rear springs

We have a 96 Impala SS. Recently, I've noticed that the rear is really sagging. I don't have a current picture, but the car has 275/40R17 tires on it and the tops of the rear wheels are about an inch from the opening trim. The fronts are about 3-4".

I have two options: lower the front or raise the rear. (or leave it alone, but it looks lame)

Although I like how these cars look when lowered (slightly), I live in rural Maine and the car has to be practical.

I have a pair of rear wagon springs kicking around. These will undoubtable lift the rear! But how high? Do you think it will be higher than a 9C1?

Another idea would be to install air bags (the cargo kind that mounts inside the coils).

Suggestions or comments?

Steve

I would leave the rears as is, and replace the fronts with 9c1 springs with 1 1/4 coil cut from them. This should level the car out, yet keep the front with a sporty feel. You might loose that feel if you cut the ss springs. But if you go that route, I would try cutting a half a coil out, but no more.

Or just find some low milage ss rear springs.

My blue 9C1 is -1 coil. -1.25 would be too low. If I were to do it again, I't do -.75 9C1.

I'm still concerned about ground clearance.

If it was me I'd go with Moog S10 springs in front.

boojum wrote:

If it was me I'd go with Moog S10 springs in front.

Sorry for the thread jack...

Jim, what's the # for the S10 springs? I like how the 5662 springs sit. Gonna test drive it Sunday.

MASShole9C1 wrote:

Jim, what's the # for the S10 springs? I like how the 5662 springs sit. Gonna test drive it Sunday.

5662, A-body, G-body,F-body, S10... One size fits all.

If that were my car I wouldn't wait 'til Sunday, I'd take it out Friday.

booth9C1SS wrote:

My blue 9C1 is -1 coil. -1.25 would be too low. If I were to do it again, I't do -.75 9C1.

I'm still concerned about ground clearance.

I only suggested the 1.25 because 1 coil will level a SS like stock. I was figuring in the sagging rear end and added another 1/4 coil.

Thanks Jim. I didn't realize they were also for the S10.

Booth, I would try those 5662 springs. I just put them in the front of the 9C1. Something like $56 from jegs or summit.

Check out the pics on my thread for an idea.

Well, this morning I had a chunk of time and decide that I would try the free route first... since I already had a spare set of wagon springs and another set of WX3 springs. The plan was to remove the squished springs, try the wagon set. If that was too high, I'd install the other impala SS springs. By focusing on the rear, I don't have to get another allignment.

I took before and after pictures from the front and rear of the car... but they are still on the camera.

End result: I like the wagon springs. They were from a 94 wagon with auto level control. The tailpipes are about 1" higher now than they were before.

My enjoyment of driving this car has improved since this morning. The rear is stiffer but still rides well. I have a [slightly] better view ov the road, less wandering of the front wheels (275s catch alot of ruts), and less body roll. And... I can drive with three people in the car, a trunk with a full size spare tire, 30+ pound of structural fire fighter PPE, and a week's worth of groceries and the rear doesn't sag.

Pics to come.

Steve

booth9C1SS wrote:

By focusing on the rear, I don't have to get another allignment.


Steve

Not exactly true.

An inch higher at the rear tail pipe seems insignificant, if your before/after measurements are accurate.

That tiny rake change shouldn't hurt your caster setting, but then I doubt you would feel that the car drove better either.

Consider that when changing the front to rear rake of the car, alignment, specifically the caster is affected.

Caster describes fore & aft king pin axis angularity relative to the level ground.

Caster alignment adjustments are locked into the chassis.

By raising the the rear, you loose positive caster, decidedly a step in the wrong direction on stock B-bodies.

Swapping in springs of varying pound rates per inch to achieve a desired rake invites other possibly unwelcome results.

Nobody here has ever seemed to be interested in my mentioning the benefits of:

A), matching F to R lateral roll stiffness (combined with correct sway bar selection), and

B), balancing F to R bounce frequencies (Flat Ride @ highway speeds).

Machine-De-Zine wrote:

Nobody here has ever seemed to be interested in my mentioning the benefits of:

A), matching F to R lateral roll stiffness (combined with correct sway bar selection), and

B), balancing F to R bounce frequencies (Flat Ride @ highway speeds).

Honestly, its more likely that most of us are more interested in form over function.

All of that info scares guys out of modding their cars the way they want.

Tho, accurate and helpful information, let's face it. I dont see anyone trying to build a race car here(besides Brian and Brandon). And if they do, it's because they want to get out and have fun, not stay up at night worrying about caster and bounce frequencies. The last things on most guys minds when a desire able stance is the goal.

I don't know a whole lot about it, I just want a slick looking ride that handles and rides good. My lowered suspension road like a garbage truck, but I replaced everything for comfort and longevity. My B isn't a daily driver or a race car. Just a fun project

I 100% understand the above point. I'm not arguing that just throwing anything you want on your car is the way to go. But most guys do do their research before modding. Not trying to make waves, but he just wanted to lift the rear end up a bit.

You could have also tried replacing your isolators.

I'm just concerned that sometimes people can get themselves hurt when modifying their cars in ways they don't understand.

If a car handles a bit soft for your taste, and you firm the ride up greatly, but with mismatched springs, , ,

It's tight ride characteristics may deceive you into believing you've improved the car's handling, perhaps if your lucky you have,

- but in fact there's the very real possibility that the car will do something very deadly, AND at the worst possible moment.

A little knowledge truly can be a dangerous thing!

All of this fairly simple engineering is built into ALL modern cars, even the most mundane examples!

I am NOT suggesting these things to help anybody build "race cars".

Just SAFE cars.

Machine-De-Zine wrote:

Nobody here has ever seemed to be interested in my mentioning the benefits of:

A), matching F to R lateral roll stiffness (combined with correct sway bar selection), and

B), balancing F to R bounce frequencies (Flat Ride @ highway speeds).

No...your WAY off here....I've been through LOTS of cars with LOTS of mistakes suspension wise & I WHOLE-HEARTEDLY agree with you.
My only problem is getting it right.

My daily is VERY close now but the 40? lbs I lost when I dumped the cast iron heads brought the front up a little more then I like.

That being said, I dont have the "best" package installed but I do have "matched" & that is definetly the way to go. I can make this car do just about anything I want.
Of course....with a few extra horses under my foot, I'm re-learning its body language...

sdstick wrote:

My only problem is getting it right.

My daily is VERY close now but the 40? lbs I lost when I dumped the cast iron heads brought the front up a little more then I like.

That being said, I dont have the "best" package installed but I do have "matched" & that is definetly the way to go. I can make this car do just about anything I want.
Of course....with a few extra horses under my foot, I'm re-learning its body language...

Let me re-state just how simple my recommendations are.

But first, you may want to modify your sentence to read:

"My only problem challenge is getting it right."

"Matching springs" means something startlingly narrow in this context.

Flat ride describes vehicle behavior after it passes over a "bump" at lets say 50-70 mph going dead straight.

The GOAL here is to achieve a safe & controllable vehicle attitude following the passing over a bump.

The front "axle" encounters the obstacle first, and so at a given vehicle speed & wheel base, the rear axle finds the same bump a short, but specific, time afterward.

A given vehicle axle's bounce frequency is nothing more than the repeating time interval in which that end of the car oscillates vertically.

To accomplish the flat ride result, the rear bounce interval should be a small measure faster so that the vehicle settles back down on the first "bounce cycle" simultaneously (front and rear axles).

Here is where properly selected shocks in good condition are important, because the event is virtually "over with" in one cycle afterward, if the damping rates are correct for the car.


Now for the problem CHALLANGE of "getting it right"!

How is this done if we are not engineers working at one of the big three OEMs, or for a top competitive race suspension development team?

Pull out all four shocks, and isolate which ever end of the car you are about to "measure".

You can insert a block of wood between the axle and the frame to keep it from bouncing while you "time" the opposite end.

Lets say you get 9 (nine) front bounce cycles in the FRONT within an elapsed 10 (ten) seconds of measured time.

You should get roughly 10 (ten) bounces from the REAR in the same 10 (ten) seconds, which is an acceptable rate matching of your springs for flat ride.

I don't claim to be an expert, and these 9 vs 10 bounce frequencies per 10 seconds are arbitrary just to clarify the concept in an example that EVERYBODY in this forum can execute.


PS. - Removing 40 Lbs from the front actually increases the bounce frequency of that "axle".

Shortening by "cutting down" the front springs to get the ride height right again will further increase your front bounce frequency!

By those two changes alone, the above example car may end up having 12 or more cycles up front vs the 10 in the rear in 10 seconds!

To conclude, unless you know what is likely to be going on with these "innocent changes", it may be very hard to discern what is or is not happening during the post-change test drive.


The next challenge would be how to intelligently select sway bars to re-balance front to rear roll stiffness AFTER the best set of four springs were installed.

This is where you tune the car to be either "tail-happy", prone to "pushing" or "neutral" as you cross the threshold, going beyond the limits of the traction envelope.

Well explained, but I still think the car rides and handles better with the stiffer rear springs... But the ones that I took out were VERY soft/flat/squished and the set I put in had been in the back of a wagon for over 100,000 miles and are probably not as stiff as they were new.

The car now lands/settles/bounces evenly over bumps (before the rear would almost bottom out). The car is now firmer around corners and feels planted (before would sag, roll, and feel less controlled). Now feels more like a stock 9C1.

It is common for me to always carry around the heavy fire gear in the trunk of the car... perhaps why it doesn't feel as bad as you make it sound.

Steve

A lot of weight in the trunk adds up very quickly compared to the front!
Perhaps you've achieved a good balance, but I'd be very careful driving that set-up with an empty trunk!

I AM listening very intently Glen, I do have a question though and in no way am I trying to be a smartass.
What would you suggest is the correct setup for my Cadillac with the air bag springs?
At full up it's like driving a truck with a ton of leaf springs, super stiff and bounces hard at the smallest bump but settles quickly. At all the way down (or close to it) it's really bouncy as well but is more comfortable.

Now I must explain I have no front shocks OR sway bar because of clearance issues. But I do have a relocation setup for the shocks that is not in it yet..
Are the airbags ok because they basically hold the same air at the same time? Or does it not matter at all because air ride is a different horse altogether?
I don't really wanna deal with the sway bar at all, but those shocks have to go back in. I've said it before I have definitely been in some scary situations with her. Any specifics on angles of the front shocks? Does it matter as long as they have full travel?

Your air bags actually ARE a different ball game as compared to conventionally wound steel coil springs.

The "spring rate" changes drastically as you vary ride height, and yes, I WAS thinking about using them, but I knew I wouldn't be able to get my desired results.

Think of the air bag as a collapsible enclosure of limited volume and you are filling it up with a compressible gaseous medium (AIR).

As the bag receives more air to raise the ride height, the pressure inside the bag increases, & at a certain point, the hardness (RATE) of the air spring starts to rise exponentially!

The best way to utilize air springs is to determine what pressure is appropriate for the ride & comfort you seek, and THEN to configure your suspension parts to arrive at a good ride height and geometry solution for THAT SPECIFIC BAG'S PRELOAD PRESSURE.


When you deviate greatly from that height, you will not have a good compromise.

As Brandon can attest, large heavy vehicles use air bags differently than how they are used in our cars.

Large buses, tractor-trailers & trains weigh a LOT more than a B or D body, and they have to accommodate huge variations in payload.

If you are willing to settle on an optimum rise height and remain at that height, you CAN get very good results!

booth9C1SS wrote:

Well . . . the set I put in had been in the back of a wagon for over 100,000 miles and are probably not as stiff as they were new.


Steve

Beleive it or not, even though those rear wagon springs have lost their "as new" installed height, they could NOT have lost their spring rate in lbs per inch, not unless they have uniformly lost substantial diameter due to heavy rust losses!

A spring's rate is derived as a function of it's overall wire length, minus the two end "dead coils", the wire diameter & coil's effective diameter, ours are 5.5" if I remember correctly.

Well, here are the pictures. Keep in mind that the tires are shorter 275/40R17 (26")

Impala SS stock suspension:



Impala SS front springs, Wagon w/ auto-level (air assist shocks) springs rear:



Steve

Those wagon rears give it.....attitude!

Knowing you need ride height I'd keep it just like that.

Looks a whole lot better then the sagging azz syndrome...
(Not that its very noticable from the pic)

Disclaimer....comments have nothing to do with safety & everything to do with looks.

sdstick wrote:

Disclaimer....comments have nothing to do with safety & everything to do with looks.

I see what you did thee.


The wagon springs actually look great!

I'd keep it just the way it is.... For practicality