Shock and spring refresh, Which to get? Options

[StarBear]

Thinking of doing a refresh of my front shocks and rear shocks/springs. All are very old though function fine. Sure I’ll see improvements in corners and ride.
Thinking of Bilsteins.
Any suggested best choices? (IMG:style_emoticons/default/confused24.gif)
74 1.8L Very stock. (IMG:style_emoticons/default/biggrin.gif)
Just local drives and some hill curves; no track or auto cross.

[L-Jet914]

Thinking of doing a refresh of my front shocks and rear shocks/springs. All are very old though function fine. Sure I’ll see improvements in corners and ride.
Thinking of Bilsteins.
Any suggested best choices? (IMG:style_emoticons/default/confused24.gif)
74 1.8L Very stock. (IMG:style_emoticons/default/biggrin.gif)
Just local drives and some hill curves; no track or auto cross.

I replaced what was in my 914 with Bilsteins front strut inserts and rear shocks. Or you could go with the AA route where they had shock absorbers made close to the factory spec Boge shock. I decided to go with the 914Rubber rear springs.

[wonkipop]

Thinking of doing a refresh of my front shocks and rear shocks/springs. All are very old though function fine. Sure I’ll see improvements in corners and ride.
Thinking of Bilsteins.
Any suggested best choices? (IMG:style_emoticons/default/confused24.gif)
74 1.8L Very stock. (IMG:style_emoticons/default/biggrin.gif)
Just local drives and some hill curves; no track or auto cross.

i did the softest spec bilsteins front and rear. they are noticeably firmer.
but i have tall boy XAS reissue tyres to take some of the sting out of them.
not complaining.

inserts at front. full units at rear. what i found was the step rings in the rear shocks do not exactly co-incide with the single spring perch in the original boges. you have to go slightly higher or slightly lower at rear as a result. then level the car out with front adjustment.
i know some folks go lower at front. but i set mine up level.

[sixaddict]

On rear springs…..stock is 90lb which makes car sit a little high. 100lb drops it a little and gives a little better handling without sacrificing ride quality. Several sources but make sure they have inventory. BTW…….Havent installed yet so this is result of extensive search/opinions.
Caveat: this is opinion of poster and does not reflect that of staff or management (IMG:style_emoticons/default/dry.gif)

[JamesM]

On rear springs…..stock is 90lb which makes car sit a little high. 100lb drops it a little and gives a little better handling without sacrificing ride quality. Several sources but make sure they have inventory. BTW…….Havent installed yet so this is result of extensive search/opinions.
Caveat: this is opinion of poster and does not reflect that of staff or management (IMG:style_emoticons/default/dry.gif)

Stock is a lot less than 90lbs/in for all the road cars.

According to documentation I have

-4s were 52-55lbs/in depending on part number
-6s were 58-62

6 GTs were 70, 80, or 90 at the stiffest.

So 100s are 10% stiffer than the stiffest spring Porsche ran on GTs.



But for some reason people still throw 225lb springs in the back cuz they are smarter than the Porsche engineers who won LeMans.

[StarBear]

Thinking of doing a refresh of my front shocks and rear shocks/springs. All are very old though function fine. Sure I’ll see improvements in corners and ride.
Thinking of Bilsteins.
Any suggested best choices? (IMG:style_emoticons/default/confused24.gif)
74 1.8L Very stock. (IMG:style_emoticons/default/biggrin.gif)
Just local drives and some hill curves; no track or auto cross.

I replaced what was in my 914 with Bilsteins front strut inserts and rear shocks. Or you could go with the AA route where they had shock absorbers made close to the factory spec Boge shock. I decided to go with the 914Rubber rear springs.

@L-Jet914 What spec/model Bilsteins would that be?

[bdstone914]

@sixaddict

' date='Feb 20 2026, 07:21 AM' post='3245994']
On rear springs…..stock is 90lb which makes car sit a little high. 100lb drops it a little and gives a little better handling without sacrificing ride quality. Several sources but make sure they have inventory. BTW…….Havent installed yet so this is result of extensive search/opinions.
Caveat: this is opinion of poster and does not reflect that of staff or management (IMG:style_emoticons/default/dry.gif)
[/quote]

Actually stock rear springs were 55lbs. We tested ten pairs at Eibach and that was the average.

Lowest aftermarket are 100 which are an improvement.
Even GT cars had 85-95 springs.

[StarBear]

[quote name='bdstone914' date='Feb 20 2026, 11:26 AM' post='3246024']
@sixaddict

' date='Feb 20 2026, 07:21 AM' post='3245994']
On rear springs…..stock is 90lb which makes car sit a little high. 100lb drops it a little and gives a little better handling without sacrificing ride quality. Several sources but make sure they have inventory. BTW…….Havent installed yet so this is result of extensive search/opinions.
Caveat: this is opinion of poster and does not reflect that of staff or management (IMG:style_emoticons/default/dry.gif)
[/quote]

Actually stock rear springs were 55lbs. We tested ten pairs at Eibach and that was the average.

Lowest aftermarket are 100 which are an improvement.
Even GT cars had 85-95 springs.
[/quote]
Thanks, Bruce! Mine are all very old (40+ years?); the front shocks may be original. So, virtually anything would be an improvement! (IMG:style_emoticons/default/piratenanner.gif)

[sixaddict]

My information came from AA……..how could it be wrong (IMG:style_emoticons/default/dry.gif)

[Superhawk996]

.

But for some reason people still throw 225lb springs in the back cuz they are smarter than the Porsche engineers who won LeMans.

(IMG:style_emoticons/default/agree.gif) X10

(IMG:style_emoticons/default/laugh.gif)

Just to be clear there are situations on race tires, with tube chassis, etc that tuning might make sense. But it certainly isn’t on a stock body road car.

[Superhawk996]

On rear springs…..stock is 90lb which makes car sit a little high. 100lb drops it a little and gives a little better handling without sacrificing ride quality. Several sources but make sure they have inventory. BTW…….Havent installed yet so this is result of extensive search/opinions.
Caveat: this is opinion of poster and does not reflect that of staff or management (IMG:style_emoticons/default/dry.gif)

Though I know this is claimed as coming from AA but let’s at least clarify what is really wrong here.

Spring rate does not determine ride height.

If all other variables are kept constant in a spring design (they aren’t) a higher spring rate would result in a higher ride height . . . Not lower as that comment implies.

This is why you don’t blindly follow tuning advice found on the internet.

(IMG:style_emoticons/default/beerchug.gif)

If you want a good book on suspension tuning written for the layman
Author: Fred Puhn

[sixaddict]

So based on last two posts……I have a question regarding track cars.
Does current tire technology have any bearing on what was done back in the day vs what people are doing today?
TIA

[sixaddict]

Hawk..
I was told 100 lb spring was shorter than 90 ( stock in their words).
Wouldn’t that change ride height??
BTW ….it was stated not “claimed”
Thx

PS ….i have Fred’s book….guess I better read it

[Superhawk996]

So based on last two posts……I have a question regarding track cars.
Does current tire technology have any bearing on what was done back in the day vs what people are doing today?
TIA

Simple answer:
Yes but not to the degree people think.

The correct, nuanced answer is complicated and can’t be addressed effectively in a forum format like this.

[Superhawk996]

Hawk..
I was told 100 lb spring was shorter than 90 ( stock in their words).
Wouldn’t that change ride height??
BTW ….it was stated not “claimed”
Thx

PS ….i have Fred’s book….guess I better read it

Yes . . . Read the book. It is time well spent if you want to modify your suspension for what ever reason.


Yes, if you were going to keep ride height constant you would have to shorten the higher rate spring which is really just changing pre-load assuming that we are using fixed spring perch OEM rear shocks. Similarly, they can also choose to alter the spring to reduce the ride height below stock ride height ie lowering.

If we use rear Bilsteins with adjustable spring seats we can control preload and ride height independent of spring rate unlike the OEM fixed dampers. The fully adjustable threaded sleeve & spring seat offered by others like Rebel just take that adjustability to the next level.

See . . . Getting more complicated already.

[Superhawk996]

BTW ….it was stated not “claimed”

Sorry - no ill intent directed at you. Poor choice of words on my part. (IMG:style_emoticons/default/grouphug.gif)

[Superhawk996]

“Lowest aftermarket are 100 which are an improvement.”

“Thanks, Bruce! Mine are all very old (40+ years?); the front shocks may be original. So, virtually anything would be an improvement! “

Chassis Engineer anal retentive issues:

What is all this talk about “improvement”. Improvement to what? Ride quality? Handling? Steering? Transient or steady state?

I know not everyone is interested in the details of chassis engineering and setup but you really have to take things with a grain of salt or be prepared to accept some built in compromises if you blindly follow the mythology.

Edit: again . . . Not trying to offend anyone nor are the comments aimed at anyone personally. You guys are the bestest.

Just cautioning that the word “improvement” which we get constantly in marketing hype need to be put into some sort of context.

[sixaddict]

(IMG:style_emoticons/default/beerchug.gif)
Good information!

[rjames]

I went from KYBs all around with stock springs to adjustable (rebound) Konis all around and 100lb springs. The ride is not too firm. The struts/shocks are all adjusted to their middle setting. A big improvement over the old kit.

[wonkipop]

@StarBear

i read your comment that basically it seems all your suspension components are original and stock and presumably 50+ years old (as were mine in 2019).

i would suggest that not only is it shocks you look at replacing but also all suspension bushings etc. have it gone right through. including sway bar bushings. given your car is an appearance group 1.8 i believe you have factory sway bars too. and don't get hard bushings. buy the soft ones. (IMG:style_emoticons/default/biggrin.gif)

its worth doing the lot. you won't believe the difference. driving around for 50+ years will have been like the proverbial boiling the frog in water slowly. the frog never notices the temp increasing from cold to hot to boiling and stays in the water. you will forgotten what it was like when it was all new. (IMG:style_emoticons/default/biggrin.gif)

i kept my original springs. my car has not been heavily used. they seem fine.
i think the spring sagging had been sorted by 74 models. you will probably find your original springs are fine. easy way to tell can be if car is sagging at rear one side or the other. though sometimes it can also be caused by a torsion bar at the front which has "softened" too.

i believe the bilsteins i got were B6. basically next peg up the ladder from original boges which were quite soft. though in my view the original soft boges combined with sway bars front and rear were an extremely well speced and practical package from the factory originally. good compromise between comfort on every day roads and road holding - ie cornering.

i agree with @Superhawk996 - unless you know what you are really doing and need to go super high performance for track or autocross work - its very hard to improve what the factory got pretty damn right from the get go. as an old porsche mechanic once said to me = "these 914s were the best porsches chassis wise straight out of the box - don't take sh$t from the 911 guys". (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/beerchug.gif)