My 87 GT needs shocks and I want Konis...problem , right. A number of hobby folk have adopted later (available) strut inserts into their strut tubes. Experienced with "reds" in NIssan and "yellows" in MR 2 it seems a reasonable route. Anyone do it? An unknown is "jounce" compatibility depending on donor selection? Then height, top press-in dia, and taper . The "fit" inside the strut tube is mostly at the strut top cutoff. Also the bottom "dome" must be strong enough for around 55 ft lbs of the anchor machine screw. I hope to find some Koni drawings somewhere. Otherwise it's an expensive crap shoot. Thoughts?
[This message has been edited by hobbywrench (edited 11-06-2020).]
there is another thread about this somewhere else on Pennocks. Also, you can check YouTube, it shows a video of someone cutting up a stock strut and installing the koni insert.
I called Koni tech about their performance inserts. They are made/sized for specific applications - and none are right for the Fiero. In doing some research, it appears that "maybe" a Neon F strut could be used at the rear. The fronts are very short and lowering the car only makes it more challenging to find an alternate shock. SO far I have one set of Koni's on the race car, keep looking for another "good used" set for the second chassis. KYB Gas-a-just would be worth a try, but no rear option....
It's actually not that difficult to build Bilsteins, but you do need to be able to weld to a good standard. If you use s/h inserts you'll likely need to fabricate, or buy, new top mounts. Gives you much better control of ride height and valving though.
You need the bottom brackets from a pair of struts. Conversion tubes with spring seats. Inserts. (40mm inverted monotube) Springs. Top mounts. (optional)
NOT cheap!
[This message has been edited by Iain (edited 11-06-2020).]
It's actually not that difficult to build Bilsteins, but you do need to be able to weld to a good standard. If you use s/h inserts you'll likely need to fabricate, or buy, new top mounts. Gives you much better control of ride height and valving though.
You need the bottom brackets from a pair of struts.
If you're bulding from scratch, you don't need the brackets.... a pair of profiled/drilled plates and a couple of reinforcement pieces would make a new taco clamp from scratch.
A survey of the "cut-a-strut" versions from Koni online shows a fairly large inventory still available for cars back to 80's ranging $144 to $200 ea. These are the style with the protruding female, internally threaded nipple which abuts inside the bottom of the strut tube which is clearance drilled for a grade 5 locating bolt. In this version the top of the strut insert is located via "bumps" on the outside of the insert which are pulled in at final fitment by the screw at the bottom, thus press- fit- locating the strut insert. The Fiero strut tube would be gutted and cut down to a suitable length. The first important dimension is the OD of the Koni inserts and this is not readily available. I need to know the ID , tube length of an 85-87 strut tube. Anyone measure a loose unit? That would provide some kind of start. Then a conversation with the Koni vendors to weedle out a measurement from them (good luck). . Yes, this exercise is fraught and potentially a costly try and discard....ha ha.
The other styles of Koni inserts seem to be the OEM threaded top style and the "Sport" which is for custom enclosure. (I am winging this from pictures).
The OEM threaded top style shown on e.g., BMW sites is a slip- in with a cap mating with either internal or external threads on the strut tube top. The 2 Sport style customs show dimensions off a (Koni?) drawing . I cannot see (pics) how this insert is retained , except one site mentioned a "stud." These Sport versions run $200 ea.
There is some price discounting on the older cut-a strut styles . I count 17 different Koni part numbers in stock. One would likely work. Break the code!
[This message has been edited by hobbywrench (edited 11-06-2020).]
Haven't stopped on this topic. One finding is the bad PDF data base dimensions for the rear 85 GT Fiero struts such as body length. It seemed weird from the start being stated as 8 inches . I measured 13 odd inches on my lowly (but working ) Gabriels. This puts any hybridization more within reason for the cut-a-strut idea. These old Gabriels work on my lowered car inhibiting motivation just now. Really need the ID dimension to advance on possible candidates from various Koni donors...Don't know whether to trust a Gabriel ID to be OEM Fiero ID so as to baseline .
[This message has been edited by hobbywrench (edited 12-03-2020).]
To add to this discussion. I'm currently driving toward installing the koni generic dual adjustable inserts into a stock fiero housing. These will require the stock housings to be cut and a gland nut adapter welded to the top. I found some near perfect koni gland nut adapters from a speed shop in Australia and currently having the ID turned to 2.005" to fit the fiero strut.
Yes, I did discover that e.g., BMW uses the gland nut along with other German makes. And the Koni you chose appears to be within the "tape" measurement dimension I made . It could be your approach is the way. Cost wise I am hoping to find a cut-a-strut in the $140 range that would only need a little tweaking of the shaft plate hole. Still seems the critical next step for me is to mike the ID of the stock (my Gabriel?) housing at the top and then somehow scan likely Koni yellows without sacrificial $$$ personal expenditures ( a garage full of yellows which won't fit).
For viewers not familiar, the cut-a-strut relies on two "attachment" points: at top of tube the Koni yellow (and older reds) has 3 formed buttons protruding from the OD which are interference fit and are drawn in at final assembly locating the insert at the top. At the bottom the Koni yellow uses a female threaded nipple which is secured with a cap screw after drilling through the bottom of the stock (Gabriel , Monroe) strut tube. I am running reds and yellows now on other cars.
BTW Iain, pretty work you are doing!
[This message has been edited by hobbywrench (edited 12-05-2020).]
Digging in on the subject has been enlightening with a vast amount of various forum data on the Konis using gland nuts to retain the top. Just a guess,but the "nubbin" style (draw-in) top retention design by Koni most likely due to the hell everyone seems to experience with the threaded gland nuts. And I remember well (now) how difficult the install was on (listen for drum roll) 1967 Lotus Elan. The fine thread used in the mild steel tube was a disaster with no apparent way to chase threads. Seems not much changed on the Bimmers , Porsches, and Nissans with many stories of pipe wrenches with 3 foot extensions,etc.
Enough blather, Here are measurements of the Gabriel rear as (my) donor if the project goes forward: extended, bottom to threaded tip: 22-1/2", spring seat to body top: 4-1/4"; bottom to spring seat: 9.0" ; spring seat to extended shaft seat notch : 11-1/8" ; OD tube 2.0" ...(not opened for measurement yet)...if other external steel thickness is used for tube....100," then tube ID : 1.80 (45mm). These measurements put the rear Fiero strut within prevailing range of other vehicles.
And if threaded (somehow) the tube could be sectioned as discussed to use the Koni racing inserts (gland nut). Still seems an easier way would be the "nubbin" route for street use. The candidate Koni insert would be around 13" (325 mm) long, OD 44.5-44.9 mm. I kick myself for not measuring nubbin height recently so I presume around a .039" ( 1mm)) would "crush" OK on draw in. Still thinking....
Energy is winding down a bit since I am running and reasonable happy with current setup. Final thoughts on what is a PAPER ANALYSIS ONLY.
Forgive a somewhat limited summary as many of you are expert at this task. But as with any forum this blather is offered as a spark or info for someone.
It still looks like a cut-a-strut is a good bet once a proper selection is made. It should avoid welding and capping a stock strut tube with a screw-on "gland nut." Cost is always a factor and once the OD, length and nubbin positions is know there is good pricing out there. Bought 2 new Gabriels to have if I go further. The most limiting unknown is the candidate Koni insert OD ...which appears to be around 45 mm. I argue with myself if I should open a Gabriel and put the ID mystery to bed. The inserts mostly have a bottom locating nipple and some Koni insert "kits" show what appears to be a collar type insert to tidy up the top fit...so make one if the nubbins are a bit loose!
Gland nut approach. On line shows stock and Koni supplied gland nuts to hold in a Koni replacement or race insert. Lathe wizards could thread a thick tube and make custom parts. Also sectioning and re weld (for length) of various (Nissan) oem struts is shown. Koni sells gland nuts with different pitches, presumably to match oem (German) threading.
Stumbled on cable gland nuts which are interesting two part assemblies up to 50 mm, some in brass and cheap. Finally, saw 50 mm bearing nuts in steel with inside thread, low cost China. Latter might be ?brazed? to top of Fieiro tube. Ideas.
Got my Aussie koni gland nut adapters back from machine shop... I'll post pics soon.
Do you know the spring rate / frequency you are attempting to or will dampen with the struts? Given that the koni cut a struts are setup for specific platforms it makes it even more of a crap shoot to get the right shock, and if memory serves me correctly they are only rebound adjustable with static jounce.
[This message has been edited by msweldon (edited 01-07-2021).]
Gland nut approach. On line shows stock and Koni supplied gland nuts to hold in a Koni replacement or race insert. Lathe wizards could thread a thick tube and make custom parts. Also sectioning and re weld (for length) of various (Nissan) oem struts is shown. Koni sells gland nuts with different pitches, presumably to match oem (German) threading.
Stumbled on cable gland nuts which are interesting two part assemblies up to 50 mm, some in brass and cheap. Finally, saw 50 mm bearing nuts in steel with inside thread, low cost China. Latter might be ?brazed? to top of Fieiro tube. Ideas.
M48x1.5 is a common large thread for gland nuts and some other applications.
It's actually not that difficult to build Bilsteins, but you do need to be able to weld to a good standard. If you use s/h inserts you'll likely need to fabricate, or buy, new top mounts. Gives you much better control of ride height and valving though.
You need the bottom brackets from a pair of struts. Conversion tubes with spring seats. Inserts. (40mm inverted monotube) Springs. Top mounts. (optional)
Got my Aussie koni gland nut adapters back from machine shop... I'll post pics soon.
Do you know the spring rate / frequency you are attempting to or will dampen with the struts? Given that the koni cut a struts are setup for specific platforms it makes it even more of a crap shoot to get the right shock, and if memory serves me correctly they are only rebound adjustable with static jounce.
I confess my weekly driver sits on cut stock 85 GT springs so the usual benefit of strong spring control is not important to me. And so rebound calculation seems less important for my simple needs which are really not pressing, but interesting . I was surprised the amount of negative comment across forums on Monroe , and also surprised that among all users the Gabriel came out at or near tops for "OEM," perhaps buoyed by domestic users. Another trivium is that unlike most chatter the "new" Gabriels I bought are made in USA according to the box (ebay great price). I realize I now talk to hard core enthusiasts so my relative indifference to rebound and other parameters may grate. Still the dialogue is good ( I think).
Couldn't eliminate hash. The "metal" designation is a bit suspect, but the part is threaded. $14 before import Hong Kong. I see brass and stainless-looking examples in UK and Australia, but very expensive.
The koni yellow single adjustables unfortunately have their 'jounce' or compression statically set to a rather high level, usually much too stiff for the average daily driver. You have to step up to the double adjustable koni inserts to regain a measure of day to day drivability, if that's what you tune your spring rate / suspension frequency. But, the double adjustable konis are almost double the price of the singles.
That was the 'relative' beauty of the koni reds, although rebound adjustable their static 'jounce' / compression was, although somewhat stiff for some palettes etc, tuned to near the highest level of stiffness for a stock spring setup. The single adjustable yellows are set to a static 'bound' stiffness well beyond that of the reds as they were made for track day / autocross needs primarily. Koni reds 'could' be converted by koni to double adjustable, for a price...
Just for clarification and discussion, all koni single adjustables only adjust rebound and turning the knob does NOT make your ride stiff or soft per say on suspension compression but rather increase or decrease the dampening effect of the unloading portion of the suspension travel after compression. Making a single adjustable stiffer effectively gives an autocrosser the ability to delay the rebound of the suspension on non-loaded side of the car at corner 'turn-in', thereby slightly reducing the total available traction at 'turn-in' and allowing the driver to dial in a desired amount of understeer or oversteer as needed at 'turn-in'..... that's it.... nothing more, nothing less..... once the car has settled into a turn the adjusted rebound does relatively nothing until corner exit where the same oversteer/understeer premise is reenacted for the opposite side of the car to a lesser degree.
case in point - if you 'over' dampen your rebound the suspension will have a tendency to settle lower and lower over a series of bumps to the point of resting on the bump stops....
Discussing dampening rates, single, double adjustable'ness of a shock is more or less moot unless you know your targeted suspension frequency. 1.2Hz for a very soft ride and 1.8-2.2Hz for a stiff track car setup.
Furthermore, talk of suspension frequency and car balance is relatively moot until you obtain your car's weight balance and size your wheels/tires accordingly, especially for a mid engine setup. Otherwise you are leaving traction/handling on the table somewhere in the equation to achieve a balanced setup.
Although I haven't done the freq. calculations of cut or fiero store lowering springs nor do I have the shock dampening dyno graph of a KYB, they seem have done their homework and do nice job of dampening such springs for a fun daily driver.
[This message has been edited by msweldon (edited 01-19-2021).]
Good discussion, Weldon. I have had the Koni reds on a NIssan for many years with good results (salvaged, no less). Their jounce is fine for street and have them set midway for rebound, Also about two years back installed yellow cut-a struts on MR 2 Spyder , again about half way on rebound. Good results , although the car is surprisingly soft with 100 lb front /200 lb rear springs.
The 85 GT with cut springs and Gabriels is enjoyable driving up and down the 2000 ft hilly blacktop roads. As noted I just tune to budget and daily driving enjoyment. Our Fieros are now (almost) antiques and I detect some shortages of parts as the NOS stockpiles dwindle and Chinese may be the only recourse
So this thread is kind of directed to those who intend to keep driving . At best the prospects of hybrid Konis is not cheap @ $ 100 ea fronts and $140 ea rears (maybe ?), plus TLC.
Here's the catalog from the vendor in Australia where I ordered my gland nut adapters and koni gland nuts. See page 2 of the catalog for the gland nut adapters.
Cost really all comes down to what you want out of your damper. You want a set of assembled double adjustable struts? ~$1K is not bad at all....
Are you attempting to dampen stock springs? Or upgraded springs? If upgraded, what rate? Once again what is your suspension frequency goal?
Loosely, but again.....Dampers are determined by Spring Rate, Spring rate is determined by targeted suspension frequency, motion ratio (suspension geometry), and the weight distribution therein of your chassis.
I would recommend you
1.) obtain the dampening rates of the koni fiero struts from koni 2.) then obtain a set of old/blown/OE fiero struts from a yard or member here to get the ID 3.) then lastly see if you can ballpark a cut-a-strut for dimensions and dampening rate through koni.
I can help you with 1 now and 2 somewhat soon...
[This message has been edited by msweldon (edited 01-28-2021).]
Do you have damping ratios for other Koni part nunbers? I picked up a set of new Chevy Citation Koni struts. They are identical in fitmemt to the Fiero struts except for perch location. Would like to know if damping ratios are different. If you have a source for info I can dig up the part number. Thanks! Marty
Various suppliers over here. I acquired a set of Avus suspension for my Z3 before Christmas that need need some work, I'll try and get the internal dimensions of both and post it in a couple of days. The DU bushes and seals are readily available, if you can turn or thread suitable tube it's an easy way to do it.
