BigOLundh

iTrader: (1)

What tire pressure do you set for auto-x events. Can you also post what brand tires and size your using for those pressure settings.

Thanks!!!

Ophitoxaemia

with the oem tires, i found 35 psi front and rear worked well for me on concrete. i had used 32 psi front and rear on asphalt. the key was to water the bridgestones so they stayed cool. i tend to use slightly lower pressures than most people.

james

ZoomZoomH

iTrader: (1)

so i'm not the only one that prefers an even front/back tire pressure for autox... on rwd cars at least...

PUR NRG

Hey, have you tried using the search function? This is one of those questions that has lots of answers if you care to look.
________
HEMP

ronbauer

Annie and I ran 42/40 front/rear with 275/35/18 Hoosiers A3S04s and it seemed to work pretty well. We were told higher pressures by Tim, but a local guy that sells Hoosiers and is a multi-time National Champion told us 40 was better. I'm not yet sure which way to go, as with the lack of camber we can get out of the front, there was a little more rollover than I'd like.

Ron

red_rx8_red_int

I first tried the low 40s then backed down to high 30s. Then on an non-autox day at the local autox site, I was playing around, and found the stock pressures to prove much better rear end grip. So then I started running 39psi front and 32-36psi rears (mostly 35-36). A couple events went OK. But after more events, I've had some very serious understeer on right hand sweepers with tightening radius. Last Sunday it dawned on me that the problem was too much grip in the rear compared to the front (rear 36, front 39). I'm now convinced that for more neutral handling, the pressures need to be more equal. Plus with the higher pressures at the rear, torque steering is more available. I have not chalked the tires to find the lowest psi that still prevents sidewall rollover, but have carefully looked for sidewall wear and have none.

clyde

On 245/35-18 Hoosiers this year, I wound up settling in at 51F/30R. We ran a two day event with 275s and started with those pressures. Ugh. Never did find something we were happy with the rest of the weekend.

I also ran a bunch of events on street tires (the OEM Potenza RE040s) and was pretty happy once I got to 36F/31R.

BigOLundh

iTrader: (1)

What brand oem tires did you have. Mazda has gone through a few different brands withing just one year.

Somebody posted about using the search function. I did, and I couldnt find the information i needed.

To everyone else... thanks alot, and keep the stats coming!!! I think im going to start out with even front/back, and adjust from there... keep the info coming, this is wonderful.

tpryor

Ron,

I went through the same tire pressure dilemma years ago, when we began running Hoosiers on the Miata. After a LOT of talking, and ultimately testing it ourselves, we concluded the higher pressures WORKED better, but the lower pressures FELT better. The Hoosier web site discusses this very point, and I think they are correct. Here is the link (http://www.hoosiertire.com/rrtire.htm), but here is the text of the "Tire Pressure" section:

===================================
Tire Pressure Recommendations
Hoosier tires typically require higher pressures than other brands. Autocross applications require higher ranges of pressure; road racing tends toward the lower end of the recommended pressures.

Reference the following chart for suggested pressures:
Vehicle size Hot Pressure Cold Pressure
1800-2200 lbs. 39-42 30-36
2200-2600 lbs. 40-43 31-37
2600-3000 lbs. 42-46 32-37
over 3000 lbs. 43-48 32-38


Higher pressures will improve the performance capability but will require a more sensitive feel to take advantage of the increase.

One characteristic of the Hoosier P-Metric radial tires is the tendency to "skate" initially (when inflation pressures are correct). It is important to resist lowering the pressure to attempt to eliminate this feeling. Dropping the pressure may improve the "feel" of the tire however it will also lower the performance and increase the wear on the tire, particularly on the outside tread edge.

The above chart is a general recommendation which is intended for a standard configuration vehicle (i.e. front engine, rear wheel drive). Factors which can radically affect your pressure set up would include front wheel drive, independent rear suspension, rear engine, McPherson vs. control arm front suspension.
===================================

However, I do recognize that pressures vary greatly due to driving style, but we have found this to be true, regardless of what our "bum" tells us. We always ran very high pressures in the Miata also, and while I'm not at your level, the Miata did win 5 National Tours in it's lifetime and 3rd in the only PRO event we entered. Sadly, because the "nut behind the wheel" isn't always tight, best I could do at Nationals was 11th.

I'm expecting to learn a lot from you guys, so please keep us informaed as you learn new things.

rx7&rx8

It seems some people are specify hot tire temps (taken after a few laps, wheels and tires warmed up) and others seem to be using cold temps (before running), am I wrong about this? When I autox this usually is about a 4-5 psi difference between the two.

On the street, tire pressures are usually specified for cold tires.

BigOLundh

iTrader: (1)

THANKS for the info guys...
I auto-crossed today for the first time in my 8. I ran 36 even front/back on my stock Dunlop OEM tires. I think the tires handled very well. 36 was the cold temp, i forgot to check them after they were warm.

The event went great. I am very proud of my car and myself. Unfortunately this was the last event of the Season for the PCCA. I can't wait till next year.

GeorgeH

iTrader: (2)

I just ran an event on OEM Bridgestones. Car is totally stock, including alignment. Ran 36 psi front and rear on asphalt, about 55 degrees & wet. I have no idea if different pressures would have been faster, but I did turn in the fastest time for my run group (PAX, mostly). OK, Jim Daniels in his CSP Miata soundly waxed me on the fourth run, but we only count the first three runs here in PDX. :D

Dark8

You beat me by a full second! And the course was a little dryer for my runs. You were 5th and I was 9th in raw time out of 105 drivers. And we were both on OEM gumballs. :D

Ophitoxaemia

i bleed tires to the target pressure before each run. i also water the tires to maintain the correct temperature. for the oem bridgestone, its pretty cool, under 100 degrees.

rx8 should be an excellent car for wet conditions!

james

GeorgeH

iTrader: (2)

I was surprised how well it did in the wet. My first run, I was getting a bunch of throttle-induced oversteer. Still, it was totally catchable and I never got into trouble. My next two runs I decided to let the front tires define my cornering speed and my times improved.

In the (wet) sweepers, if the car started understeering, it was easy to balance the car by adding/removing throttle. So yes, this is a good rain car. There were at least two AWD cars in my run group (R32 & WRX) who were a little surprised by my times. And the R32 driver is at least as good a driver as I am, if not better (he did beat me PAXed).

Dark8, you did well too. It was a good course for the RX-8. Lots of transitions and the sweepers were shorter than normal for PDX. Your car looked good on the JICs - not much body roll and the body motion seemed very well controlled. And it sounded good winding out just before that first chicago box.