AutoX/Track: What tire pressure are you running?

[Fobio]

Having been to Dunnville this past wknd, I'm really interested in researching the factors involved with getting a good setup for the autox/track. Now, I said GOOD, not ideal, cuz I know there's no such thing as perfect. So let's try and tackle one of the biggies first..tire pressure:

1. Some are running even pressure front to back, and swear by it.

2. Some run HIGHER FRONT than rear to promote crisp turn-in and mainstain rearend stability. (read: planted read end)

3. Some are running HIGHER REAR than front (as I'm considering) to promote rotation of the rear at the cost of a lesser rear contact patch.

Please share your insight.

Some refernce: http://www.mazda3forums.com/index.php?topic=99322.0

[Fuman]

#2. Just the way I was taught. I run 34 / 32 psi on the street. (If RS-As, 37/35)
good read:
http://www.turnfast.com/tech_handling/handling_pressure

[Fobio]

I knew this sub-section comes at a "cost"...hehe...

CDN Tire shopping list:

1. 12V air compressor.
2. Tire temperature gauge (off ebay? http://cgi.ebay.com/ebaymotors/Infra...spagenameZWDVW)

I already a digital pressure gauge from CDN Tire, but I have feeling that it may be not up to par.

[Fuman]

I knew this sub-section comes at a "cost"...hehe...

CDN Tire shopping list:

1. 12V air compressor.
2. Tire temperature gauge (off ebay? http://cgi.ebay.com/ebaymotors/Infra...spagenameZWDVW)

I already a digital pressure gauge from CDN Tire, but I have feeling that it may be not up to par.

how come not up to par?
Unless you are doing Solo I, I doubt you need a PSI gauge accurate to decimal places.
I'm still using the digital ones at Petro Can, lol

[Fobio]

Next session, I'll most likely spend more time adjusting tire pressure then just driving like a mad man...

The $15 digital one I have I believe is good to 0.5 PSI, but with these instruments, I'm not so sure about the correction factor. Then again, as long as left to right are the same readings, and relative to the rears, then I'm set. Altho it doesn't have a bleed valve...

[mleblond]

Good source for tires is here

Basically says for tire pressure ".....a good place to start might be about 5 psi less than the maximum pressure stamped on the tire. From there you can use the old autocross trick of marking the edge of the tread at the sidewall with shoe polish or chalk to determine how much roll-over you have and adjust pressures accordingly. Or, if you want to buy or borrow a tire pyrometer (a thermometer for taking tire tread temperatures), that is the best way to determine correct tire pressures. Your goal should be even temperatures across the tread of the tire. And don't forget to get a precision alignment to get the most out of your tires."

[Gizzmo_jr]

When I was running 35/35 on stock RSA's the fronts cupped really bad. I upped it to 38-40 and they stopped rolling under(signified by side wall scuffs).
It also made a fairly big impact on turn in, so when I go again this summer I'm going to run higher in the front.

[Fobio]

In the article(s), they stress about measuring your pressures at certain temperatures/condition. The way I figure it, is that with a pyrometer (I like that word) it boils down to science and you can basically adjust according to tire temps.

The art/old school way is to "read" the tire, checking for scruffs and all the physical conditions. Though less accurate or scientific, I think this method is time-tested but it does require one to be experienced and know what they're looking for.

Personally, I haven't played with the tire pressures while out but I did double check that they were 37.5PSI all around when I got to the track. I've always been taught 32-34F/28-30R but those are not performance oriented numbers and likely applies to cold tires.

I'm contemplating formulating a tire pressure test regiment for the next session so I can gather some hard data.