So I was driving along on an AutoX course with the FXO Turbo and noticed something that was odd to me.
Let me preface by saying when I do an AutoX in real life, the common sentiment is that you fill your road tires to about 40 psi. The idea being that the added pressure gives you better sidewall support for tighter cornering.
However, according to LFS, it is better to have less than the required pressure. I did a few laps in the FXO using Bob's road going set to simulate an average car. I found that I was quicker with about 30 or less psi all around and slower with 40 psi all around. I also tried it with the XRTT and found the same results.
So who's right? What should I actually be doing at these Autocrosses? I know lower tire pressure gives you a better contact patch and sticks better, but I was under the impression that the amount of rollover of rubber would even things out. I guess not. Give me your input!
There was a discussion about this before, either on rsc or this forum, I don't remember (don't worry, this ain't a 'yuo should have searched' post, as it'll be good to get newer LFS peeps opinions on this).
As far as I know, the benefits of lowering the tyre pressures outweight the lack of support from the air to a point, in terms of grip. Much like the higher pressures are reduced flexing of the carcase helps to reduce tyre temps in real life, up to a point.
This thing is that LFS isn't quite perfect there. For max grip people still run lower than what would or should be optimal, and for tyre longevity people run pressures that in real life would cause chuncking of the tread and quite a lot less grip. Hopefully it's something that the next patch will fix (but thats a wish, NOT definitive).
With autocross it is all about grip and FEEL. In LFS, because of the non-mechanical connection to the wheels (electric signals, and FFB) and no 'seat-of-the-pants' feel, the effect of losing tyre rigidity is lessened considerably. Whether or not thats something that can be fixed by more realism or less is debateable.
If we have a prefect tyre simulation (hypthetically) then in theory we'd run our tyres just like real life. But if, because of the nature of a simulation, and how we perceive and interact with it, we can take advantage of something in that perfect recreation of physics that real life cannot allow. So what would we want? A sim that is 'realistic' but due to the drawbacks of simulations we can take advantage of, or physics that are, compared to real life, inherently flawed but less susceptible to grossly unrealistic misuse?
I think, and I'm sure lots will disagree with me, that thats a strong point. I look forward to hearing what people say.
Good points, and I'm glad you took the time to re-analyze this concept.
I agree foremost about the feel of the real world vs. LFS. I've never run below 32 psi before, but I imagine if I tried going as low as 30psi in real life, the car would feel pretty bad. It might stick better, but I probably would not feel in control because of the chunkiness of flabby tires. Hence, I would be slower...unless I adapted I guess.
I'm the type who often needs definitive answers to settle my mind, so it looks like a few test drives are in the cards. Maybe I'll go out somewhere and hit a few curves with 40 psi then head back out with 32 or 35 and see if I even feel a difference. The problem with real world testing, at least for me, is that there is so much tactile information to take in, a subtle difference like that would be hard to detect without things a like a g-meter and/or constantly being aware of cornering speeds. Who knows. For now, I'll stick around and await some more input.
Some other thoughts.... I think there's way more to take into account here, a big one being the height of the sidewall. This should have a profound impact. IRL I can feel the difference in NORMAL driving from 32PSI to 38PSI, it feels way different to me as soon as I drive away - so I suspect you'll notice a difference when pushing your car! (my tires are not exactly "low profile" LOL)
I would think that sidewall flex would act as a bit of a buffer and make your envelope at the ragged edge somewhat wider. I can really feel this in LFS too. It's amazing how much "feedback" you can really get from LFS, it's that well done IMHO. Perhaps the faster laps times are due to a less tempermental car... Lower pressure in LFS seem to create a car that warns you far ahead of time just like IRL. Now I've lost my train of though because I am on the phone. crap. back later
After thinking about this, I do see some funky things about LFS' tire physics. Not completely wrong physics, but just some small discrepancies that seem odd.
I've autocrossed too, and can agree that 35-40psi in some econo or performance tires really makes a difference for controllability. I own an Integra, and when first driving it for several months, I had the pressure kind of low (I think it was around 30-32). There were times at which it had some great grip, but in a lot of sweeping 's' corners that go up and down, loads on the tires became really intense and it felt just like LFS has. So I put the PSI to around 38 -40 and the car really does handle better. Even when I had lower pressures, the rear had a tendancy to feel like it was 'swaying out'. With high pressures, a lot of loads on the tires are cured, and the car is much better in both twisty backroads, and autocross.
LFS is correct with the reaction and feel of low vs. high pressure tires. You DO feel the difference.
-Go low pressure, the car feels washy and grippy, but not rigid and overall... has very poor response. In LFS you really only take advantage of low pressures because you want the tires to heat up faster. This is also why I completely disagree with LFS and its pre-heated tires. Your car has to suffice to crappy washy handling with loads of understeer (FWD) or oversteer (RWD) because the low pressures is the only thing that can give you the best possible grip and heat. The car should still be driveable at cool temperatures, even with hard tire pressure. Not possible in LFS.
-If you go hard pressures in LFS, it just gets worse. Poor grip on VERY HOT tires???? Come on now. If anything that is the only drawback to using a medium/high tire pressure on the road cars. High pressures have many advantages... mostly depending on the track, like higher speeds, better road feedback and feel, less sluggish feel or more responsiveness overall. When driving a FWD car (like the FXO) and you use high realistic pressures in the front and you just can't steer for shit at low speeds... that is absolutely incorrect because with cool tires at low, no-throttle, turns, you can do some VERY sharp turns with hardly any understeer. For FWD cars, the soft pressures is the only way to go because it is the only way to alleviate this, its bullshit. In autocross, it is just worse, because to tackle a tight slalom, then to do 2 parallel hairpins instantaneously, it is a low speed struggle of fighting the car's understeer or oversteer. If you had low pressures, it would be easier, but also present a very loose steering feel that doesn't give you any ability to be very precise in pointing the car where to go AND how the car is reacting.
We all hear people say low-speed grip is very wierd, and it is. It is very difficult even at pressures that most car manufacturers recommend. It doesn't have 'bite'. Add that with a car's tires that feel like they are sagging, and you are struggling more with trying to regain traction back and forth than trying to take the turn with precision and proper racing line (Especially at Auto-X).
I really was hoping that the LOWEST pressures you could choose would give good grip, but also poor handling/response. It does this somewhat in LFS, but not quite the case because of the stupid rapid heat. And if MEDIUM pressures would give good grip, and good cornering stability, that would settle this, but they don't really. HARD pressures would not have as good of grip (couldn't be that far off from medium psi), but be able to take a corner far better -- It almost seems the hard pressures 'rock hard feel' and their lack of grip overcome the cornering ability they can truly present. Harder pressures CAN make the car handle better overall (we aren't talking like 50psi, more like an adequate level). And I don't think that the harder pressures should be so excluded from heating up properly --- which is why I said I really hate the fact that the tires are pre-heated in LFS, and STILL the cars cannot handle well with 40 psi :rolleyes:
I'm rambling on, but this is my view on it after some feedback of trying all kinds of variants for the past few months in LFS, and realizing it is somewhat different than a real car.
Yeah it's weird the tyre pressures have swapped since S1. While it used to be "set them as high as they would go", now it's "set them as low as you can without melting them".
Only minimum tyre pressures, and on certain cars, does the handling really begin to suffer. LX/MRT5 are extreme examples, even with minimum tyre pressures you can't get the tyres up to temperature. But handling doesn't suffer too much.
On the plus side, we're getting closer with each update. Only a matter of time...
I just wanted to bump this thread back up again now that the new patch is out. I haven't done much extensive testing, but a few passing tests have led me to believe that the tires act pretty much the same way as before. I get bad understeer with ~40 psi in road tires and I feel much more in control if I drop it to below 30. Still is a bit odd to me. I cannot really feel any decent rigidity out of high pressure tires...just a nice plow!
Anyone have any additional comments after patch T has come out?
Before the patch I was happily lapping KY Nat at sub 2:00 times in the FXO with quite low (20psi) pressures, now with the patch I couldnt even get close with the same set, I need to get up to 30psi before I could start to lap the same times.
I think that the tyre pressures are now more realistic, my road car needs upwards of 32psi (40 profile tyres)
you are right! the pressure/grip relationship is still as before or even worse (with road tires), what has become even worse is the new deformation model that requires the maximum tire pressure lfs allows to get phisics behave less unrealistic, put also that the temperature/grip relationship on road tires is still wrong and you got this ugly unrealistic patch.
for slick tires it all seems good (but i dont have real experience with slicks) and i guess it because of BF1 (i assume michelin gave the devs the telemetry data for slick tires)
