wanna911

So I have a spring rate issue. I got 600/1124 lb (a little bit KW style) spring rates when my car was AWD because it pushed horribly. The car is RWD now, and while entry speed on corners is good and turn in is awesome, exit speed is touchy and power hard to put down resulting in loss of speed into next braking zone.

So the question is - which direction would yield better results, going up in the front, or down in the rear? I'm leaning towards down in the rear so as not to mess with the turn-in, but I'm a little worried about too much body lean at high compression tracks (Road Atlanta). Car already feels like the suspension is overwhelmed in Turn 12 and I don't want a slower responding car. Is the gap big enough where I can add front rate and still keep awesome turn-in while not adding push on exit?

Car is 3100 lbs.

Veloce Raptor

How are the sways set?

wanna911

They were one off full soft in front and one off soft in rear (5way front, 4 way rear). I change the rear springs to 900 yesterday and went one hole stiffer in the rear. Won't be testing until Feb. but am about to order another set of springs so want to get an idea of which way to go. I've considered trying the 900 in front and keeping the 1100 rear, or putting the 1100 in the front and going even heavier in the rear.

Right now I have 600, 900, 1100 lbs springs.

onefastviking

Type and year of car ? Wing ? Tires ? Driver experience level ? Shocks ? Are they valved for that much spring ? Tracks driven on ? Or auto cross ?

wanna911

Car: 2003 Turbo (498 whp)
Wing: Getty 61", front cup undertray with small splitter
Tires : Hoosier A6
Experience: Advanced?
Shocks: JIC valved for 800/1100 (until I get MCS)
Tracks: Road Atlanta, Barber, CMP primarily (no AX)

I drove on the A6 for the first time this past weekend, so was feeling them out, did not test the limits much. Was still getting faster after 8 heat cycles so I know I wasn't really using what they are capable of.

NaroEscape

A6's? A6 tires are primarily for Autocross. R6 is for road race applications. Be careful with the A6's as they will wear out extremely fast on the track, especially with a heavy car.

http://www.hoosiertire.com/tctips.htm

jrgordonsenior

I'd keep the 900's back there and move both sway bars 1 notch stiffer. You probably need more aero up front like the WSC front splitter but a decent rake is paramount. Cup car run 35mm difference F to R which is too much for your car, but I'd drop the front as low as practical keeping a minimum of 20mm rake. Also take some bump out of the front shocks and run some slicks...

wanna911

I am aware of the nuances, however I use them for time trials and they aren't that bad for 3-5 lap sessions. Any other time I use Kumho V710's.

My rake is 21 mm (probably a tad more with the Hoosiers compared to height difference on the Kuhmos).

Can't run slicks, too big of a penalty for NASA. Well, I could, technically, but I'm going to stick with the A6 for the time being as I have a new set and ordered some more from contingency winnings.

Won't reducing front bump make the car more prone to over steer?

coryf

Whats the specs on your diff?

Veloce Raptor

'twas going to be my next question...

jrgordonsenior

Yes usually but you've softened the rear spring rate considerably so you have some wiggle room up front...

wanna911

Diff is OS Giken 60/40.

coryf

I'd go back to the 900 front. the 600/1100 is too much split. Do you know the break away torque for the giken diff? What is the alignment setting? Whats type of rear sub frame, toe links and controls arms do you have? A lot of time exit over steer comes from a mid corner push. The driver induces the over steer at exit because he weights the nose so much mid corner to try to make it turn that he becomes impatient once the front bites and is too aggressive getting to full power. Once the nose does bite it also causes the car to slightly over rotate which is then just amplified by adding power for corner exit. Ever had a pro drive the car back to back with you to compare data?

Veloce Raptor

Yup. Agree especially with the bold.

Dan Jacobs

Cory
You're the real deal, Man