I have been researching this topic for a while. This seems to be somewhat of a taboo subject. This post is a little long. I just wanted to get as much information out there as possible.

I am working on a coil-over project with Penske/Mallett drop shocks. Currently this is my thinking. If I have overlooked something please let me know. Anyones opinion is welcome.

750lbs/in in front
600lbs/in in rear

With the 2.25 inches of total travel in the Penske drop shocks.
The total vehicle weight of roughly 3400lbs.
Weight distribution 51% front 49% rear (Motor Trend)

867lbs (1/2 of 51% of 3400lbs) sitting weight on each front spring will take appx. 1.156" of shock/spring travel. Leaving 1.094" of travel remaining.

833lbs (1/2 of 49% of 3400lbs) sitting weight on each rear spring will use appx. 1.389" of shock/spring travel. Leaving .0861" of travel.

This should mean that the front springs will be "bottom out" at 90% of the rear vehicle weight on them. I don't think that under extreme braking that more than 90% of the rear weight will transfer to the front of the car.

In the rear suspension the springs/shocks would effectively bottom out at 60% of the of the front weight being transfered to the rear. I know I don't have that kind of grip in the rear.

From my research I have found this information (most of it off the forum)
Stock Z06 front spring ~620lbs/in
T1/Extreme springs 900lbs/in and 700lbs/in rear

I currently have the FE1 suspension (I know, I know). I will need to get some sway bars to compliment these springs/shocks. I am planning on going with Z06 bars for price reasons.

Thanks everyone!

 

I think you will have ride and handling problems if you have a higher springrate in front than rear. Do a search in the archives about people trying higher rates in the front.

Check out this post with recommendations from DRM http://forums.corvetteforum.com/zerothread?id=216027

Also check my sig, the 600 rear and 450 front are the optimal setup for roadracing. DRM ( http://www.dougrippie.com ) are the number one when it comes to coilovers and selecting the best combination of springs, shock valving and swaybars. DRM have been building race cars with coilovers since the earlie days of the C4 on now the C5.

:cheers:

 

Great thanks for the info Seanr. I could have really made a mess of things.

Through a little more research (and the link you provided), I have found this information.

Z06 front 525lbs/in
Z06 rear 700lbs/in

Z51 front 525lbs/in
Z51 rear 633lbs/in(manual) and 645lbs/in (auto)

The number that you mentioned are
450 Front
600 Rear

It would seem to me that this would be a very compiant and soft suspension. I'm not sure if the term "roadracing" is my intention with this car. It is a street car.

I am trying to learn about this subject so please bear with me. Why would I want to use a softer spring rate all around? T1 sway bars, to my understanding, are matched with stiffer springs. I can see now that everyone insists on using a softer spring in front. I can agree with that. Wouldn't I want a stiffer suspension, if I have less shock travel? Which shocks are you using?

Thanks again for your time. :confused:

 

Stock leaf springs are heavier than a coilover setup. You may want to check out this post -
http://forums.corvetteforum.com/zerothread?id=473364

 

I think you have the difference in springrates because with a leafspring it's a single spring with 700lbs(Z06) rating. With coilovers you have 600 on the left side + 600 on the right side=1200. Please also note that the rear coilovers are mounted in such angle so a 600lbs spring are more like a 525lbs which would be 525+525=1050 compared to the Z06 leafspring with 700lbs.

In the front you would have 450+450=900lbs with coilovers. You do not have as low angle as in the rear so the 450 is about a 440 which ends up to 440+440=880lbs.

So if I would compare a stock Z06 with my setup......
Z06, rear 700, front 525
my, rear 1050, front 880

Running a stock C5 with Z51 feels very soft compared to my setup so I think comparing leafspring rate with a coilover springrate is like comparing apples with oranges :)

To get a good answer from someone that really knows, give Doug Rippe Motorsports a call at 763-477-9272

:cheers:

[Edit] forgot to tell...

I use Ohlins 46HRC 2-way 20 point adjustable with external reservoar(see my sig)


[Modified by seanr, 8:31 PM 2/10/2003]