Do you know the difference in the spring rates of the JIC versus what you are running now? I am looking for some good real world comparisons and it seems like you have been there and done that.

 

Caution on anything over a 1/2 and you may need toe and camber arms for the rear to correct alignment. So be prepard to spend some monies on them if you do need them.

 

humm...I guess I'll wait until I've driven the car for a few months and then figure out what to change. I leave tonight for Seattle to pick up the car!

 

I ran the JIC in a hybrid setup with 10 kg (560 lbs) front and 9 kg (502 lbs) rear. I then switched to 12kg (672 lbs) front and kept 9 kg rear when using the stock sways. The JIC package is supposed to be configured with a 10 kg front and 12 kg rear. I have no idea why they chose such a stiff rear but I suspect their setup is tuned for stock sways and stagger tires. For my setup of 245/40 all round and Hotchkis sways med f & r, I think 10(f) and 9(r) was the perfect street/track mix with a JIC package.

The Hotchkis is quite a bit softer than the JICs (don't forget we're talking about different dampers here as well). The Hotchkis front is 340 lbs while the OEM is reputed to be 310 lbs, and the Hotchkis rear is 330 lbs versus the OEM 350 lbs.

Right now, the Koni with Hotchkis springs feels a little soft - even on the street. If I were to select custom springs for a liveable street setup with very good track behavior with the Konis, I'd go with something like 450-500 lbs front and 350-400 lbs rear. Or, I could simply get the compression on the Konis revalved and bumped up a bit.

 

That's what I've done, but not exactly custom springs. At the suggestion of Gordon & Lee at Koni and one of the guys in the rebuild shop at ProPartsUsa.net, I raided the Koni motorsports catalog and picked up a pair of Koni sleave coilover parts. Tein makes tapered springs for the Basic coilovers that allowed me to avoid the massive headache of what to do for top mounts that work on the car and allow 2.5" diameter springs. All I had to do was imagineer a adaptor to allow a 70mm I.D. spring to sit on the Koni threaded perches. I ordered some 1/4" sheet aluminum with a stronger grade for strength and made my lower mount adaptor. The Tien springs are 448lbs in rate, for the rear since I'm still in the concept phase of things, I have revised oem Z shocks (CD300's) with 375lbs Tein H-techs.

It works fine, but I've discovered some things. One, the shocks have no where near the rebound range that everyone at Koni feels they do (no disrespect to them, but it's my reality). I'd like about 10% less high speed bump and about 50% greater rebound adjustment. And with what equals a 1/2" 350Z drop, I only have about 1.5" of bump travel. So, I'm going to see about shorting the bodies and piston shaft's. I have a idea on how to make give the shocks height adjustable lower mounts, don't know if it can be done however

 

Very nice work there sir, you should write up a how to on it when you are done. Thats if you don't mind sharing.

 

So if I’m sticking with stock dampers/springs for now what front sway bar is recommended?

 

350 evo makes some really nice sways...

 

Excellent dicussion guys !

Dumb question from a french speaking guy here. What do you mean "porposing" ? Do you refer to an instability at high speed ?

I've experienced that at Le Circuit Mont-Tremblant in turn 1 (downhill, offcamber, taken at 90 mph) and 2 (over a crest, flat out, 80 mph). The car was "wingling" everywhere. I belive that in that situation the OEM dampers aren't stiff enough.

I'd like to reduce scat and dive also. This points to stiffer spring, alosr reducing roll.

Anybody ever ran stiffer spring and dampers with stock roll bars ?

 

The problem with the Z suspension (which may have already been fixed) is that the was a mismatch between the stock springs/shocks, the springs being stiffer than the shocks. "Porpoising" refers to when the shocks can't control the rebound of the springs quickly enough which usually occurs on highways. Say for instance, you're travelling along at normal highway cruising speeds and hit a series of bumps in the road. The car acts kind of like a dolphin or a "porpoise" by bouncing up and down. The shocks are trying to control the rebound from the first bump when it hits the second bump which makes the first bump worse than it would have been with properly matched springs/shocks.

 

You are quite right, a write up on how to would be great. I am still studying my options to be sure that whatever I do I do it right. So if that means camber plates, toe adjusters and magic alignment dust I'll do it right the first time.

 

I don't mind doing a how to, I took pics for that when I did the assembly. But, I am leary until I have a truely working setup without any vises. I remeasured and I'm actually at a oem Z ride height. Even with the bump stop's trimmed, I'm hitting the stops with just 1.5" of bump travel. What I might do is a post to make sure that I've done the right things up to this point and haven't forgotten anything.

 

Are tires a “suspension modification?”

 

Nope, tires are tires...

 

Most would say tires are the first mod. I assume the disscusion is after tires and wheels.