Just bought some ground control weight jacks and springs (used). The springs that came with it are total road racing springs...fronts are Eibach 1100# and the rears are tagged as 225# springs. I won't be doing any autocrossing with the car at all...it's mainly a street/strip weekend warrior. It will be mainly cruised with on nice weekends and occassionally taken to the track. I mainly bought the jacks to tweak the ride height of the car....I lost some weight on the front end with the new engine and I've got some low points on the car with the LT headers and dual exhaust. I'm looking for opinions on spring heights and rates. I'd like to be able to adjust the height from the stock 1LE spring height and lower....so I'm thinking around a 9inch tall spring. Please post your weight jack spring specs and comments on them...ie. manufacturer, height of spring, rate of spring, and how you like it - would you recommend it. I'm thinking somewhere around a 750# front and somewhere around a 175# at the rear. Thanks! - Joel

I am running 700# front, 150 rear. with 1LE sway bars.

Depending on your use, you might want it a little less tail happy than I have mine set. Maybe 700/125.

My car is slammed down, I am tucking the front wheels, If you plan on going that low, you will have to look at changing or modifing your bump stops.

being street strip, you may want to go a little lower rate than even what I have, maybe 600-650 with 100-125 rears. That puts in the factory IROC/wS6 range for spring rates. You will hae to watch your ride height at that rate though, as goign too low, and you will smack the bump stops all the time.

--John

Thanks for the info and advice!

I definitely won't be able to lower the car that much due to my exhaust....I just want to play around with the height to see what I can get away with on the street.

BTW: I'm running Hellwig solid front/rear sway bars...big beefy bars and also Koni Red struts/shocks.

Thanks
- Joel

I know there are more guys on here with ground control jacks.......
Anyone else have an opinion?????????????

Thanks!

I think springs between 9" to 10" tall will work good for what you want to do, height depending on how low you want to make the car. If you don't plan to totally slam it I'd go with 10" tall springs. As for the spring rates, I agree you don't need stiff springs because you're not gonna be autox'ing or roadracing the car, its a cruiser and you mainly want these weight jacks to fine tune the stance. This is pretty much the same mindset I have with my 91Z. On that car I went with 10" tall springs front/rear and somewhat soft rates, 700# fronts 150# rears. If I did it again I think this setup is still a little too stiff to be considered comfortable, would done 25-50# less on the spring rates F/R. As long as you choose the right rates for the front you should be OK, changing rear springs after the fact is really easy, especially with these weight jacks and short springs. Good luck!

Even changing fronts is easy, you just adjust your weight jack to the lowest height, and then you don't need a spring compressor, the spring will just fall out if you unbolt the spindle, and lower the a-arm with a jack.

Thanks for chiming in guys! I'm learning alot!
Looks like definitely a 10 inch tall spring then.

So CrazyH...you've got 700F/150R and you think they're still a little too stiff for a street car.

Dewey...you've got the 700F/150R and you say the rear is a little to stiff and will swing a bit...what is your opinion on the front?

It sounds like the highest I'd run at the rear would be 125# and would you guys recommend a 650 or 675# for the front??

I won't be lowering the car much really from stock height...with the exhaust I only have a small window of room that I can adjust the height...I'm just going to play around with the height and see where I can get it and be comfortable without smacking the headers.
Thanks for the help guys....once I decide on the rates based on your opinions I'll get the order on the way.
Any recommendations on where to get the springs from? I've heard ground control has been really flaky...any other places you recommend???

Thanks!
- Joel

PS: Here's a pic of the current stance with the stock springs...due to the weight loss with the new engine and setup you can see how bad it looks.

I've wanted to do this for years, but never went anywhere with it. I want to be able to lower my car as much as possible without tearing the bottom of my car apart. On my SS i chave around 2" of clereance for my exhaust so i know how to take it easy and avoid bumps. I'd like to just tuck the tires in the front and back. i dont think the sportlines will lower the car as much as i want. I love the way your 91 Z looks crazy, i love the stance of both of your cars.

My car wont be for racing or anything, just looks mostly, street driving, not a daily driver.

any suggestions? can you guys point me in the right direction as to what i need to buy.


sofar this is what ive found.

Ground Control Suspension Systems

is this what i need? and just pick the spring rate? are coilovers and weight jacks similar or the same thing? or do they go together? im not really sure what exactly a weight jack is. and is this the $459 for all 4 wheels? or each? or front only?

thanks in advance for the help.
thanks

Ok, there is a lot to cover here, and a lot of info about cornering dynamics that are going to come in here.

Your ride height, is going to effect the balance of the car with the given spring rates. Since hte front/rear roll centers migrate diffrently on are cars. On my car, with the sway bars I have, and the alignment I have, at the height I am at, my car is VERY neutral, so oversteer comes in with just a bit of throttle.

Now, My same setup, but sitting at stock ride height, is going to understeer more than it does now. This is because the front roll center has moved close to the CG, and the rear has not changes nearly as much (if any).

It is very hard to say exactly how it is going to behave is hard to say. IMO 700# is ok for a street car, but that is 100% opinion. It may be too stiff for some, not stiff enough for others. It is very hard to give a good answer about "ride quality".

You also have a lot of tuning you can do, if you do 700/150 and it is more tail happy than you would like, you can just go with a slightly smaller rear sway bar. So it is easy to fine tune your balance. Springs are also pretty cheap, so it isn't a big deal to change those either.

I would say, try 650/125, and see how you like it. If it is close, you can tune it with junkyard sway bars.

As for other places. Contact Strano Parts, they carry the GC stuff.

I'm just looking for a good place to start, would 700/150 be good to start? from there i can change and ajust and fine tune to get it how i want. might have to put different springs in or change sway bars and such.

I guess im just looking to see if i buy that kit i posted i'll have everything i need to do the install, along with the usual things you'd do when just putting in lowering springs.

how big of a deal is it which shocks or struts you have.

lastly, the higher the spring rate = rougher the ride?

Again, there is no good answer.

700/150 is what I run. I drive it every day and love it, I also race it on the weekends. But, what *I* have, is not what everyone else wants. So what you can do, is look at other springs, and gauge from there. The stiffest factory springs are in the 600# or so range for the fronts. That is about the best baseline you can compare to.

The kit that you posted, seems to be a coil-over conversion kit. That is not waht you want, if you are wanting to do weight jacks, in the stock location. I really suggest calling Strano Parts, and speaking with Sam Jr. He will work with you on spring rates, and get you the right parts.

As for shocks/struts. They make ALL the diffrence. They are a much bigger part of performance than the spring rates. If you are trying to modify on a budget, spend all that you can on shocks/struts. That is where peformance comes from. It also has a huge impact on the ride quality.

Gneraly most people say higher rate = rougher ride. While, again, subjective. Higher rate springs, mean it takes more force on the wheel, in an upward motion, for the same amount of deflection. So, yes, as the rate goes up, the less like a soft lux. car it is going to feel. Does that always indicate a harsh, or bad ride. No. Again, the rebound rate, and control from the shocks/struts will have a large effect on ride "quality". Also remeber, that you can gain roll resistance, in ways other than just spring rates. There are many things that you can do, to change roll rates, without effecting the actualy spring rates.

I know I am rambling, and didn't give a real concrete answer like you were looking for. But bluntly, I can not tell you what spring rates you want, because I can not begine to quantify things like ride quality, or harshness. That is something you will have to descide. You may end up trying several spring combinations, before settling on one. Honestly, unless you really want/need the adjustability and the freedom in spring rates, that you can get from a weightjack setup, there are tons of aftermarket spring kits out there. Maybe one of the Eibach kits would fit your needs better??

ive never seen a car with just lowering springs as low as i would like.

what im kinda getting at is, i dont want to start off to one extreme or the spring rate. i'd like to start somewhere in the middle and go from there. I do like a rough ride, how rough will the 700/150 setup be? that i dont know, but theres only one way to find out. im sure it wont be too rough for me, and seem like a good starting point.

the only reason i want this system is to lower my car as much as possible without an air ride system. is there any difference in ride hight between the 700/150 and the 650/125? will one allow me to go lower than the other. if theres no difference, i'll go with the 650/125 to be on the safe side. if its still not rough enough i'll do what i need in order to make it how i would like it.

i'll contact strano and go from there.

thanks for all the help and info. i'll let you know what i decide to do and when i think im going to do it.

The bump stops will limit your lowering, before the spring will. That is one other thing you have to keep in mind. If you are planning on going REALLY low, the bump stops are going to be an issue. You will want to run a stiffer srping, to keep from being on the stops all the time. You may also want to modify the bump stops a bit, or run diffrent ones.

I like the ride at 700 myself, it is firm, but bearable for me to commute in. But it is also stiff enough, that when I am racing, it transitions well. Now, granted my car is setup based on max performance, the lowering was secondary to the performance.

Glad you brought ride height and its effect on balance up. You're right lowering the car overall will make it tend toward oversteer. But you have the roll center (RC) migration backward. Lowering the front makes the RC go low in a hurry in a third-gen (not so on a 4th-gen, I think). It moves further away from the CG because the RC moves downward faster than the CG and can even move underground. Therefore greatly increasing the roll moment at that end of the car (i.e., the car rolls more at the front for a given lateral force). So up front, you've lost a ton of roll stiffness. In back, the RC (as determined by the midpoint of the panhard bar pivots) still moves down, but at only about half the rate as the rear CG moves down. So the RC is indeed moving closer to the CG in back, and therefore the roll couple is reduced as it is lowered and the roll stiffness increases (this all assumes a non-adjustable PHB, but you could put the rear RC wherever you want if you can change the PHB height). So the combination of increased roll couple in front and decreased roll couple in back is just like going with a smaller front swaybar and bigger rear swaybar, with oversteer (or less understeer) as a result. BTW, the more the strut inclination angle, less quickly the front RC migrates downward, which is one thing that makes a third-gen handle better than Fox and SN95 Mustangs. At some extreme SIA, you probably don't lose roll couple with lowering.

In terms of rates, my general experience has been that if you are going any lower than stock, you need to seriously increase spring rates or you are going to have a bumpstop festival every time you drive your car. Bumpstops make the ride much worse, and the handling much less predictable, than nice high-rate linear springs. I wouldn't recommend lowering the car a ton even for autocrossing and road racing, especially if you're not prepared to delve into adjustable PHBs, adjustable LCA heights, adjustable torque arms, etc. As point of reference, I had a 97 Mustang Cobra (which has somewhat similar front spring lever arm ratios) where I nearly tripled the stock front spring rates from about 450lb/in to about 11lb/in. It was my daily driver and it was not objectionable, and it didn't hit the bumpstops. Most people wouldn't believe me when I told them the spring rates if they had ridden in it! I would not screw around with 100lb/in increase over stock if you're going lower than stock. I'd be looking for 40-50% stiffer than stock.

I also agree with Dewey316 that shocks really make a big difference in handling and ride quality. You will notice more harshness from stiff shocks than stiff springs, by a lot. To give you an idea, a shock can easily put 10000lbs of momentary force on a shock tower when going over sharp bumps at high speed, whereas any reasonable spring only ever puts a fraction of that force into the frame. This is because damper rates vary with the piston speed inside the chamber, and a sharp bump results in a very quick compression of the suspension and therefore a high piston speed. And that is force you can feel in your behind. That's why damper companies put so much effort into digressive valving, in order to provide a tolerable ride over high-speed bumps (high speed as in the speed of the damper's piston) while still being able to control low-speed dynamics such as squat, dive, and roll. For drag racing, damper requirement get really funky really fast. That is a whole new thread's worth of info, at least. You might benefit from looking for adjustable shocks with relatively low damping rates overall. In the same Cobra I mentioned above, I used Koni double-adjustable shocks and I could have a reasonably smooth ride or a ride that literally hurt, depending on how the dampers were set.

I hope this all helps.

mmiller,

I think we are saying the exact same thing. I was comparing my lowered setup to moving it back towards stock height (increasing RC height or moving it closer to the CG in front).

I also mentioned bump stops, Where my car sits, I have about 5/8" from the very tip of the front bump stop, to the a-arm, this gives me enough wheel travel, that I never hit the stops at the track. I do hit them now and again, when I am driving around town, if I hit a descent sized bump.

The thing about the internet, is there are so many things that are very hard to explain, especialy when you get into interactions of parts, and the dynamics of something as complex as a cars suspension. Which is why I really suggested he call someone like Sam, who can really help him pick things for his car. Much better than we could do for him, typing away on the interweb.

Sounds like you have a mustang racing background? Where/what do you race now?

Oops, I see that now. I just misunderstood what you wrote. Sorry about that!

I have mostly autocrossed for almost 20 years, with a little bit of HPDE/open-track time thrown in. I started in a 75 Trans Am, then moved to a 1989 Mustang purchased from Texas DPS, then moved to the 97 Cobra, and for the last five years or so have raced my 92 B4C. A local friend purchased the B4C from the DPS at auction in 1995 or 96, and then was owned in sequence by two other friends of mine, until I bought it. So I'm the 4th civilian owner and everyone of us has raced the poor car. It's had a hard life, but it's still going strong. I have competed mostly in SCCA Solo II and also in autocrosses with the Texas A&M Sport Car Club (I'm a former president of that). I have kept the Camaro in F Stock, whereas the two Mustangs were raced in Street Prepared and the old T/A was modded haphazardly with no plan.

Since this topic seems to be hot im going to hijack.

Heres a picture of the ground control weight jacks which I stole from one of crazys posts. I used the measuring tape in the photo to take a rough guess at the measurements. Can anyone here verify these sizes so I can piece together/fab my own setup? Other angles that would aid in fabrication of these jackers would be appreciated.

So I've been reading up here and there and I'm thinking 125# springs in the rear no higher and I think 600-650 for the fronts would be do-able for a mainly street driven ride.

- Joel

I wouldent bother fabbing some up whan you can buy an adjuatable spring spacer or weight jack from any place that sells dirt track parts for like for like 50 bucks and they have the parts so you can build your own if you want

yeah..well these parts always a one size fits all deal, so the measurements are still important. if you have a proven alternative setup I would love to see it.

all thoes are is a standard 5 inch spring coil spacer with an audjustment in them dirt circle teams have been using stuff like this for years to change wedge for track conditions personally I plan on using an afco audjustable coil spacer and a 800# spring in the front of my car and going coil over rear

dewey i see you keep talking about the bump stops and changing them. what have you done to the bumpstops on your car. i just took mine out and it has bottomed out in the front once or twice. i would like to find an aftermarket lower profile bumpstop do you know where i could get something like that?

Koni sells tapered bumpstops in diffrent lenghts, diffrent tapers, and so forth. They attach to the shock pushrod. Idealy you won't hit them much, so you will be ok with them mounted like that. You want a soft-ish bump stop, so that it will not cause a crazy sudden change in wheel rates.

They are listed on page 31 of Koni's motorsport catalog.
http://www.koni-na.com/pdfcatalogs/K...ortCatalog.pdf

I also think the round-control sells some tappered bumpstops. You will want to get down there and measure to get the righ size. YOu want enough there to stop the sudden impact, but you don't want to hit the stops under normal conditions.

I have been road racing for a number of years in SCCA American Sedan. I qualified 6th at this years runoffs and I was the track record holder at HPT.

I have been following this thread for a while and here are my thoughts.

Go Soft. I use 700 and 175 springs in my race car. This would be super stiff for the street and not needed. If I can set track records against some of the best drivers in the country using this set up there is no reason to go stiff. We like the NASCAR have been going softer over the past 5 years. Jay Morris set ups are a little outdated to what we are currently running in the 3rd and 4 get F bodys. I know the set up on John Heinricy National Champ car and I can assure you that he is pretty soft also.

Shocks are much better today then they were 10 years ago and we are working very hard to keep the tires on the ground. I run a 1LE bar in front and the smallest factory rear bar.

When installing weight jacks in the rear make sure that you take into consideration the fact that the factory springs have a pretty big offset. DO NOT PUT THE REAR WEIGHT JACK IN THE CENTER OF THE PERCH. It needs to be set towards the back of the car about 1.5 to 2 inches.

Let me know if you have any other questions.

#54 A/S

Philip

I appreciate all the excellent replies/opinions in this thread...it's definitely helping my decision process. So at this point now I'm thinking about 550# fronts and 125# rears both 10" tall springs. I'm leaning towards 550 front due to some excellent reviews I've read about Sam Stranos new lowering springs of the same rate.
Any comments appreciated.....
I hope to order them this week.
- Joel

I am almost certain that the lowering springs from Sam that you are talking about are for the 4th gen. Call Sam when you have at least 20 minutes to spend on the phone and do listen to his recomendations. You need a higher rate front spring. Between 700 and 800. The AS cars can perform with realativley low rates because they are lighter than thier street driven bretheren. I have 800/175 which would be great on a track but is a tad stiff in the rear for autocross. I agree that there is no need to go to a 1000# front spring which was once common for AS cars.

I was just going to say, make sure Sam wasn't talking about a 4th gen.

I run 800 lbs. front springs, and it is a bit stiff on the street, but autocrossing along with my alignment and a 34mm solid sway bar the car turns in very well and transitions in slaloms quickly for a car of its weight. In the rear I'm running ether 125 lbs spring / 22 mm bar or 150 lbs spring / 19 mm bar.

You guys are correct...I was referring to his 4th gen springs...but now that I think about it we're talking about a completely different front suspension than our 3rd gens. That totally slipped my mind.

Sounds like I'd want a 10", around 650# spring or so on the front.
I'm running the Hellwig solid sway bars...front is 1 5/16" ~ 33.3mm and the rear bar is 1" ~ 25.4mm...since it's a good size rear bar would it be safe to assume a 125# rear spring would be fine and help limit the *** swing on the car? or would a 150# be better? I don't want to be tail happy on the street.

How much do street camaros weight? My race car comes in at 3295 at the end of the race with driver.

I do not think that an extra 100lb of spring has much impact on the car. The most important is that the car is balanced.

Philip

I doubt you want the 150# springs in the rear. The higher the rate the more tail happy the car will be, this works for swar bars too.

2930lbs without me! *happy dance*

Thank you very much everyone!
I'm going with 650# front and 125# rear.
I won't be slamming the car at all....just tweaking it...does everyone agree going with a 10" tall front and 11" rear?

Thanks! - Joel

10" tall will likely be to tall in the front.