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Spring Rate Data

The material used has almost no variation within the iron alloy family. But when measuring the spring, knowing the coating is important. Powdercoating can add a mm to the wire thickness, most paints 0.5ish mm.
 
Does anyone know the difference between a sedan and wagon HD overload springs from FCP/ IPD I have a pair here I am 99 percent sure are wagon springs.

 
Not me. Early on in this project i hoped to borrow lots of springs like that and measure them. I did borrow a few sets, like some of the lowering springs.
 
Hey everyone! I'm looking for some advice for my 81 245 on STS coilovers and lowering springs with an adjustable perch in the rear. The rear still feels like a pogo stick, thinking it might be too stiff after installing chevy S10 front shocks for my rear.

Here's the run down of what I've installed onto my wagon.
1. STS coilovers, 325lb fronts and 275lb rears, bilstein touring struts in the front and Chevy S10 front shocks for the rear -> I'm thinking this is my problem, too stiff for the wagon? I'm fairly low in the front, so it feels perfect with my BBS RC090. I can barely fit my pinky inside from top of the tire and fender.
2. Rear end is where my concerns at. I've completely taken out both bump stomps and the one by the diff, but I believe I'm still hitting the rear crossmember.
3. kaplhenke panhard bar, IPD torque rods and poly trailing arm bushings.

Any help would be much appreciated!
 
You can start a new thread in performance, but the main thing i see is you have not factored in the rear control arm motion ratio (squared).
Multiply the rear spring rate by 1.5 and that is what the vertical rate is.
The front loses a little bit (5%) due to the angle.
Also, s10 shocks only work with 11? springs or shorter.
 
mikep said:
You can start a new thread in performance, but the main thing i see is you have not factored in the rear control arm motion ratio (squared).
Multiply the rear spring rate by 1.5 and that is what the vertical rate is.
The front loses a little bit (5%) due to the angle.
Also, s10 shocks only work with 11? springs or shorter.
Click to expand...

Sorry about that! I should have posted there first, but thank you for the advice about the squared factor. I will give that a shot and see what numbers I get!
 
1974 164:
Front springs
Wire diameter - USA - 16.7 mm = .657”………Other - 16.4mm = .646”
Outer diameter - USA - 126.7mm = 4.99”……..Other - 126.mm = 4.97”
Springing coils - 8.4
Load - USA - 7239-7730 N…….Other - 6429-6920 N
Length fully compressed - USA - 135.3mm = 5.33”…
….Other - 132.3mm = 5.21”
Spring Length - USA - 202.4 = 7.968”………Other - 199.5mm - 7.854”

Rear springs
Wire diameter - 12mm = 0.472”
Outer diameter - 128mm = 5.04”
Springing coils - 8
Load - 2070-2207 N = 464-495 lb
Length fully compressed - 112mm = 4.41”
Spring length - 287mm - 11.3”
 
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This might need its own topic, but let’s say you were going from a completely stock suspension to a bne coil over set up on a 240 wagon. Koni yellow shocks/struts. What spring rate would you want to run and what length? Let’s say we’re setting the car up to autox and/or do some laps around road Atlanta.
 
Marvelous3 said:
This might need its own topic, but let?s say you were going from a completely stock suspension to a bne coil over set up on a 240 wagon. Koni yellow shocks/struts. What spring rate would you want to run and what length? Let?s say we?re setting the car up to autox and/or do some laps around road Atlanta.
Click to expand...

Ben helped me choose spring rate for the rear of my 242. I bet he could help you choose a good setup, too!
 
When Towery started with the stock car spring idea, he went with 11# tall by 5" dia 200# in rear. I inherited those springs, and went from there. This was when we were treating the rear like most other cars with the spring on the axle or on a strut.
After learning about motion ratios, and going all over in rates, I have found that 13" 225# in the rear of a sedan (337.5# vert, less in roll), with 9" tall 5.5" pigtails, 350# in front (close to the rear number in vert due to the strut inclination) was very good. Not too stiff, very good handling with 23mm front, 19mm rear bars. 1" or so lower than stock.
In my current wagon I have 13" 275# rear (412.5# in vert) with suburban Gabriel Ultras and 425# in front with very stiff bilsteins. This will be for rallycross and autocross. In my first wagon I originally ran the 275s in rear with the 350s in front, and it was awkward on concrete and bridges.
 
The Koni yellows handled the 350# springs well in front.

I think the reason that some suburban shocks (1" shorter than stock at the shock, but even shorter at the spring) don't work well on the rear of a 240 is that the stroke is really slowed down at the shock. The gabriel ultras are not know for finesse, which works better at the slower stroke rate when installed in a 240.
The bilstein shocks that came stock on the front of the 88(?)s10 4x4 did very well with a 3"-4" drop and very stiff springs. I still have the set I used on the rallycross 244.
 
Bumping this because I have a spring question.
What happens to springs as they age on your car? Does the rate get stiffer or softer? I have a set of front GT springs on my wagon and they have one coil(the dead coil, lol) removed. They seem to have stiffened up in the last couple years and ride rather harshly am considering something like the Lesjofors 30mm drop springs.

Thinking they may be a bit more comfortable while still giving decent handling.
 
Neither. The rate stays the same but they can sag (sag, droop, ?take a set?).
The torsional modulus of steel is pretty consistent across the alloys and hardness range. Too soft and it sags. Too hard and it breaks. But the springiness is pretty consistent.
 
240 240 said:
the ones on my car are 5 yrs old so probably not an accurate measurement as they have sagged.
Click to expand...
The free height might have changed, but the rate will be unchanged.
If you have before and after pics, load/unloaded pics, etc those are useful.
And just a wire thickness and free coil count (assuming standard OD) would be great. If you find a paint chip, include a wire thickness there. If the difference at a chip on one side is 0.5mm we can deduct 1.0mm (my usual coating assumption) for the stiffness calculation.
 
After reading this thread many times over, I calculated and had custom springs made for my 1992 244 sedan. The aim was to achieve both lowering and ride comfort. The cost was about 400 USD for all four springs.

Front 98 lb/in
410 mm free length
165 mm overall Diameter
13 mm wire diameter
4.65 free coils
5.5 entire coils
205 mm installed height sitting

Rear 120 lb/in
300 mm free length
127 mm overall Diameter
11.5mm wire diameter
5.14 free coils
6.64 entire coils
163 mm installed height sitting
71 mm block height.
※Rear springs are used with BNE rear coilover.

As a result, it became a car with an exceptionally comfortable ride. It's ideal as a family car for city driving.
 

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