neophile_17 wrote:We will be changing tire/wheel sizes from last year.
Last year:
225-50R16 on 6.5" wheels 200TW as required by rule pamphlet
Front Camber -0.9/-1.0 (Maxed out)
Caster I forgot
Front Springs Stock with 1 coil cut maybe 220lb/in.
Front sway-bar stock, solid bushings
Rear Camber -0.5" (Maxed out)
Rear Springs Stock 250lb/in.
Rear sway-bar same as front, rubber bushings
All suspension bushings are Polyurethane
This year:
205-50R16 on 7" wheels
We now have smaller diameter springs in the rear so rear camber is open. I bought/cut these to be stock spring rate but they feel slightly softer.
Any advice is appreciated!
Ok those are pretty narrow tires but you're running the same size front and rear. Not much need to adjust brake balance then. You won't brake hard enough to transfer too much weight forward and you don't have wider tires in the rear to make up for the extra weight back there.
You can (and should) run higher static camber in the front and rear. Slot/file/grind whatever you need to in order to get more adjustment. Make sure caster is maxed out. Steering effort will increase from the caster but the feel will be better too.
Because your springs are so soft, you'll need to run quite a bit of static camber to keep everything in check --- possibly -3* or more. Check tire wear and tire temps (3 points -- inside, middle, and outside) after a hot lap.
I'm not sure what the 84-87 front motion ratio is but I suspect your front spring rate is not sufficient to balance the car. The rear struts operate at ~0.95 motion ratio which gets you ~225 lb/in (0.95^2 * 250 lb/in) at the rear wheel. On the other hand, the front motion ratio may be something like 0.7 (this is a guess; you should measure), which gets you 108 lb/in at the front wheel (0.7^2 * 220 lb/in). You need a bit more wheel rate in the rear because you have a rear weight bias (probably 45% front 55% rear but that's just a guess), and also a bit more in the rear so it can "catch up" with the front after hitting a bump.... but double the rate is not reasonable. Some 400 lb/in front springs from WCF will get you close depending on what your actual front motion ratio is. Then bump up the rear a bit more. This is about the limit of what Koni reds can handle.