AutoX today leaves me with questions

[mikecg]

I went to the AI autoX at Ripkin today. I was running on race rubber for the first time. For some reason my rear bumper had an identity crisis. It kept thinking it was the front.(read: The car kept trying to spin) I've never had the SVX oversteer on me while autocrossing. Usually it understeers, even with the rear bias tranny.

Ok, now the explination. The last event I went to was at FedEX field. The car felt very controlled. This time I was at Ripkin and I was exstremely sloppey. The car was all over the place. He's a list of what was different.

FedEX:
Tires: 225-35-17 BFG KDW2 tires. PSI was the same all around. Equal wear all the way around.
Weather: 98 degrees Sunny, light breaze
Suspension: Stock(read installed at the subaru plant) except for the Motorsports springs
Tranny: 6-speed JDM STi
Engine: ECUTune Stage III
Race: Fedex has a long fast course. I was running in the low 70sec range. Most STi's were runnig in the mid to high 50's


Ripkin:
Tires: 245-45-16 Victor Racer V700. I ended up running 35psi front and 25 rear. fronts = new, rears = approx. 1.2 life left
Weather: 65 degrees, sunny, windy
Suspension: Same
Tranny: Same
Engine: Updated software that gives a good bit more power in the upper RPMs
Race: Ripkins as a little less room then FedEX, but they made a pretty fast course. My scores were as follows:
1st Run = 161.??? (Spun 180 and stalled. Battery issue delayed restarting car)
2nd Run = 58.??? (had the car nearly 90 degrees in 2 corners)
3rd Run = 54.??? (I finally learned how to skate on ice. I could feel to rear going all over the place. I just road it out)
4th Run = 51.774 ( I used the loose rearend to help me line up for the next gate and just hammered the throttle. Figured I had nothing to loose.
Competition: Best time I hear was a 48. I think that was a Cottingham 7. There was a new STi running SM right behind me. I was spying on his times. He was in the 51's the whole time.

He's he questions.
1) Why did my car feel so much more controlled on street tires? Are the Street tires better? Or is the combination of more power and running closer to the competition times over powering the rear tires?
2) I'm running tomarrow. Should I run the older tires in the front and new ones on the rear? or just run my street tires?
3) What can I do to better set up the car for tomarrow. (There is a chance of rain. If it rains I will be running my street tires.)
4) why am I so long winded with this post. ( )

[SVXRide]

Mike,
1. Well, the R-comps have to get warmed up before they stick really well. When they're cold, they probably stick less than street tires. This is why you don't want to hammer them on your first run (i.e., this is why you spun....don't worry, I almost spun the first time I ran on cold R-comps ). Make a habit of putting your hand on the surface of each tire immediately after each run to see how they're heating up. This, along with the shoe polish trick mentioned below, will go a long way to getting the tire pressures just right. (note: 95 degrees ambient versus 65 degrees ambient is HUGE when it comes to tires warming up. You also didn't mention how much time you had to wait between runs. The ambient at the last FedEx event was ~70 degrees and I had to wait so long between runs that my tires never really got heated up - which meant that even on my last run it felt like I was driving my old '68 Camaro!)

2. You're going to want to crank in at least 1.5 degrees of negative camber front and rear to help the handling and with getting the tires up to temp faster.

3. Might want to play with the tire pressures a bit -- 25 is really low for the rear. Might want to start with 32 rear and 38 front and then check the pressure after each run (i.e. they'll go up as the tires heat up). Try the white liquid shoe polish trick on the sidewalls (perpendicular stripes 180degs) and then see how much of the polish has worn off after your run -- this will tell you how much you're rolling over on the tires. There are little triangles on the VictoRacers' sidewall and you want to roll to the top of them and no farther.

4. With the s/c you're putting a lot of power down to the ground, so you'll want to pay more attention to how you modulate the throttle. It took me until my fourth run when I was driving Dave and Ben's "RaceCar" to get used to its throttle response (due to its much lighter weight).

5. Finally....let's see you were 20 SECONDS behind the STis at FedEx and now you're within single digit seconds of them . As long as you're getting faster with every run, you're doing the right things!!

-Bill

[TomsSVX]

Well I would say it has a lot to due with the nature of the tires... While the BFG's are good tires, they are not enough for your car. You easily lost traction with the front tires because well... they sucked. Now you are losing traction in the rear like you are supposed to. With the rear bias and less weight in the rear, of course it is going to come around easier. I would do what Bill said on tire pressures and try and modulate the throttle a little better. It is a race car now... push it to the limit but once you have gone over that limit, there is no comming back... Finding the limit of your car is crutial to be able to make it perform to the best of it's abilities and your own... Good luck and once LAN gets our tuning figured out, lets hit a dyno sometime

Tom

[SVXBart]

Mike at what time are you runnig tomorrow?I missed you today i was thinking you gonna run this afternoon.
I would like to do some pics tomorrw,if you dont mind.
Bart

[mikecg]

Originally Posted by SVXBart

Mike at what time are you runnig tomorrow?I missed you today i was thinking you gonna run this afternoon.
I would like to do some pics tomorrw,if you dont mind.
Bart

I ran second heat this morning. Tomarrow I will be in heat 4, in the afternoon.

[Chiketkd]

Nice runs Mike! Good luck tomorrow!