Shaun R

Keep going back and forth on what rates to run, wanting to stick with leafs. Below is my setup, let me know your thoughts.

96 Coupe
30/24 swaybars with poly bushings and heim endlinks.
Control arm bushings are poly.
Rear suspension will be heim/adjustable, have not decided on who I will order it from yet.
Tires will either be 275 or 315, would prefer a square setup for rotation purposes. Tire compound will either be a semi race (kumho/nitto) or a V710. Car just needs to be tolerable on the street and handle both rough/tight courses (h2r) and smooth high speed tracks (COTA).
Will leafs around 650/350 be enough, or should I consider something a little stiffer? Care is in the process of a compete suspension rebuild, after 17 years of abuse it was due. Just cannot decide on what rates to go with.

Aardwolf

I'm running Z51 springs from indianavette at $100 a piece. I believe he has more. Search his name in C4 parts. If you need shocks TPIS has some road course valved at only $180. The shocks made the car a bit rough but it's tolerable for street driving to me.

Solofast

The C4 is pretty limited, you can't go much more than Z07 springs in the back, or you have to start backing off on bar stiffness. For that reason they are about as good as it gets. You already have the right bars, so just upgrade the springs and you are there.

The Z07 springs are pretty stiff, when coupled with an aggressive set of shocks it's about all you want on the street anyway. With too stiff a shock you will start shaking stuff in the car apart (don't ask me how I know this).

The costs quoted by ardwolf are pretty reasonable, you probably won't beat that so I'd say go for it.

Shaun R

That's about what I was thinking. Already have Koni SA shocks, forgot to mention that in the original post. They are about 10yo, 20K miles, but they are still holding their fluid so I'll sick with them. I was considering going with the VP&B extreme front spring and a Z07 rear, then just using the rear sway bar and end link adjustment to fine tune my handling. If it's not worth it, then I'll just track down some stock Z07 springs and spend my money on other things.

racebum

when i raced my c4 i used 750/500 VBP springs with koni sports and poly bushings. it was actually a fairly balanced combo and would work well with a tire like the kumho xs

still a tad soft for R comps and especially slicks but the c4 is limited on what it can handle

you could probably run an R888 with those springs or similar tire and have good results, just me be a touch floaty at high speed

#1 place you can pick up time is your driving skill though. sticky tires increase the fun factor but there is usually a lot of time to be had practicing your braking and line setup. each extra mph you carry out of a corner translates to tenths to seconds by the next corner.

i remember having to use the little base suspension rear sway and forgot what i had in the front, think it was an fx3 bar

Shaun R

Consistency and reliability are the main goal. The stock setup was so soft that it was very bouncy at speed, especially on the rough tracks. Between that and keeping oil/coolant/brake temps in check, it was difficult to have consistent lap times on the road courses. AutoX and time trials I could keep it within one or two tenths, but those were slower speed shorter track environments. Car is now 17yo and I have been racing it for 10 of those years, so it's due for a rebuild. Right now all I want to do with the car is the occasional open track day and limited street use, so that's how the suspension will be setup.

Solofast

Yup, that's exactly what I mean by the C4 being limted. If you go to bigger springs in the back you have to back off on the rear bar or the car will experience jacking due to the fundamental geometry. There just isn't a lot you can do.

If you go bigger with the rear spring, you can go to a bigger front spring, but you will have to back off on rear bar stiffness, and that also limits your front bar stiffness in order to keep everything in balance.

Easiest and best thing is to go Z07 springs and bars and then tune gently from there. If you are lower you can be a bit more aggressive than if it is higher, but the real problem comes under braking or under trailing throttle. When the back end lifts the roll center comes up and the car gets unsettled (or worse) and thing get exciting.