DIY coilovers

Wow that is quite a response

Yeah our performance assumptions are a bit different which may explain the differing points of view.

1) I planned for limited jounce and rebound ("compression travel") appropriate for a performance suspension (will have to look at my notes but I think it is 4" total) (not sure what is stock but I can't see it more than 6" total)

2) I have a machined spacer allowing the strut top to nestle better into my camber plates however in previous designs I used the stock bell shaped aluminum piece to do the same for the stock strut mount.

3) I use both 10" (QA1 for the cost - silver ones) and 8" (Eibach for the rate selection - yellow ones) springs - no rub issues, I do prefer the 8" however, my wheel backspace is 3.5" but my brake rotor hub is slightly thicker than stock, I run 245s on the rear and 205s on the front

4) Adding a weld collar for the perch is pretty much the norm, my strut inserts even came with a set of rings to weld on but I prefer using a piece of tube with a split in it - not complicated

5) Don't see how the spring could come loose, my springs are always in compression even in full rebound (maybe just my design though - see first point), I think Brad Garska used helper springs in his design though

6) The thrust bearings are bomb proof - again pretty common, I don't do anything special but I do expect the occasional Preventative Maintenance (PM), once a year or every two year re-oiling, I don't see how Marks design is better concerning this point

I am not sure you mentioned it, I missed it if you did, but I think the BRP upper allows more clearance to the strut tower allowing more camber/caster adjustability. I ran into this problem so it is a key point for me and the BRP has been great for that - mms count.

I think you may be looking at a "set it and forget it" set up where I expect to be adjusting and tuning the suspension constantly. Our key design criteria and philosophy are different, for me the BRP (smaller) upper perch is necessary. I expect to be doing PM work to keep it all working right, swap spring rates and make camber and caster adjustments. If you are not doing that then you are right and it may be an unnecessary cost.
 
Here it is doug it's an 83 with KYB stuts, i believe stock springs and tire size is 185 60 13, the front measurement is 23.5 inches and the rear is 22.125 inches, i hope this helps.
 
Reply

Thanks Dom. Yes, was very helpful.

DallaraX19: Yup it seems we are at opposite ends of the performance spectrum. Me at the street end and you at the track end. If I chose, like you, to use a solid uniball type upper mount, then I agree the Bicknell upper perch would be best.
Don't know how you found an insert with only 4" of travel - must be some sort of race insert ? Yes, my Tokicos have about 6"
And good on you for ensuring you still have spring tension at full extension. You'd be amazed at the amount of folks - racers included - who run around with loose springs. Looks like you too put a lot of thought into your design.

By the way, I liked your street video. Had to laugh at the nmber of times you checked your rear view mirror looking for officer Bob...
 
Shocks and springs

Some random thoughts.

In most ways, the Rabbit insert is ideal for use in an X1/9. The body length is almost identical and both share a 20mm shaft size with a 14mm upper straight portion of the same length. Which means we can use modified X1/9 upper bits. There is a great selection of Rabbit performance inserts widely available at reasonable prices. There is a slight complication in that most Rabbit inserts have about 3/4" less compression travel and about 1 1/4" more extension travel than an X1/9. Thus about 1/2" more shock travel. Which does complicate matters and makes it even more difficult to maintain spring tension at full extension.

It would create even more of a problem if you were using a Rabbit insert in a stock X1/9 housing. You could run out of compression travel.

But having said all that, there are some real limits on how much you can - or want to - lower an X1/9. At full compression -and at full steering lock - the tire cannot be allowed to hit the fender. So unless you are prepared to flare the fenders - I'm sure not - then this is the limit of travel. Ideally you want the ride height to be about halfway between full extension and full compression. That's the goal. Set the ride height too low and you will have maybe only 1" of travel before you bottom out. Not good !

By using every trick in the book -raising the mounting brackets, counterboring the spacers, and chopping off the recesses - I was finally able to compensate for the Rabbit inserts "shortcomings". Using the inserts and springs that I wanted.

For inserts, I chose Tokico Illuminas. Part # BZ1073. Gas filled and 5 way externally adjustable.

But although I seemed to have solved the physical aspects of this conversion (fitment, proper travel, etc.) there is still one unknown : whether the valving is ideal for an X1/9. Although the Tokico's valving is adjustable, the compression and rebound valving adjustments are not independant - they are both adjusted together. So In am plunging a little into the unknown here. We dont have much real life experiences with them. The only report I could find was that Pete Whitstone has these exact inserts on the front only of his Scorpion, and seems quite pleased with them. I believe that Mark Plaia had them on his X1/9 front and rear and was very happy with them, but Chris Obert swears they were Rabbit REAR inserts. But Rabbits NEVER used a rear insert so I guess now we will never know.

There are many other Rabbit inserts to choose from. I think Bilstein make 3 different settings and Koni several as well. The Koni website is very confusing. Different Rabbit inserts appear in one section and nor another !

I think MAYBE that some of the Bilsteins or Konis have a reduced extension travel than stock VW ones. Sport versions meant for lowered VWs. IF this is true, then it would allow you to run even stiffer springs and still have spring tension. For sure something to look into.

The one big advantage to using a stripped VW housing on your X is that ANY make strut insert for a Rabbit will fit. The one thing I did notice when collecting different Rabbit inserts is that they were all slightly different in diameter, top shape, etc. BUT what they ALL had in common was that they all came with spacers and bushings to fit into a stock VW housing. Which is why I decided not to build housings from scratch. Unless you could EXACTLY duplicate the bare VW housing - an almost impossible task - then a housing built for say a Tokico would NOT accept a Koni without making special bushings and spacers.

Just a note - if you intend to use Bilsteins, some of my upper mount instructions may not apply. I think the shaft size is bigger so you may have to make some changes for that. I have never actually seen Bilsteins for a Rabbit so I don't know for sure. And it also seems the Rabbit Bilsteins have a smaller body diameter and can be persuaded to fit inside early X1/9 housings. See this thread http://xwebforums.com/forum/index.php?threads/13174/
Great work Paul. Could then also be converted to coilovers.

Onto springs..... Here is where I know I am going to get a lot of flak (go ahead - just be civil). I like the stock X1/9s balance and nice ride, but felt there was room for non-radical improvement. I still want a comfortable ride and not need a kidney belt. And I wanted the X to be able to absorb large bumps and uneven pavement without tossing me off the road. Lots of compliance and control.

Thus I simply chose to keep the stock balance but uprate the spring rates 20% front and rear. I chose:
Front - 10" x 2 1/2" - 150 lbs/in
Rear - 10" x 2 1/2" - 185 lbs/in

The chosen Tokicos also have quite a lot of gas preload - about 25 lbs worth by my estimate - which sort of stiffens the spring rate all on their own - so I think that this is as stiff as I want to go.

There is an interesting spring I almost chose: http://www.qa1.net/qa1_motorsports/drag-and-street/springs/2-5-in-i-d-variable-rate-springs.html Might work great. Should yield rates about 175 front/200 rear at normal X1/9 ride height.

Many here seem to like 500 + lb springs rates. Maybe for racing and autocross this is suitable. But not for the street !

If you want much higher than my spring rates, then maybe see if the Koni sports indeed do have a reduced extended length. That would maybe (?) let you get up into the 250 lb spring range. Just a guess.

Higher than that and you will have to use some helper springs. Then the sky is the limit as far as spring rates are concerned. For reasons of cost and simplicity I tried really hard to avoid using them, and was successful in meeting all MY goals.

Remember that - if you really think about it - that no matter how you build an X1/9 suspension, that say a 500 lb spring with 6" of suspension travel is simply a mathematical impossibilty without helpers.

Now I think the reason some here like really high spring rates is an attempt to increase roll stiffness. But I think there is another way to accomplish that goal. Yup, I figured that out too. Cheap, easy, and very nice. Stay tuned. Hint - look really closely at some of my pics and see if you can figure out what I am up to.

Are there other X1/9 shock options out there ? Yes, but not much. X1/9 specific Konis haven't been available for about 20 years. Bilstein never made a direct fit. Yes, there are still KYBs available (and at a great price) and yes they could be converted to coilovers. But be aware that a year or two ago KYB changed the design of X1/9 struts. It looks like the new design would be much more difficult to convert to coilovers. Maybe try to find some of the older stock while they are still around. They work well, up to a point.

And yes, there are a couple of off the shelf complete coilovers available - D2, Gaz, XYZ - but some dont seem to be too well thought out. They sure look nice and score high on the bling scale, but I couldn't help thinking what are you going to do in ten years from now when one strut starts leaking or one part fails?. Think about it...

But if you prepare your own housings like this project, you should be set for life. Leaking shock ? Just buy another insert. Popular VW inserts should still be available. Want to change spring rates ? These are common racing springs. Uppper perches and mounts ? Just stock X1/9 stuff. Bend a strut in an accident ? Just build another housing.

Yeah I know it is a bit of work but it really is easier than it looks. So give it a go. With enough feedback of insert choices and spring rates maybe we can really get somewhere.

Of course, any comments - good or bad - just fire away - but please be civil. Any feedback - please. Questions - fire away.

Cheers, Doug
 
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Revision

Well I'm somewhat ashamed to admit that on final assembly a small problem surfaced. The dust boots were bottoming before the bump stops. So back to the drawing board....

I ended up revising the upper spring perches, modifying the dust boots, and choosing different bump stops. No big deal.

Everything has now been cleaned, blasted, and epoxy coated. Looks way better now. Pics of completed units:

Front








Rear











Although it seems (by the number of views) that there is a lot of interest out there in reading about coilovers in general, it would also seem (by the response when I asked for some simple help) that there is little appetite out there for this particular method. Which is okay. So I guess I wont bother to document the latest revisions with pics and specifics. If, however, anyone out there decides to build a set like this, please just contact me and I'd be happy to share the details with you.

Cheers, Doug
 
Doug, I was under the understanding...

rx1900 said:
Although the Tokico's valving is adjustable, the compression and rebound valving adjustments are not independant - they are both adjusted together.
Click to expand...

That the Tokico adjustment affected only one side (compression I think), not both. But I don't know for sure.

I totally agree with your spring rates for your X. Very sensibe for the street. I have gone down the road of super-stiff spring experimentation, and it was one I retreated from. I think I landed on 250 front/200 rear for the Scorpion, which is driven occasionally at best. And have considered coming down from there to 200/175.

The spherical bearings up front absolutely increase harshness. IMO you can get away with stiffer springs if you use a non-solid upper mount.

Pete
 
Reply

Hi Pete. Great to hear from you.

According to the Tokico website,it would appear both compression and rebound settings are adjusted together:
http://www.tokicoperformanceshocks.com/c-6-illumina-series.aspx

I think maybe (?) the Koni reds only adjust the one only (and require dismantling to do so). Maybe that is what you are thinking of ? I think the Koni yellows (sports) adjust both together (from the top) like the Tokicos. And the Koni racing units have independant compression and rebound adjustments (one adjusted from top, the other through the bottom) ?

My choice of Tokicos was really just my best guess - based mostly on your positive comments - and the fact I got them really cheap !!

I think you now have Bilsteins on your K20 X1/9 ? Which setting ? Any gut feelings between them and the Tokicos on your Scorpion ?

And do you really like stiffer front than rear springs ? Ever tried the other way round ? Not critisizing at all - just curious. I tried quickly to find stock spring rates for an Elise - should be some to learn there. Looks they they run softer in front than rear, but the only rates I could find were in kg per N or something. And I think I recall early NSXs had softer front than rear springs, but changed to the reverse in later models ? Hmmm....

I think maybe those QA1 variable rate springs MIGHT just work ?

And I haven't forgot I still owe you a favour....

Doug
 
Cool!

I didn't know they were 2 way adjustable (albeit not independently). Good info.

I do run the Bilsteins on the K20. As far as I know they are not adjustable, at least, the ones on my car are not. I'm not 100% positive they are the same model# you referenced. I have a pair in the box in the shop, I'll take a closer look at their model number maybe next week. Laid up with knee surgery right now.

The recommendation to run stiffer in front comes from Steve Hoelsher, but I have not tried the other way around. I'm very happy with the neutral balance the set-up puts on my Scorpion. I think I'm going to have to try it in the wet to see what happens at the limit, I really haven't had an oversteer/understeer situation in the dry. After I found I could take 90 degree corners at over 50mph, I stopped trying to find the limit, too dangerous on the street.

Pete
 
Doug's updates

Doug, thanks again for all of your efforts on this subject. I can tell you have done a lot of research at every step of your development. Very well done.
While I am not currently in a position to build a set of coil-overs, it is a project I plan to do in the future. After reviewing several different approaches to this, I think your's is the most practical method (for my goals). Therefore I greatly appreciate you sharing the results of your work with the rest of us. If you feel like it and have the time I would be interested to learn the latest changes you made to the design.

Regarding the choice of stiffer front springs compared to the rear rates, I seem to recall reading prior posts indicating it was one approach at achieving the effects of having a front sway bar...without actually having a front sway bar (but I could be mistaken). Naturally there are numerous aspects that contribute to the overall handling outcome. Although I have not used them myself, there are several suspension software programs that allow you to input a bunch of parameters and play with different settings to predict their effects. But as Pete alluded to, it is my opinion that the choice of front/rear rates should be made to produce a neutral handling balance (along with the other related components of the suspension system). And I also agree with your view on overall spring rates being compliant and tolerable for normal driving conditions.
Thanks again, excellent job, your efforts are much appreciated.
 
Comparing spring rates

Hi Doug,

comparing spring rates between different cars is not easy, because the geometry of the suspension makes the spring rate into a wheel rate - which would indeed be comparable between different cars.

So a bunch of info would be need from both cars to compare spring rates.

The stiffer front springs will create a neutral balance for racing, but makes for an uncomfortable street ride.
I use spring rates where the rear is 50% stiffer than the front (front 40, rear 60) with an ADDCO front bar.
I run this setup with r-compounds at trackdays.
Neutral with at times a hint of understeer, very stable corner entry, never ever any oversteer unless you lift.
On tighter roads, nice rotation on lift.
 
Sorry to resurrect an old thread, but seems better than making a new one.

It might be a stupid question, and might be obvious if the pictures in the OP worked, but I'm wondering: what's the purpose of using the VW Rabbit struts rather than just modifying the ones on the X1/9 and adding the collars, retainers, bump stops, etc?

Thanks
 
The X1/9 uses strut tubes of very small diameter.
They are to small for most aftermarket internals.
 
Yeah, sorry the pics are gone - went away with PB issue some years back. I don't have the originals to fix it in my thread (linked in my sig), I do have the drawings with dimensions though.

As Ulix stated, you need tubes that will be a more common tube length/ID size for available aftermarket inserts. VW for one has a much broader base, which is why I used them on RX1900's recommendation.
 
While using VW struts allows much better options for the inserts (dampeners), it also brings some compromise. They are longer so the ride height will be taller (exactly the opposite of what's needed on the X). There were some "short" versions made for VW's that would be closer to the X's length (although still a little bit longer), but they are now difficult to find - the VW guys want them more than we do so the prices have shot up ridiculously (if you find any at all). Plus getting new inserts for them has become difficult. They also require some mods at the top to work on the X.

I recall some old posts that said they used VW inserts in the early X1/9 struts (the ones with removable inserts). But I do not see how, they do not fit inside the tubes. Unless there were some particular aftermarket VW inserts that were narrower and could be modified to fit. Although they would still be too long, so I really don't think it can work.

One option is to find a set of Koni struts for the X and do the coil-over mod to them. That way you can rebuild the inside to have a desirable dampening effect. That's what I did (I think I posted pictures that should still be alive). However those have also become difficult to get.
A better option might be to make new coil-overs from scratch, using one of the universal kits with blank tubes, etc.
 
Ah that makes sense. So potentially turning a sleeve on a lathe and then putting that sleeve around the strut tube to interface with the collar diameter, welding the sleeve in place and putting a retaining ring on the sleeve to hold the collar would do the trick. And then I'd retain the stock mounts and have the same valving and travel. Is this reasoning correct? I've only ever bought the pre-made coils for my VWs, so I might be missing something.

RE: the images, it's a huge shame that photobucket effectively burned thousands (millions even) of person-hours of work and knowledge built up on forums over the last two decades. It's a problem on literally every forum I come across - some old thread has exactly the info I want, but photobucket is holding the images hostage.
 
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Rozap, I'm not certain I followed your description? What do you mean by "sleeve"?

The threaded cylinders that the new "coil-over" lower spring perch fits on are universal parts. They basically slip over the strut tubes, after you remove the stock lower spring perch. You need to add a way to secure the bottoms of those threaded cylinders so it rides appropriately against the strut body. That may be what you meant by "sleeve"? On mine I just welded a section of steel tube onto the strut housing; it is from some basic steel tubing with a ID just larger than the strut OD, cut about 1/4" long. The threaded cylinder sits on top of it.

If you do this with stock X struts (the type with removable inserts) then everything fits the car like a stock strut. Effectively you have just replaced the stock spring with a narrower aftermarket spring that has a threaded lower mount (for height adjustment). The only thing is finding good inserts for the stock X struts.

Agree about the whole PhotoBucket thing. I've noticed even the 'new' version that people are paying to use, and supposedly allows images to be posted, still does not work - those images are blurred by PhotoBucket unless you also have an account to view them through. Greedy bastards. :mad:

Here's a couple pictures of the Koni's I modified for coil-overs. For the most part they are the same as stock X1/9 strut bodies, so the same construction techniques would apply:

001 - Copy.JPG

The front struts (above) have lower mounting tabs (to the left) that sit higher on the strut and are square to the sturt body. Therefore the threaded cylinder (black) can ride directly on it. Inside the threaded cylinder are "spacers" to make the threaded cylinder securely fit over the strut body. More on that in the next photo. One thing to keep in mind, depending on the particular strut you are working with, the top nut for the strut insert (far right of pic) may be larger diameter than the ID of the threaded cylinder. So some modification may be needed.

002 - Copy.JPG

The rear struts (above) are longer and the lower attachment point (far left) is at an angle. So I needed to make a separate larger collar (orange arrow) for the threaded cylinder to sit on. It is from a piece of heavy wall tubing, I ground the welds around the bottom at an angle to make it look cleaner. The two black arrows are similar collars made from thinner wall tubing. They are merely spacers to make up the difference between the OD of the strut body and the larger ID of the threaded cylinder - to keep it centrally located and not rattle. They are a tight interference fit, which together with the spring pressure keeps the threaded cylinder from moving around.
One option for the upper most "spacer" collar (the black arrow to the right). When you cut off the stock spring perch, if you leave enough of it remaining on the tube then you can grind it to fit the ID of the threaded cylinder. That will act as the upper color to keep things centered. But this will depend on the length of threaded cylinder you get (they come in different diameters and lengths); too short and it will not reach high enough to fit over the remains of the stock perch.
 
rozap said:
Sorry to resurrect an old thread, but seems better than making a new one.

It might be a stupid question, and might be obvious if the pictures in the OP worked, but I'm wondering: what's the purpose of using the VW Rabbit struts rather than just modifying the ones on the X1/9 and adding the collars, retainers, bump stops, etc?

Thanks
Click to expand...

Hi rozap. Certainly not a stupid question. And yeah - sorry some of my pics have disappeared. Would have made everything easier to understand. But luckily most of my pics on the second page have survived. Just look at those.

As for why I used the VW struts...well read the whole thread again. Lots of info there. And read this thread too:
https://xwebforums.com/forum/index.php?threads/strut-info-needed.14085/

Yes....i had lots of reasons for ending up using the VW struts. But basically...I wanted better shocks, slightly stiffer springs, more clearance to the struts. and to be able to lower the ride height a bit.

Basically, there are no longer any really good shocks available for the X1/9. There were Konis, but they were discontinued about 20 years ago. Bilsteins never were available. All that is currently available are some KYB sealed struts for the later X1/9s. But they are really just stock-type replacement shocks - not a performance upgrade. Yes - you could convert them into coilovers - much like I did to the Rabbit struts. Or yes - you could convert your existing stock struts into coilovers - but being nearly 40 years old by now they are likely pretty pooched.

What year is X1/9 rozap ? That kinda affects your choices.
 
Dr.Jeff said:
I recall some old posts that said they used VW inserts in the early X1/9 struts (the ones with removable inserts). But I do not see how, they do not fit inside the tubes. Unless there were some particular aftermarket VW inserts that were narrower and could be modified to fit. Although they would still be too long, so I really don't think it can work.
Click to expand...

Here is what I did:

https://xwebforums.com/forum/index.php?threads/bilstein-shock-installation.13174/

With stock springs, my car is over shocked. If you jump on the bumper it does not move. I still like it though, it feels stiff, and is comfortable on the road. It makes quick transitions well. On corners on the track there is still body roll, but is is well balanced.

Paul Davock
 
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