Coilover question: spring rates

[greesha]

Several questions about you guys running custom coilovers
Based on your threads, most seem to be running 350-500ish spring rates.

Since I don't think my V8 is going to be much of a daily driver, probably just a being obnoxious car, id like something very stiff

I was thinking 650 front 700 rear, or 700/750. Is that going to be spine shattering stiff?

Also, questions about revolves. My V8 came with a set of Koni shocks.

I purchased a set of sellholm tuning custom made coilers for the front that use audi 5000 uprights.
similart o viewtopic.php?f=27&t=224
The rears came with QA1 coiloversleves on their old carrera shocks, which are toast.
For my rears I am thinking of doing this: viewtopic.php?f=28&t=443

I was thinking of reusing my Konis, just getting them revalved. Any suggestions on places to do this?

[loxxrider]

I'd go 650\700 if you really want it stiff and trackable. It wouldn't be too nice for the street though. I think if I had to do it again on mine I might go 550/600 or so for an aggressive Street setup.

[speeding-g60]

650 front and 900 rear was on my drag car since i built it.

but dropping the rears to 200 made it squat hard and grip like no other out of the hole.

if i would drop the pedal too hard, it would buck and bounce and all 4 tires WOULD leave the Earths surface. BTDT.

[pilihp2]

Springs that stiff will without a doubt require some revalved shocks.

[greesha]

Springs that stiff will without a doubt require some revalved shocks.

definitely

I'd go 650\700 if you really want it stiff and trackable. It wouldn't be too nice for the street though. I think if I had to do it again on mine I might go 550/600 or so for an aggressive Street setup.

thanks for the advice, stiffer in the rear is to help with understeer, correct?

650 front and 900 rear was on my drag car since i built it.

but dropping the rears to 200 made it squat hard and grip like no other out of the hole.

if i would drop the pedal too hard, it would buck and bounce and all 4 tires WOULD leave the Earths surface. BTDT.

with a stock v8, i wont be bounding, no matter how hard I launch it

since bilstein and koni are the only ones offering them, you guys see any different? I know both are going to need revalving

question about adjustable koni shocks. are all the shocks for our car adjustable? or is there a separate line of adjustable ones?

[loxxrider]

Stiffer in the rear is to help the car understeer less, yes. At low speeds it will still plow, but at moderate cornering speeds the difference is nice. If you want a drag car, follow Aaron's advice.

[20VAvant]

I have a 91 200 Avant
550LB in the front
650LB in the rear

Re-valved and shortened(front) Bilsteins for the shocks.

It would be pretty uncomfortable for city driving, but I live out in the suburbs where the roads are nice and it's a great ride.
I don't daily drive mine though.

It's a beast in the windy roads(for an early 90s station wagon that is)

[WOMBAT]

I'm running 400/450 and its a comfortable yet firm ride, but the shocks really need to be revalved even for those. 90% sure mine are blown (Bilstein Sports)

[40v4kq]

IIRC Jimmy (vomit comet) was blowing out his Koni's left and right when he went above 450 or 500lbs on his springs. A re-valve will definitely be in order for you no matter what brand you stick with.

[greesha]

Thanks for all the advice! I will definitely have them revolved, just need to find somewhere to do this, hopefully close by

All thats left to do now is figure out what strut inserts I have in my sellholm suspension.

[lucidmatt]

I have a 91 200 Avant
550LB in the front
650LB in the rear

Re-valved and shortened(front) Bilsteins for the shocks.

It would be pretty uncomfortable for city driving, but I live out in the suburbs where the roads are nice and it's a great ride.
I don't daily drive mine though.

It's a beast in the windy roads(for an early 90s station wagon that is)

when shortening the bilsteins, what was your technique for shortening the strut/wheel bearing housings? I wish I had Ed shorten mine when he modified mine... but hey, live and learn... did you section and weld, or is there a tap available to match the gland nut? Im hoping there is a tap, as I'm more comfortable cutting threads than I am with welding.

[paradox11235]

I'm going to be doing coilovers on my 200 20v avant very soon. I have a set of 400# springs already, so i'm thinking either 350/400 or 400/450. I have H&R 29771 springs on my sedan (S6 race springs) and love how it rides and handles, so I'd like to get pretty close to that. I'm going to call H&R and see what they can tell me, but...

This is going to be my DD also...

[loxxrider]

I have a 91 200 Avant
550LB in the front
650LB in the rear

Re-valved and shortened(front) Bilsteins for the shocks.

It would be pretty uncomfortable for city driving, but I live out in the suburbs where the roads are nice and it's a great ride.
I don't daily drive mine though.

It's a beast in the windy roads(for an early 90s station wagon that is)

when shortening the bilsteins, what was your technique for shortening the strut/wheel bearing housings? I wish I had Ed shorten mine when he modified mine... but hey, live and learn... did you section and weld, or is there a tap available to match the gland nut? Im hoping there is a tap, as I'm more comfortable cutting threads than I am with welding.

It's best to shorten it below the steering arm to preserve steering geometry. Josh has pictures of this finished up in his thread. My diy coilovers thread shows how to section and weld a strut as long as you have someone who can use a mig.

[20VAvant]

I have a 91 200 Avant
550LB in the front
650LB in the rear

Re-valved and shortened(front) Bilsteins for the shocks.

It would be pretty uncomfortable for city driving, but I live out in the suburbs where the roads are nice and it's a great ride.
I don't daily drive mine though.

It's a beast in the windy roads(for an early 90s station wagon that is)

when shortening the bilsteins, what was your technique for shortening the strut/wheel bearing housings? I wish I had Ed shorten mine when he modified mine... but hey, live and learn... did you section and weld, or is there a tap available to match the gland nut? Im hoping there is a tap, as I'm more comfortable cutting threads than I am with welding.

It's best to shorten it below the steering arm to preserve steering geometry. Josh has pictures of this finished up in his thread. My diy coilovers thread shows how to section and weld a strut as long as you have someone who can use a mig.

This^

I took both assemblies to a band saw and chopped the top thread off with probably 3" of good material left. I turned the excess 1" material off in a lathe and made a custom "plug" that matched the ID of the housing. I slid the plug into the housing and slid the 1" shorter upper piece with the threads on over top to keep concentricity of the tube. I then had a friend TIG them up for me. Still hasn't fallen apart yet after probably 1.5" years and ~10K miles...

[speeding-g60]

all that above, remember to mark the geometry and the position of the steering arm. you can get out of shape quickly otherwise. you want the arm to remain clocked in the original position for sure.

[loxxrider]

So you didn't shorten below the arm on yours Nick?

[20VAvant]

So you didn't shorten below the arm on yours Nick?

Nope, I shortened above the arm.... Haven't had any issues so far...

[greesha]

UPDATE: it terms of my suspension rebuild.
Conies are being sent out to be revavled, as they are already leaking
Took my fronts apart. They are using an audi 5000 upright, with a 40mm inverted damper. Its a bilstein unit, but before they started putting their logo on things, so it is old. Go in touch with them to help identify it, they finally just asked me to send them in, oh joy.

You guys are talking about shortening the shocks, this is done because you are shortening the upright. This requires you to use shorter springs, because you are shortening the suspension travel, correct?

[loxxrider]

Shorter springs compared to stock? Yes. You are actually increasing suspension travel at a given ride height by shortening the strut housings. It allows you to lower the car while keeping the strut more extended.

Be careful with bilstein if you ask them to revalved and shorten. Both nick and I have been through hell with them trying to get it right. They can't seem to figure out what we want and always shorten the strut in a completely useless way lol.

[greesha]

Be careful with bilstein if you ask them to revalved and shorten. Both nick and I have been through hell with them trying to get it right. They can't seem to figure out what we want and always shorten the strut in a completely useless way lol.

All they are doing is revalving them. I emailed them asking to identify my dampers, after 2 weeks, they asked me to send them in, so fingers crossed they can be rebuilt.

Has anyone combined different rate springs? Was glancing through the eibach site and had an idea: stacking the springs



Would this be something you guys would recommend?

[mushasho]

I'm going to be doing coilovers on my 200 20v avant very soon. I have a set of 400# springs already, so i'm thinking either 350/400 or 400/450. I have H&R 29771 springs on my sedan (S6 race springs) and love how it rides and handles, so I'd like to get pretty close to that. I'm going to call H&R and see what they can tell me, but...

This is going to be my DD also...

Spring Stacking is something I'd like to do as well... mix a linear rate spring with a progressive tender... I'm trying to find that right balance combination/rate for use with a standard Bilstien... shortening and revalving is not an option right now ATM... but a suspension that bottoms out isn't either... I also have 29771's and like the ride, I really just want another 1/2" to 5/8" more of a drop. My research from years back says that 29771's are 340F/330R for rates. Another thing I think we forget to consider is that our front "sway bar" also progressively adds to the rate & increases stiffness as it compresses... we might not need super stiff rates up front, which in return might increase longevity on stock sized/valved units while being comfortable for daily use.

In the mean time I'll be building my set around these 10way Adjustable Spax Units (#1056-2A) I have laying around in my basement.
I'll see how they cope at the stiffest setting...
All I'm looking for is a compliant ride that doesn't bottom out, using stock replacement struts. So I'll mate these to 350 Linear with an Eibach 0200.250.0550 Tender spring to avoid bottoming it out (.pdf attached) ... I wonder if Hyperco carries them as well...

[loxxrider]

FYI if you do that your effective spring rate will only be 213 lb/in Obie.

It will be 213 lb/in until one spring or the other fully compresses, then it'll be whatever the spring rate of the uncompressed spring is. There may also be some different rates somewhere in the middle as individual coils begin to touch each-other near the spring ends, but you get the idea.

[mushasho]

FYI if you do that your effective spring rate will only be 213 lb/in Obie.

It will be 213 lb/in until one spring or the other fully compresses, then it'll be whatever the spring rate of the uncompressed spring is. There may also be some different rates somewhere in the middle as individual coils begin to touch each-other near the spring ends, but you get the idea.

So what exactly did I just do here...

[loxxrider]

Springs in series (stacked on top of one-another) are like resistors in *parallel*. If you have two 500 lb*in springs and stack them on top of one-another, you won't end up with 500 lb/in springs. You'll get 250 lb-in.

The math goes like this:

1/effective rate = 1/spring1 + 1/spring2

[Aktapod]

Springs in series (stacked on top of one-another) are like-

*Ahem* Resistors in parallel