar?
I thought psi was the commonly used metric value, even though it is pounds per square inch, which are both imperial
 
Magic Town
I have a question too, I have my measurements in metric so I have kw, km etc but my pressures are in bar?
I thought psi was the commonly used metric value, even though it is pounds per square inch, which are both imperial
Click to expand...

Nope. In the metric system, bar is the standard unit for pressures. Although pascal is the official unit, bar is widely recognized and used commonly (1 bar= 100,000 pascal).
 
1 bar is close to atmospheric pressure at sea level, so if you can remember that the earth's atmosphere is ~15psi, mentally converting between bar/psi becomes pretty easy. I like bar when it comes to a boost gauge; 1.0 bar on the gauge means the engine is getting ~2 bar, or double the pressure of the air outside.
 
from what ive read, you get the best traction when your tire temp is around 180-210 degrees fahrenheit. what do is go to test drive mode and run a hot lap around the track, and then i turn on the telemetry so i can see how the tires are doing. i try to get all tires warmed up so that they'd be around 190 degrees when im on a straightaway. increase pressure to increase temp, and vice versa.
 
Temp and pressure are directly related in real life. Never having tuning experience in Forza, I basically do what Viper2788 does. I keep it at 30/30 and let the tires get to their max temp then adjust. I tend to keep my tires about 180-185 through the turns. Anything above 190 and I tend to lose grip. And the tires cool in the straights (about 172-175) which seems about right to me. But I feel it is more important to keep the tires at the right pressure through the turns than through the straights.
This is all stuff I have picked up on my own testing live in-game. I never used a calculator or anything like that yet.
 
I thought decreasing pressure actually increased the Temps.
Actually I'm positive thats what happens.

Run my tires at 30 when heated BTW.
 
If that's the case, it is backwards than what it is in real life. For every three degrees temp loss in the outside air, the pressure in the tire drops one psi. That's why where I work, we over fill customers tires slightly so if there is a temp drop the next day, customers don't come back blaming us for not doing our job.
Now, I could see the tires getting too hot if the tire pressure is extremely low. That is possible but would however lead to a shredded tire sooner than later.
 
You also have to take the track/event into question, the pressure for a race at silverstone will differ to those being used for a drag race ... I personaly use 35 on the rear, and 45 on the front on RWD cars in a drag race ..... alot of tweaks on the suspension but thats a different post.
 
The tyre pressure changes how much the tyre surface is allowed to deform as it contacts the ground. This deformation raises the temperature of the rubber. (bend a metal spoon backwards and forwards quickly until it breaks and feel how hot it gets, this is the same principle). Therefore less pressure=more deformation=more heat.

As for putting more air in when the weather is cold. this is because colder air is denser than warmer air therefore occupies less space, reducing pressure(see Boyles Laws of thermodynamics). so more air is needed to counteract this. if the tyre of a normal road going car is below normal this increases wear therefore reducing the life of the tyre.

Sorry for the physics lesson.
 
Quote" If that's the case, it is backwards than what it is in real life. For every three degrees temp loss in the outside air, the pressure in the tire drops one psi" end quote.

In Canada we set pressure around 34 pounds in summer. We get as much as 80C (144F) difference between winter to summer.
According to the stats above when winter rolls around we would have -14pounds in our tires (tyres)...HAHA
 

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