I know people have been looking for good pictures and more info about Weight Jacks or Spring Perches for our 3rd gen F-Body. While rebuilding the front suspension of my 89 IROC-Z, I decided to take more pictures and even some measurements. People have explained what these are in the past, but there has not been much discussion about what springs to use or pictures of what they look like. I had to make a guess as far as what height springs to use the first time I went with this setup, hopefully this will help anyone that is considering it but isnt sure what height springs to order. This first post will be the fronts only. When I get some more time I'll get some pics/info about the rears (they're already installed forgot to take pics).

First picture, an OEM FE2 spring on the left, Ground Control Weight Jacks at full up with 8" Eibach spring in the middle, and full down on the left. Wanted to take this picture to show how much adjustability you can have over the stock springs. The Weight Jacks w/ Springs in this picture are upside-down (they are installed with the Weight Jack on top).



So what are Weight Jacks or Spring Perches? Its essentially two plates with a screw in the middle. The plates are threaded in the middle and the middle screw can be turned (through the hole in the lower control arm) with a 1/2 drive to effectively adjust the height of the plates. There are many different manufacturers of these weight jacks, and you can actually buy the individual pieces and make your own to save some $$. My example here covers the pre-assembled Weight Jacks from Ground Control Suspension Systems. There are two versions, weld in and non-weld in. I'm using the non-weld in version. When I originally made this post I was installing them wrong. Thanks to the help of other forum members I now know the correct way to install them. The non-weld in front Weight Jacks should be installed on top of the spring and sit between the K-member and the spring.

These weight jacks or spring perches allow you to individually adjust the ride height of each corner of the car. They can be usefull to fine tune your stance on your street car, or to fine tune the cornerweighting of your car (on a scale) for track use. Here's a picture showing the full adjustability of the Ground Control unit next to a measuring tape. These units offer about 2 and 1/2 inches of adjustability.



So what springs do you use? Few things to consider here including OD of the spring, type of spring, and rate of spring. According to Ground Control our cars use a 5 and 1/2 inch OD front spring. The stock FE2 springs on my '89 IROC-Z have an uncompressed height of 13.7 to 14 inches and an unknown linear spring rate. I've read its around 550 to 600 pounds but I have no way to verify this. Anyway, lets focus on the height of the springs since thats what we all really want to know (I'm sure you all probably have specific spring rates you want to try). From my experiences, between a 8" and 11" tall spring will give you good adjustability options in the front and what you choose should match up with what you plan to do. Street cars will probably be better with taller springs and softer rates.

The spring I'm using in this example is an 8" tall Eibach roadrace linear rate spring at 900#. Taking into account the height of the Weight Jack units themselves, this allows me between 9 and 1/2 inches to just below 12 inches of range as far as the total height of the Spring and Weight Jacks. You can compare this to the height of a stock uncompressed spring to get a good idea of the type of drop and range you'll have (general idea, no specifics).

A 10" tall spring would give you the ability to get close to stock FE2 spring height, or as much as 2 and 1/2 inches shorter. So depending on what ride heights you want to experiement with hopefully that can help you choose the height of the spring you want to use. Also, keep in mind all these examples are of the uncompressed spring heights, might be different results when compressed (aka installed)



There are two manufacturers of custom linear rate springs for our cars that I have dealt with. They are Eibach and Suspension Spring Specialsts. They are both good and offer custom height springs. Its entirely possible to run progressive rate springs with Weight Jacks but I dont know of any manufacturers that make then short enough to be used for our application.

Next up, the rears ...

 

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I'm using these with Tokiko Illuminas. These Eibach springs are temporary while I wait for my other springs to come in the mail. This car is track only, but 900# is too stiff for our track, the road surface is not very good. I am going to eventually run a different set of Eibach front springs, 8" tall and 775# linear rate.

 

great information and pictures!!!!

keene

 

Also keep in mind that since the spring is in the middle of the arc, the adustment is a lot more than 2-2.5" of adjustment. I can go from stock to resting on the liners..

Kevin D.

 

im currently waiting on Spohn to release his new modded kit of his current front coilover set up (which should allow us to lower our cars to the floor while keeping proper strut travel) but he told it would be out like 4 weeks ago and still nothing. so im considering using weight jacks up front and was wondering if those Ground Control ones will work with a set of Spohn Tubular a arms with the boxed spring perch? also how much weight will i add using these?

woops forgot to add, what would be the best strut to use in a very load stiff suspensioned car?

 

I don’t get how you can be so consistently wrong and get away with it.

Suspension frequency has nothing to do with spring length. It doesn’t matter if his 900lb/in springs have 2 free coils or 10 (most are somewhere in the 3-5 range). Natural frequency is always proportionate to spring rate and load. To be exact you can calculate it:

Natural frequency = 3.13 * (Wheel rate/Sprung weight)^1/2

1 to 2.5Hz is considered comfortable, below 1 you start “floating” and people get seasick, significantly above 2.5 and your body starts getting very uncomfortable compensating for the giggling…

As far as the rest of this thread, I’d replace the top pocket with the weight jack/seat to keep from increasing unsprung weight, and remember that as your spring rate gets higher your free length has to get shorter to sit at the same ride height, so don’t worry about matching the free length of the softer spring.

Actually, I bet that you can get an appropriate rate spring by trimming something like a v6 or RS spring (some quick math shows that some BXW, F41 RS front springs cut to 2.5 free coils will have a spring rate of 904lbs/in). The one thing that you have to be careful of is that as the number of free coils gets lower the steel of the spring will fatigue faster/easier (It doesn’t matter if we’re talking cut stock springs or high $$$ aftermarket), and if you increase rate with a shorter free height and not decrease number of coils you need to make sure that you hit the bump stops before coil bind.

If it was me (IE, if you’re a cheap bastard) I’d start raiding all sorts of stock springs (ultimately just use MOOG HD replacements, which are cheap compared to custom or aftermarket springs), I know that at least ford and GM used tons of springs with the same 5.4-5.7” OD as GM did on the f-bodies (no, not all f-body front springs have a 5.5” OD), and I’d bet that you could find either JY springs or cheap replacements that will work perfectly for whatever rate you want to end up with.

 

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Listen dumbass… I quoted you exactly, specified your issue with free coils and explained, with a formula based in some very simple, almost HS level physics why your answer has no basis in reality.

What more do you want?

If you want to **** and moan that you suddenly can’t post crap without fear of it being called crap… don’t worry, I have no clue where you have the time to post so much of it and I don’t have the time to respond to every piece of misinformation that you post, and the fact is that you’ve convinced most of the people that do not know the basis of most of how this works that you’re some sort of suspension ***.

 

Thanks for the indepth examination Hawaiian. I've been really interested in those from the time I heard about them on your car and how they functioned. Now to set aside the dough for them.

For a street car would you reccommend an general area for springs rate? I've got sportlines right now for the height but I think they're down around 700#? I obviously don't want to run the almost solid 900#, is it just a test and tune to find the right ones? How much to eibach and SSS charge for their specifc springs?

 

The sportlines are somewhere in the 600lb range, the Pros are right in the 700lb range.

I personally like stiffer springs and not as stiff a sway bar, and have run 900lb springs on the street in a setup that was much more comfortable to drive then a set of eibach pros and the typical 36/24 WS6/Iroc sway bars.

To get the cheapest prices on the specific rate springs, especially the SSS springs, I’d recommend finding a shop that deals with some of the vendors that deal with circle track goodies, like motorstate. You’ll find that in some cases, depending on the springs, you can get those springs for less then you bought your sportlines. If you can’t find someone local email or PM me and I’ll find someone for you…

 

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Wow, that went from some possible good information to **** in a matter of nothing....

Where is that rear information

 

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Why can't we all just get along?

I enjoyed the pictures.

It was kind of you to post them.

I have been wondering how the GC ride height adjusters worked.

One potential issue that I noticed, would be the need to possibly reset toe after the adjustment.

Thanks for sharing this info with the group.

 

Woa big boy… I just got home about 20 min ago… Donno what you do but I actually work for a living. I suspect that between a persistent net connection at home and using my home laptop at work I may pop up on and off all day, but I haven’t even been near a PC since about 2pm today and I rarely pay attention to message board BS during the day.

This is very simple dumbass… when you cut a spring coil frequency goes up BECAUSE SPRING RATE GOES UP. There is no direct relationship between free coils, overall coil spring height or wire length and frequency. Repeat after me: spring rate goes up, frequency goes up, spring rate goes down, frequency goes down. A suspension using a spring with 2 free coils and 900lb/in rate will have exactly the same frequency as a spring with 10 free coils and 900lb/in rate.

Now that even the average 2nd grader knows what’s going on, what more do you need me to explain so you understand, RTFC?

For those of you with more then 2 or 3 brain cells, see my previous post if you want details and even how to calculate the frequency, acceptable ranges… RTFC, you may want to try http://www.hookedonphonics.com/ first since you appear to need a little help.

Have a nice day.

 

looks like time for a mod lock to me....

 

battle of the egos... with respect to both of you, as both contribute lots of information the users... Drop it

 

.If done here. This guy isn't worth getting banned for.

 

I'd also like to remind everyone to keep their suspension geometry in mind. Most off the shelf springs wont cause any huge problems, but when you goto a custom setup like this there is a greater possibility of running into issues with geometry.

SSS Springs through Ground Control are $59 to $69 each. Like 83Crossfire said, you can get them cheaper through shops related to stock car racing. In fact, the cheapest way to go in general is through those types of places (thats also where you can buy the individual parts to assemble your own weight jack). I'm sure there are other quality manufacturers besides SSS, I just haven't found them yet.

 

No problem, my pleasure! I've learned so much from TGO, I wanted to give something back. You are correct, you will need to adjust the alignment after changing the ride height. I personally had a real problem with toe after swapping from Eibach Sportlines to this style setup on my 91 Z28. In that setup I'm using GC Weight Jacks, a 10" spring 700# linear rate and a set of 2 inch drop spindles. It was so bad I was not comfortable driving to the alignment shop. I had to use string and whatnot to perform my own little ghetto alignment job to get the car "safe" to drive to the alignment shop for the real alignment. Good point, be prepared for this.

I should have pictures and measurements of the rears by Wed this week. Mods, if you can hold off on locking this until then that would be great.

 

How much space does that adjuster actually take up in the pocket? I’ll have to do some measuring, but I’d be very surprised if an 11” tall free height, 800lb/in spring would allow you to reach any kind of a low ride height.

You also mentioned that this allows you to swap springs without pulling the A-arm… how?



If you do a little poking around you’ll probably find that there are only 2 or 3 manufacturors that make almost all the springs out there. I wouldn’t be shocked if the SSS springs were eibach springs, since eibach contracts spring manufacture to probably the majority of other aftermarket spring companies. Koni even used to (may still sell) “Koni by eibach” (in small letters on the corner of the box) springs.

I still think that you’d be better off finding a moog spring to use, you should be able to get them in pairs for about the same as the best that you’ll do for a single SSS spring.

The fact is that there is no way to get technically correct information onto this forum without kowtowing to RTFC or taking a load of crap from him. Since I’m not going to do the first and see no reason for anyone to, and he isn’t sanctioned when he does the second, I’d rather just take the offensive as soon as he starts.

My point being: nothing against your thread and _I think_ that I added a lot of useful information to it.

Now that RTFC has deleted his posts most of his incorrect info is gone. Problem solved, of course, who knows what will happen in the future. Sorry about the noise

 

The weight jacks themselves take up between 1 and 3/4th inch to 4 and 1/4th inches of space depending on the setting. With a 11 inch spring it would be around 12 and 3/4th inch tall combined at full lock down, right around the uncompressed height of the Eibach Sportline or Eibach Pro-kit. You're right thats not very low, but everyone has their own idea of acceptable ride height, so I figgure its good to give a range of heights and let em decide.

Apparently I've been running these Weight Jacks the wrong way for quite some time. I've been running the Weight Jack on the bottom of the spring, between the spring and lower control arm. When running them this way I was able to swap out the springs without dropping the lower control arm. But now that I found out I've been running them wrong (effectively upside-down), I'll have to re-install them correctly and see if I can still swap springs like I used to (the trick is, if they are short enough to get them sideways above the lower control arm by wiggling them around, you can twist them and they'll thread themselves out)

I know neither of you are intentionally doing any harm to the thread, and I agree you guys have added good information. But with the way its going, it very well might get locked before I can finish up this post with information on the rears.

 

Huh… are you literally putting the weight jack in the spring pocket on the LCA without mounting it somehow? Are you installing the spring like in the first picture (bent pigtail down instead of up)? Are you making any effort to index the end of the spring or to use a spring isolator in the top? Do you have to pull the sway bar or anything else out to get the springs out?

Damnit, a little bit more and I’ll have to go in to the shop and snag a set of weight jacks and cut up some old, softer springs to play with this, and I’ve got too many other things to do to really mess with i, but I always intended to use weight jacks as a “someday when I have time” thing. I miss how low my ’83 sat.

 

I've edited this after the fact. I did originally install these as shown in the picture (and they still worked great) but recently I've found I was installing them wrong. The Weight Jack should be mounted against the K-member, on the top of the spring with the pigtail coil indexed against the lower control arm. I always do what the manufacturer recommends, so I'm gonna be swapping them to the correct position. So I'm not sure if I'll still be able to swap springs w/o lowering the control arm in the correct position. From eyeballing it, looks like the weight jack stud will prevent the spring from getting enough angle (to twist them out).

Sometimes you cant index the shorter springs with the suspension unloaded because they do not fully take up all the space between the a-arm and K-member. You can adjust the weight jack up to seat the spring properly in the K-member and index the spring with the suspension unloaded, but then it would also depend on what adjustments you want the weight jacks at. I also like my cars low, so most of my experience, I am not able to index the spring properly until I start lowering the car.

I know what you might be thinking. I also wonder what would happen if the car actually went airborne for a split second and the front suspension unloaded in the air. Not sure if I want to find out ...

 

You may want to try some tie wraps to hold the spring, if possible.

Mark.

 

Good springs for anyone who's wondering and if you have a good set of struts/shocks it can actually be comfortable on the street. I have well...a lot of suspension. But anyways I have Koni Adjustible struts/shocks and with the GC Weight Jack system it rides damn smooth. Actually it feels better then most stock cars I've driven. Only problem is when you accidently hit the pot holes. Then it's a little stiff...but even then it's not that bad.

 

CH

I have 9 inc 900lb springs in the front of my car. I used a spring spacer that sat on top of the spring and sat in the spring pocket in the k member.

Mine was non adjustable and so i had to cut it to length on a lathe.

I tried 12 in 900lbs spring originally but they gave me a 4x4 stance.

The 9 inc were not tall enough to hold up the a arm.

my springs are afcoils / circel track stuff cost about $50/ each.

I run 6 inch 300lbs in the rear with a weight jack which is hand adjustable.

 

Again

Thanks for the great post CH

Do the weight jacks require equally stiff struts/shocks?

 

It will depend on the spring you use. If you used a spring that was close to stock then off the shelf shocks/struts would work fine. If you went with some race springs like the ones in the example you'd probably need higher quality shocks/struts that either allow you to adjust the compression/rebound, or allow you to specify compression/rebound specs (custom). Two things to consider, the spring rate and the spring height. When you increase the spring rate you increase the rebound resistance and decrease the compression resistance. So if you knew what was optimal then you could order some specific rate shocks/struts and have a bang'n setup. The main problem I run into is that I have no clue what compression/rebound is optimal for whatever height and rate spring I choose. So I went with some adjustable shocks/struts and hopefully they'll allow me to match it to the spring somewhat. The only problem there is I still wont know what specific compression/rebound settings I have, I rarely see one that actually tells you what the settings are. Usually they have a generic 1 through 3 or 1 through 5 settings that dont mean much when it comes to comparing the compression/rebound ranges of the adjustable shocks/struts out for our cars (Koni has a nice graph). The other thing to consider is the height of the spring. I know there is more too it, but all I know is that you need to make sure the shocks/struts dont bottom out. The lower the car sits the lower the internal shafts will sit, and if they compressed all the way on a setup that was too low they might possibly bottom out. For my setup in this example I'm using Tokiko Illuminas and the HMS strut mounts with a 1 inch raised top. It wont be optimal but the HMS mounts should provide some extra strut travel. Unfortunately, nothing I can do for the rear. I know the height of the spring also relates to optimal compression/rebound, but dont know enough about it to give any good info. Dean and Mark probably know more about that stuff.

 

Unless you’re running a very factory alignment, or have extensively modified the tops of the strut towers, there is nothing that you’re going to do to the top mounts that will increase travel. The top of the strut body will hit the strut tower well before the top mount is any sort of an issue.

If you’re actually going to get **** retentive about shock rates, then the actual sprung and unsprung weights, sway bar sizes, the type of use… have as big an impact on valving as the spring rates.

BTW, I noticed that Carrara also makes some springs that would be appropriate for this application, sold by free height and rate…

 

I would consider the HMS mounts to be extensively modified..

Kevin D.

 

The HMS mount, just like any other mount does NOTHING to the tops of the strut towers. If you align for more then about 3-3.5* castor and any reasonable amount of camber it doesn’t matter what you put on top of the strut tower, the stut body will hit the edge of the hole in the top of the strut tower well before bottoming will be an issue.

Though they are pretty.

 

Actually, while I’m at it, the only good solution to this is to totally relocate the location of the upper strut mount. On my ’83 TA I actually separated the top of the strut tower at the spot welds and rewelded it further back and in slightly to give me room for a more radical alignment and still have full strut travel. If I was going to do it again, I’d probably just cut out the center section, section it and reweld it.

Of course, after you go to this trouble, you’ll realize that you’re still limited by the bump stops on the LCA’s and even when you shorten them, with the stock a-arms you’ll find that the back of the control arm contacts the K-member before the strut travel would have been an issue. Then your stuck doing more cutting and welding or different control arms… of course, whatever you gain there will pretty much just give you the ability to slam the tranny pan/oil pan/k-member against the pavement. Next step is to start looking for the sylasto/koni strut rod bump stops…

Nutshell…don’t worry about it unless you care to open a whole can of worms

 

I understand what you are saying about the angles of the strut rods in relation to the towers and how there is only so much you can do without major modification to prevent contact. But I still think a mount with a raised top will help with strut travel when compared to stock. With the minor testing I've done so far I have not had a problem with the top of the strut body contacting the undersides of the towers, or the bottoms of the internal shafts bottoming out. Of course the only real test here is taking it out on the track for some hard driving, and I hope to be taking care of that this week Saturday (day at the track for lapping woohoo). I really do hope for no issues, but if I do have any I'll be sure to post it here for everyone else to hear about.

I didnt know Carrara make springs (or is it Carrera?). Soon as I work out shipping with TVP I'm gonna get my hands on a set of struts they made with shortened shafts. I've been meaning to contact them and ask more about these struts but I have had a hard time finding their contact information. Kinda cool to read about them by chance in this thread. If you have any contact information for them can you let me know? Thanks!!

 

I spend some of my spare time “working” at a speed shop, I have or can get contact info for just about everyone out there…

There is also another manufacturer (forgot the name, starts with an L ) that I ran across in our distributor’s catalogs that list 5.5” springs from 4” – 16” free height (the 4”, 8” and 9” free heights are probably the most useful) with rates 350-1800lb/in with a lifetime warranty and are guaranteed to never sag more then 2%. If someone is looking for specific info I could get it for you, but like I’ve already said, any decent shop that deals with a distributor that covers circle track stuff should be able to help you…

 

As far as angles, strut upper mounts… with most struts nothing contacts before the control arm, so most of that part of this conversation is irrelevant.

 

Ahh.. Gotcha. Thought you meant it would hit the strut bearing/mount, not the actual body of the car.

Good info.

Kevin D.

 

Here's a quick pic of the front setup used in this example at full lock down. The car is too low to exit the driveway (I tried and did burnouts lol), but the wheelwells are not resting on the tires. If I had more chassis clearance I think this might actually work out, maybe a little bit higher. Looks like I'm gonna need to make further adjustments and get a different crossmember.

 

So what set-up is on the car in the last picture you posted. I wan't my car to sit just a hair higher then that.

Will the kit from ground control give me that low of a ride, also was it hard to install. Any help would be appreciated.

By the way that looks badass.

 

The setup on this green car is the same setup I've posted in this thread as the example to explain what Weight Jacks are. Its the Ground Control Weight Jacks with a 8" tall Eibach RR spring at 900# linear rate. The Weight Jacks are at full lock down in this picture, a total of about 9 and 3/4th inches uncompressed height (spring + weight jack unit) compared to the stock 13.7-14 inches uncompressed height. So around 4 inches shorter than stock uncompressed. I was supprised to see that there is still clearance in the front wheelwells at this setting, even at full lock the tires do not rub. My problem with this ride height is chassis clearance. Spohn crossmembers create issues with chassis clearance on lowered cars. The Weight Jack units allow me to adjust the suspension up to 2 and 1/2 inches up to my desired ride height (gotta go experiment w/ different heights).

 

I also have to add the front tire in this setup is a smaller overall diameter/height than stock, so maybe that helped give more clearance in fronts. Its a 235/40/17 on a 17x8.5, about 1.25" shorter than the stock 245/50/16 setup on a 16x8.

 

So the kit from Ground Control Includes the springs you are using on the green car right now.

What have you done to the rear suspension to make it sit so low.

 

Damn, I hate it when I miss reading Dean's hilarious inferiority complex rants

 

When you call Ground Control you can specify what springs you want. I posted this example to try and help people decide what springs they want to use. There is a good range of choices. I had planned to run a SSS front spring, 9" tall and 700# linear rate but Ground Control seems to be having a problem right now and they never shipped them to me and nobody is answering the phones.

The rear of this car also has Ground Control Weight Jacks and short height springs. In about a day or two I'll have the info on the rears just like I did the fronts (pictures, measurements, etc).

 

Great info, I have a problem with my suspension after changing my wheels with a lot of fender well.
My Car Suspension

 

Thats some good info ill have to read it all later when I have time sounds like somethin I might want to do I also like the idea of changing the springs with out dropping the a-arm.

 

Here's the info on the rears. Rear Weight Jacks are installed very similar to the fronts, just the other way around. The weight jack sits under the spring and is adjusted via a threaded stud. Here is a closeup of the rear Weight Jacks, one at full lock down, the other at full lock up. These rears give you about 2 and 1/4 inches of adjustability:



Here is a picture of the rear spring I'm using in this car, its a 10" tall SSS spring at 150# linear rate:



I've found between a 9" and 11" tall rear spring to work well with these weight jacks and give you alot of adjustability between slammed and stock. I think stock rates are around 100#, so keep that in mind when ordering your springs.

Here is a picture of the rear Weight Jacks installed (doing a swaybar swap hehe):