924Board.org

[Kaos]

Don't know if this is the right place for this post, but hopefully someone will have some answers. Here's the long explanation:

I have a 1988 924S SE with M030 suspension. I currently have it prepped for SCCA E-stock autocross duty (stock except for: 27mm front sway bar, lowest ride height on the front coil-overs and rear spring plate adjuster, 3yr old Koni Yellows, custom stainless cat-back, 225/45-15 Hoosiers all the way around).

I recently had the Koni Yellows run on a shock dyno, and was very un-impressed. The front struts have roughly 2-1/2 turns of adjustment (rebound only), and the dyno plotted out curves for every 1/4 turn. For many of the 1/4 turn settings, the damping curve did not change at all. Essentially there were only 3 possible damping settings - Full stiff, Medium stiff, and way too soft. Both left and right shocks showed the same effect, and both rears also showed a similar effect.

So, for racing purposes, the shock is only a two position - Full hard and medium. This really isn't enough range of adjustment for me.

The outfit that performed the dyno work has recommended that I look into Bilstein shocks. Apparently they are very easy to rebuild/revalve (you can even do it yourself in your own garage), and the valve stacks are interchangeable and inexpensive. I realize that I would give up the adjustability completely, but the Koni's only have two positions anyway.

For the rear shocks, they have recommended the Bilstein SN. This is a high end shock used in NASCAR with 1/2" rod end eyes on either end. Some adaptors will need to be fabricated for the 1/2" eye to 12mm and 14mm bolts on the rear, but it probably isn't a bid deal.

As for the front struts, I noticed that Bilstein has several options:

Porsche 924 Race Strut Left AK1130
Valving Rebound / Compression: 141/102 Body: Steel Conventional Body

Porsche 944 Turbo Strut Left AK1110-A
Valving Rebound / Compression: 380/150 Body: Steel Threaded Body

Porsche 944 Turbo Strut Left AK1120
Valving Rebound / Compression: 600/180 Body: Steel Threaded Body

Some internet research reveals that the AK1110 is refered to as the "Firehawk" shocks and the AK1120 is refered to as the "Escort Cup". I can't find any information on the AK1130.

The "Firehawk" and "Escort Cup" are listed for the 1987 and later 944 Turbo/S2/968. I assume that these won't fit, as the lower control arms, upper strut mounts, spindles etc are different. Does anyone know for sure that these won't fit???

As for the AK1130 - anyone ever used this strut and/or seen it or pictures of it? I need to know if this would be a direct bolt in (except for the spring perch which I would have to remove for to install the M030 Aluminum adjustable spring perch). Anyone?????

I am not worried about the valving, as I will have whatever struts revalved. Any info would be appreciated.

Jon A.
1988 Porsche 924S SE -Black
1985/2 Porsche 944 - Black

[924RACR]

The AK1130's are no longer available, sorry. Thanks for providing detail on your experiences with the Koni's - backs up what we've heard and repeated for so long with real data!

I'm running Bilsteins all around on my racecar. Rears are those NASCAR shocks as mentioned - don't remember the exact part numbers, I've posted them in the past. The rears can be purchased user-serviceable for minimal extra cost, and you can have your local shock shop revalve them as needed.
http://www.vaughanscott.com/construction.htm#SUSPENSION

For the fronts, I'm using leftover 933 struts. You won't be able to get these unless you find them used somewhere. However Bilstein does make a VW A1 chassis strut in their motorsport line that should fit. I can't remember the number, don't have my catalog handy. Search my old posts, I have referenced it in the past. Search on "Bilstein shock" in my posts. I should also reference my valving, though you'll probably need different valving with different rates. Call Bilstein Motorsport, give them your corner weights and spring rates, they can make very good recommendations for valving. BTDT; the rates they gave me were spot-on out of the box, I haven't needed to change them yet.

But my fronts aren't revalveable except by Bilstein; I think these VW struts are likewise, meaning you'd have to send them in to change. Still better than Koni's though! Like I said, I've not yet needed to change my valving, and I've been on them for 2 years. These VW struts are set up to take a stock size (5" dia) spring, not a 2.5" racing spring, so you'll still need to use the coilover collars (unlike my struts). Not a big deal, though, just an FYI.

Again, search my old posts, that should give you pretty much everything you need.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Kaos]

Thanks for the info. I read your old posts, and they are very informative. Good to see someone else has gone through this before.

How sure are you that the VW A1 struts will fit? I notice that there is no left/right fitment, just a single part number for both sides. Maybe no big deal, as the only difference on the 944 struts is the brake line bracket.

Do you know of anyone that has tried the A1 struts on a 924? I don't know if I want to blow the $400 on a set and not have them fit. Also, would they provide the same amount of camber adjustment? My stock M030 struts give me -2.5deg.

Looking at the picture of your rear shocks on your website, those are the same ones that I had in mind. I read your post on having to modify the upper strut mount to clear the schrader valve. I wouldn't be able to do this mod per the stock class rules. Any other suggestions?

[924RACR]

The schrader valve comes with the user-serviceable feature; don't get this or mount them the other side up.

Our struts are A1 struts; furthermore I had the guy at Bilstein Motorsport compare my 933 struts, when they were in for revalve, with the A1 struts on the shelf, and he confirmed that the front upright mounting was the same. Which you can also see from the part numbers of the stock strut tubes, they're VW A1 chassis parts (just like the A-arms).

Yes, I would expect the same degree of camber adjustment from the struts.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Kaos]

The following info is from eShocks.com:

VW Group I Rallye 74-84 Strut V36-0059
Valving Rebound / Compression: 270/100 Body: Steel Conventional Body

VW Group II Race 74-84 Strut V36-0103
Valving Rebound / Compression: 230/80 Body: Steel Threaded Body

You say that the Group 1 steel conventional body strut will fit our cars. How about the Group 2 Steel threaded body struts listed? If they are both for A1 they should both fit, right?

The shock guys I am dealing with (Dennis Grant at ATI Motorsports in Wixom, MI), say that the only reason you need to send your shocks to Bilstein to be revalved is because there is no easy way to gas and de-gas the shocks. They typically drill and tap a hole at the top of the strut shaft and install a schraeder valve. This way you could revalve your front struts at the track yourself.

[924RACR]

Correct, either one would work, since they're both for the A1 chassis. When I was last talking with Bilstein, the threaded body shocks were not legal for IT, where I race, so weren't an option for me. I would have (if I needed new front struts) bought the conventional body and added coilover sleeves. Now, if I were to buy, I would choose the threaded body struts, since they are now legal IIRC for IT. But of course I already have mine.

I am still thinking about a set for the next car (my turbo).

Dennis is correct; that said, you do also still need proper tools to service the "user-serviceable" shocks, most importantly a little manifold with a pressure gauge and regulator to properly set the shock pressure. Glad to hear there's another Bilstein vendor in the area; I've been working with All European in Royal Oak, but they're a little balky sometimes, and once I start to beat their Volvos up at Waterford the service and parts supply may dry up... - well, unless I can get a sticker from them for the side of the car! LOL

Again, don't know about the struts referenced above, but my 933 struts are not of a design allowing user serviceability. Then again, $55 ea to have them changed over properly is fine by me, makes sure I don't have the opportunity to screw them up...

You can actually, if you have the manifold and a nitrogen supply, tweak the shocks slightly at the track simply by adjusting the gas pressure. But I've also been informed that it's an excellent way to F the response up totally and slow the car right down, if you don't know what you're doing. I've resisted the temptation pretty well, so far, since the car handles great.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[924RACR]

One more note - Bill Hindorff was the guy at Bilstein Motorsport I talked to - 800-537-1085 IIRC.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Lemming]

Kaos,

Did you ever buy the struts? If so, did they fit and how are they working?
_________________
Tim
'95 968 (White/Cashmere)
'88 924S? (sleeper

[Kaos]

Well, I didn't end up going with the Bilsteins after all. For autocross use, quick and easy on-car adjustment is a must.

Right now I am looking at getting my front Konis replaced under warranty.

I am also looking into making a front strut housing for a Koni 8611 double adjustable insert. The stock class rules in SCCA dictate that the strut may be replaced, but must have the same range of adjustment as the original (ie same camber, caster, and ride height adjustability). I am making up some drawings to duplicate the stock strut housing, but will accomodate a larger diameter strut insert.

If anyone else is interested, I could post the drawings when I am done.

[924RACR]

Check the Carrera catalog - I recall that they have some housings, might have one that'd do the job for you...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Lemming]

I called Bilstein a few times and no one would get back to me with an answer, so I went with the Leda coilovers front and rear
_________________
Tim
'95 968 (White/Cashmere)
'88 924S? (sleeper

[Kaos]

Lemming,

Which Ledas did you get? Non Adjustable, single adjustable (both bump and rebound together) or double adjustable?

From reading the Leda website, it seemed like the adjustability was more to account for different spring rates than for handling tuning (ie. we use spring rate X with shock setting Y at track Z, but spring rate A with shock setting B at track C).

[Lemming]

Single adjustable rebound only. However, they are being set up to be fully upgradable to remote gas double adjustable.
_________________
Tim
'95 968 (White/Cashmere)
'88 924S? (sleeper