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Salanis
Salanis SuperDork
1/23/09 11:20 a.m.

So, I'm thinking I'd like to jump to some stiffer springs on the Miata. I'm thinking a threaded coilover sleeve and some 2.5" springs would give me lots of options.

Using the Ground Control kit as a guideline, they have different options based on which shock they are mounted on. What is the different to work with different shocks? I have KYB AGX shocks now, but say I want to switch to Koni Sports, or something else, down the line, would I not be able to use the same sleeves?

Keith
Keith SuperDork
1/23/09 11:39 a.m.

The difference is how the sleeve mounts to the shock. There's a bit of hardware inside that needs to change, and I believe GC can provide you with that.

Salanis
Salanis SuperDork
1/23/09 11:59 a.m.

Is it a difference in shock body diameter? Or just how they hold on at the bottom?

What if I go the cheap route and buy an inexpensive sleeve kit on E-Bay, and just source good springs?

mw
mw New Reader
1/23/09 12:07 p.m.

I'm not sure how the kyb's hold on, but on konis for a miata, the lower spring perch slides off and the GC kit mounts over a circlip that fits on the shock body. If the kyb's have removable spring perches, then shock body diameter would be the only concern. I think the ebay ones use set screws to hold them to the shock. This would work for either as long as you trust the set screws. I would guess that you might be better off getting your sleeves from fat cat motorsports since they specify that their sleeves will work with different shocks as long as you have the correct inside hardware. From what I've experienced, they are more willing to sell individual hardware bits than GC.

Keith
Keith SuperDork
1/23/09 1:58 p.m.

The KYB perches are removable, but only once and you get to use a hammer. The GC stuff works as long as you have the correct inside hardware. The sleeves are the same. We've had customers change them out.

Salanis
Salanis SuperDork
1/23/09 2:20 p.m.

Thanks. What kind of spring rates can the KYB AGX handle? I've got FM springs, and "6" seems to be the right number for those. What kind of rates can I run if I crank them up to "8"?

I'm frustrated that I got these shocks not that long ago and feel like I might be ready to graduate to something better already.

Keith
Keith SuperDork
1/23/09 4:26 p.m.

375 is about as much as they'll handle happily. They get harsh pretty fast.

Woody
Woody Dork
1/23/09 8:51 p.m.

What can the Koni Sports handle for spring rate?

Keith
Keith SuperDork
1/24/09 9:42 a.m.

They work best with stock springs in my experience :) I don't know how stiff you'd want to go with those on stock valving. I'm not saying you can't go stiffer, I'm saying I don't know. Generally, though, I like to use those on a mostly-stock suspension. It's how I fitted out my father's car, which has never seen an autox course.

Salanis
Salanis SuperDork
1/24/09 11:55 a.m.

What is your recommendation for damping higher springs rates, on a budget? Say 500#/350# or so? Since Spec Miata uses them, I'm guessing the Bilstein HD is okay with those rates.

Although, I think my spring rate is not the weak point in my suspension right now. I think I should replace the bushings first.

Keith
Keith SuperDork
1/24/09 12:56 p.m.

Specs are underdamped. Remember that Spec racers run that suspension because they're required to, not because they want to. And they have a 700 lb front spring.

For 500 lbs on a budget, I'd probably go with Tokico Illuminas. Normally I'd say they max out at 450 or so, but I've not tried them with 500s. The short spring they have to use with the Ground Control kit does limit options somewhat though.

Josh
Josh Reader
1/24/09 1:00 p.m.

I LOOOOOVE my Konis. I have the race valved in the front, sport valved in the rear. Figure $250 each for the fronts and $125 each for the rears. The koni spring perch adapters are very well made, and fit perfectly for WAY less money than GCs. I have 650f/375r rates, which may be a little extreme for the street but work great for autox. The race valved fronts can handle up to around 1000 and the sports in the rear up to 450 or so. Most of the top STS guys are around 700/400 or so (not that I am one, by any stretch).

I also highly recommend the Energy Suspension bushing kit for the money. Around $170 for the whole car, which, as you know, is something like $4 a bushing on a Miata :). I'm sure Delrin would perform slightly better, but would be a bigger pain on the street, and cost 4 times as much.

Basically I did the whole deal (konis, sleeves, used 2.25" race springs, bushings, NB style rear top mounts) for just about $1200. Phenomenal results for that price. This does not include the Racing Beat hollow front swaybar/brace that I assume you already have. If you don't , drop that $200 or so first :).

Salanis
Salanis SuperDork
1/24/09 3:13 p.m.
Josh wrote: I LOOOOOVE my Konis. I have the race valved in the front, sport valved in the rear. Figure $250 each for the fronts and $125 each for the rears. The koni spring perch adapters are very well made, and fit perfectly for WAY less money than GCs. I have 650f/375r rates, which may be a little extreme for the street but work great for autox. The race valved fronts can handle up to around 1000 and the sports in the rear up to 450 or so. Most of the top STS guys are around 700/400 or so (not that I am one, by any stretch). I also highly recommend the Energy Suspension bushing kit for the money. Around $170 for the whole car, which, as you know, is something like $4 a bushing on a Miata :). I'm sure Delrin would perform slightly better, but would be a bigger pain on the street, and cost 4 times as much.

Hmm... I'm actually running stock sways. I could certainly upgrade those, for cheap, for the performance gain.

You got the whole energy suspension kit for $170? I'm seeing the full kit running from $215~$300. There's a less expensive kit, that's just the control arm bushings, that's pretty cheap. Hmm... but if I'm going to upgrade my sways, I don't necessarily need those bushings. The control arm bushings are where I'll see the biggest gains.

Edit: I also want to say that the differential bushings are probably okay. The diff had recently been put together for Spec Miata usage, and probably got new bushings at the same time. But I didn't look too closely at them when I put it in. There is still the 2-5 shift issue. I'm pretty good at not grabbing 5th, but sometimes it takes an extra half a second to find 3.

Josh
Josh Reader
1/24/09 3:31 p.m.

I would think about leaving the rear sway stock unless you find looping your car at track days lots of fun. The front is really all you need. The hollow RB bar/brace combo is the way to go.

Brace Swaybar

These guys are the cheapest source I found for the full ES set, which includes the diff mounts.

Bushings

I did buy the full kit, but haven't installed the diff mounts yet (I have a VLSD to install, and decided to wait for the offseason. Better get on that soon...). The control arms are all you really need if you don't want the diff mounts and have aftermarket swaybars. But if you want the diff mounts, the full kit for $238 is a great deal.

Keith
Keith SuperDork
1/24/09 4:02 p.m.

It's funny, Miata sway bar setups that used to be described as "neutral" now get accused of massive oversteer. I'm not sure exactly where the change came from. I think it showed up about the same time it became popular to put NB mounts in an NA. Personally, I can't make a car handle with a stock rear bar unless I'm running a lot of rear spring. Someday I'll figure out what's different. Josh, what are your alignment numbers?

The swaybar brace is something you need if you're going to run a big fat front bar - say, over an inch. Another alternative is to fit the Mazda Competition mounts, as they're a better solution.

The diff bushing upgrade is useful even when compared to a brand new stock bushing. You'll find it cuts down on shifter movement quite a bit.

Josh
Josh Reader
1/24/09 4:34 p.m.
Keith wrote: It's funny, Miata sway bar setups that used to be described as "neutral" now get accused of massive oversteer. I'm not sure exactly where the change came from. I think it showed up about the same time it became popular to put NB mounts in an NA. Personally, I can't make a car handle with a stock rear bar unless I'm running a lot of rear spring.

It may have something to do with the massively stiffer overall spring rates that have become popular in the last few years. With stock rates, or even double that, stiffer F and R bars would probably work well. At the rates I'm running (~4x stock +), the bars aren't preventing roll as much as they are front toe change. Then again, when I first got mine I put the RB bar on with everything else stock, and I thought it was great by itself for such a cheap upgrade. As a recovering FWD driver, was an oversteering mess for my first couple events in the 100% stock Miata.

Hmm, I would think NB mounts with more travel would prevent snap oversteer, not contribute to it.

Keith wrote: Josh, what are your alignment numbers?

Alignment is a work in progress. At the end of the season I was at approximately 1/8" front toe out, 1/16" rear toe in, 1.75 degrees front camber, 2.0 degrees rear camber, ride heights about 12.25" front, 12.5" rear. Numbers are approximate since I had been tweaking rear ride height at events to fine tune rotation, I plan to get a new baseline with a proper corner weight for next season.

Keith wrote: The swaybar brace is something you need if you're going to run a big fat front bar - say, over an inch. Another alternative is to fit the Mazda Competition mounts, as they're a better solution.

A better solution structurally, but way illegal for some classes :). And much harder to install.

Woody
Woody Dork
1/24/09 8:10 p.m.
Keith wrote: The swaybar brace is something you need if you're going to run a big fat front bar - say, over an inch.

I have a used Racing Beat sway bar brace with hardware and instructions, if anyone is interested.

Salanis
Salanis SuperDork
1/24/09 8:56 p.m.

Josh,

Are you using those alignment specs for Auto-X or track duty? Or both? I'm going to need to realign the car after doing bushings and thinking of maybe changing my alignment settings.

A friend is also borrowing some good alignment tools for a couple of months, and this is my opportunity to experiment some.

Right now I've got 1.5 front and 2.0 rear with 0 front toe and 1/16" rear toe in.

I'm more interested in open track than auto-x.

Josh
Josh Reader
1/24/09 10:01 p.m.

I haven't tracked the miata yet (reluctant to install a rollbar), so those are autocross/street specs for me. It's about a 3/4 time daily driver for me in the summer. I would feel comfortable with the same alignment on the track though, it's pretty neutral and controllable. I should also note that I autocross primarily at one of the faster sites in the country, Fort Devens, where courses routinely see sustained top of second gear/occasional third gear speeds. The car is amazing in high speed sweepers. I will probably hit the track next year if I can afford it :).

Keith
Keith SuperDork
1/24/09 10:29 p.m.

The Spec guys run as much front camber as rear, from what I understand. Of course, they're also saddled with a non-optional spring set that is really stiff up front - about a 2:1 ratio whereas I prefer something more along the lines of 3:2.

I'm thinking the extra travel afforded by the NB mounts is starting to show some odd camber gain behavior in the suspension. Either that or one end is hitting the stops first. An NA Miata on stock bumpstops is basically running a rubber suspension (like a Mini!) in corners. Then again, my Targa car has as much travel as is physically possible in a Miata suspension and I end up running more rear spring and more rear bar than just about anyone. I haven't completely figured it out yet. I need to get my hands on one of these "oversteer" cars and see what's going on.

I've never met a Miata with snap oversteer, other than one with very very very cold tires on a wet track...yesterday.

It's true that as spring rates go up, sway bars have less of an effect. And autocrossers have often run setups that would be described as too understeery for road course work because of the nature of the sport - violent maneuvers with generally more power than traction.

I don't think the Mazda comp mounts are difficult to install. Remove two bolts, drill out a spot weld, install with four bolts. That's about it. Legality, well, that's someone else's problem.

Xceler8x
Xceler8x HalfDork
1/24/09 10:39 p.m.
Keith wrote: It's true that as spring rates go up, sway bars have less of an effect. And autocrossers have often run setups that would be described as too understeery for road course work because of the nature of the sport - violent maneuvers with generally more power than traction.

I have installed H&R race springs on my track Miata with stock sways. The springs rates, from H&R, are 280 lbs front and 250 rear. Body roll is non-existent even with stock sways.

This data comes from driving the car at VIR and Summit Point.

Keith
Keith SuperDork
1/24/09 11:48 p.m.

On the H&R race springs, you're probably not getting body roll because you're sitting on the bumpstops. They're a little low for their spring rates from what I recall.

Xceler8x
Xceler8x HalfDork
1/25/09 9:59 a.m.
Keith wrote: On the H&R race springs, you're probably not getting body roll because you're sitting on the bumpstops. They're a little low for their spring rates from what I recall.

That could be the case! The car those are on rides like a rock. Possibly because the right height is Low. What little suspension travel it had is now gone with slightly stiffer springs in an attempt to compensate.

njansenv
njansenv New Reader
1/25/09 12:16 p.m.

My experience with (most) RWD cars is that they suffer "oversteer problems" if owned by someone with only FWD experience. This isn't aimed at anyone, but an observation based on seeing many people with FWD experience (who are used to needing some more "ham handed" inputs) "graduating" to more balanced vehicles.

I could be totally wrong. :)

MCarp22
MCarp22 Reader
1/25/09 1:25 p.m.

I'm probably one of the FWD -> RWD = oversteer problems types. This corner for example:

Photobucket Video... probably.

The car was a stock '90 and while it wasn't spinning of into the weeds, it had just enough oversteer to scrub off speed in a way that i didn't care for. I'd imagine my current car, with it's much larger front swaybar, would probably have been more planted there.

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