AutoX Tire Pressure
For the OP, I have run my 9 at one event and a few fun runs with the OEM tires and I settled right in on 42F 38R, (car was bone stock) so you might be right in the ballpark. I found that as the tires got hotter they needed more pressure. IMO the car is down right frustrating to drive in autox with the OEM tires.
As for chalking/ shoe polish on tires, keep in mind that if you cook the front tires on turn in on just one corner all evidence is lost and the test means nothing. THe same can be said for pyrometers, autox is so dependant on driving technique that these tests can really send you heading in the wrong direction. Using a pyrometer on consecutive days taking averages over those days, and over the width of the tire, throwing out the numbers acquired when making driving mistakes, etc. would probrobly help considerably. That said, I dont do any of it. I personally go by feel (mostly), and run times comparing myself to other drivers in PAX and raw time.
In regards to 710 pressures, last Saturday, I went all the way up to 47F (275's) 42R (245's) and was still getting faster as the day ended. 1st in Pax, 3rd fastest raw. AS evo, 710's are mounted on 17x8 wheels.
As for chalking/ shoe polish on tires, keep in mind that if you cook the front tires on turn in on just one corner all evidence is lost and the test means nothing. THe same can be said for pyrometers, autox is so dependant on driving technique that these tests can really send you heading in the wrong direction. Using a pyrometer on consecutive days taking averages over those days, and over the width of the tire, throwing out the numbers acquired when making driving mistakes, etc. would probrobly help considerably. That said, I dont do any of it. I personally go by feel (mostly), and run times comparing myself to other drivers in PAX and raw time.
In regards to 710 pressures, last Saturday, I went all the way up to 47F (275's) 42R (245's) and was still getting faster as the day ended. 1st in Pax, 3rd fastest raw. AS evo, 710's are mounted on 17x8 wheels.
On competition tires it is easier to see where the edge of wear is. Warr had a good point mentioning that it takes different pressures for different cars based on how the rest of the car is set up to handle.
Chalking isn't perfect but it is cheap and a good starting point.
Chalking isn't perfect but it is cheap and a good starting point.
i may give it a try though with more pressure in the rear. right now i am fairly happy with how the car is feeling, but it will certainly be worth looking in to. basically at this point i am trying to get my driving more consistant with my current setup more than anything else. i've changed alot over the course of this season, and i want to make sure the nut behind the wheel is tight before i go mucking around too much.
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From: Clifton New Jersey Lived: Daytona Beach, Florida Lived: Port Orange, Florida
i am completely stock. well i went with the higher front tire pressure and it felt like i was under steering a bit, so i let some out and it improved a bit. I think it might be the tires since the car only has 4000miles on it so the tires might still be 2 new. But on the other hand i did manage take first for novice class LOL.
All of the fast Evo autocrossers I have met (including Mark Daddio and John Winchester) use higher pressure in the rear, regardless of suspension setup, or tires. The Evo is a classic front-heavy understeering pig of a car, and it takes every trick in the book to make it loose enough for competitive autocross. The top drivers are using spring rates like 12k front / 16k rear and 3 - 7 lbs more pressure in the rear. They have also done other stuff to reduce understeer, which I am only now becoming aware of. I have to use 7 - 12 lbs more in the rear to make the car rotate like I want it to.
Also, you can't fix the understeer with a big fat rear sway bar. All you will do is lift your inside rear wheel.
I recommend starting with about 38 F / 42 R with stock Advans and working up or down from there. Rather than using a chalk test, the best test of whether your car is balanced properly is this: take a fixed radius turn at the limit (at autocross speeds), and lift throttle. If your car doesn't spin, it's not loose enough. :-)
Also, you can't fix the understeer with a big fat rear sway bar. All you will do is lift your inside rear wheel.
I recommend starting with about 38 F / 42 R with stock Advans and working up or down from there. Rather than using a chalk test, the best test of whether your car is balanced properly is this: take a fixed radius turn at the limit (at autocross speeds), and lift throttle. If your car doesn't spin, it's not loose enough. :-)
now there is recommendation.........for those of you running A6's be careful how much you lower your pressure or you will be sorry.
I'm running my A6's at about 33 F / 40 R for the first run, and then I let the rears creep up (but not the fronts) as necessary to make the car loose enough. What pressures do you use? (Assuming you have an Evo.)
On the stock tires, I've run between 38 and 42 on the front and between 40 and 44 on the rear. It depends on the course and the temps.
I also take the approach of adding pressure in the rear to aid in rotation. It does remove overall grip from the rear, but with completely stock suspension tire pressure is really the only way to change handling characteristics.
I also take the approach of adding pressure in the rear to aid in rotation. It does remove overall grip from the rear, but with completely stock suspension tire pressure is really the only way to change handling characteristics.
I'm running A6's for the first time (got them in late August). So I really need to know: do you mean "sorry", as in bad performance, or "sorry" as in the tires will be destroyed?
I'm running my A6's at about 33 F / 40 R for the first run, and then I let the rears creep up (but not the fronts) as necessary to make the car loose enough. What pressures do you use? (Assuming you have an Evo.)
I'm running my A6's at about 33 F / 40 R for the first run, and then I let the rears creep up (but not the fronts) as necessary to make the car loose enough. What pressures do you use? (Assuming you have an Evo.)
Okay, thanks, not a problem -- I have -3.5 degrees of camber, and do not have any rollover problem with my suspension.
Yep, I know he was talking about tire rollover; my point was that with -3.5 camber in front and 500 lb / 700 lb springs, my front tires never reach an angle that would cause tire rollover with a front pressure of 33 lbs. The front starts to feel a little squishy at 32 lb, but I think I get even more front traction at that level. It's also important to note that I have 285-30/18 tires on 10" wheels up front. Narrower tires generally need higher pressures. The best tire pressure all depends on your setup.
(Welcome back from the Nationals, by the way. Hope you did as well as you expected to.)
(Welcome back from the Nationals, by the way. Hope you did as well as you expected to.)