General info for an uneducated AX'r, Primarily tire pressure Options

[jd66921]

Hi,

I've been doing AX's for a little more than a year.

Currently I'm driving Howard's old car "Suzi". She's a pretty much
stock 914 2.0l. She's been lightened a little. She has fiberglass hood and
bumpers. All her heat and ventilation has been removed. Weight is 2050 lbs

The engine is a stock 2 l as far as I know, and has an unmolested MPS.
The transmission is stock.

I do not know what kind of shocks are on her. The rears are yellow and do not
seem to have any adjustments. The rear springs seem fairly soft to me? There
are sway bars front and rear, I do not know what size they are. The fronts are
adjustable with a number of holes in the horizontal arms. They are set to the center.

I typically run about 10-12 seconds behind Corvettes, A Birkin, and a well
setup Mustang Cobra. I am typically 3-4 seconds behind set up Miata's,etc.
This is on courses that I would generally say favors the high powered cars.
Generally, the courses are two 180's at each end, fast stuff down the middle,
and most of the courses I can take flat out or with minimal lifting., except for the
real corners, of course.

Wheels are 5.5 inch Fuchs, with Falken Azeni RT-615's.

My big questions is: I am now running 25 psi front and rear in the tires.
Is that in the right ballpark? Should I go higher/lower, and why? The car
feels good most of the time, with a little bit of mostly controllable oversteer. I
can get some wheel spin off the line, and a little on right hand sweepers.

What will changes to the front swaybar make? I've never understood them! I
would prefer an answer like "increasing the front rate will increase grip" instead of
"decrease over steer".

Anyway, I seem to have reached the limit of my improvements without help, so
I 'd like any help I can get!!

Thanks,

Jeff




My first question is

[Joe Ricard]

secret to going fast at Autocross.

"Gas is on the right, it goes to the floor""
Brake in in the middle use it hard or not at all
there are gears past 2nd. try using them.

35 PSI is really where the Azenis wil be most happy. drive it harder and lean on the tire "it will stick"

[grantsfo]

I agree with Joe. Trust us guys who have driven lots of AX's on these tires. Truly 35 is going to result in better times. 25 will likely result in more predictable (with falkens ...sloppy) but slower tire. Suspect your slide off course wasnt due to tire pressure.

But really you need to chuck the Falkens and get the new RE11 from Dunlop. Far better tire.

Speaking of tires what are your alignment specs?

This post has been edited by grantsfo: Jun 8 2009, 09:37 PM

[jd66921]

I really appreciate all the info!

I really don't know what I am doing. I've run maybe 15 autocrosses in two 914's.
Suzi is my favorite! At least she has some power!

I was running 35 psi, but I spun off course once and decided to reduce tire
pressure. The tires do not roll over onto the sidewall, that is why I have been
reducing tire pressure. I will try higher the next AX and see where I go.

Sorry, right now I can't afford more expensive tires. I use the Falken's as
street tires as well, so it isn't practical. I'm not sure I have enough wheels
to dedicate some to race tires yet.

Of course I need a LOT more experience to figure out what to do, that is
why I am asking. It seems like I should be closer to the fast cars though, even
with the HP gap! It's tough though, with them doing 80 and me doing 50 down
the straights!

Alignment specs, ?? Stock as best I know. No sure I can tell the difference!
What should they be set to?? And why??

I'll be asking more later, thanks!!

Jeff