Garth S

Prompted by responses to Chuck's poll (https://rennlist.com/forums/928-forum/181580-if-you-had-a-choice-between-sport-suspension-or-not.html) and an ulterior motive to learn more about oem springs, I searched all suspension options listed in PET5 for US/Can models and ROW 'euros' from the beginning of the S4 production in '87 to the end of GTS in '95.
While PET5 is not the most definitive source, it would appear that code M474 is a shock only option, and is the replacement of standard Boge gas shocks with Boge Sport shocks (928 343 055 07 std. with version 09 in front, and 928 333 051 16 std. with version 17 rear). This option code is consistent as are the part numbers from '87 - '95 inclusive. [ i've not included the Bilstein option noted available to '91].
Regarding springs, the standard front is code 404 'brown 928 343 511 09 inclusive for '87 to '95. There is a (sport?) spring option M637 listed as available from '87 through '91: This front option M637 spring set is 504 'orange' 928 343 511 12. This sole spring option is not available on any 928 model in any market from '92 to the end - for these years only the standard spring set 404 'brown' front is available.
For the front, this would imply that sport springs and sport shocks were two separate options: to get both, the purchaser had to tick two option boxes - up to the end of '91: From '92 on, there was no sport spring option ????
The rear springs '87 - '95 all fall under one part # 928 333 531 14, with three groups designated by 1,2 or 3 coloured bands (301,302, and 303): these may represent spring rate changes for sport option, rear air, ... ??
So, what is a "SPORT SUSPENSION" - shocks only as M474, shocks combined with stiffer springs M637 - at least until end '91 ???? - and what of '92 on, where it appears to be shocks only.

My ulterior motive in looking at this is that I have a fresh set of Konis for my S4. I wanted to evaluate any linear spring options available as a potential upgrade from my standard spring set ( strangely enough, these same std springs appear to be good enough for all the GTS cars, even with sport shocks).
To further confuse the issue, it has been frequently stated that in addition to the standard S4 springs ( 404 'brown' stripe) there are both GT and CS versions available: as a matter of fact, CS springs are advertised for sale as the '504' group by 928 Specialists. Does this mean that the 'garden variety' GT has the std '404' spring set?
Is there a simple answer - like PET5 is incorrect? or ....... Can you spring experts set me straight? - at least enough to allow me to correctly respond to Chuck's poll

Thom

I am no 928 suspension expert but for having looked at all 944/968 suspension variants both through PET5 and the WM I'm willing to give it a try (FYI there are no less than FIVE suspension-related equipment codes on 944s).

It is in my undestanding that no other 928 than the CS can feature the 637 equipment code. Actually, if a 928 features the 637 equipment code it means it is a CS. To me that means that the 474 equipment code on 928s refers to shock absorbers only and that CS only had specific springs.
Besides, looking at the 944 section of PET5 reveals that M474 consisted both in specific shocks and specific springs. If the 928 474 equipment also consisted of specific springs as a complement to specific shocks those springs would necessarily be related to as 474 equipment, which is not the case.
Now if we consider the fact that a 928 CS comes both with the 637 and the 474 equipment codes, and if PET5 refers to the 637 equipment codes as specific springs, that means that any non-CS 928 featuring the 474 equipment code only has sports shock absorbers and the usual "brown" springs.

Just my €0.02

FlyingDog

WSM has some more description of the options. If I can find my CD, I'll look for the S4+ options. I've only looked at the S options before.

FlyingDog

Volume 4 Page 40-46
"Coil Spring Part No. 928 343 511 09 (brown)
Used in: 928 S with Boge gas-pressure dampers as standard and optional
extra (sport)
- 86 models onward

Group / Color code / Spring force F& / Ordering Index / Free length (new springs)
1* / 1 x brown* / 6375 - 6570 N / 401 / approx. 340 mm
2 / 2 x brown / 6571 - 6766 N / 402 / approx. 340 mm
3 / 3 x brown / 6767 - 6963 N / 403 / approx. 340 mm

& Spring force F where length LI = 191 mm"

Greens are for Sept 83 to end of Model year 85 Boges, and for Bilsteins from 84 on.

(various printing dates of 1986-1988, so this may be out of date for your question)

drnick

garth, are your konis externaly ajustable? if not then you would do well to find some knowlegable advice on setting them before install, with whichever spring set you choose. eibachs are definitely a performance option while IMO the factory 'sport' spring is really only how a standard car should have been optioned, originaly - i have these in my SE. the standard springs are tooo soft IMO.

Vilhuer

'87-'91 years in PET might come from how data is grouped in it. Factory seem to treat 928's in four different groups, '78-82, '83-86, '87-91 and '92-95. New PDF format PET uses this grouping also. So part wasn't necessarily used in all years within group even though it is listed there.

AFAIK CS/SE had different front springs but same rears as all other period 928's. Not sure if '89 GT has these also. '90-91 GT should not have them. Reason why I asked spring data few days ago was that I was looking it for comparison purposes.

https://rennlist.com/forums/928-forum/180982-s4-and-later-spring-forces.html

It seems only spring force number missing in WSM is CS/SE. Little surprising GTS is using same springs as '86 S. Would have thought different ones would be needed to compensate additional weight.

jpitman2

FWIW, my 83 Euro has M474 listed on owners manual and factory invoice, and it has Bilsteins. Didnt notice a spring colour when I replaced fronts though.
jp 83 Euro S AT 48k

Garth S

Thom,
Vous avez raison, et puis, nous sommes bien d'accord! Yes, I also believe that to be the case, at least since the beginning of the S4 series.
I have often read of the 'sport suspension', but also believe that in 95% (or more) of the cars, that is more correctly stated as 'sport shocks' mated with standard 404 'brown' front springs: this includes the GT and GTS models. I became curious when almost bidding of an advertised set of "GT" springs on ebay - when questioning the seller, they started to sound like the set already in my S4 - no upgrade there! A true upgrade in spring rate then would be the M637 - the CS type you have indicated.
There are always exceptions - and the terminology used for the '83 - '85 cars as noted by Matt and JP is one: M474 appears to include Bilsteins with optional springs as a complete package. JP - thanks for pointing that out - I just checked over my spares: I have a spring set from a '85 euro w. Bilsteins, marked 928.406 with two green stripes. They are 340mm free height, 14.5mm diameter wire, and 7.5 coils. That will be compared to the 404 browns of the S4 as they are removed ( maybe I already have a stiffer set of springs ).
Nick,
The Konis are the internally adjustable ones ( for rebound): I have had an identical set of these in service for 12 years on the '80, paired with '85S springs. You are correct in noting that setting rebound is perhaps an art - I had them out twice before it seemed correct at +5/8 turn: now, with the latest version Konis, one can jam a long allen key down the top to compress the piston rod into the foot valve - and adjust as installed. I will likely do an initial set up near +5/8, depending where the spring hunt goes ....
Now, I'll go back to Chuck's poll - and look for a box titled "sport shocks"

Erkka, in your search for spring rate data , if one assumes that the same grade of steel is used (?), the control variables are wire diameter , coil diameter, and number of coils: free height should not be an issue - the limiting issue would be coil contact (bind) under compression, as these are all linear rate springs. Does the '85 euro data mentioned above compare favourably with any of your springs?
Thanks for the information guys

ROG100

Garth,
On my 89 S4 I have orange/red colored shocks both front and rear.
I do not have any record of the option codes applicable to the car.
However I do have extensive service records and nowhere does it show replaced shocks.
I thought they were just aftermarket shocks.

When you talk about colored shocks is this a colored ring on the schock or is it an overall color?

Where do I find the part number on the shock?
Thanks,
Roger

Garth S

Roger,
The coloured bars referred to are code markings on the springs only - not on the shocks. ie., one brown 1/2" wide splash, two greens, etc.
The red/orange shocks could be either the optional Boge sport shocks (m474) or aftermarket Konis. They are quite easy to identify: Start with the rear suspension. Just under the adjuster, Boge normally stamp their nameplate - on the std. S4 blue/grey shocks, it reads 'Boge Gas' etc. It may take some neck twisting and a rag to clean the area to easily see the stamping. Konis are more likely to be stamped as such halfway up on the body.
If your shocks are oem factory, 99% certain they are the Boge Sport.

ROG100

Garth,
Thanks - I will get down under later this afternoon.
Fingers crossed they are Boge Sports as they seem to be favorite with everyone - all the better when I sell this beauty.

What a fabulous forum and great people.
I learn something new everyday.
Thanks,
Roger

FlyingDog

Garth, if you look at the M-code list in PET5, it says M474 is "shock absorber (sporting) front and rear". If you look at the data on page MG-4 SG-02 for different years, M474 seems to have changed from Bilstein to nothing to Boge.

UDPride

Hate to bring up an old thread, but no sense in starting a new one. Were 474 Sport Shock Absorbers standard on the 1989 GT, or optional equipment? I know they were optional on the S4, but not sure about the GT. Im looking at an 1989 GT that has 474 -- just trying to figure out if its part of the GT package or an add-on. I know 220 Limited Slip was standard on the '89 GT.

Rob Edwards

The option codes on U.S. GTs are weird- All but one '89 has the M639 and the M474 code, denoting '89 GT. There is one Canadian '89 GT that lists neither M639 or M474.

For '90, no '90 GT lists M639, and 44 of 144 list M474, For '91, only 6 of 145 '91 GTs list M474.

All U.S./Canadian '89 GTs list M220. None of the '90s or '91s list either M220 or M221.

For whatever all that trivia is worth.

UDPride

That is weird. Like one guy ordered a 928 GT with a makeshift GT Delete Package. Okay he did get a few more horses.