Seefo

iTrader: (5)

Becareful with the numbers you get from the FCM spreadsheet. A user on here found an error in it, and it hasn't been fixed since.
https://www.miataturbo.net/suspensio...in-salt-71140/

I think the FRC tends to be a few percent off (which it already is a bit off due to some assumptions we make).

OptionXIII

Hell yes, Failure you da man. If we got exact dimensions for the regular NB shocks that'd be all I need. MSM shocks are probably close enough in travel to use your numbers and subtract the difference in free length. I'll measure when I take them off again.

I'm thinking I might do a tad less than an inch of extension at my ride height. The fronts can probably stay stock.

bahurd

iTrader: (8)

If you're going to lower the perch to the point you're concerned about needing helper/tender springs then you also need to put the spacer/coupler in between the springs.

Not a lot of sources for those so be prepared to spend;

You can also use Hyperco springs if all you're concerned is with keeping the main spring planted. They are less expensive and have a low block height (which is what they're at 99% of the time).
https://www.google.com/shopping/prod...ed=0CFAQpiswAA

But, with the ebay sleeves you're limited as to how far you can drop the car (and why do you want to get below the usual 12 - 12.5" anyway) because the sleeves seat "on top of" the clips without extending below.

sixshooter

iTrader: (12)

iirc, Fast Mike is the guy whose shock valving FCM copied.

Failure

Ah, I'd read that thread but forgotten about it. Good call. It's possible to bandaid around the bug by dividing spring rates by 2 when calculating FRC, right?

Once again, good call. These couplers with the PAC helpers and cheap mains are a bit cheaper than just buying new Swift or Hyperco springs, but it's probably worth the difference to just buy the good springs. When I get home I'll ballpark the price to have a delrin coupler made.

http://www.wideopendesign.com/Product/56/2.5-Tender-coil-Slider.aspx

bahurd

iTrader: (8)

Hard to beat the price of the spacers you listed and I assume they're steel; 2.5" Tender Coil Slider :: Wide Open Design.

The Hyperco springs I linked are 2.5" x 4" tender springs. Not main springs.
Hyperco CS100 Take Up Spring 2.5in. Autoplicity.com | Discount Performance and OEM Auto Parts, 100% In Stock

I looked at PAC products but couldn't really find any technical information other than basic dia & rate. The wire looked a little thick to me in the picture and I thought that, considering they spend most of the time fully blocked, the additional thichness would add to the blocked height. The blocked height of the tender springs + the minimal spacer thickness all detract from the ebay sleeve height capability. That's one reason why it's best to start with the better sleeves IMHO.

I may be wrong, not the first time.

SchmoozerJoe

iTrader: (2)

Well, Fast Mike was the originator, at least.
FCM picked up where Fast Mike left off.

At least, that's what Mike tells me.

I'm running a set of factory revalved Bilsteins that Mike (and Ramon from Bilstein) put together.

They're amazingly compliant with 600lb/350lb springs. Very close to Xida dampening on the streets and live-able when you factor in the cost difference between them.

Failure

Those Hyperco helper springs have single digit spring rates. We established early on in the thread that we like sexy Xida-style tender springs but not lame riceland helpers.

bahurd

iTrader: (8)

Well, actually they're 2.5" x 4" - 25Lbs and actually work quite well thanks. So, do you actually know what the Xidas use???

Failure

2.25 x 2" 150 lb/in, IIRC. It's around here somewhere.

bahurd

iTrader: (8)

I'll wait for your link...

150lb spring rate seems pretty high for a "helper" spring. If the purpose is a "tender" spring then sure.

I don't recall ever seeing definitive "proof" on this site on what the Xidas are and I doubt anyone at 949 is going to give you their spec sheet.

But anyway, you do your thing and I'll run my setup as I built it. Take care.

Leafy

iTrader: (1)

Dude what? Its a spring, the spring rate is printed right on it. Its 150lbs.

Failure

I don't get it. Are we arguing? What are we arguing about?

bahurd

iTrader: (8)

Thanks for clarifying.

bahurd

iTrader: (8)

No, not at all. Although it does seem so. Take care.

Failure

I measured wrong here. It's 10" between mounts, and 10.5" from the center of the eyelet to the shoulder of the rod. That means my top hat depth should be 0.5" + the thickness of the compressed bump stop, measured from the mounting surface of the top hat.

Seefo

iTrader: (5)

tender springs tend to be very low lb/in and are used as a method of keeping the primary spring in contact with the tophat.

Xida's helper springs are more akin to a dual or triple spring setup you would see on off-road racing/rally setups. I think they are also used in some GT cars.

There are similar springs to Xida helpers sold by some company in the UK, but the pricing is more expensive than the add-on for Xidas.
You can. I don't like to do that every time, so I just made a google spreadsheet with it corrected. You can find it in my post earlier. keep in mind all numbers are changeable on the doc. Including motion ratios, unsprung weight, sway bar arm length/motion ratios, etc.

basically, new numbers have been measured that deviate from what is in the FCM spreadsheet. Those numbers are available to play with, if you so choose. As I am sure you understand, they can have a significant effect on the final FRC.

PatCleary

Would people be interested in a 3" long 100 or 150lb tender spring? I'm putting together a set of Ebay coilovers and it's crossed my mind. I've been thinking about calling a few spring venders to see if anyone would make some up for me, hopefully for substantially less than the Eibach's. I'd probably want to order a couple dozen at a minimum though.

Spoolin6er

I'm interested.

OptionXIII

You're not going to get a custom spring for less $$$ than what's already available unless you're ordering in much bigger quantities than this thread has participants.

You're best bet might be trying someone like Riceland and asking to buy some of their helper springs. But yeah, I'd be interested in a group buy for helper springs.