Cobra on 200 TW street tires

Cobra #3170 · #1 (**permalink**) 03-23-2014, 03:09 PM

I have been developing my car to see if I can make it work on 200 TW street tires as required by Good Guys autox rules since our loss in November of 2013.
I revised the steering system to increase steering angle and speed up the ratio. Good Guys uses lots of U turns and has some pretty tight corners too.
I reduced the spring rates to about 1/2 of what I use with Hoosiers because these tires (Falken) cannot take a spike load anywhere near what a Hoosier A6 can take. Next steps are to improve shock tuning and experiment with front and rear camber angles as well as toe front and rear. This is a video of my Friend Scott Fraser ( SCCA 2012 SCCA National autox champion) driving the car at our first event this year. We have made significant progress but have a long way to go. I thought some of you autoxers might like to see an in car video.
The joke between drivers was how much throttle could be used between corners without blowing the tires off.

[ame]https://www.youtube.com/watch?v=Pk_7FPUmPNM&list=UU0CJQuj-tI4J89NccUhpJ1Q[/ame]

vatdevil · #2 (**permalink**) 03-23-2014, 04:43 PM

Wayyyy more open space than our local autocross courses. Would you be willing to share spring rates?

Cobra #3170 · #3 (**permalink**) 03-24-2014, 11:03 AM

Quote:

Originally Posted by vatdevil

Wayyyy more open space than our local autocross courses. Would you be willing to share spring rates?

Spring rates won't help because I have different motion ratio's than other Cobra's. The wheel rates are now 150 lb/" front and 180 lb/" rear, you can use these numbers to work backwards just divide these rates by your motion ratio squared to calculate the required spring rate. Front bar is 1.25 ID 1.00 ID with a 10" arm, rear bar is .625 solid with an 11" arm.