Budget NA Miata autocross suspension?

I'm really frustrated attempting to autocross my '96 Miata. I do really like the car, but I find autocrossing it an exercise in frustration as it seems inconsistent in what it's going to do from one corner to the next.

A couple of reference points:

1.) I've been racing the car for almost 6-years, starting on the original stock suspension, upgrading to KYB AGX shocks on stock springs with an FM front bar, then installing Racing Beat springs(207lb/in front, 145lb/in rear, IIRC) and a Racing Beat rear swaybar. Alignment is pretty mild at ~ -1* camber front/rear, and 0-toe front/rear.

2.) I've used several different tires over the year, none have significantly affected the inconsistency issues. I do have a set of Rival's on 15"x9" wheels on order.

3.) While I'm no pro driver, and there's always room to tighten up the nut behind the wheel, I've been doing this since '98 - with the same club, on the same site, and against many of the same drivers(usually matching/beating them in their own cars), so I really feel it's more than just taking time to learn the car. I'm pretty sure it's time to work on a decent setup.

4.) We run on ~60-year old USAF concrete, so it's a bit bumpy in spots.

I'm looking for budget conscious(sub $1k) suspension options focused around autocross performance. While I'd love to have a set of Afco's or FCM's, it just ain't happenin'. It seems like my options below are limited to single-adjustable(which I'm OK with):

V-Maxx XXTreme setup from Flyin' Miata(504lb/in F, 336lb/in R, 0.67 R/F) $895 + shipping.

K-Sport Kontrol setup(487lb/in F, 335lb/in R, 0.69 R/F) $923 shipped

Megan Racing Street Series(560lb/in F, 448lb/in R, 0.80 R/F) $855 shipped

D2 Racing RS(504lb/in F, 336lb/in R, 0.67 R/F) $942 shipped

What I've been reading on the interwebz seems to point toward 0.63-0.67 rear/front spring rates, so the Megan setup would need a new pair of springs to be in that range. All of these setups seem to get OK ratings, there are people who put them down(sometimes by default, I feel), yet there are others who have been very happy with them in competition.

Can any of you provide input/insight to help me decide?

I have the VMaxx classic on my track rat Miata with the FM bars and poly bushings throughout.

I'm happy with the price/performance ratio, although I wish I had gone ahead and gotten the Track Pack ones when they came out because of the stiffer rates.

What are your goals for the car? Street tire - the 9" rims set you out of STS into STR where the car might not be in the hunt....

anyway, one line sticks out - "seems inconsistent in what it's going to do from one corner to the next." that sort of hints at something loose or worn out like bushings, wheel bearings, brake discs, bump stops. The car ought to handle predictably right out of the box, if it doesn't then shocks/springs might not help. My stock miata with hoosiers is constantly bouncing on the bump stops, making the car a handfull, but not unpredictable. If that's the problem then stiffer springs/shocks will help.

You've probably already done this, but it's worth getting the car on jackstands and shaking/wiggling/inspecting everything to find worn or broken parts. Set a good baseline and work from there.

IMO For $1K, you could get a 80% of the way to the common STS/STR setups...

Get the V-Maxx coilovers Remove/Sell the rear bar Dial in 2-2.5 degrees of camber all the way around

Then get a bigger front bar and/or bump the front spring rate up

How low is the car? Why is it unpredictable? The STR Miata I co-drive was a little "snappy" until we removed the stock rear bar. Then it stuck real well, but was a little unpredictable on bumpy surfaces. Raising it about 1/2" all the way around got it off the bumpstops and made it much smoother.

FWIW, that setup, which is very similar to most full-prep STS/STR setups for NA/NBs was approx: 650 Front, 350 or 400 rear, no rear bar, bigass RB front bar, ~2.5deg camber all the way around.

I'm never really sure when the back of the car is going to break loose, though it seems worse when turning left. Also the transition from understeer to oversteer is almost violent, and difficult to predict/correct.

I've been under the car numerous time through the years looking specifically for anything bent/loose and never found anything. It certainly could be a bumpstop issue, given that I'm on the stock NA top hats in the rear, but I've not heard good things about either the Racing Beat springs or the AGX shocks(which I believe might be why FM stopped selling them?) so I think they're probably aggravating the problem.

I've don't have a measurement for ride height. Since the current setup isn't adjustable I haven't really worried about it.

I'm running the FM 1" front swaybar - is that large enough?

And yes - 80% of the way to the top STR setups would be fine, as you're correct the car isn't the right car for the class. But I feel I should be able to place mid-pack pretty consistently against our local/regional competition if I can get the car setup better.

1" FM front bar should be plenty for now. Leave messing with that for last.

I forgot that you are on springs, not a coilover setup - I doubt the car is sitting on the bumpstops.

If I were you, I'd try disconnect that rear bar. I bet the difference will be night and day - although with such soft springs the roll will be much more noticeable. Then if you want to be more competitive, upgrade to that V-Maxx (or similar) setup with higher spring rates, and get yourself some more camber.

I have no Miata experience, but for inconsistency on track, I would start with a good look at all the rubber parts in the suspension. Take this comment for what it's worth.

Keith should be there shortly.

petegossett wrote: I'm never really sure when the back of the car is going to break loose, though it seems worse when turning left. Also the transition from understeer to oversteer is almost violent, and difficult to predict/correct.

I don't think upgrading to fancy coilovers is the answer. First, look to anything broken. Then, replace bushings. They will do more to get your suspension working the way it's supposed to.

It does sound like you are bottoming out the rear suspension on the uneven pavement. Your springs are probably too low and too soft (145# rear is soft). If your shocks are fine, I would upgrade to a set of new FM springs and get their rear shock mounts to increase suspension travel. That plus poly bushings will cost a lot less than those fancy coilover setups you're talking.

I would also move to a smaller rear sway bar (maybe back to stock, or just the absolute softest setting on what you have) and dial in a bit more camber. Something like -1.2 front / -1.5 rear. If you want more stability, go -1.7 rear.

If nothing is loose/broken, then I would agree that the broken surface you run on is causing you to hit the bump-stops. Plus, as mentioned above, that's a pretty low spring rate. And, KYB's kinda suck.

I have a set of FM rear top mounts for the AGX sitting around somewhere that I won't be using, if you're interested in seeing if they'll help.

Will

From your description and the parts list, I think you're whacking into those rear bumpstops and your rear spring rate is spiking. The low ride height and soft rates of the RB springs are going to make this more likely, and if you're running unmodified stock bumpstops I suspect you're on them pretty much 100% of the time.

Borrowing Will's rear mounts would be an interesting thing to try. I suspect it will help and it's a pretty low-risk experiment. Upping the overall roll stiffness might keep the car off the stops and decrease oversteer. I know the FM front bar is adjustable and I'm pretty sure the RB rear is - do you have them on the stiffer settings?

As for the original list of parts, the V-Maxx would be my choice But I would say that. I am in the enviable position of being able to do something about it if I don't think the FM bits aren't competitive.

In reply to grafmiata:

I really appreciate your offer Will! But I've vowed never to disassemble these struts/springs, as assembly felt like a near-death experience.

You see, my standard coil spring compressors were simply too large for the tiny Miata springs - by the time I had the coils compressed enough to get the top hat on, the compressor was permanently wedge between the coils. The only way I could get everything together was by building a "hey y'all, watch this" device using the rear triangle of a cheap MTB hinged off my workbench and a piece of pipe for leverage. Unfortunately tightening the top nut on required my face to be directly in the line of fire. Yeah, probably not the smartest thing I've done, but I did survive.

In reply to Keith Tanner:

Keith, how are the spring rates on the V-Maxx for bumpy surfaces? I've seen people list rates all the way up to 700lb/in for Miatas, and I think that would probably cause me to skip around the course like a kart. Obviously the Racing Beats aren't strong enough for the job either though. Is 504/336 too much, or maybe not enough?

In reply to petegossett:

Damn... I was hoping that they would have helped "just enough" to convince you that you also needed the Ground-Control kit for the AGX that I also have sitting on the shelf.

But ultimately, the KYB's really don't handle higher spring rates well, so it's a pretty crappy setup.

Definitely not worth risking severe facial damage!!!

petegossett wrote: In reply to Keith Tanner: Keith, how are the spring rates on the V-Maxx for bumpy surfaces? I've seen people list rates all the way up to 700lb/in for Miatas, and I think that would probably cause me to skip around the course like a kart. Obviously the Racing Beats aren't strong enough for the job either though. Is 504/336 too much, or maybe not enough?

Depends on how bumpy we're talking. I ran the Targa this year with 550/400 lb springs, and that car will suck up just about everything.

The V-Maxx aren't quite as well damped as the AFCOs (as you'd expect given the price difference) but they do pretty well. They will push around a flexible chassis, though. If I was running the Targa on a set of V-Maxxes, I'd have the softer spring set - which is what the two cars that have run the race on V-Maxxes used.

A second spring set for the V-Maxxes costs $130, so you could always just pick up both the Sport and Track Pack springs and see which ones you like.

Thanks Keith! I do have a Hard Dog Hard Core bar, and that made a huge improvement in rigidity. The club/course designers do a good job avoiding the worst parts of the lot, but it's certainly not smooth-as-glass asphalt either. At least we don't have speedbumps like the Targa.

If your current set-up is:
- KYB AGX shocks under Racing Beat springs (207lb/in front, 145lb/in rear)
- FM front bar, Racing Beat rear swaybar
- Alignment roughly -1* camber front/rear, and 0-toe front/rear

The cheapest, easiest thing would be to look online for springs with rates high enough to keep off the bump stops (min. 300/200). For a bit more dough, pair them with some microcell bump stops (aftermarket, or look online for comparable Civic/Integra OE part numbers). These alone may net you the consist feel you're looking for.

The really really budget thing to do in the meantime is switch back to stock springs. Your rates may be softer than the RB's (not by much, I think the RB are only 10-20% stiffer), but you'll have enough ride height to stay off the stops, and should be doing pretty well with decent shocks and some good sways.

Why not just buy some koni's and ground control sleeves? You can ask for whatever spring rates you want. And if you ever want to step up your game further down the road, you can revalve the Konis.

In reply to wrongwheeldrive:

when you say that do you mean these sleeves: http://www.ground-control-store.com/products/description.php/II=43/CA=23

and these shocks: http://www.gomiata.com/konadshocab8.html

so.. 429+(159*4)= $1,065

or he could just save 20 bicks and get a the complete track package from flyin' miata: http://www.flyinmiata.com/index.php?deptid=5635&parentid=0&stocknumber=13-16750%20%201990-93%20NB

or.. am I missing something?

I'd say your alignment would make the biggest difference.

I ran -2.3F -2.0R and 0-toe on my 96. I was also running basic VMAXX's with NB tophats, a solid FM from sway and stock rear sway. Tires were 195 Toyo R1Rs on 15x7 rims.

I went from being frustrated (but sill competitive) with stock(ish) alignment settings to setting faster raw times than one of our most experienced autocrossers in an Elise after the alignment.

That's reassuring to hear Dave!

Based on other's comments, I think I'm bottoming out in the rear also, so before I go for an alignment I might as well get the parts swapping done first.

In reply to SCARRMRCC:

Koni's mean lifetime warranty, and you can revalve them to be even faster when budget allows for it. Bang for your buck, you probably aren't going to beat that

I've never seen vmaxx coilovers on a sts/str miata running towards the front of the pack. The rear bar in the "track pack" is unnecesary on a miata anyways, and I'd say a hollow front bar is preferable for weight savings, too. All just my opinion though.

In reply to wrongwheeldrive:

Thanks. My miata cam WITH koni yellows, and I was just making sure it is logical for me to stick with with them, and just get some nicer springs.

Im sure even keith will agree that the koni and whatever springs are leagues ahead of vmaxx. But that said you could save money with ebay perches over ground control. Ive got revalved bilsteins with some brand perches and 700/325 eibach springs fm front bar and no rear it rides fine (on really crappy mississippi roads) and handles great and only hits bump stops good when theres 200lbs of battery in the trunk like now haha. I do have nb top hats but I believe keith said they dont do anything, im am looking at a set of isc top hats for the rear though. Sorry for the ramble but I though it might be pertinent to your situation

I wouldn't agree, no.