So, in my everquesting cheapassness, i was able to source coilover springs for the miata in fages close enough to what i want for $30. For all four.
The problem is their free length. They are 8 inches, whereas i have a hard time getting to proper height on 6 inch springs.
So, cut them! Thays the solution (yes, i know that will increase the spring rate, which is a good thing). That leaves me with a pigtail end on the springs, like a gm coil spring would have. Not the flat and parallel ends every coilover spring seems to have.
Gm has a screw thread shaped seat to accommodate the pigtail. The spring boosters for lifting sagging springs have this thread on one side, and flat on the other. Just like what im wanting, except its 5.5 inch diameter, not 2.5
So, does a pigtail seat for coilovers exist? Googling comes up with nothing, but i suck hunting Google for this kind of thing.
Of one does not exist, could one be 3d printed and used safely? Is there another option (other than buy different springs) im not thinking about?
Intrax has "spring rate adjusters" that look sort of like what you're talking about:
Probably not cheap though. I'm also seeing a "sprindex" thing that looks similar.
Heat the cut coil to flatten it and grind to finish it.
According to Eaton you can't cut those type springs. That said I'm planning on cutting that type spring for the Buick.
In reply to Don49 (Forum Supporter) :
I'd be concerned about what heating does to the temper of the spring. Unless you're suggesting a final heat treat afterwards.
Koni Sports for the ND Miata come with a removable perch that has the ramp you're looking for, but they're too small to go over top a threaded perch as-is. Still, a piece of pipe might do the trick...
Pics here: https://www.flyinmiata.com/ND/nd-koni-sport.html
Or take your cheap springs to a swap meet and see if you can swap them for some shorties.
Other alternatives:
-shorten the shock body to bring the ride height down
- raise the upper spring mounting point (if you've got an NA, you can build a new upper mount out of a piece of flat steel easily and that will drop you by 1/2" or so)
- move the perch down on the shock (can be a challenge on some shocks such as the Illumina, but is easier on others. Keep lowering until you hit the upper control arm (front) or the halfshaft (rear). If the former is a problem, modify the upper control arm)
We use 8" springs on our NA/NB Fox coilovers. What rates are you using?
Bilstein front shocks for an NB Miata have a cast aluminum seat that has a pigtail ramp. Maybe you can find someone who has purchased the shocks and converted to coil over sleeves, leaving the spring seats cluttering up their garage. They'll be a 50mm ID, if that would work for you. I had a set , but be damned if I can find them.....I'll keep looking.
How about bending and welding up a sheet metal adapter to sit in between the spring and the standard flat spring perch? I'd use the examples above as a bit of a template for the proper angle of the ramp so the spring sits nicely on it. By the fourth I bet you are pretty good at it!
I forgot about the aluminum perches on nb.
I threw mine away. Years ago.
Im doing the coilover sleeve on a bilstein hard s nb shock, on my nb. Adjusters at max low and some spring sag finally got me to a 12.75 fender height. With 6 inch springs.
The 8 inch are 12kg and 10kg.
If i could safely figure out how to cut new circlip grooves, i coul lower the skeeves two inches before i hit control arms or axles.
In reply to Dusterbd13-michael :
You just need to find someone with a lathe...
Found 'em.... I sold the shocks to classicjackets and he has them for sale on FB Marketplace here in Michigan......
But you can see the sloped seats in his picture.
CAinCA
HalfDork
9/8/21 11:38 a.m.
In reply to Dusterbd13-michael :
My brother has a set of Bilsteins on his 356 kit car. He sent them to Bilstein and they cut a new set of grooves for a REALLY reasonable price. I think it was $10 per shock. You should call them.
In reply to Dusterbd13-michael :
What brand of sleeves are you using? Years ago I had some with the inside step close to one end. You could use them either end up and change the height by a few inches. I've also had a set with a step at both ends and you could machine one off and drop them well below the C-clip. I think they were from Ground control.
Anyone with a lathe should be able to cut new grooves. There's a nice exemplar right there on the shock :)
Thinking about this, the factory take-offs probably won't work as they're designed for a 3" spring and not 2.5". I think the approach of getting the perch lower will help, but with those spring rates you likely will need shorter springs.
Note: that's a pretty oversteery spring combo.
Agreed that the rear is a little higher than i think it should need. However, with the v6 swap, chassis stiffening, etc....
Right now its 550ish with a full round of spring rubber, 425ish. And more prone to understeer than over. 1.25 front bar, base rear.
The sleeves are some no name ebay brand. I remember thinking they should slide over the circlip, not rest on it when i built them, but neither way i tried the adjusters made any difference.
However, im willing to listen! If different sleeves would make an improvement, awesome. If lowering the circlip is it, great! If both are needed, sure.
At some point ill quit being cheap and buy good stuff. But that will be after i get to using what i have to its its greatest potential. Im way off yet.
Keep in mind that you may be getting understeer if the front bottoms out or coil binds in corners, as that will give you a very high temporary spring rate. I'd make sure you're not bumping up against some sort of edge case before you start throwing all the rear spring at it.
Keith Tanner said:
Keep in mind that you may be getting understeer if the front bottoms out or coil binds in corners
Or... because of the tires. 
I drove OPs car and I don't think it was hitting the front bumpstops. I had a STR prepped Miata that hit the rears (until we raised it slightly) and the behavior was very noticeable. The sudden infinite rate and immediate breakaway would be very apparent up front as well, even if not coupled with rotation. The Miata I had was way more oversteery with that bar setup, to the point where I did disconnect the rear bar at some events, but had higher front and lower rear rates.
All of that said, I don't know that I would chase suspension issues (meaning engineering new mounts & whatnot) before resolving the wheel/tire problem, unless you plan on sticking with the Federals for the long haul. Its going to behave differently once you give it a bunch more grip.
I have used these. Had to cut the sleeve off, but they worked.
In reply to drock25too :
Have a link? Or part number?Cant seem to find them.
Michael, are the circlips inside the sleeves or are the sleeves resting on them? On my 2017 Challenge Miata the Ebay sleeves sat on the circlips so I "machined" a lip around the inside with a Dremel to get them inside. With the sleeve containing them they can't go anywhere. Also, as Keith suggested, it wouldn't be hard to cut new grooves, just measure the minor diameter carefully and don't overdo it.
In reply to DeadSkunk (Warren) :
The circlip is NOT inside the sleeve. Just resting on top.
Always kinda made me nervous.
I had not thought about modifying the id of the sleeve to sit down over it.
As far as the lowering the circlip, could i do it with a pipe cutter with dull discs? Seems like the groove would be enough, especially if the sleeve is over it doubling as a retainer
In reply to Dusterbd13-michael :
Wouldn't the pipe cutter deform the inside diameter and interfere with the piston? Find someone with a lathe and do it properly. While they're cutting new grooves also have them cut a step in the sleeves.
In reply to DeadSkunk (Warren) :
Yes. Didn't think about that...
Ill see what goodmans machine shop will charge.
In reply to Dusterbd13-michael :
I got them off the Bay of E. I'll look in the shop tomorrow and see if I saved one of the packages. I usually do in case I need a replacement. I did find this on the Bay. I believe they are the same ones I bought.
edit: Energy Suspension 9.6119G Coil Spring Isolator
Brand:Energy Suspension Part Number:9.6119G
Note(s):Coil Spring Isolator Set; Black; ID 2 1/8 in.; Lip OD 2.5 in.; OD 3.25 in.; H-1 in.; 5/8 in. Riser Height; Performance Polyurethane; Rear Lower; Rear Upper;
Dusterbd13-michael said:
In reply to DeadSkunk (Warren) :
Yes. Didn't think about that...
Ill see what goodmans machine shop will charge.
I think my suggestion further up the thread got missed. Lathe ready and waiting...
