Auto-Xing the ACR

[SNKBYT]

I will be Auto-x my09 viper tomorrow. The course is 1.5 miles long. Lap times are around 1:30 seconds.
Question #1. What would be the best shock settings. I am currently set up/using for rough track specs.

#2. Which tires would work best?

The temperture will be around 60-70 degress. partly sunny. I have both the stock pilot sport cups, and a set of PS-2s. Would the ps-2 work better in this short time because the Cups will not have time to warm up? Anyone with experience with the ACR?

 

[mjorgensen Woodhouse]

IMO the PS2's would probably be MUCH better. The SC tire takes forever to warm up and is down right horrible till it does.

If you run the PS2 you would really benefit from more camber 2.5 or more in front and 1.2 in the rear. I would also add a 1/4 turn of toe out per side in the front. (if it were mine anyways)

Shocks should be at full soft now? With the stiff springs I would stay there.

 

[SNKBYT]

Thanks Mark! I have adjusted the rebound and compression to track settings. I lowered the car using the rough track heigth specs. Should I go back to full soft on the shock settings? rebound and compression. I won't be able to change the toe or camber settings before tomorrow am.

 

[JonB]

If PS-2, do you have the ACR 295s size? 315s? OE 275s can plow-push, <1" skinnier.

The lower CG is good.

All of what Mark said, negative camber is critical, or you will scrub off your shoulder rubber and plow-push. Plus ADD PRESSURE in the PS2 for AutoX....maybe 36 cold? Take Mark's advice, Id start at 36 since you wont build any real heat in 1.5 miles.

If you get a lot of runs, try 3 clicks on everything, but use full-soft for starters to learn your baseline....


LONG AUTOCROSS! Viper should do GREAT

 

[SNKBYT]

I have the 295s in the PS-2 as well. I will run the PS-2 at 36psi. (thanks JB) Should I return the shocks to full soft or dial up the compression and rebound settings, like the recommendations for rough track?

 

[Alan Patterson]

I'm not sure about the new ACR's, but I'd guess your car is likely to "push" in the corners rather than be loose. You can lower the rear tire pressures relative to the front to improve this situation. I used to run 4 more PSI in the front vs the rear of my 06 coupe. Now I have increased spring rates and adjustable sway bars front and rear so no longer need to run staggered tire pressures.

 

[mjorgensen Woodhouse]

Fast transitions in autocross need a little softer shock settings so you don't over load the contact patch and make the car plow. At 36psi you will leave a little on the table but the tire will not wear as bad. I guess it boils down to whether you want to win or go home with ok tires.

 

[JonB]

I have to defer to the X-perience of AlanP and MarkJ, but I think we are al saying the same thing. [I helped Alan get started a bit, but HE is now the Master!]

I agree to start soft, and MAYBE add up to 3 clicks all around later if not pushing....very glad to hear you have 295s up there, the OE zize on ACR, less likley to push-plow.... I bet AlanP had to run oe 275s sizes in his class in 06?

Have you X-d before? if not, "LOOK AHEAD" is the #1 pc of advice you can apply, and HAVE FUN!! Look very closely at Mark's Avatar< You can see he is emerging from a Right-hander, and yet dialed LEFT on steering input whilst his rear tire is rolling its shoulders a tad as he sets up for the next lefty ahead.....if you enlarge it, I garantee you he is looking beyond that next turn!

 

[Alan Patterson]

Jon... I did originally run 275's MX's on my 98 GT2 which was no fun. Eventually went to 285's... I have always run 315's on the front of my 06 (Hoosiers) and they work great. By the way, the real master at autocrossing a Viper is Jason Rhodes who just finished second at the Nationals in the largest, toughest, class there is! (super stock) ...Congrats Jason! Mark Jorgenson did not do too bad either and deserves Kuddos...

 

[SNKBYT]

Without reguards to tire wear, what is the Best pressure for optimal traction? I want to be competitive and hold my own against some vettes and cobras! Sounds like full soft on the shocks, at least in the front is the way to start.