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SVreX
SVreX MegaDork
10/26/14 1:11 p.m.
MrJoshua wrote: Mumpkin suspension builder here. I'm not sure I would consider our suspension simple. Well, maybe simple, but I doubt you will find a duplicate of our parts list on any other Miata made.

...and much more next year!

alfadriver
alfadriver UltimaDork
10/26/14 7:50 p.m.
MrJoshua wrote: Mumpkin suspension builder here. I'm not sure I would consider our suspension simple. Well, maybe simple, but I doubt you will find a duplicate of our parts list on any other Miata made.

Last version I saw, outside of the bracket you needed to use the shorter bike shock, the chassis work was for the most part CSP.

You may reall a few years ago, I got into a nasty argument with the Miata guys about the requirement to spend $15-20k on a CSP Miata, and, if I'm not mistaken, your work very much proved me right. Thank you very muchl.

Like I posted a few years ago on the build thread, the car makes me think of another Challenge car.

Outside of an Alfa, the idea of making a CSP legal Miata that fits under the challenge budget is quite appealing. Moreso if I could find a national driver who would take it to Kansas.

MrJoshua
MrJoshua PowerDork
10/26/14 8:18 p.m.

The bathroom stall wall bushings are a little outside of the norm.

The problem I still run into is how to get enough shock for the front spring needed. (We have illuminas that I believe are only alive because there was so little travel they didn't have to do much) If your class allows top shock mount modifications then you just use the readily available Konis or bilsteins with whatever rate you want and let the top of the shock body go as high as it needs without bottoming. Sleeves and springs aren't complicated. Circle track stuff may be the answer but even they are getting pricey.

For the mumpkin next year we have a no compromise solution for the front that should be as good a most of the high dollar options. It's a bit of good shopping and a tiny bit of engineering but it's mostly being willing to go-"hey, that might work!"

alfadriver
alfadriver UltimaDork
10/26/14 8:48 p.m.

So you changed from the motorcycle shocks? 6 years ago, you were using R6 shocks.

I'd have to double check the rules, but shocks and springs are free. But I suspect that the shocks would need modified befire the car did.

Bushings are totally ok. Odd. But totally fine. I'd do the same thing.

For CSP, the top removal would be ok, but a lot of the other lightening would not... so there's that. But I'd also have to stick with a NA engine- have to run some models to see, but a '99-00 would be the easiest on a chanllege budge. Shave the head to legal min, convert to E85, and calibrate it like there's no tomorrow.

It's an interesting thought experiment. Especially with how quick your car is.

MrJoshua
MrJoshua PowerDork
10/26/14 9:09 p.m.

The motorcycle shocks had the spring millimeters from the A-Arm up front. I'm pretty sure they just hooked and made it solid. It scared me so we went with the illuminas. The "top" removal thing was about the shock top hats. You lower a Miata any at all and you basically ride around on the bump stops. Something about the shock body having to come up through both a arms before you mount the spring puts it in a grey zone where most shocks end up way to long and you use 1" of travel that has you bouncing off of bump stops. Stock Miata shocks seem to be short body shocks on stilts. A cheap "fix" for aftermarket shocks is to make tunnel style top hats that allow the top of the shock rod to mount several inches above the top of the spring and let the shock body travel as far as it needs with one consistent bump stop free spring rate.

Mazda did an interesting suspension design that used a moderate spring rate that fully collapsed multiple coils even at full droop and made heavy use of bump stops for spring rate even at stock ride height. I know very little about OEM suspension design so I don't know whether it's really cool or somehow flawed. I know it's hard to build better cheaply.

alfadriver
alfadriver UltimaDork
10/27/14 7:04 a.m.
MrJoshua wrote: The motorcycle shocks had the spring millimeters from the A-Arm up front.

I seem to remember seeing a post about that- but didn't remember who posted it. Was that because the spring was to large of diameter or to low in the spring/shock assembly?

A few years ago, there was a post about more motorcycle shocks, and I even made a thread asking about it- someone sourced a really nice spreadsheet that the Locost guys put together.

Not sure if any one of those would work better or not. Or worse.

There are a lot of cheap miata coil overs out there... but it's hard to tell if they are any good. The bike ones seem like they should be good- and one could change the fluid on a lot of them...

Anyway, of the whole project, this part seems to be one of the harder to solve to be a national CSP car.

MrJoshua
MrJoshua PowerDork
10/27/14 8:26 a.m.

A bit of both. The spring was down in the hole of the upper a-Arm (to low), and because it was to low it was to big to fit the hole well.

What do the CSP guys run?

alfadriver
alfadriver UltimaDork
10/27/14 8:54 a.m.

In reply to MrJoshua:

Not specifically sure, but they all seem to think that one has to run the multi-thousand dollar shock package just to top 10. I've not been on the Miata autocross boards for a few years.

(a quick search at the miata forum finds Koni 2812's, Penske, and some other custom built aluminum shocks- from $1000 and up just for the shocks)

The other high end part they "require" is a PCM that can run the 2001+ VCT motor.

alfadriver
alfadriver UltimaDork
10/27/14 8:55 a.m.
MrJoshua wrote: A bit of both. The spring was down in the hole of the upper a-Arm (to low), and because it was to low it was to big to fit the hole well. What do the CSP guys run?

can the springs be changed easily on bike shocks?

SVreX
SVreX MegaDork
10/27/14 10:57 a.m.

Just like any other coilover, with any spring rate you can find in a 2" dia.

Swank Force One
Swank Force One MegaDork
10/27/14 11:15 a.m.
MrJoshua wrote: Mumpkin suspension builder here. I'm not sure I would consider our suspension simple. Well, maybe simple, but I doubt you will find a duplicate of our parts list on any other Miata made.

Is this the setup with the bike shocks/springs?

I met a dude at MATG that was doing the same sort of thing, but he also had custom spindles and a weird articulating arm setup in the rear.

EDIT: Suppose i should finish reading before posting.

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