Ispeed

My motorcycles are soft next to the 928...

ROG100

The Eibach - Boge combination is by far the best way to go unless you want your teeth smashed.
Everything else is by far toooooo harsh for street use.

SeanR

I have to agree with Roger on this (surprised anyone?) I've been in a lot of them with different set ups and it will all depend on what you want, and how you drive it.

My car was used for a lot of commuting so I wanted a good ride w/o loosing fillings in the teeth. I chose the Eibach/Boge set up and am glad I did. It is a bit stiffer than the wifes with stock springs/boges but is not anywhere near as harsh as the Koni set up.

Now that I don't commute as much, I sort of wish I had gone with the GT springs but it really doesn't matter much. The car handles way better than my driving ability.

Hilton

Shoot rennlist user Leonard928 a PM. He's a local GTS owner who runs in classic rallys etc here.

He recently fitted fixed-rate Eibach springs to his '95 GTS - so he should be able to give you either part numbers or spring measurements/rates.

Edit: For those who might ask, I'm not confusing his Eibach's with the 928intl progressive ones - I have the progressive ones on a shelf in the garage, although I have yet to fit them.

linderpat

That's what I put on my prior 86.5. It was a nice combo, but my only complaint was that the car was lowered as a result, by an inch or so, and it bottomed out in the front too much on bumpy roads or in/out of driveways, etc (Carl's skid plates are a must in this configuration). I don't like it when these cars sit too low - takes some of the fun out of the spirited driving imho.

Chuck Schreiber

RKD,
Do you still have the Devek setup on the car?

If you have not changed it, you probably still have the 600/400 Hypercoil-Koni setup that Darrin put on the car many years ago. Those springs are linear.

GlenL

Sounds fun.

The "progressive" springs are actually two rates. I recall (?) that Eibachs are 220 and 350 lbs/in. So when you're turning the body rolls first into 220 and then into 350. The inside springs are extending at a 220 rate. Then when the car turns the other way, the former inside pushes up with 350 and then with 220 while the former outside (now inside) loads up with 220 and then 350. The two rates means the body rolls quickly at first and then more slowly. Easier to control from the driver's seat if it's one rate, and a higher one. And in hard braking the nose pitches down more and the back comes up more with progressive springs.

The purpose of progressive rates is to absorb road irregularities more smoothly while having more firm cornering. Most street driving is long, separate corners compared to most road courses, or autocross courses.

Ya know...

I've got some unidentified single-rate coils in the garage. They're a lot stiffer than stock 928 springs and I suspect they're the old single-rate Eibachs or some sort of aftermarket part. Unmarked from what I can see and not stock. Got them with some other Koni's. I'd be willing to sell them plus some fronts to use on the rear. I could test them for spring rate and dig up perches that work. Some years had different diameters. I can make sure they'd work, or not. PM if interested.

Rick Carter

I have progressive Eibach/Bilsteins and like the set up.

GlenL

Hi Rick.

Lot's of people do. The micro-thread is why racers use single-rate springs.

Lizard928

I have to agree with Glen on this

And the OD of the Koni shocks are a standard size. You can walk into any of the tuner shops and get adjustment sleeves that will work on our shock bodies. You can then get upper perches for the 2.5"id springs to sit on up in the top. The springs are iirc 7" front and 12" rear for 600/400 on the bilstien shocks. The bilstein shocks do not require a threaded collar as the body is threaded.

Stephen Porter

What are the rates of the stock springs?

I have a set of OEM Boge shocks from Roger. Should I be looking at replacing the original springs as well? About 100K miles on stock setup.

Fogey1

I have to ask.

Has anybody here ever gathered data on old springs? Checked their take-offs? Do springs actually "wear out," i.e., change their rate over time/mileage?

What do the engineering texts say? S.A.E. papers?

I don't recall seeing this discussed previously.

Bill Ball

Yes, I did absolutely hate the Eibach springs with Bilsteins (intolerably jiggly, nervous, odd ride behavior with normal everyday driving), had trouble with 2 sets of Konis that were terribly underdamped at any setting, causing the car to wallow uncontrollably when pushed hard (other friends' cars have konis that are perfect) and am now pretty happy with my old stock springs and Bilsteins. I was surprised how much better the car handled when I borrowed some 18" wheels with PS2s for the last race - totally transformed the car into a much more stable ride versus my 17" BFG KDW2s. Hard for me to explain. I need a little more control out of the Bilsteins, so I am going to revalve with more damping and probably up the spring rates (600/400 or a bit less than that) like 928andRC51 did. Konis should be fine despite my incredibly bad experience unless something has gone wrong with their manufacturing. George Suennen has Konis on his car with stock springs and his car is a sled, rock stable in corners and at VERY high speed with beautiful control over bumps.

Lizard928

Bill, fwiw, I have tried the KDWs and dont like them that much.

RKD in OKC

Thanks Chuck, Yes Darin's setup is still on the car. I knew the springs were linear and that they were HyperCoils (they have ProCoil printed on them) but not that they were 600/400. All I've done to date is add some Ott stearoid drop links on the rear. Mechanic is working now to try to get the front Devek bar working without bending tie rods, etc.

The progressive setup I was refering to was on the suspension setups I did on my 944 Turbos compared to other 944 Turbos with non-progressive setups.

Glen, Your description of progressive springs is not quite right. Yes progressive springs have two ratings but do NOT work like two rates. If they were rated 220/350, that means the rate starts at 220 and increases the rate to 350 as they are compressed. Not that they magically switch from one rate to the other. Also having a lower rate might cause the end or side of a care to compress a little more than a fixed rate spring, it does NOT let the unweighted end rise more. In fact the unweighted end rises LESS as there is less spring for lifting that end as the spring decompresses.