Koni vs. Bilstein vs. Boge question
 

Re-using the Stock springs in my 86.0...

I'm quite happy with the stiffness of the stock springs, they maintain
ride height so I'm pretty sure there's some life in them. I'm looking to
replace only shocks because they are stock and I'm at 125K miles.

Does anyone have experience with Koni vs. Bilstein vs. Boge vs. ??? shocks?
When used in conjuction with Stock springs?

I don't know much technically, but I never really considered anything but Bilstein as a replacement.

I put Koni's on my previous '84, and they worked well for me. Good stiff ride that handled well at speed in the turns....

I also am very interested in this thread since the stepson is needing replacements all the way around
I put adjustable Konis on the rear of the black car and was amazed how well it rode after

Rich,

I put new Boges on my ex- early 86 at about the same mileage. I was happy with the performance over the old shocks- strictly spirited street driving.

Brian
90GT

Rich,

Also, if you haven't done this already, now would be the ideal time to replace your motor mounts as you'll be part way there when you do the front shocks.

Brian
90GT

RichS,

I replaced my oem leaking shocks last winter on my 86S with koni adjustable units.
Total job was around $750 including corner balance/ride height adjustment and alignment.
I wished I had swapped out the springs too as it wouldn not have added to the labor.
The stock springs are not a good match for Konis dialed up for stiffness.

Now I will have to fork over another $700 to change out the springs as it is virtually the same job as the shocks.


RDS

I had new Konis dyno'd, and the results indicated that the Konis are not damped enough for stiff springs such as those on my 89 with sport suspension option. They should be fine for standard springs according to the suspension shop where I had them dyno'd. Boge are probably good, as well. I have a set of Bilsteins now and I'm not sure yet, but they may be best suited for sport suspension rather than standard springs, but I haven't run them that way yet.

My car originally had the M474 sport suspension. I removed them some years back to go to a harder adjustable Koni setup. I still have the M474 assemblies if you're interested, PM me.
Thanks, Hammer

Great question but I think you'll find that most of us who have changed/replaced the original shocks did so because they were wore out so there's little comparison from a new set of Konis to a new set of Bilsteins and/or Boges. Money and time being large factors although now I've done it once I'd like to try a set of Konis.

My experience was from the stock springs and Boge shocks to a new set of Eibach and Bilsteins. With the old tierd set the car would 'wallow' if pushed too fast through some bends; the same bends are taken flat with the new set up. The old set up absorbed most small bumps and speed ripples; the new set up rattles your teeth. Super high speed got the car 'nervous' with the old; steady as a rock with the new.

The only other changes made have been an alignment and new PS2 tyres.

Hammer.............dibs on that set up for our good freinf Garth..............he's been looking for an age for a set. Sending PM

On my GTS I am going with stock boges and Eibach springs. Road use only. Chose the springs because of price compared to stock. Work not done yet so cannot tell how it rides. Prefer the stock setup because others I have driven seem harsher.
My springs were sagging at 90k miles and need replacing stock units were expensive.
We will see.

Bilsteins seem more.... Robust then the Konis, quality wise. Because of Bill's findings with the Konis I may have to hold off from installing them and the Hypercoil 600/400 kit from Devek and have Koni possibly revalve them.

OEM manufacturers spend alot of time and money making sure the ride is good but the handling is taught. They don't always get it right.

Thanks for the thought guys! :thumbup: - but I currently have the '85 euro S #204 springs ( M474) installed over Konis .... a pretty nice combo on the 200# lighter 16v car. :cheers:

Unfortunately I haven't driven more than two different 928's and I was being gentle when I drove one so I'm can't say how one differs from another. I currently have Koni's and am very happy with them. They keep the tires stuck to the road very well and the cars handling is very predictable. The ride is also comfortable so long as the bumps aren't too big.

On past cars I've had Koni's and Bilsteins. One of my Koni's did fail shortly after installation, it was warrantied but I still ended up paying to install them and realign the car. Bilstein sports worked great and had no problems.

Where do you live? It might be worth finding a few other guys that already have new shocks installed for comparison purposes.

I have Bilsteins and M474 springs currently and they are really sweet on smooth/whinedy roads. They are donkey on many of the roads in San Jose, where there is rapid and sharp road surface changes. I find the return up from a fast down to soft. It feels like a bottom out. I have a box of eibach's but after Bill B's stories about the mix, it leaves me wondering.

We we're thinking of our snow bound friends :D

Hammer........please still consider my PM for myself; pehaps I'll play a little this winter. :eek:

I also switched to bilstien eibach. The car has a tendancy to follow road undulations, riding the waves like a dolphin. My stock setup would float over that. My feeling is that on many other surfaces the ride is much better, and the bumps are absorbed while retaining contact with the pavement. BTW, the springs can be set to normal ride hight.

Overall this is less of a luxury ride and more sports oriented, but still very nice on the highway. I live in rural upstate NY, so I drive some pretty tough roads. I would do this again, and add sways if I wanted more, and probably will. Before I did this, the car would sometime bottom out during certain combinations of corners and bumps. Now it never does, and I am contemplating lowering a tad, as I now feel it is safe to do so.

The point has already been made, but replacing tired shocks with fresh stockers would also feel pretty good I would guess. I was told by a good suspension man that my original shocks were still good at 60 K, but I can't say for sure that they were like new.

BTW , if you are serious about shocks and can't make up your mind, call Carl Faucett. If you tell him how you like to drive, he will hook you up with a combo that will match your style.

Currently I have stock non-sport suspension on my S4.....I rode in BillB's eibach-Bilstein setup.....I didn't like it.....neither did Bill.....I would describe it as "bouncy".....when I need to replace my shocks....I would do one of two things.....get factory sport springs and the red sport boges....or get konis and keep my stock springs....I think stock springs are 300lb front and 200lb rear vs 450 front and 300 rear for sports? I drove Afshins 928 & it handled very well...with stock springs and Konis

Can you elaborate on bouncy?

Bouncy -- fscking washboard where your arse goes NUMB! Driving down cobble stone streets in Charleston, SC on a racing 10-speed!

Don't forget that ride height can make a big impact as well.

I had the Bilstein/Eibach combination on my former 90GT, along with a Devek HD front swaybar and polyurethane swaybar bushings. If set near the factory ride height to as much as 10MM below, the ride and handling was great. Firm ride, flat cornering.

If lowered beyond that, as many owners do, the front end would porpoise. By this I mean any bump would set off a short cycle of very noticable up and down oscillations.

My installer assumed I wanted it set to race car specs. I don't recall the exact height, but I'm guessing it was 140-150MM. It definitely looked lowered. I was NOT pleased with the initial results. It may have been fine on a track, but for street use the front end porpoising was very annoying. A quick adjustment with the Motion Pro shock spanner height adjustment tool, bringing it up to within 10MM of spec, and all was good again.

Just my experience, YMMV.

Hmmm. Its all so subjective. How was the actual handling?

THAT is interesting. My car is lowered to about 150/150 and the Bilstein/Eibachs are not happy. To look at my car you wouldn't call it lowered. There is a 2-finger gap between the front tires and the fender lip. But it measures 150 at the correct points. I've ridden in cars at 120/120 that handled better... but they may have had spacers, for all I know, to raise the spring back into its usual preload. In open road racing we set the cars low, but the issue you raise may explain my awful handling and day-to-day road manners. This had not occured to me in my struggles to regain the handling I had once a long time ago. Thanks for bringing this up.

Don't forget that early cars at least came with tires that had some sidewall to absorb some of the bumps. Two inch sidewalls and "sport" shocks may be only practical on the track.

Sounds like a neat suspension shop if they can actually test the shocks.

It seemed too stiff......like the bilsteins were valved to harsh on intial movement....then once moving didn't have enough rebound damping.....however I've only experienced one 928 like this...others really like the setup?

I like my Ledas with Hypercoils. Adjustable from "the track" to the railroad tracks!!. Whatever you select, make sure that the shock is matched to the spring.

My ride height is set aound 145-150mm. I never experienced a "porpoising" problem or ever felt my car would bottom out with my Konis.

I can't see how anyone can subjectively define what is "better", especially for street use, when there are so many combinations of tires, springs, shocks, sway bars and links, bushings, ride height, alignment, etc. Just changing the caster angle will change the effort it takes to turn the wheel (at least what I heard).

Some one please define the points on the care where ride height is defined.

It's in the WSM. Photos there worth a million words.

By the way, lowering the car should not affect ride as long as shocks are ok. It may affect cornering, as the roll center changes, but not ride; as long as you don't hit bump rubber or bottom the pan.

Sharkskin posted it a while back:

https://rennlist.com/forums/showpost...4&postcount=11

edit:
This seems to get asked a lot:

http://members.rennlist.com/fabric/ride-height.html

Wow, 30 replies in one night, Thanks guys!
I tried to keep the subject concise but there's just obviously a lot of
non-definite opinions out there on this subject.

My biggest problem is what I have to compare to. The most spirited driving I've ever
done was in a Chevy S-10 that didn't even have a sway bar. So as you can imagine
the 928 is already night and day. Yes, I waited and saved and actually made the jump
from the pickup to porsche... With this in mind you should know that even the softest
928 would seem like it's on rails to me.

I did get a chance to drive an 85 with Stock springs and Bilsteins.. however I couldn't
really push it, but it did seem a bit harsh for my liking and the shocks were old.

So I'm trying to accomplish two things here. #1 stop the really rough ride, #2 possibly upgrade
and consider a future spring upgrade.

I live in Seekonk MA now but I'll be moving to Colorado soon and the roads are much smoother there, less huge potholes and no frost heaves. I'm running CUP IIs with Kumo 712 tires, 225/45-17 & 255/40-17.

I'm going to be doing the work myself. I'm leaning towards just replacing the stock Boges right now
but for $200 more it's very tempting to have the flexibility of an adjustable Koni.

So to narrow this down: Thoughts on Boge vs. Koni with non-sport stock springs?

Bear in mind folks, the OEM Bilstiens can be rebuilt at Bilstien, last I checked for $65 per. And can be custom valved at that time too....

Perhaps worth noting...."it's very tempting to have the flexibility of an adjustable Koni." that the standard Koni is ONLY half adjustable. The compression valving is fixed and all you play with is rebound rate.

The WSM pages 44-2b and 44-3 gives the ride heights and pictures of where to measure.

I have the Bilstein/Eibach combo on my car, and live on some of the world's crappiest roads. I think the Bilsteins could stand a little more rebound damping, but generally soak up the small to medium bumps pretty well. My car is lowered quite a bit, and on really big bumps will contact the 'skid plates' on the pavement. Also need to remember if lowering the car, to cut down the bump-stops on the shock. Bouncing off the bump stop will produce the 'bouncy' ride and porpoising. On the track, the combo works fairly well for the occasional weekend. I think they are a good compromise for street/track, but definitely too stiff for a 'luxury' ride. For comparison, when stock, I was able to get the car to move up and down 1-2" on the suspension by pressing and releasing the front bumper, and the rear above the bumper w/ hatch open. With the new stuff, I can JUMP on it and get nearly zero movement. No bounce at all.
I think my car is set too low for for comfortable street driving, I always worry about breaking the A/C bracket or something against the ground on a hard hit, but, it handles very predictably on the track, and I'm too lazy to change it every time I go.
Just my .02....

Steve

Steve

RichS,
I have been very satisfied with the combo described in post #15 - ie linear springs over Konis .... set at 165mm heights: this setup is unperturbed by nasty pavement, very stable, etc. You can sense every pebble without feeling in in your butt - and equally as Steve has noted, I cannot 'bounce' the suspension.
Having stated a preference, many are justifiably very pleased with Bilsteins, generally with progressive springs: I have Bilsteins with progressive MO30s on a 993 ... at a mere 128mm - absolutely great, but perhaps as pointless to mention other than to illustrate that what is correct for a 928 depends largely on your driving style and preferences - and available roads.

The front ride height measuring point is very hard to get to if you are on the ground. I measured the difference between the point and the lowest point of the surrounding walls of the A-arm bracket as 10mm. It's much easier to put a ruler against the outside of the bracket and add 10mm to get the correct number.

I must have gotten bad shocks from Koni both times. It was easy to bounce my sport spring suspension up and down quite a ways, although less so with the second set.

That is true, good tip Bill! I"ve added that info to the page.

Taking a mental straw poll from this and other threads discussing "odd" or "unsatisfactory" handling with new shocks, it seems that the common factor is ride height less than factory settings.

Spring "preload" is not affected by ride height, ,the only thing that affects that is the static weight on the spring. So spring behaviour is unaffected.

Got me to thinking that shocks could have different damping rates depending upon whereabouts the "piston" is in the overall stroke of the shock. ie bump damping increases as shock is compressed, rebound damping reduces as shock is compressed and vice versa.

Assuming the shock is designed with the normal ride height "at rest" position in the centre of the stroke, by lowering the ride height so the shock sits at say 4/10ths extended that would change the damping behaviour from as designed, to being more bump and less rebound on initial displacement.

Any merits in this theory?

Dunno, Jon. All I know is George Sunnen has Konis on his 90 S4 sitting at 120mm with standard springs and the road handling is superb except for those pesky speedbumps.

Borg to Bilstein Conversion is it worth it, adaptation required ?
 

Ready to replace my shocks have Borg factory now; will this require changes to the struts to add add Bilsteins? All the menbers have an idear on the B and K but not much on the Borgs. I'm not going to race this car; will I be happy with the Borgs or go do a change if required, :banghead: for another type. How about ride hight with the large tires in the rear any problems with this set-up?
Tires
Rear P-255-50zr 16
Front P-225-50zr 16

What are Borgs? :confused: Eh, I know what you meant, but what year is your 928?

Borg orginal replacment for an 85
 

Borg is the factory replacment for my 85 S

Most people stick with Boge so they don't have to worry about being assimilated... http://members.rennlist.com/sharkski...Assimilate.gif
:icon107:

The original shocks are 'Boge'.

I don't know if there's anything wrong with them other than by now they'll be well wore out and the technology is perhaps a little old.

Two options
 

Gas and old oil style are avaliable, I would go for the gas type. As you may know the B ans K's come highly recommended so is the price :nono:
do you know if any mods are needed for the other brands, seems like there of as different length.

Don't know of any other brands other than Boge, Bilstein and Koni that fit the 928. I went with Bilsteins as I'm a fairly aggressive driver and we have wide open empty highways to explore the high cruising speeds of the car.

My car was originally fitted with Boges that were well worn so I can't give a comparo to the new Bils.

LOL. Nice smiley! :D

M 474 suspension ?
 

Did this suspension come with Borg or Bilstiens and if so is it a direct replacment for the borgs if all the set-up is included?

Tampa...........the shock are 'BOGEs'.

The M474 suspension is BOGE red shocks and stiffer springs...............not sure if red BOGEs are available..........if they are it may be through your local Porsche dealer $$$$$$$$$

ps...........Borg was a Swedish tennis player no?

maybe he was thing borg-warner

but i think they make transmissions or friction parts or something

Yes the original equiptment was Boge, but you can alternately buy koni or bilstien.

The M474 sports suspension consists of red sport boge dampers and different springs, supposedly only the fronts are different but who knows for sure.

I credit my friend Dave Benson with coming up with the easiest way to measure ride height.

Take one of those pocket sized collapsible pointers (the ones that extend like a radio antenna), sit the base on the ground and extend until it touches the datum point - pull it out and plop it against a ruler. Season to taste and yer done.

James

He is Tampa 928s of Borg. Resistance is futile. You will be assimilated.

Yes, Björn Borg. :rockon:
Fantastic player from the same time as John Macenroe.

/Peter

How the hell did you fine that borg icon? Now that I am copying your post I see its on your page. Interesting. Do you have a "I'm watching you"

I've had that for a while... At one time I spent a couple hours rooting around through various smiley archives, collecting the ones I liked. Also, when I see one I like I generally save it and upload it with my next site update. I don't think I have an "I'm watching you" but one of these might serve the purpose...

http://members.rennlist.com/sharkski...Eek-WeirdR.gif
http://members.rennlist.com/sharkski...c-OhReally.gif

Cool. I was just thinking of the Two fingers, pointing at your eyes, then pointing out.

ANother somewhat relevant one from my site: http://members.rennlist.com/sharkski..._Cool-Eyes.gif And the one attached I found with a bit of help from http://members.rennlist.com/sharkski...Google-It2.gif

/hijack (sorry)

Coming back to drop in a couple of pics of how I check ride height. I'm lucky enough to have a 180mm/7 inch ruler - just the right length. A longer ruler gets in the way, at least upfront. Just cut to fit.

The rear is easy. This is 163mm.
http://billsworkshop.com/P928S4/xpics/ridehtrear.jpg

The front checkpoint is in the middle of the lower A-arms rear bracket, very inaccessible unless the car is on a lift, as shown here.
http://billsworkshop.com/P928S4/xpic...htfrtcheck.jpg

As I mentioned before, this checkpoint is about 10mm above the bracket's outer lip low point. You can get to the outer lip of the rear bracket from behind the front tire. It's a bit awkward but even my short arms can rearch it. Here it is, reading 139 (there is a little paralax error from the camera angle). Add 10mm to get 149.
http://billsworkshop.com/P928S4/xpics/ridehtfrt.jpg

Yes, I'm probably going to raise the front 10mm.

Awesome. Thats exactly what I was looking for.