Ultimate miata suspension

So, in the planning stages of my nextproject. 

2000 miata.

Xp/mod class, butdoesn't have to be legal anywhere but the challenge. 

Ignore engine and trans

Base model, open diff 

Stone stock suspension at the moment.

What would you do to the chassis, and why? Take budget out of it for the most part.

Extended ball joints? Boxed crossmember? Train springs? Super high springs and no sway bars? Spool?

Let you brain go wild, but justify the answer. 

Tires first, work from there. Look at what DP or XP Miatas are running. If I just wanted to go fast I'd gut the car, pull the windshield, build a rollbar that had diagonals that went down and tied the front and rear suspension. Again, look at prepared Miatas. You already know how to make flares, so maybe a 12 inch hoosier (or similar) and the power to spin it. Spend some time looking at bump stop rates, it worked for the Corolla and I bet it will work here if you can get a stiff enough shock.

In reply to Dusterbd13 :

How heavy?

We did a lot to the Mumpkin, but it was about 1850 lbs. 

I hear bump stops work good.

Bumpstops work well for the price, but not as well as damped springs do. I would go with the Fox setup because, well, if I didn't think it was the best I'd change it until it was! Might tweak the damping if it's a trailer queen to give it wicked fast turn-in and load up that outside front quickly, but that's relatively easy to do. As Mazdeuce said, I'd start with tires then do what the tires wanted to be happy.

Get a Giken diff. A spool isn't going to want to turn in unless you set the car up to lift the inside tire like a kart.

Chassis stiffness isn't as important for autox as weight is, so I wouldn't go nuts for a cage if this is a parking lot warrior. Pulling out as much weight as possible is a given.

I know DB suggested not worrying about the budget, but isn't a Giken LSD kind of non-cheap?  OR, how decent are the OEM options that might be more affordable?

If you want to win, you run a Giken. If you want cheap, you run a factory Torsen and work hard to make sure it never lifts a wheel. But "ultimate" means the Giken.

So, what does a giken do differently, and what is it from?

Keith Tanner said:

If you want to win, you run a Giken. If you want cheap, you run a factory Torsen and work hard to make sure it never lifts a wheel. But "ultimate" means the Giken.

I want to second this. They really need the correct fluid and setup though to get the max out of them. 

Fox shock at least the one miata that I got to use with them are beastly better then anything I have eer personally tired. Blackbird fab works has a 4 way adjustable set of 8300 series Penskies that they sell around 12-14K I think for the Miata that would also be worth looking into. I run the same shock series on the ACR and they are astonishingly good. 

The biggest question is- if given the chance to make a tube frame under a Miata body, how would you alter the suspension design?

If that answer ends up being really close to the original design/layout- go with that.

Then you ask- can I make them lighter by fabricating the arms (I'd not do the upright, kind of a PITA to make your own, relatively speaking).

Then you ask- for the sub frames- what is the next weakest link?  And can I do the exact same function, but lighter?

All of the above noting that the duty cycle and the safety margin question is quite a bit different.  Instead of going over rough roads and dealing with a lifetime of corrosion, it's now just there to keep the car off the ground, and strong enough to deal with suspension loadings using racing slicks.

For a real XP/Mod car, there's no W/S, so all you need is the min requirement from the challenge rules.  I'd also look into a solid cover for the passenger side, and try to keep the cage and seating stuff above that body work as clean as possible, so that any rear aero is most effective.

That's kind of how I've played the exact same question out in my head.

Dusterbd13 said:

So, what does a giken do differently, and what is it from?

It's from OS Giken. It isn't a junkyard part. It's a clutch pack with a ridiculous number of clutches inside.

If I had full control over the pickup points, I'd be looking at duplicating the ND geometry. It works really well. At Laguna Seca a couple of weeks ago, I was seeing similar cornering speeds to Spec Miatas when I was cruising around in a 2600 lb ND on 200TW tires. That same car can pull 1.07g sustained on the classic skidpad test. The grip level on the new car is fantastic and it's far less upset by mid-corner bumps.

If you're looking to recreate the subframes, pay VERY close attention to the support around the rear pickup point for the front lower control arm. That's where your braking forces go, and the tubular subframes on the market are far weaker than stock there. It's worth noting that this was the location of the first factory brace added to the car, and that brace got bigger with time. Braking loads tend to be quite strong in autox so this is important. Same for control arms, I don't think anyone's managed to improve on the stock front lowers yet.

Keith Tanner said:

Dusterbd13 said:

So, what does a giken do differently, and what is it from?

It's from OS Giken. It isn't a junkyard part. It's a clutch pack with a ridiculous number of clutches inside.

From a budget stanpoint, has anyone documented how to set up an OEM clutch LSD to work a lot better?  In the Alfa world, how to set the clutches up is pretty well documented.  Granted, part of the reason is that there's not enough market for a Giken to market one...

There aren't any OEM Miata clutch packs. There are some other aftermarket versions, but the top-level autoxers are getting better results out of the Gikens. I've not spent any time with the other clutches, so I'm not sure how tuneable they are.

I swapped out a Torsen for a Giken on my car. With no other changes to setup, I dropped a full second on my local kart track. That's out of a 63 second lap and running about 170 rwhp. If I wanted an oddball final drive ratio, I'd also consider a GM diff like a Camaro or CTS-V unit. They hook up very well in the V8 cars.

In reply to Keith Tanner :

I thought the early Miatas had clutch style diffs.  Or were they something else....

Hmm...

So, the car should be north of 300whp.

And that may influence the giken/everything else rear diff. Hadn't thought about the strength of the rear diff, just traction. 

Would there be a diff swap that also nets adjustability/mucho better limited slip? After pricing the giken, that would be a sizable mortgage payment. 

I think I remember someone saying the OS Giken made a significant different in lap times.

The current supermiata formula I think is V8roadster kmember/control arms with like Xida coil overs.

I'm not sure if I want Xida's or the Fox but I would likely get the Xidas with 800/500

Dusterbd13 said:

Hmm...

So, the car should be north of 300whp.

And that may influence the giken/everything else rear diff. Hadn't thought about the strength of the rear diff, just traction. 

Would there be a diff swap that also nets adjustability/mucho better limited slip? After pricing the giken, that would be a sizable mortgage payment. 

The GM swap used in V8 swaps would satisfy and allow some more tuning of final drive.

The old Ford 8.8 IRS swap used in earlier V8 Miata projects is probably more affordable than the GM Getrag 3rd member swaps being discussed.  Good options for LSD's and ratios as well.

Jaynen said:

I think I remember someone saying the OS Giken made a significant different in lap times.

The current supermiata formula I think is V8roadster kmember/control arms with like Xida coil overs.

I'm not sure if I want Xida's or the Fox but I would likely get the Xidas with 800/500

That would have been me in my last post.

Supermiata does not use any V8R parts. The choice of coilovers is open, but since Supermiata is 949's pet race series you see a lot of Xidas.

Why the Xida over Fox?

Early Miatas (1990-93) used a fairly ineffective viscous LSD wrapped in a weak ring and pinion. Unsurprisingly, the 1994-05 rear is a popular bolt-in update.

A Torsen should hold up to 300 whp. They start to show weakness in the 400 hp range, especially when wheel hopped.

Sorry Keith this is me thinking about my 99 that will be a track car not really a street car

http://949racing.com/NB-track-Miata-Build.aspx

Also I think I got confused I remember reading something with using V8 roadster something besides the framerails.

I had a FCM setup on my old NA and I really appreciated how compliant it was. I would absolutely choose ease of driving and compliance over absolute limit handling. The Xida vs Fox comment was more about spring rates but it looks like you did do some higher ones for the V8 track car

I am honestly a big fan of fox in other platforms and would like to try them

Keith Tanner said:

Early Miatas (1990-93) used a fairly ineffective viscous LSD wrapped in a weak ring and pinion. Unsurprisingly, the 1994-05 rear is a popular bolt-in update.

 

Thanks for the reminder.

800/500 springs, no rear bar, biggest front bar you can find (Small Fortune Racing is the new go-to), 275/35-15 A7s on the lightest 15x11" wheels you can find.  A 4.3 torsen should hold you till you sort out the rest of the things that will crop up.  Extended front ball joints (bought mine from FM), rear upper control arms from PACO Motorsports.  Caster doesn't particularly matter, camber wants to be negative 3+ degrees.  In an ideal world Penske shocks but Koni race will do, I limped along on spec miata Bilsteins and still pulled 1.45G on concrete.

Jaynen said:

Sorry Keith this is me thinking about my 99 that will be a track car not really a street car

http://949racing.com/NB-track-Miata-Build.aspx

Also I think I got confused I remember reading something with using V8 roadster something besides the framerails.

I had a FCM setup on my old NA and I really appreciated how compliant it was. I would absolutely choose ease of driving and compliance over absolute limit handling. The Xida vs Fox comment was more about spring rates but it looks like you did do some higher ones for the V8 track car

I am honestly a big fan of fox in other platforms and would like to try them

My personal track car runs 750/500 Fox, and there's room for more spring rate if I ever feel that's necessary. I tend to let the car move around a bit more than some.

it doesn't seem logical to be discussing Xida and Fox suspensions for a car that is meant to be "Challenge legal" per the original post. 

Lof8 said:

it doesn't seem logical to be discussing Xida and Fox suspensions for a car that is meant to be "Challenge legal" per the original post. 

True, but "ultimate" and "challenge legal" are a bit at odds.