Z06Fix

I'm looking at building a nationally competitive ASP car. Over the winter I plan on picking up a set of PFADT sport shocks and I have been considering going stiffer on the springs. Just trying to decide which route to go with. It seems like most people go way up on the front but only a little stiffer in the rear. What does this do to the balance on the car? Looking at the stock spring rates, the factory has them setup much stiffer in the rear than the front. What is the reasoning behind this? If anyone has any thoughts or suggestions feel free to fire away

Spring rates I have found by searching: (If any of these are wrong please let me know)

C5 Z06: 526# Front, 714# Rear
C6 Z06: 531# Front, 782# Rear
C6 Z51: 526# Front, 645# Rear
T1 (C6): 582# Front, 850# Rear
C6 Base: 420# Front, 657# Rear (VBP measured: 400-420 F / 600-620 R)
T1 (C5): 582# Front, 793# Rear
Hyperco HPS (Street/Track): 565# Front (12405HPS), #765 Rear (12406HPS)
Hyperco HPT (Track/Solo): 625# Front (12407HPT), #850 Rear (12408HPT)
VBP Sport 990# Front, 650# Rear
VBP Extreme 1050# Front, 855# Rear

Solo2GS

Most I have talked to are running 990-1050# front with the 714# rear. This is a fairly common national ASP / SM2 champion setup for years.

The problem you will run into, if you have not already is, if you use the factory rear spring and lower it to a gap about 2 fingers between wheel and fender, the rear spring will chew the backside of the wheels. So many, myself included, run a VBP rear spring at the factory rate.

Shocks are on my list as well, likely to have more benefit then springs to begin with.

Why those settings? Not sure, but if it works well for a multi-national champion car its likely to work for me I hope!

Z06Fix

Great info. Thank you sir.

One question: You mention that you are running the VBP rear spring that is the same rate as the stock C5 Z06 spring. Whats the advantage of the VBP over the stock? You mentioned that it doesn't chew up the wheels. How is it different? Excuse my ignorance, as I'm still learning all this stuff.

Eric

Solo2GS

Other then being a hair lighter and not likely to dearch over time, it is not as long. With the factory spring when using after market lowering bolts if I lowered it too much, where I wanted it to be, the outer edge of the spring (outward of the lowering bolt) would come in contact with the back of the wheel when compressed. If lowered more it could come in contact with the inside of the tire. Perhaps not all the time, but as auto-x lots aren't the smoothest, when the suspension was under load it had a greater chance of contact. The inside of my wheels (the lip) was where mine came in contact a lot. If it was the tire, it probably wouldn't last too long that way.

I am sure different offset wheels or spacers might change this, but a competative SM2 friend had the same problem and he runs CCW wheels and brought it to my attention on my car when we were going to lower it to more of a proper height.

I don't know if it happens on all cars, but its something to keep an eye out. You should be able to look and see how close the outside edge of the spring is to the wheels.

XPC5R

The added front spring rate is somewhat compensated by running a larger front wheel/tire package (usually 315's). Ditto on the rear spring interfering with wide wheels when lowered. It is less of a problem if you go with 18" rear wheels.

Springs are not absolutely necessary to be competitive, especially if you are just starting out. We ran '02 in ASP with stock springs, T1bars, T1 front arms, 285/18 fronts, 315/17 rears, penske doubles, and were competitive with Popp, Thomason, etc when they were in the class. (2nd that year in the pro solo finale, 8th in the Solo II, the car set fast time on the north course for all of ASP)

I would use the $$ for the best shocks you can afford, then bars and wheels.

Z06Fix

I just want the car to feel more crisp. It almost feels sloppy through saloms. I'm thinking upping the front spring would really help with this. I will call VBP and see what they can make up. So everyone seems to be going with 900-1000#+/- and the stock 517# rear?? I wonder if the PFADT shocks will work that much spring?

Z06Fix

I really hate to use the term "sloppy" in description but it feels that way compared to others in the region that are running stiffer springs.

I am by no means in need of upgrading the car, as I'm still catching up to what the stock suspension can do. I'm just planning ahead

thehammer69

The Pfadt shocks should easily be able to adjust in more rebound to control the higher spring rate. From my understaning, the rebound rate change is very linear with position. Not like some shocks that only have a very narrow range of usefulness in adjustment.

PushinTheLimit

Is it bad to mix and match different brand of springs? If I upgrade my springs, I would go with what most are using that are competing nationally. No need to reinvent the wheel when you find something that works.

I probably won't be able to do springs until next year, but this is all good info to have. I'll be saving this thread for future use.