customblackbird

iTrader: (15)

Finnally got my car on the ground after a long winter/spring of mods.

I changed up my suspension a good bit and thats where my new problem lies. I replaced my 200lb 5x11" Afco rear springs with weight jack and KYB gas a just rear shocks for my new setup. The 200lb springs seemed to sit just a tad too high for me at the lowest setting and since I went with different front springs I decided to go for a softer/smoother ride. I put 150lb 5x10.5" springs with the same style weight jacks and new double adjustable viking rear shocks. Now The car sat so low on the lowest setting that I had to adjust the rear weight jack for 2" increased height to get it back where it was roughly. This is at the top of my adjustment for the most part and I want to increase the height with either a billet 2" spring spacer for the top or get a taller spring and maybe alittle more rate. I was looking at a 175lb 5x13" spring instead and get some 7/8" rubber spacers in case. Or I was looking at getting some billet 2-2.25" spring spacers to use with my current springs. The 150s seem a bit soft for me just pushing down on the rear with my weight and I have done some suspension changes. I've also used the founders panhard bar relocation so the bar is lowered at both the axle and frame for the dual exhaust.

So my rear options are:
1. Keep the 150lb 5x10.5" springs and get 2" spacers for a 150lb 5x12.5" spring for like $55
2. Get new 175lb/200lb 5x13" springs and rubber 7/8" spacers for $100

Now my front is also doing funky things. I swapped out my stock Kmember for a Racecraft moly Kmember and reused my UMI tubular Aarms. I swapped out my cut moog 5664s which had a 26 5/8" fender height and roughly a 12" free height with I believe a 900lb ish spring rate. I fabbed up my own weight jacks using a design almost identical to the weight jack companys. I run a 850lb 5x9.5" spring, the adjustment plate and poly spring isolator add the same 2-2.5" to the top of the spring for a total spring height of 11.5 - 12". So it should be close to the same ride height as before with simular spring rates and free heights. I verified that the springs are fully seated and Im at the lowest ride height on the jacks but my ride height now is at 27.5". I also have full and easy suspension travel pushing down on the strut towers so nothing is hanging up. The suspension seems softer than the old combo as its much easier to compress the front end than before. I also changed my KYB AGX struts from the firmest setting to the softest so maybe thats why.

So can someone explain why the front is 1" higher than before? The look is killing me, given it hasn't really settled since the car isn't being driven for at least a full month.

Also is the 150lb spring with a 2" spacer a better fit or the 175lb spring with the front 850lb spring setup. I think the 175lb spring is a better suited since it was also recommended by a member here for the front spring change. I had 200lb and with the front cut moogs the car felt stiff on the road and wanted to soften it up a bit hence the lower spring rates.

What do you guys think?

taonindo

Is your torque arm loose? Wouldnt explain the front being weird. How long does it take fro new springs to take a set? I dont know that either. Cant you just cut a coil off or is that something only broke racers do lol FIDO

QwkTrip

iTrader: (22)

This is actually really easy since you have a known combination that produces a known ride height. A handful of quick calcs will let you estimate what new spring length to order.

Here is an example using data from my car. This is exactly how I decided what free length to order when I changed spring rates. Just substitute your own numbers. You can do the same kind of calcs on the front but you need to account for the 2:1 motion arm on the springs.

Example:

Existing springs are 150 lb/in with 9" free length. Weight jacks have been raised 2.0 inch at ride height.
Want to change to 180 lb/in. What spring length should I order?

Rear weight from scale: 1480 lb
Unsprung weight: 350 lb (educated estimate, see note at bottom)
Weight per spring: 565 lb --> (1480 - 350) / 2

Baseline with 150 lb/in springs

Spring rate: 150 lb/in
Free length: 9 in
Compression: 3.77 in --> (565 / 150)
Compressed length: 5.23 in --> (9 - 3.77)

New 180 lb/in spring

Spring rate: 180 lb/in
Free length: 11 in
Compression: 3.14 in --> (565 / 180)
Compressed length: 7.86 in --> (11 - 3.14)
Change of ride height: 2.63 in taller --> (7.86 - 5.23 from baseline)
Weight jack adjustment to zero = -2.63 inch

It would take 2.63" drop of weight jack screw to hit the same ride height as before, but I only have 2.0" of adjustment available from baseline. Either order a shorter spring, or accept the slightly higher ride height.

Note: I didn't totally guess at the unsprung weight. I measured the compressed length of spring in car to validate my guess.

QwkTrip

iTrader: (22)

Upper and/or lower spring pockets aren't in same location as stock. That's what happens with aftermarket parts... things get all jacked up. (see what I did there )

You'll probably want stiffer rear springs after that change. Lowering the panhard bar lowers the rear roll center, which increases the leverage of vehicle center-of-gravity on the roll center. Basically the rear of the car will roll more in corners. People usually increase rear spring rate and/or sway bar at the same time.

QwkTrip

iTrader: (22)

So what are you trying to accomplish? Street driver, drag, cornering? I'm really confused about the direction you want to go when looking at your mix of parts.