IcemanG17

So I find the value of the spring rates in the WSM, but its all in "N" which I assume is for newtons...I wanted to get the conversion to lbs, so I better understand what weight springs the germans originally put on the car.....but I can't find an online conversion that works...everything is WAY too high....the #'s listed in WSM range from 6375 N to 6963 N for front springs and 4710 to 5010 N for rear springs..... the standard conversion of .2248 to lbs puts the front springs at 1200-1500lbs...which clearly isn't right.....

I dunno....I thought stock S4 front springs were around 200-300lbs...

brutus

what is the height measured in in inches ?? or metric. N per what ?

the flyin' scotsman

Brian..........perhaps your answer is here:

http://www.928motorsports.com/parts/hypercoil.php

IcemanG17

The springs are listed at 340 to 350mm...so I guess the measurement is newtons per mm....but I still can't figure it out.....

Malcolm
I saw that, but the springs seem awfully light, since the eibachs are 399-550(?) progressives? I thought stock was around 300lb front 200lb rear.......

Ispeed

I think the stock rates listed on Carl's site are for OB's, they seem too light.
I have the 600/400 and feel like I could have gone 700/450 anyways. The ride is fine for me.

a4sfed928

In order to calculate this you subtract the WSM L1 length from the free length and divide the result by 25.4. This is the compression distance in inches. Next convert the N to lbF by dividing N by 4.45. Divide the lbF by the compression distance and you have the results in lbs/in spring rate.

IcemanG17

This is exactly what I was looking for.....okay for 86+ gas pressure shocks 928's the range of front spring rates is 244 to 266 lbs.....

The rear was harder to figure out...since the free length was not given...estimating a 350mm spring I came up with between 266 to 287 which seems too heavy....so I am guessing the free length of rear springs is longer than the front...does anyone know? The front springs are about 26-27% heavier than the rear....so that would put the rear springs around 178 to 195 lbs....

the flyin' scotsman

Brian...........the rear springs are much longer.

I have the OEM set in the garage.............do you need a free length measurement? Metric ok?

Okv

Spring rates, calculated from workshop manual spring specifications (NOTE: Not necessarily 100% correct, and spring rates may change between models and years):

Front Rear ib/in
PET 1991 GT 257 186

Front Rear N/mm
PET 1991 GT 45.02296549 32.58471433

IcemanG17

Malcolm
A metric measurement is actually better.....but PET does list a few different compressed lengths ranging from 270ish to 250mm?

Okv
Your PET lists the acutal english spring rate...very nice...I wish mine did!

the flyin' scotsman

Brian..............the free length of the rear spring is 410mm.

That's the stock spring off of my '88 sitting on the bench; blue stripes.

IcemanG17

Malcolm
Great just what I needed.....so the rear springs range from 167 to 180lbs..... But how many blue stripes do they have? PET lists three different weights 1-2-3 stripes with 3 being the heaviest...now I need to jack up mine and look!

So its official 244 to 266 for the front and 167 to 180 in the rear.....I wonder what the club sport springs are....since it doesn't list it?

This is all coming together now....when I rode in an S4 with Bilstein-Eibachs it seemed really stiffly sprung to me with 399-550 progessives....which I understand collaspe to the 550 rate right away....

the flyin' scotsman

No worries Brian...........my OEM rear springs have 2 blue stripes.