What tire pressure do you guys recommend for the track? I plan to fill up the morning of the event (Willow Springs). The car is stock with no suspension mods of any kind and running 245/275-18. Thanks for the advice.

 

There should be good "race air" at the track.

Usually, you need to take air out of the tires when tracking.

I ran 29fr and 31rr morning cold on RA1's as a starting point. The hotter the day/track, the lower the pressure.

 

It will depend on your tires and driving style. I get enough air in the fronts to use all the tread, and then adjust the rears for balance. Some people use shoe polish or chalk lines on their tires to see how far the tire is "rolling over".

If you are rolling onto the sidewall (beyond the tread) the tires need more air.
If you are leaving some of the tread untouched, you need to let some air out.

I run RT 615's and use 39F and 35R. (But I have different tire sizes and suspension.)

 

+1 good advice...each tire, track, and driver will be different and require slight changes.

IMO a good place to start is low 30's cold in order to aim for 40 PSI hot...but this is just where to start, from there you need to tweek it to fit your specific situation.

 

I'm not sure I agree about that.

Playing with tire pressure to compensate for bad camber is not going to help with the car's balance. Not if performance and good tire wear is what we're looking for. It might work for autoX, where tires run cold all the time, but on the track, I'm not convinced.

Professional drivers might chime in on that.

 

try 37 hot front and rear as a starting point.

 

try a pyrometer its the only way to definately know. I used one and now its my best friend I call it pyro, put a little picture of drew barrymore on it. If the middle of the tire is a lower temp than the edges put air in and if its the highest temp let air out. There is a much better and more indepth explanation than that but thats basic. BTW that was a firestarter reference.

 

really depends on your tires. A048's have really stiff sidewalls but my KDW's were rolling over when I was running an S2K CR to the point that the lettering was touching the road...at 33 PSI. A048's would probably be well suited to runnin low 30's whereas my KDW's need to be at 36+

 

What brand and model of tire? Start there.

 

Thanks for all the good advice so far Since its my first time, I'll be running with what I have (Ecsta ASX). A friend told me that I should go with what I have for my first couple of times to find the limits of my car (also its shortcomings) and upgrade accordingly. Hopefully the car wont be sold before my second time.

So far from reading the responses, I'm thinking of going 32-34 psi cold in the morning and figure that I should be between 38-40 psi throughout the day. As far as marking with chalk, can someone explain the process with more detail?

I think "pyro" will come later on if I get a chance to track more.

 

You wet chalk (the white stuff people write on glass with) your sidewalls in a few spots to check for tire rollover. Someone at the track can help, guide, direct you.

 

I should have been clearer;

I used the rear tire pressures to make minute adjustments to the car's (stock suspension) balance.

There are a lot of better ways to adjust the Z's balance and, with the exception of driver inputs, they all cost money.

 

Yes. we can play with tire pressure to affect the balance. I agree (didn't word my previous post very well). But trying to prevent the tire from "rolling over" with increased pressure is not a very good idea.

A "clean" side wall is not a sign that the thread is contacting properly.

 

Agreed my sti tires are ****ed. I ran 35-37 cold and found 36 all around on a colder day made me happy.
Ps my sti is now in my garage all stock with bald stock tires about to be traded in For another 350z. Its a sad but happy day in the life of Zspectrum. This is 350 number 2.

 

You can use white shoe polish from one of those little applicator bottles, or "white out" fluid that one used to use in typing and still can be purchased at Staples or Office Depot. Just be very cognizant of where you start and draw your stripe down so you can recall how much has been scrubbed off! You don't have to draw a circle doughnut all the way around the tire, just a couple of verticle stripes on each tire.

The type and weight of the car, its suspension set up, the track conditions, the air temp etc. all influence your psi decision. In general, start a touch high, with the intention of bleeding air at the end of your first run. Measure the tire temp with your pyrometer in three places across the tread, outside-middle-inside, as fast as you can after pulling in from your run. Target something for street tires in the range of 37psi hot for this car. Big Willow does not typically heat up the tires as many tracks because it only has 9 turns, several are pretty fast (or in the case of 7 hardly worthy being called a turn at all). The temp challenge there is that being in the high desert if you run in July, as opposed to March, the surface temp can be scalding hot and air temps well over 105 degrees F. In any event, get your practice runs in, adjust your hot temps to your chosen initial target, paint the white markings on, then take your second run and see how it feels. Then adjust again by putting a bit in or taking a bit out.

The real key is being safe. You are going to be delivering faster lap times through attention to the driving line and maximizing corner exit speed, hitting your apex points and making your turn in and corner entry as perfect as you can, and paying attention to proper braking incept and threshold pressure. A couple of psi on the tires is just not going to impact driving returns for folks like us until those elements are really under control. Big Willow is a bit different than some tracks in that there are three turns where mid corner speed is very important....specifically turns 1,2 and 8. These are all high speed and long turns, so lap times are significantly impacted by managing the mid corner. The difficulty is that car control skills at high speed are essential and the consequences of a mistake without those skills are potentially severe. SO be careful. And if you have not driven this course, respect turn 9 like you would a strange Rotweiller. The entry is fast, the radius sharply diminishes and the apex is later than a child support check from a deadbeat dad. If you run out of surface on the corner exit at track left you can roll the car at triple digit speed. Just don't challenge there, because a couple of psi one way or the other is not going to be at the front of your mind coming through 9!

 

Thanks guys for all the help. 2 more days until I de-(track) virginize my Z.

I think I'll follow your advice Eagle/Julian and shoot for 37psi hot.

 

thanks for asking, I was about to post something like this. see you tomorrow Andrew

~Robert

 

It is going to be a gorgeous day up at Rosamond today. Be sure to give us a write up on your experience, and some pictures too!
Good luck and be safe.