Alan

I need to replace my shocks and am considering Bilsteins rather than replace the Boges. I could keep the stock springs - although I feel they are a little soft - but the state of my shock makes it hard to tell how much crisper just new shocks would make everything...

I don't even know if there are fitment problems with Hypercoils over the Bilsteins (perches?) - but like to know? I would also like to know if this provides additional clearance for very wide tires (say over 305mm).

Seems the spring diameter is reduced quite a bit but are there other limiters in the rear suspension geometry that make this a moot point...?

Any data based on experience anyone ("should fit" doesn't count.. have you/someone you know actually done it...?)

Hopefully Carl at Motorsports may chime in as a retailer of both products...

Alan

Ispeed

I did the 600/400 hypercoils and all works out well with the Bilsteins. There is more room for a tire front and back, and I have 9.5 et68 front wheels with 265s. They didn't rub with the eibach springs either. However, you have to get some jb weld in between the shock body and the spring spacer that keeps the spring away from the shock. It will rattle over bumps and sound like a looose centercap.
I just posted a thread about revalving the Bilsteins as I found the dampening too light for the 600/400s. I am happy with the result, and was $65 a corner.

Alan

So the JB weld is to stop lateral movement...? is this the spring perches or a top spacer/locator cup that is too loose...? or is this some other looseness...

Alan

Ispeed

The "spacers" are collars that space the spring away from the shock body. They sit on the threaded adjuster as the spring does, there's just a loose fit that lets them rattle on bumps. You will see when you put it all together.

Bill Ball

Tim Dey has Hypercoil main and tender spring setup on his 200+MPH Beast. I think the front is a 300/600 combination (sounds low, but I believe it is what he said). Of course, he has Penske shocks, but with that spring combo I found this to be the most comfortable yet controlled 928 I had ever been in. I mean, cruising around, it just utterly soaked up the bumps and cracks as if they weren't there. When he put the 575HP hammer down and we entered some high speed turns, the car just handled like a dream. So, this is like a progressive spring, but I never felt the downside that progressives can have.

Okv

Interesting - I had to look up what tender spring means, as I thought may be it is like a helper spring, which it is not.

Judging by the comments from many, it seems like the Hypercoil - Koni combination is a good vaule-for-money set-up.

I have now completed the install of new Bilstein coilovers on my shark, it is Bilstein BM5 (9 click adjustable, both directions simultaneous, sort of a motorsport version of PSS9 i assume), linear springs 500 and 350.
I am not completely finished yet, some issues remain to be sorted.
It is aligned, and I have driven the car some.
First impression is that it is a comfortable ride with no excessive body roll or motion, grip has probably improved significantly.
Still, I would like to have more precise steering feel, and better transient response and transient stability.

The problem is, that my DD now is a Cayman S, a car that corners at around 1 g stock, mid engine, more than 200 kg less weight.
The 928 has other qualities, it is a totally different car, but still, I kind of expect the 928 to behave more like the Cayman, which, of course, is physically not possible.
But, the stability issues and mushy feeling must be fixed.
After all, what the 928 should have, if anything, is stability.

This set-up has two major faults; it is pricey and it needed a lot of work and thinking because the coilovers are custom made for the 928.

Now am waiting for some alu parts for the steering rack, found out the rack is moving in the alu bushings, this has to be fixed.

andy-gts

My car was wallowing at high speed curves and I replaced the red boges with 93k on the clock with bilsteins and the ride is firm but very planted and do not think replacing the spring s would have added anything....but I don't do autocross either.( the car is very firm in the high speed curves ie 110 to 120mph ORR)

Tom. M

Hey Alan,
John D and I just did this on our track cars...he found a spring and hat supplier and we re-used our existing bilstein shocks...We are running 750 front and 500 rear ...John was able to put the package together for a measly $200. That and some labor..and we're good to go..will let you know how they are on the street....

Ispeed

Okv: you probably have other issues that are not the fault of your suspension. You already mention the rack is moving. Tell us what wheels you are running and your ride height. Some rebuilt racks are crap too because the bushings don't get replaced.

Tom: I don't think normal Bilsteins would have enough dampening for super stiff springs. I think the valving was only geared for stock 300lb front and 200lb rear oem springs.

I will be able to give a lot more feedback on my set up after SITM. 2000 miles round trip with as much as 500 miles of twisties as well. Looking forward to it!

Alan

Tom - I see you have a zip tie around top of the spring/hat - is that for rattle reduction too...?

hacker-pschorr

What The Hell....is that Donald Sutherland???

Okv

Yes, that is why I now have some alu parts on order from a local mechanical yard, to make the rack mounting completely rigid.
The problem is that the alu bushings from Carl is not tight enough around the rack mounts, and it is not fixed at all in the vertical direction.
This may be due to different dimensions on different rack versions.
I have a late type rack, it has been replaced once.

Ride height is now 155 mm front and 170 mm rear.

Alignment data:

Date 08052008.
Front
min degr
Camber -54 -0.9
Toe 9 0.15
Caster 5.2
H 155 mm

Rear
min grader
Camber -54 -0.9
Toe 10 0.166666667
H 170 mm


Wheels are RH 2 or 3 piece, with Dunlop Sport something on them (I have to look on papers or on the car to find out exactly).
Front ET is marginal, but should be ok.

F: 18" x 8.5", ET 59, 235/40-18.
R: 18" x 10", ET 54, 275/35-18, now with 5 mm spacers.

When I get the parts for the rack, I will first try to adjust the tire pressures.
Will now try 2.5 bar F and 2.6 bar R.
Then I can play with the damper settings.

Tom. M

Well, that plus it holds the hat in there nice and snug. I was able to grind the outer edge of the stock adjuster (just a little bit..not enough to affect the integrity of the adjuster) so it fit right inside the spring so it now doesn't even move around...

and Hacker..nope..that's the infamous John Davis...

BC

A couple things:

Rack bushings make a bigger deal that many would think. You are on the right track for that. I think some other changes that you could look to are upper a-arm bushings - urethane bushings do seem to make a difference. New Tie Rod inner ends as well.

I think alot of 928s seem to have that listless feeling at turn in. It gives them a bad rep. Taking the rubber out of these places helps as well. The front and rear sway bar links - these should be heim joints in my opinion.

In all the years of reading these threads and email lists - it seems that these cars are EXTREMELY sensitive to alignment. Night and Day.

BC

Another thing - its clear now that the racks in these cars are a bit loosy goosey, even rebuilt stock. Bushings in the end of the rack - that hold the rack rod much stiffer in the rack body. This was not my idea - search for it on here and you will find it.