Contour Enthusiasts Group Archives Forums General Autocross and Open Track Autocross results...more tire pressure info

Competed in my first autocross in the SVT yesterday. Not a big turn-out, but a fairly quality one with many out-of-region cars using Hoosier autocross tires.

My first run was a disaster. With the 40 front/42rear set up, low fuel the car oversteered horrendously under drop throttle. I did not spin but came close 4 or 5 times. Hit 2 cones but should have been more. I'm pretty good at going through gates sideways. Time was 53 something before cones.

Dropped tire pressure to an even 40/40 but now had initial understeer, followed by not quite as bad drop throttle oversteer. Made two consistent 52.28 runs, still hitting cones and still feeling wild.

Went to gas station and filled up tank to cure initial understeer, hopefully, and raised tire pressure to 45/45 because fronts were rolling over bad on the concrete surface. Result: 50.854, dropped substantial time and no cones. A nearly perfect run, with good balance.

After a crappy 5th run, I made a consistent 51.353 and 51.411 on runs 6 and 7 so that tire pressure set up seems good. Lost time by trying to go too fast.

Beat the Factory Five AC Cobra, but on fun runs, he got better coming very close to my last 2 runs. Checked his tires and he was not even rolling over onto the sidewalls with 32/32 on concrete! His car weighs just 2100 lbs. and with 245/45ZR 17 front and 275/40ZR 17 rear he had too much tire for the light weight of the car. But your tires would last forever on such a light car.

Lost to all cars running Hoosiers, as to be expected, but even the Z3 M roadster only ran 48.2 during his record 6 runs. He ran as low as 46.45 on fun runs. He made about 12 runs trying different set ups. Without Hoosiers I felt good to be within 2.6 seconds.

Also lost to a new Miata on Hoosiers that was transported in a huge enclosed trailer and ran a 49.2 in the record runs and 48.8 on a fun run. Several other Miatas ran but I beat them.

Lost to the 2000 Southeast Solo II Ladies Champion in a D Stock Neon. She ran on Hoosiers and beat me by a second. Keep in mind that autocross tires are good for 3-4 seconds.

In my class beat a flight instructor who had an Audi A6 Quattro twin turbo w/ Dunlop S9000 tires. It was only his 3rd autocross but he ran well, with a 52.9. He was mad that he lost to a Contour, but did not realize that we had 6 cylinders.

For those that doubt pony car capabilities, a 99 Z-28 had a 53.053 and a 88 Mustang GT a 53.603. A street prepared 240Z had a 53.289.
These were competitive times with the 2nd and 3rd place Miatas that ran 53.5 and 54.0. Believe me, there were no straights on this course to favor the pony cars...it was purely a handling exercise.
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Kickimus Maximas Buttimus
98 EO SVT Toreador Red
97 F-150 W/ 2 horse/habit

[This message has been edited by SVTCole (edited February 12, 2001).]

[This message has been edited by SVTCole (edited February 13, 2001).]

SVTCole

Vern Kilburn in a 99 Contour SE and Myself in a 2000 Contour SVT have been running autocross for a about a year. What we have learned is, depending on tires, surface.... you need about 44 to 48 lbs in the front tires, and the determining factor is how much your tire is rolling over (i.e. run as low a pressure as you can, but high enough to keep from wearing the sidewalls.

The pressure in your rear tires is what controlls how loose or tight the car is. I can run 30lbs in the back and the car is tight (understear) but if I bump the pressure up to 35 in the rear, it has a tendency to be loose, and 40 in the rear, makes my car very loose, with very pronounced oversteer.

What is funny, is that Vern's car and mine are now very simular, in that we both have koni's front and rear, We both have progressive rate spring that lower the car, same size front sway bar, ...... Even though his car is an SE and mine is an SVT, the suspensions are very simular. This weekend, he was fighting a very bad case of the loose butt (oversteer), and I was try trying to loosen my up some to get a controlled amount of oversteer. I was raising the pressure in the rear tires, and Vern was lowering his.

I quess my point is, try a lower pressure in the rear tires to tighten up the car, but every car is different, and what works for me may not work for you.



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David Mimlitch
davidm@hpnc.com

'00 'Tour SVT T-Red
'99 F250 SuperDuty Powerstroke Diesel 15.1 second 1/4 mile time

This is Vern,

Yes my SE was very loose! She would four wheel drift like a rear wheel drive car! Have
a great video of it!! Not sure and does not make sence! I am running SVT front swaybar 19 mm and a SE rear at 18mm Running 17" yok
A520's running 45 to 48 in front adjust for widewall clearence and adjust rear to control
balance. Started running Konis one half turn from full soft in front and one half turn from full firm in rear. The car rotates like a top! finally ended up at:
Front: tires 47 lbs koni's full firm
Rear: tires 30 lbs koni's full soft
she felt better but you needed to keep both eyes on her! Nothing is loose or broken Checked night after race. I am wondering since the suspension mods I gained alot of
"sharpness to driver input" and I am just wondering if the car is faster than I am . My times are the same as with the SE suspension but with the SE suspension I felt
when she was going to let go. Now I am just along for the ride! I'll ask David to run my pax runs next event to get a second opinion.
am open to any two cents in autocross land!
Vern

Thanks David M and Vern. The SVT is a great handling car before you get to the limit, but it can be super squirrely under drop throttel at the limit. I can see why so many young guys are crashing theirs. Hit the on/off ramp at full tilt boogie, and then back off as about to merge...recipe for disaster. Check those tire pressures everybody and don't run more air in back than in front if you want to keep your toy in one piece. The problem with mine and I suspect most is that you tend to have initial understeer that forces you to back-off. This is without a doubt the wildest handling car I have ever autocrossed. But based on the competition it hung with it is also the fastest!!

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Kickimus Maximas Buttimus
98 EO SVT Toreador Red
97 F-150 W/ 2 horse/habit

David M, after rereading your post, I speculate that you are running the OE KDWs while Vern is running Yokos. That may explain the difference in under vs oversteer.

You both have extensive suspension mods so I have no clue what that does vs. stock. I also guess there are differences between my 98 EO and the later SVTs in handling, or at least shock valving. I thought I had heard that shocks primarily influence slaloms and transition back and forth in "s" curves. When you stiffen the Konis does that act like stiffening the spring rate? If so the rule of thumb is stiffen springs/bigger sway bar in back to fix understeer, and stiffen springs/bigger sway bar in front to cure oversteer.

Vern, how do you know you are running the same times as with your original suspension? Interpolation with other guys you ran against last year before the mods?

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Kickimus Maximas Buttimus
98 EO SVT Toreador Red
97 F-150 W/ 2 horse/habit

http://www.grassrootsmotorsports.com/shockstech.html

Read that and it will tell you how Shocks/Struts work...

Shocks do not affect overall spring rate. Springs compress a set distance, almost instantly, based on load. Shocks compress at a variable velocity based on the acceleration rate of the shock piston.

Single and double adjustable shocks allow you to tune a suspension for compliance, transient response, and (to a small extent) the rate of load transfer. Triple and quad adjustable shocks allow much better control of compliance, transient response, and load transfer - to the extent that you can run much smaller anti-roll bars.



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John Coffey
johnc@betamotorsports.com

Alot to answer so little time. I was speaking with David and other friends and we think the migration from the SE's "sport tuned" suspension to koni single adjustable,H&R sport springs,SVT front sway bar and 17" wheels makes my SE "VERY RESPONSIVE" to driver input. I am use to having to anticipate the bodyroll last year with the SE tunning and wait for the car to respond. Now when I flinch she turns! I have no problems with nice 4 wheel drifts in sweepers car felt very responsive to driver input just the transitions in the slaloms kill me. I understand I will need to change my driving style to a "smoother" flow on the course. Like I was telling David (00 STV)
I have a greater respect for the SVT
and the performance of a well setup autocross car now.

On the times I figure how much by percentage
a given driver was faster or slower to me over the course of rhe season and use the average to offset bad days. Since we never run the same course twice it is hard to scale
you performance over the course of a season.
The figures are close .4 of a second in autocross time this is forever but for my first full year they are close for goverment work.

also I still do not have my rear swaybar yet.
Bat's still on backorder! on their 22mm.from what I understand as as a rule of thumb with a SVT 19mm front and a 22 mm back this should increase my oversteer. Which I am a little worried about. I am now running SVT 19mm front and Stock SE 18mm in rear. Hoping this will stabalize the body movement in the
transitions and not upset the balance of the car. I think I addressed all your questions.
thanks for the two cents!
Vern

I think you are right that the 22mm rear sway bar will increase oversteer even more. And you already seem to have very low rear tire pressures so you can't compensate by lowering them further. I'm not sure I would put that thing on, or try it, you can always go back. You'll just need a precise driving style to go near the limit but not beyond. I can't do that...controlled abandon is my style with smooth brake/steering/throttle inputs and transitions but at speeds that generally require temporary drop throttle due to initial understeer. It is that drop throttle thing that sends me into the sideways, slower, but somewhat controlled mode.

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Kickimus Maximas Buttimus
98 EO SVT Toreador Red
97 F-150 W/ 2 horse/habit

Have any of you tried a good rear spoiler on your car? this will increase downforce and add a little weight to your shakey rear end. One of those nice touring wings I think should do nicely. Nothing to ricey though I don't want anyone to ruin there car over this. hehehe