Hey all,
Tomorrow, 3/30 will be my first AX ( or any race in a car for that matter ). On the SCCA website is lots of intel. Regarding tire pressure, everyone is recommending adding 6 to 10 lbs of additional air pressure. Also, they recommended checking with folks who are running "cars like yours" to help get answers about pressure, setup, etc. I fully expect to be the only SRT tomorrow so I'm hoping some of you experienced XF autocrossers can give me some help as to how much air to run. My stock conti's say 51psi max load. Should I increase it as the website suggests, or maybe do a run and see? Right now they have 45 psi in them, I pumped 'em up a bit from the 34 I'd been touring with.
Thanks in advance.

 

Got it sorted out
Had a great day, anxious to do it again.

 

Hey, Wedge.

How did it go? What pressures did you end up using? Did you have access to a pyrometer?

What class were you put in and how well do you think you did?

 

Hey R,
After chatting with a guy pitted next to me, I went with 43psi all the way around. Seemed like a good place to start. After 3 runs the pressure only increased by 1psi. Pyrometer, no. Don't know what it is or how to use it. First ever, of any type, car race.

It was a cool day, low 60's I think, and the track was so short, and my speeds so slow that, when it was over I realized I didn't need to worry about about heatin' up my tires. I also chalked the tires, didn't seem to be any rolling over and the "stiction" felt good, didn't slide the car at all, so the pressure seemed like the right choice. I do realize that I need to find the edges of this car and that'll require getin' her to break loose.

As far as my success? When classed against my group, not counting my Novice status, I finished 9th out of 11 and de-creased my lap time by 7 seconds from run 1 to run 3. And run 3 actually felt like racing. I wasn't figuering out the course or my car, just attacking. And it was great.

 

I'd say you did quite well, Wedge. I'm no AutoX expert, but shaving 7 seconds off your first run is a huge amount of time. Guys win AutoX on tenths of a second. How does your fastest (lowest) time compare to others in your group? That will indicate to you whether you are on the pace or need to do something about tires/pressures/suspension. In any case, I've seen way too many guys get wrapped up in the technology and what they really needed is to improve their driving. "Slow down to go fast" is what they say.

A tire pyrometer is used to measure the temp across the tread of a tire. It can help you see whether you have your pressures set properly for the conditions. After your run, you measure the outsides and center of the tire tread to see if there is a variation. Hotter outside and cooler middle indicates too low pressure. Other variations can mean different things, but it's probably good that you don't get into all that now until you get better at handling your car on the course. I'm sure there are some old veterens around that can give you guidance.

My guess is that the Crossfire, particularly the Coupe, is going to make an excellent AutoX and track car. I'm a car nut and you can do whatever you want with your baby, but drag racing a Crossfire doesn't make sense to me. The thing was built to carve up the road.

Dude, knock yourself out and let us know how you do!

 

I participated in 6 AX events last year with a local Mercedes club in Virginia. I have never run an AX so it took me several tries at tire pressure before I got it right. My 2005 Limited with BFG KDWII tires I run 36 PSI on the street. At most events I found 41 PSI to be perfect.

 

NovaTim, Nice

 

When you're new to autocross, the best advice about tire pressure is to set it and forget it. I'd get them all up into the 40-45 range before the event and then focus on other things. A few psi here and there is going to be insignificant noise compared to the variability from your line/driving.

 

Good advice.

 

Advice taken