Stock:
Normal? (Black Showa; I think I remember someone mentioning this, but I've never seen it)
Sport (Black Showa; this is what's on most cars)
Hard Sport (Yellow Bilstein)
R-package (Yellow Bilstein)
MSM (Silver Bilstein)

Aftermarket:
Bilstein HD (aka B6)
Bilstein Sport (aka B8, shorter body)

 

thanks for the info. deff cleared some confusion about b6 and b8 not being an oem option

 

Still finishing mine up. However, my ebay sleeves came with ~460 lb/in springs. I have 550/350 QA1's on the shelf, so these aren't really needed. Might hang onto a set, but if anyone needs springs in that range I'll let a set go.

Edit: To clarify, I'm willing to let the Ebay 460 lb/in springs go. They're just over 6" long.

 

What length are the 350 QA1's?

 

Spoon feed me?

I just picked some new NB bilstein sports from Curly. I'm looking to build some adjustable coilovers and need help with spring rate/length. These will be going on an exocet race chassis that will weigh about 1550lbs wet. It will be mostly track day/weekend canyon carver. I don't need a cushy ride, but I don't want to see the chiropractor after a cruise on the street either. I've done my research unfortunately there is not any good info as far as exocet suspension spring rates.

I plan to order allstar sleeves and the Honda bumpstops.

Any thoughts?

 

Exocet has identical suspension geometry to the Miata, right? Just use the fatcat spreadsheet to find what springs give you reasonable frequencies.

 

Yes it does now that I have my spacers. I'll look into that. Thank you.

 

The exocet will weigh much less than a Miata so it will need less spring rate (with the same sway bars). I would want to know the size and compound of tire you plan to use to make a reasonable recommendation. Adhesion of the tire will determine the necessary rates.

 

I'm thinking something like a 225/45/15 bfg rival on 15x9's. I'm still up in the air on sway-bars. I need to get these things ordered and get my build on the move.

 

I would recommend an adjustable sway bar because it aids in fine tuning the balance. I believe the RB and the FM bars are all multi-hole adjustable rate bars but I'm not sure of the others. ISC Racing makes a really trick-looking adjustable front and rear bar as well that comes with aluminum arms on a hollow splined steel center with roller bearings for chassis mounting. If you end up with a non adjustable then you may have to play with changing spring rates a little more to find your balance. Since the weights and balances of the Exocet are different from a Miata because of the completely new chassis, I would expect the FCM calculator to be somewhat useless other than a starting point.

If you are planning on the 225 Rivals (which have been out of stock everywhere for awhile) on a 1500lb chassis, depending upon your sway bar choices, I would consider 400/275 or 400/300 as a starting point. And I would recommend 7 inch springs for good travel without binding. Lighter rates generally need more length for travel to not bind. Larger rear bars than stock mean you can achieve cornering balance with less rear spring rate so therefore everyone has a different idea of "right" according to their package as a whole. Guys with stock rear bars will want more spring in the rear. But I enjoy the adjustability of both the front and rear as a way to fine tune without changing springs. The sways and the springs work together to achieve balance because sway bars are simply torsion bar springs that borrow spring rate from the opposite side of the car.

If you were running Hoosiers I would have advised slightly higher spring rates (450/300 or 450/325) or higher as a starting point. But since it will be used on the street and weighs as little as it does, you will find the lower rates far preferable and will end up with better tire adhesion over uneven asphalt.

Summit Racing's house brand is still the best deal on springs outside of "guess the spring rate" Ebay springs. I have had no problems with my Summit springs or heard of anyone running them with a complaint.

 

Some proper spoon feeding here!


For all the ninnies on the interwebz that say mt.net is too harsh and too scary to visit...look at the kind of info they're missing out on...

 

I am inexperienced in this area, so you will need to do your own testing (and take this with skepticism). But if you wanted the same ratio of roll stiffness to weight as what the track guys are running, you are looking at 450/300 with the RB hollow front & MSM rear. 600/375 with stock sway bars.

obviously these are rough gestimates, and I am not sure that roll stiffness is chosen based on chassis weight as much its chosen based on a combination of weight and tire grip. I would probably go for a bit stiffer, because your lower weight will get more out of your tires. So my final suggestion would be something more like 500 and 300-400 (with the sway bars).

Blonde moment. Yep this is a good suggestion. my numbers match up closely to the 800/500 suggestion on the miata.

 

Actually, the less grippy tires will need less spring rate. And less body weight will want less spring rate.

 

this is true, but I am not sure where you are getting "less grippy tires". I am using equivalent grip to 225 rivals and would really like to move to the 800/500 setup. SPM cars run 225 RC-1, which based on the NT-01 numbers, is maybe 1-2s faster than rivals.

I think you maybe missing that a lower weight car with the same tire & size will have more grip. The car will need less spring rate overall too. my first set of numbers match more with the 700/400 setup, the second ones are close to the 800/500.

Otherwise, on a guess and minimal math I am sure my numbers are not ideal. I think the responsibility falls to him to figure out what is ideal.

 

Thanks for the advice guys. There will be some learning to do and trial and error for sure. I'm new to performance cars and setting up suspension. My plan is to get something decent for now and pick up some xidas next year. To be safe and more comfortable i will be using something that has been used (just looked into the uk exo race series). I'll be going with 350/250 and a tubular sway bar. Enough of a thread hijack. I'll post some pictures when I have them built.

 

Small fortune racing also sells the same style bar. I'd trust it more than the ISC stuff.

 

Damn that thing is expensive. Don't have the budget for that just yet. This car is already way over budget.

 

Less grippy than SM6 or SM7 Hoosiers.

It will go around corners faster but will not impart as much force into the springs as a heavier car with the same tire.

 

Yeah, maybe you forgot that grip is a function of friction, and friction is a function of weight.

 

I'd suggest starting at 750/400 and fine tune from there. On a fast track with elevation changes 550/350 is a slight bit too soft for a stock Miata.