ok its late and i did a search, but if i missed a thread asking the same question just post a link plz.
i found this one, but its about daily driving.
https://www.rx7club.com/suspension-wheels-tires-brakes-20/tire-pessure-353184/

i am wondering what is the best tire pressure for racing and day to day driving.
would it be best to keep it at what is listed for that car or should i max it out. does it help at all to leave a little room in the tire (fill it up, then release some air to let is sag some), or does that keep you from doing the best that your car can do?

 

Your tire pressures really need to be set according to the track you're at. I'm still learning this stuff myself, hopefully howard coleman or damonb will jump in too, but generally you raise or lower your tire pressures depending on how the car feels. I've seen howard suggest starting with 30lbs front and 28lbs rear cold pressures so that could be a good place to start.

I also know you can adjust tire pressures to try to cure under/oversteer but I don't know yet which end does what, IE lowering the front to cure ___steer, raising the front to cure, etc.

 

There is no set rule for tire pressures. At the very minimum different tire brands will like different pressures along with different cars, different suspension settings, different track conditions etc. There is no magic number to use.

The quickest way to set pressures for performance use is to put some chalk or shoe polish on the shoulder of the tires where the tread and sidewall meet. When the pressure is close to optimal in corners you should see the chalk wear off from the tread about a 1/4" or slightly less. If you're wearing less than that drop pressure. If you're wearing more than that raise pressure. This will get you in the ballpark of what the tires like but from there you still must fine tune the pressures of front vs. rear to balance the car.

When I'm at the track I always recommend lower tire pressures than what I run to novices with identical cars and setups if they ask. The lower pressures give up some ultimate grip but it makes it easier for the novice to drive the car and so their performance is actually better. If the car frightens the driver or does things he doesn't understand he surely will not go fast. Driver confidence will always outrun a faster setup.

 

Damon
When I ran at VIR every one told me to pump my tires up to 38 -40 psi to prevent sholder rollover. I have Goodyear eagle F1s very stiff sholder Should I start out at recommended pressure and then check for sholder wear I will do the chalk trick when I run in NOV.

Johny

 

Seems that the Corvette guys have told me in the past that those tires are different beasts and don't require near as much tire pressure as we're used to seeing because of their very stiff sidewall. Start off with the tires at normal pressure and mark the sidewalls. Then adjust your pressures from there by what the marks say.

On a roadrace track you want to be certain you're talking hot pressures. As the tire heats the air pressure goes up, so you have to counteract that by starting off with lower cold pressures. Hot pressures in the mid to high 30's seem to be common for the majority of tires and cars but that's just coincidence. It's amazing what a difference just 1 or 2 psi can make at the limits of the car.

In autox you don't have time to put much heat in the tire so you start off with cold pressures considerably higher than what you would run at a roadcourse.

Beware of drag racers as well because they are only interested in traction in a straight line so they run really low rear pressures to make the contact patch as large as possible. The downside to this is that the tire won't corner worth a darn because it will just fall over, but that's not an issue on a straight drag strip.

 

With competition tires and many of the performance street tires, the old chalk method doesn't really work. This is due to the aforementioned stiff sidewalls. Other than hit or miss testing, a probe type pyrometer is really what's needed to get your tires where you need them. Really not any other way that I'm aware of.

 

The GM factory recommended tire pressure for the F1 Supercars is 26psi. I've run them at 28psi and felt pretty decent about them. The Supercars are more or less an intermediate between a street tire and an DOT-R.

 

oh ok, so depending on the type of tire and conditions you should give or take some. for the most part its pretty close to 30psi?
thanx

 

Start with 30 Front, 28 Rear. Do some laps and see how it feels, adjust as needed.

 

What kind and size of tire are you running, and on what car? Would help to give you better info. I've run as low as 25 and as high as 50 on various setups.

 

im not asking for a specific tire size and setup, i was just asking a general quesiton. lets assume im talking about....3 gen. RX7 with...18x9s and 18x10s

 

ok i just read up on some other threads and saw that 18s would rub, is this true?
if so plz dont give me crap about it

if 18s rub lets change it to 17s, same widths, unless they are too wide

 

Lots of people run 18" wheels. In general, wheels clearing your fenders and liners depends more on wheel width and offset than diameter.

 

oh ok thanks for the helpful comment...first one in a while
....havent you told me that before? for some reason i think youve said that or something very similar in one of my old threads
ok ive got some rims in mind with some tires, but the website isnt up right now, so ill get back to you as soon as i find the specifics and ill see if you or anyone else can give me any insight on it.

 

The only time I rag on you, and not just you, but anyone, is when they ask a stupid *** question or make a bullshit comment. Fair enough?

Then why didn't you search instead of asking?

 

yeah its fair enuf
i dinn search because its late, im going to tomorrow, i just figured youd be able to remember before i could read it all