Spring Rate Data

[mikep]

Are the IPD springs you tested wagon version or sedan? I missed it if you specified. I was thinking they might be the wagon version looking at that rate.

Thanks for this Mike!

Sedan. I found another set, too. I will test those when I test the 7 series IPDs and anything else I find.
Probably going to take the stock 945 springs off when I head back down.

 

[petebee]

So I understand, it sounds like a car with old black IPD springs is undersprung at the front? Where are you testing these springs? I live in Mooresville right in the thick of Nascar

I have a 1990 240 Wagon with black IPDs and Bilstein HDs and the ride is not great.

 

[Mueller]

So I understand, it sounds like a car with old black IPD springs is undersprung at the front? Where are you testing these springs? I live in Mooresville right in the thick of Nascar

I have a 1990 240 Wagon with black IPDs and Bilstein HDs and the ride is not great.

One of the coolest race shops I've ever had the pleasure of getting a private one-on-one tour of.

(Went to N.C. for a Fanuc class)

Mike, it would be nice to have a link in this thread or maybe a sticky of your other spring information for our cars.

 

[mikep]

So I understand, it sounds like a car with old black IPD springs is undersprung at the front? Where are you testing these springs? I live in Mooresville right in the thick of Nascar

I have a 1990 240 Wagon with black IPDs and Bilstein HDs and the ride is not great.

Yes, I think the IPD black springs should be split up and the rear paired with stiffer fronts, the fronts paired with softer rears.

Drew's work is where we did the graphs. I stay with Drew near lake norman when I'm there.
I do a low-budget test here at work (high school auto tech shop) with a dial indicator and a scale. It comes pretty close.

One of the coolest race shops I've ever had the pleasure of getting a private one-on-one tour of.

(Went to N.C. for a Fanuc class)

Mike, it would be nice to have a link in this thread or maybe a sticky of your other spring information for our cars.

Yep, it's an insanely nice shop (or set of shops).

I have some broken links in the stock car spring threads, and I haven't looked for towery's threads lately. He started using stock car springs in the rear, I stole his idea. He also did the pvc sleeves with coilover springs.
If I have time after the seniors leave next week, I'll put in some links.

 

[mikep]

Still looking for loan or donation of stock 740 springs and any early stuff.
I?ll do WWD as well.

Going to Charlotte again at the end of June.

 

[mikep]

Round 2

IPD blue 7-9 series sport springs, stock 240 springs from a GT that turn out to be the softest 240 springs ever (swapped, probably) and some cheap coilover shocks and springs from Lawrence.

Black front 240 spring, from an unknown donor (taken from the front of a GT by VB242, hoping they were sweet springs).
85#/inch.

Next up, IPD blue 7-9 series sport spring, front.

Starts around 130#, 145# avg, 150# peak. Some rise due to seat issues. Not a progressive spring.

Next up, 240 rear, unknown donor. Was found in a 242 GT.

poncy 95#, but 50% stiffer when in a 240 rear arm due to motion ratio.

Next, IPD blue rear for 7-9 series.

What? The same as a stock 240 spring? No, there's more. It's progressive.

The rise at the end is unresolved, so we had to test to a higher pressure. We chose a distance, and that distance wasn't enough.

95# rising to 140# and staying there.
So at normal ride height, cushy. In a turn or under load, you get less compression.

teal coilover, 350#. (not volvo related)

Shock time.
(not volvo related)
"made in canada" Pro Shocks T40902SA
(below that WB 735)

As set, good for 300#ish springs, didn't try adjusting them. Didn't see how to.
These are still available in black, starting around $80 each in a variety of dimensions.

 

[mikep]

I'll measure dimensions later. School is starting, need to sign off for a bit.

 

[towerymt]

1988 Hartford CT 244
Front springs 80 lb/in
449mm (17-5/8") free length
166mm overall Diameter
13.2mm (.520") wire diameter
5.5 free coils
11.5" installed height hanging
8.5" installed height sitting

Rear 91 lb/in
415mm (16-3/8") free length
129mm overall Diameter
11.85mm (.466") wire diameter
7.5 free coils
15.25" installed height hanging
12.25" installed height sitting

Measured the springs that came off my '92 240 sedan.

Front:
17-1/4" free length
0.540" wire

Rear:
16-1/4" free length
0.475" wire

Rear springs had some blue on one coil. Fronts are still covered in undercoating.

 

[jwernerny]

I've got rear springs from a '94 964 (Mk I IRS), and a '92 944T if you want to measure them. PM me.

 

[mikep]

Cool. I would like to measure towery's springs, too.

 

[towerymt]

Cool. I would like to measure towery's springs, too.

 

[mikep]

I mean, i?ll buy you fried chicken first..

 

[towerymt]

I mean, i?ll buy you fried chicken first..

Now yer talkin. Schmaltz me up, big boi

 

[Marvelous3]

Should ride like **** with the 1.5:1 motion ratio squared in back.
Rear vert rate would be 222lb/inch.
Front you lose a little, so 130-ish.
If I had that much rate out back I'd want at least 250 in front to keep it from pitching.

What is considered a "good" ratio for us? Grey car is 300 front and 200 rear and seems to ride super predictable. I sort of guessed when I bought springs at those rates but maybe I got lucky? I'd always read you wanted more spring up front than in the rear.

 

[mikep]

What is considered a "good" ratio for us? Grey car is 300 front and 200 rear and seems to ride super predictable. I sort of guessed when I bought springs at those rates but maybe I got lucky? I'd always read you wanted more spring up front than in the rear.

Good question.

Most cars have more weight up front, so you need more rate in front for a similar frequency as the rear.
Even with a 50:50 balance, most o.e. engineers go a little higher in front so it doesn't "pitch" over expansion joints or small bumps in smooth roads.
For performance, it really depends on the suspension type, your driving style, surfaces, etc.
A solid rear axle has an odd motion ratio in roll, so to avoid a huge rear bar, some people go higher in rear. Some anti-roll bars (like ours) have a huge motion ratio as well. In front, it's half as effective on the control arms, compared to on the strut. The rear is even worse, since the effective arm length is the length of the control arm it is bolted to.

300 front and 200 rear gets you roughly equal, which is a good starting point. The wagon with 350 front and 275 rear handled great with mild sways, but was bad to ride in on a bridge. The sedan we put together with 350 front and 225 read was very good. I think it had a 25mm ipd front, 19mm rear.

 

[woodenpudden]

The sedan we put together with 350 front and 225 read was very good. I think it had a 25mm ipd front, 19mm rear.

Correct, its only fault was a tendency to plow, but behavior on bumpy roads etc. was excellent

 

[towerymt]

I wouldn't commit to a ratio front:rear, but I think I'd settle on about 3:1 as my favorite.

For example, I could like 300lb front /150lb rear, but I would never do 2:1 ratio with 800lb front springs.

I've used as high as 325lb rear springs. Went back down to 250lb on the autocross car. Have used lowering springs or cut overload springs on the rear as well. Soft rear springs seem to work fine for handling.

Daily driver: 300 fr / 125? rear (IPD lowering springs in rear, stock bar)
Lemons: 475 fr / 150? rear (cut wagon overload springs in rear, no bar)
Autocross: 550-700 fr / 250 rear (no rear bar)

I've also tried Jamex front lowering springs (they were soft), and 200lb rear springs (a LONG time ago). Car would rotate! Great for street tires and not a lot of camber. Didn't rely on a ton of front grip to make the car turn in. Toe-out and rear spring rate can make a 240 turn as well...but it's not as easy to drive. That was an early autocross setup.

 

[mikep]

^those 200# stock car springs were what I used after you figured out to use the top cones on the bottom of a 240 rear set-up.

For anyone comparing my post about front-rear balance, remember that RWD Volvos have a 1.5:1 motion ratio (squared) in back, and a strut car loses a bit of rate from the SAI. (5%)

200# in back becomes 300# in vert.
350# in front becomes 333#.

 

[Marvelous3]

Good question.

Most cars have more weight up front, so you need more rate in front for a similar frequency as the rear.
Even with a 50:50 balance, most o.e. engineers go a little higher in front so it doesn't "pitch" over expansion joints or small bumps in smooth roads.
For performance, it really depends on the suspension type, your driving style, surfaces, etc.
A solid rear axle has an odd motion ratio in roll, so to avoid a huge rear bar, some people go higher in rear. Some anti-roll bars (like ours) have a huge motion ratio as well. In front, it's half as effective on the control arms, compared to on the strut. The rear is even worse, since the effective arm length is the length of the control arm it is bolted to.

300 front and 200 rear gets you roughly equal, which is a good starting point. The wagon with 350 front and 275 rear handled great with mild sways, but was bad to ride in on a bridge. The sedan we put together with 350 front and 225 read was very good. I think it had a 25mm ipd front, 19mm rear.

What shocks and struts were you using? Off the shelf koni yellows or something custom?

 

[mikep]

Koni single adjust worked ok, chris had those in the wagon and sedan.
I like the r-sports and bilstein inverted struts a lot. If you ever need numbers to get them revalved, John V can steer you straight.
I just welded volvo tops on 260z struts to use bilsteins.