Shock Valving, Spring Rates

[Series8217]

Anyone have experience with higher-than-stock spring rates with Koni Reds in the rear of a Fiero?

I'm currently running ~375 lb-in, and wondering just how high I can go and still have adequate damping from these struts.

[The Dark Side of Will]

They were designed for stock spring rates. I have a set on the Storm Trooper (Formula) and they feel great set full stiff with stock springs.

I have a set on The Mule and I feel like they're a bit underdamped with 325# springs and no sway bar.

However, the Koni custom shop can modify/revalve your struts in pretty much any way you can imagine, including converting to double adjustability. They should just need motion ratio, weight per corner and spring rate to get the adjustment range right.

[Series8217]

They were designed for stock spring rates.

Were they tuned for the '88s, or the earlier cars? Doug Chase reported that the 88 rears are 142 lb/in, and I heard that the '84-'87 were "much higher" but I can't find any numbers.

[The Dark Side of Will]

Yes, the Koni part number for the strut is the same for 84-87 and 88 cars.

173 is the number I've seen for the 84-87 spring rate. However, the '88's also have the rear sway bar, which affects roll rate and requires extra roll damping.

[Series8217]

Do you know what Koni charges for a revalve on the single-adjustables? I contacted them but haven't heard back.

[FieroWanaBe1]

Koni food for thought.

http://farnorthracing.com/autocross_secrets18.html

Not like fieros have a lot of choice though.

[The Dark Side of Will]

Do you know what Koni charges for a revalve on the single-adjustables? I contacted them but haven't heard back.

You're probably better off getting the Koni custom shop on the phone. Let me know if you can't find the number... I'll see if I can dig it up.

I'm guessing $100-125 per strut. IIRC, a few years ago they wanted $175 per strut to revalve and convert to double adjustment.

Koni food for thought.

http://farnorthracing.com/autocross_secrets18.html

Not like fieros have a lot of choice though.

Good article... lots of material at that site... I'll be reading up on that for a while.

That's kind of in agreement with the extremely vague impressions of the various MFG's that I'd come across.
Bilstein's great if you don't open them.
Penske's are expensive and predictable.
Koni's are for street cars (Who else makes shocks for trains? Talk about unsprung weight...)

That being said, check these out: http://www.koniracing.com/2817.cfm (Also in the hard to find parts thread)
Some assembly required for Fiero use. Since the Far North guy has never worked with the Koni Motorsport units, we don't have the benefit of his insight. For something like $1200 per, those should be no-shit shocks.

Also, Vorshlag is an AST/Moton dealer, and is VERY impressed with their performance. I don't know right off if they dyno their own, but I'd be mildly surprised if they didn't.

[Series8217]

Do you know what Koni charges for a revalve on the single-adjustables? I contacted them but haven't heard back.

You're probably better off getting the Koni custom shop on the phone. Let me know if you can't find the number... I'll see if I can dig it up.

I'm guessing $100-125 per strut. IIRC, a few years ago they wanted $175 per strut to revalve and convert to double adjustment.

Cheaper than I thought. I'll look into it. Depends on how long I'm keeping this car really.

I'm going to an SCCA Autocross next week to get a baseline and see if its worth trying to further develop the chassis, or just move on to an M3 already. With Rodney's tapered roller bearings coming out, there may no longer be any major part problems stopping me from keeping the Fiero as a track-only car.

Also, Vorshlag is an AST/Moton dealer, and is VERY impressed with their performance. I don't know right off if they dyno their own, but I'd be mildly surprised if they didn't.

Vorshlag still hasn't gotten around to test-fitting all the manifolds I sent them for the LSx BMW swaps, so they're probably too busy to design some Fiero stuff for me. I may look into that in a few months though. Yes, they do dyno their own shocks. I've seen pics of their shock dyno on their website.

The front is still going to be a problem. I wonder if Bilstein makes anything that fits the front of an 88?

[The Dark Side of Will]

The front is still going to be a problem. I wonder if Bilstein makes anything that fits the front of an 88?

The flavor of the month for the Ryane/Held/HMS hardware is now "Arraut Motorsports". It may be better to convert to coil overs if your class allows it.
http://arrautmotorsports.com/suspension-information/

Are you running SM2?

I have Konis on the front end of my Formula... are the '88 fronts no longer available?

[FieroWanaBe1]

Koni still lists the 88 shocks in their catalog.
8040 1092

[Series8217]

The front is still going to be a problem. I wonder if Bilstein makes anything that fits the front of an 88?

The flavor of the month for the Ryane/Held/HMS hardware is now "Arraut Motorsports". It may be better to convert to coil overs if your class allows it.
http://arrautmotorsports.com/suspension-information/

Yeah I dunno about those guys. I'll talk to Chris West if I decide to go with tubular arms and coilovers.

Are you running SM2?

There are 3 boosted Miatas running in SSM (it's called Super Street Modified now instead of SM2) here. They have huge Hoosier slicks, giant wings, and 250 to 450 whp. I would need boost and a big tire budget to be competitive in that class.

We have a set of regional classes called California Street Modified and California Street Touring. If it can be legally licensed in California, it's legal to run in these classes. In CSM, any DOT-legal tire is allowed. CST requires a treadwear number 140 or higher.

I'll be running in CST for now. My tires are pretty old and my setup is untested. I don't expect to be competitive at the next event. If the car does alright I'll be getting some much stickier rubber to match up with what competitors are running. Most are using the Hankook RS3 255/40/17. It looks like I can fit some 275 or 285 rubber in back with some wider wheels I found. I'd match the front tire width to my weight distribution.

The fastest car in CST at the last event was an E36 M3. I don't know what mods it had, but it was damn quick. It may have been supercharged, otherwise perhaps an S54 swap. At least that's something with similar curb weight to the Fiero.

I have Konis on the front end of my Formula... are the '88 fronts no longer available?

Chris West mentioned that I got one of the last sets for the front. I guess they stopped making them? Maybe they are back in production. Mine are probably OK for now, but I don't have a shock dyno so who knows.

Chris has some Bilsteins on the front of his 86. Maybe some can be made to fit the 88.

[The Dark Side of Will]

Are you looking at raising the inner pivots on the rear lateral links or going with something like FieroGuru's outer pivot lowering attachment?

The '88 front geometry feels pretty good, but I think the rear needs improvement.

[Series8217]

I'll stick my Go Pro on facing the wheel so we can see what it does. I feel like the solid lateral links do a lot to help. I know they don't change the static geometry, but even the static geometry wasn't being maintained well with the compliant bushings in there.

[FieroWanaBe1]

There was a video on youtube of the suspension of a stock 88 during an autocross:
http://www.youtube.com/watch?v=fJndkuoU ... c7Drz3NDUw
It looks like it had a broken cradle as well.

To go along with the Koni motorsport strut mention, penkse has developed a line of strut type shocks for race mustangs:
http://www.penskeshocks.com/Penske_Shocks_Struts.php
Penske has the one of worse websites of any major motorsports leader I have seen. But their reputation more than makes up for it.

I also know bilstein has been making universal struts for WTCC and Rally cars for some time.
and sells universal inserts.
http://streetwiseparts.com/new-bilstein ... ts-struts/

[Series8217]

Cool video, but that car sure is in bad shape! I'll have to experiment with different camera positions. Looks like lighting may be an issue to.

Those Bilstein and Penske struts look great. Nice that the Bilsteins come with a weldable housing and blank top. Should make adapting them easy. I'm going to look into fitting some of those on my Outback....

[Series8217]

The Bilstein motorsports AK-series dampers have the right attachment styles for the Fiero. If the length and stroke are correct, it may be possible to pick one out with the right damping for some proper springs. Page 9 of the catalog shows the valving and dimensions. The 88 Fiero uses "T-bar to pin" style mounting. Unfortunately, the AK series are not rebuildable so they can't be revalved either. Luckily there are a lot of valvings available from Bilstein.

To accommodate rebuildable shocks will at minimum require modifying the upper shock mount on the crossmember. It may be possible to build a T-bar that goes in the bottom of a standard eyelet shock, and fits on the 88 lower control arm with few or no modifications. The upper is going to be more trouble; the spring perch will have to be cut to accommodate an upper bar. The other problem is the rebuildable shocks are at minimum 2" longer than the Fiero shocks. I don't see a motorsports shock from Bilstein with a remote reservoir. It may be possible to convert to a remote reservoir that has its own dividing piston. Then the shock shaft can be modified to remove the dividing piston and shorten the top.

[AkursedX]

I wonder if they are G-body front shocks. I know they are pretty darn close in dimensions to the '88 Fiero fronts.

[The Dark Side of Will]

To convert to rebuildable shocks will at minimum require modifying the upper shock mount on the crossmember.

Don't the upper shock mounting hats unbolt from the crossmember?

[Series8217]

To convert to rebuildable shocks will at minimum require modifying the upper shock mount on the crossmember.

Don't the upper shock mounting hats unbolt from the crossmember?

It's welded to the crossmember.

Not the best pic, but here's what the upper mount looks like:


There's not really any room to make it wider without moving the upper mounting points for the upper control arm. I think Bloozberry on Old Europe calculated that moving the front control arm mounting point outward and shortening the arm actually improved the camber curve, so it shouldn't be relocated inward for shock clearance.

[Series8217]

I measured the rear unsprung weight on my '88 today.

Here are the specs:
* Rod-end lateral links
* Polyurethane bushings in stock trailing link
* Stock knuckle & bearing
* 12" Corvette rotor with WCF bracket and aluminum centering ring
* Stock caliper and hardware
* Porterfield R4-S pads
* Raze R-74 17x8-48mm wheel with aluminum hubcentric ring (IIRC the wheel weighed 20 lbs)
* 255/40/17 BF Goodrich g-Force T/A KDW 2 (listed as 27 lbs on Tire Rack)
* Koni Red strut with spring perch removed and replaced with full-length aluminum coilover sleeve
* QA1 2.5"x10" spring (350 lbs/in)
* Hypercoil 4" helper spring

If you can think of any relevant item I forgot to list let me know and I'll add it to the spec. Next time the wheel/tire assembly is off the car I'll try to remember to weigh it so I can calculate the weight of the wheel.

I measured by lowering the spring perch to unload the spring and helper spring completely, then I lifted the wheel assembly and stuck a scale under it, and let it down. I used a bathroom scale, so to be safe assume something like +/- 10% accuracy.

The result was 108 lbs. This is actually much lighter than I expected. Since I didn't disconnect the top of the strut, there was still probably some force from the gas charge, so the value might even be slightly high. I'll measure again when I get a more accurate scale.