Spring Rate?

FrankM1 · #1 (**permalink**) 06-01-2008, 07:07 PM

Hey Guys,

I adjusted my Superformance preload this week-end, and it looks like the spring rate of each spring is different.

I had to crank the rear right corner to the max to get 26" (I have the 17" wheels), while the left side seems to be right in the middle.

It's the same with the front, the right side is almost totally unscrewed, while the left side is right in the middle of the adjustment.

The numbers on the spring are the same, I have the Eibach springs.

Can somebody explain this, is it possible, that the car as the wrong spring at each corners? If it's the case, where can I order a set of springs?

Thanks.

Kenm4187 · #2 (**permalink**) 06-02-2008, 02:01 PM

Frank,

I have changed springs and corner weighted mine 4 times in the last few months. I see a little variation but not much. I don't think it is a spring issue.

First, you did not say if you had disconnected the sway bars. Both of the sway bars should be disconnected on one side. You need to make sure you don't have any pre-load on them.

Second, adjust the spring perches on the back shocks so they are the same (from a point of the shock). Then the front ones so they are the same. Then drive the car around the block.

You should be very close from the left side to the right side. Then you can make final adjustments. Try to adjust all of them a little rather than one alot or at least in pairs (LF-RF, LR-RR, RF-RR, LF-LR). I found on my car, that after I adjust the ride height I had to lower the car 2-turns LR-RF and raise it 2-turns RR-LF to get corner weighting at 50%. Reconnect the sway bars, you may need to shim them.

I was not sure what you had done so I hope this helps.

Ken M 2560

JCoop · #3 (**permalink**) 06-03-2008, 05:44 AM

1st thing, 26" is too low for the SPF, IMHO. recommended is 27"; I have set mine (with 17" wheels) to 26.75" all around. With 26" your camber will probably have too much negative and may need a major adjustment.
What motor is in it? With a small block, the springs up front are usually 375lb and 10", and the rears same rate but 12". With my big block, fronts are 425# 8" and rears are 225/475# variable rate and 10".

If adjusters are all the way up, your springs may be too soft but I doubt they would be different rate springs L to R.

I suspect you made the adjustments with the swaybars on. Adjustable rate shocks should be at their softest setting. Swaybars should be disconnected, and then when your ride heights are good, reconnect them tight but with as little preload as possible, and then reset the shocks as needed (halfway is a good starting point then check the ride) Also, make sure you bounce and roll the car after making spring adjustments.

FrankM1 · #4 (**permalink**) 06-03-2008, 09:11 AM

I thought about the sway bars, but I didn't know that it could affect the preload that much. If I disconnect the sway bar and adjust my springs, how do I re-install the sway bar after? Do I use the sway bar to fine tune the preload?

Quote:

Originally Posted by Kenm4187

Frank,

I have changed springs and corner weighted mine 4 times in the last few months. I see a little variation but not much. I don't think it is a spring issue.

First, you did not say if you had disconnected the sway bars. Both of the sway bars should be disconnected on one side. You need to make sure you don't have any pre-load on them.

Second, adjust the spring perches on the back shocks so they are the same (from a point of the shock). Then the front ones so they are the same. Then drive the car around the block.

You should be very close from the left side to the right side. Then you can make final adjustments. Try to adjust all of them a little rather than one alot or at least in pairs (LF-RF, LR-RR, RF-RR, LF-LR). I found on my car, that after I adjust the ride height I had to lower the car 2-turns LR-RF and raise it 2-turns RR-LF to get corner weighting at 50%. Reconnect the sway bars, you may need to shim them.

I was not sure what you had done so I hope this helps.

Ken M 2560

FrankM1 · #5 (**permalink**) 06-03-2008, 09:17 AM

Hello Ray,
I was aiming for 26.5" but could not go higher than 26" since my springs are tighten to the max.
My engine is a Roush 427, and the code written on the springs is the same all the way around 00-003-00014.
I will disconnect the sway bar and start all over again. Thanks.

Quote:

Originally Posted by JCoop

1st thing, 26" is too low for the SPF, IMHO. recommended is 27"; I have set mine (with 17" wheels) to 26.75" all around. With 26" your camber will probably have too much negative and may need a major adjustment.
What motor is in it? With a small block, the springs up front are usually 375lb and 10", and the rears same rate but 12". With my big block, fronts are 425# 8" and rears are 225/475# variable rate and 10".

If adjusters are all the way up, your springs may be too soft but I doubt they would be different rate springs L to R.

I suspect you made the adjustments with the swaybars on. Adjustable rate shocks should be at their softest setting. Swaybars should be disconnected, and then when your ride heights are good, reconnect them tight but with as little preload as possible, and then reset the shocks as needed (halfway is a good starting point then check the ride) Also, make sure you bounce and roll the car after making spring adjustments.

Kenm4187 · #6 (**permalink**) 06-03-2008, 09:36 AM

Frank,

My car is 2560 and came with 350# (7") springs all around. You can order 350# X 8" (or longer) springs so you can raise the car. I went to Penske shocks and have 7" (450#)springs in the front and 10" (425#) in the back. As for the sway bars you will need to add some shims so there is no preload on the sway bar. It's not much, I added two washers on one side. I have my shocks set at what I will be running. I am also not looking as much at height as I am looking at the suspension angles. At 27" my lower a-arms are angled up (toward the car). My front is at 26-1/2 and my rear is at 25-3/4. 17" wheels all around. I am using mine for auto-cross. Good luck on yours.

Ken M 2560

Silverback51 · #7 (**permalink**) 06-03-2008, 12:39 PM

Remember when setting your ride height, that the recommended 27 inches to the wheel well opening is with the stock tires.

Change the tires to a different diameter tire and the ride height will also change.

I just went with the Goodyear Billboards and they are .45 and .60 (if I remember right) less in radius front and rear respectively. So that means if you tried to raise the height back to 27 inches you would have a larger gap between the tire and wheel well opening.