rithsleeper

So I did all this already with my 89 and love my combo of the z07 and continentals. Now I just instructed a student this past weekend with a 85 c4. I immediately could tell his front spring was a lot softer and really didn't do as well keeping the car flat.

My geometry is different in the front so we cant just copy my setup. Should I just recommend the 84 z51 springs and sways since those are the stiffest or does anyone else have any ideas. I believe he has bigger sways on there now just from looks and his front spring is a FJH and rear is a NYR or NYU can't tell because it is scratched a bit.

Anyone with experience would be appriciated.

indianavette

FWIW...Tommy Morrison ran BMB fronts and NYU rear springs on his earliest ('85, '86, '87) showroom stock Vette racers. Then, he graduated to a softer shaved FHB front spring but kept the NYU rear.

rithsleeper

When you say shaved do you mean the rubber insulator between mounting points was shaved or the ends were shaved to fit the different geometry of the post '88 spring on a pre 89 car? I didn't think you could run a later model spring up front but I thought the rears were identical....

rfn026

You want really stiff springs. This is not ideal but the problem is we can't get C4 sway bars that are large enough. Normally I'm an advocate of soft springs and huge bars. I can't put that package together with the C4 Corvette

With the C4 you want Corvette Challenge springs and Z51 bars.

You also want an adjustable rear sway bar for tuning purposes.



Three settings for the rear bar allow you to tune the handling.You need to determine what the car is doing on corner entry and then adjust from that.



You're going to need a set of custom shocks for this package. Remember shocks are a tuning device. Once you get the spring package and the sway bars right you can think about shocks. Shocks are the final step.

Here's an old article I did on all of this.

Richard Newton

rithsleeper

Well in your article you say you like the biggest sway and a 26mm rear is almost impossible to find. Well I found one and didn't use it because everyone insisted I have the 24mm so I don't get push/understeer.

I'm pretty happy personally with the 30mm/24mm sway setup with koni yellows (half hard front and full soft rear). I really like the idea of an adjustable rear bar.

Original question is for a student I instructed. I guess I'll tell him to go with heaviest front spring and the medium rear (nyu) and big sways.

One thing that confuses me is why the 84 came with such small sway bar combo and stiffest rear spring of all the year. Why the small sway bars?

Has anyone tried strengthening the bars?

Solofast

You will find that an 84, stock, with that setup will have problems with the rear end jacking under high G loads. The combination of too much rear roll stiffness, combined with the stock geometry (rear roll center height) results in jacking if there is too much rear roll stiffness.

On high G corners, under trailing throttle, (like coming down a downhill on-ramp) the back of the car will lift a bit, step about a six inches sideways, and then set back down. If you add power, to get the rear end to squat, it will hook back up, but it can be very unsettling when it happens. If you get too greedy it will make the car undriveable.

You get roll stiffness from both the spring and the sway bar. For a given spring, you can only put in so much bar an still not have a jacking problem.

Bottom line is that if you go with the bigger spring, you have to back off on the rear bar to keep it from jacking. If you look at the Hib Halverson's "cheat sheet" you'll see that only when they backed off the rear spring rate (like in the ZR-1's or the 96 model year cars) could they increase the rear bar size to 26mm. The 91 model year Z07 had a stiff rear spring and the bigger rear bar and it also had a jacking problem in stock form.