Hey guys I got a set of fortune auto 500 series gen 7 true rear coilovers about a year ago. Knowing nothing about spring rates I assumed the stock 10k 8k spring rate would be fine and sounded like a good balance for the front to rear ratio. Now that I’m learning the rear wheel rate is far higher than the front (rear being about .96 and the front being about .65 from what I’ve read in the forums) after doing some research I’ve settled on a 13k front and 5k rear with swift springs. I’m running a carbon hatch in the rear with the trunk gutted and maybe 10lbs of sound dampening added in (big difference in road noise vibration especially at highway speeds definitely recommend). For more detail on the the front of the car I’ve got all spherical bushings beside the upper control arm which is gonna be spherical soon too, so there shouldn’t be any bushing binding or friction. The rear is almost all stock rubber bushing besides a spherical shock mount and camber arm so there’s some good tension from the bushing there. I’m planning on running my hotchkis bars on full soft front to help battle my understeer issue ( 265 / 295 continental extreme contact sports (basically Michelin ps4s)) and the rear on second to soft or full soft to help keep my outside rear tire from spinning like it does because of my stock vlsd (no money to go built lsd right now I know that’s a big help). Anyways I was wondering what y’all thought of that 13k 5k setup. Would a 14k 6k setup better suit me? I do abunch of tight technical driving on the dragon so I need body roll to a minimum. Would the 5k rating be too soft it sounds soft to me but that’s what seems to be the recommended to get a good front to rear frequency? Also worth noting I had my car scales the other day on a cat scale, came out to 3060lbs (2003 touring) with about a 1/8 tank and no driver. Doing calculations the car should actually be sub 3klbs. About 160lb taken out of the car and that’s about 100lbs of gas out of it from the 3250 curb weight, the cat scales aren’t that accurate for light vehicles.

 

After racing the Z33 platform in SCCA W2W racing for the past 14 years, the spring rates you are proposing are WAY too high for what I assume is a street/track driven vehicle. A 1300-1400 pound front spring will do nothing but provide terminal understeer and a bone rattling ride. If body roll is your prime concern, you may need stiffer swaybars than what your Hotchkiss are providing, but in the meantime, try setting them to full soft in front and try a medium setting in the rear. In addition, going to adjustable upper control arms and learning how to adjust camber properly can also help you plant the Z better in hard cornering.

By contrast, my SCCA T3 racecar is mandated by rule to use no higher than 700# springs and depending on the setup, is drivable in both dry and wet conditions at racetracks throughout the U.S..

 

Interesting, where are you getting the 1300-1400 spring rate is that being calculated off the wheel rate? The car is street driven but I don’t really care for comfort. I do a bunch of track like driving in the mountains and have plans to move towards tracking it every other month. I was scheduled to go to Znationals in Atlanta Motorsports park but they said I wouldn’t pass tech because of a slightly cracked windshield (upsetting). As of right now with my stock 10k front progressive springs it feels like I’m bottoming out. And looking at cornering pictures im able to see the suspension almost fully compressing about 2 1/2 inches and I can feel it too. I can also feel the rear not having any travel and being too bouncy? Would the 5k rate still be too high for the rear? What would you recommend in the front I thought a 13k /750in lb in the front would be okay with linear springs being that I’m also dropping down a notch in the front sway bar but I guess not? What spring rate would you recommend for undesteer. I’m at -2.2 degrees of camber and plan on going up to -2.8-3 with adjustable front uppers.

 

12k with 5k rear is a nice setup, and very comparable to the Nismo t2 springs.

only issue , I se you have 30mm stagger to cause extra understeer

 

Sorry, I'm used to using different spring terminology and was confused by your descriptions. I think a 700# spring in the front with 500-550# rear would work as a start. Do you ever use a pyrometer to check your tire's contact patch to dial in camber? It's a useful tool.