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Index of Pages: 1-Introduction , 2-Tires & Wheels , 3-Suspension , 4-Alignment , 5-Performance , 6-Exterior , 7-Interior , 8-Autocross & Track , 9-Adventures & Trips , 10-Paint Protection , 11-Maintenance , 12-Safety .
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SUSPENSION
Equipment: KYB AGX 8-way shocks on stock springs, Flyin' Miata anti-sway bars, Flyin' Miata front STB, Beatrush rear STB, Polybush touring/comfort Bushings; ~13.5" ride height all around (with driver in car).
BUILDING THE SUSPENSION -- One Step at a Time:
In sequence of which changes I made first, the following are the combinations I've tried on my search for that Holy Grail of comfort and better-than-stock handling.
Note -- When I began researching options in 2000, the original concensus for somewhat better handling and great ride quality was: adjustable shocks over stock springs, with slightly stiffer anti-sway bars.
Original : Stock springs, stock shocks, stock anti-sway bars. A bit floaty for my tastes. Smooth and comfortable. Bottoms out at the rear frequently, particularly when anything is put into the trunk.
KYB AGX 8-way adjustable shocks: Nice improvement in control. Much more solid at speed. Similar body sway given the stock springs and stock sways.
Flyin' Miata front STB: Small improvement in chassis twist over uneven surfaces. More-stable in cornering and transitions. A bit less cowl shake over rougher roads.
Beatrush rear STB: Fairly noticeable improvement in how the rear end feels 'planted' to the ground in hard cornering. Much better gains than I thought it would be. More-stable on uneven surfaces. More-capable at autox. More stability at high-speed track events. Twice as much benefit as the front STB. I was amazed.
Apex 'yellow' lowering springs: Nearly undriveable, scraped on everything, high-centered on a very small speed bump. Ride height was under 12in hub-to-lip. Very springy, bouncy ride quality with KYB's at 1-4. A dentist's dream between 4-8.
Ground Control coilover kit: GC over KYB AGX shocks, with bump stops cut: Extremely good control as compared to the stock springs. Bump in handling prowess, better in transitions. Able to handle much higher cornering loads. On smoother roads, ride quality often seemed better than stock. On rougher roads, it occasionally got fairly rough. Occasionally still bottom out on the rear unless KYB's set at 4-5+.
Ride-height variations: At 13.0" hub-to-lip, ride quality suffered and bottoming out was frequent. At 13.4", dramatic increase in ride quality and only minor reduction in cornering abilities. At 13.6" (preferred), this seemed to be the best combination, for me. Tremendous differences in ride quality, between the different heights.
Flyin' Miata sway bars added back to the above setup: Very well-anchored to the road in esses and mountain driving. Good manners in all situations except rougher roads. Noticeably stiffer than any of the above combinations, but at such a boost in handling feel. Strong overall grip. Can't imagine keeping both the stiffer sway bars and the coilovers, given the road quality; must choose one or the other.
Removed sway bars completely: The day before an autox session, the rear sway bar mount broke. Removed both bars. Achieved such a level of grip on the autox course I was astounded. But, this autox course is fairly broken and uneven. On the road, much better ride quality on city streets, though much more floating at speed and wallowing around through hard sweepers and corners.
Stock sway bars added back: Good compromise, with most of the floaty behavior erased. Still, with steadily worsening road surfaces, ride quality continues to deteriorate.
Removed the GC coilover kit: Went back to stock springs with the KYB AGX shocks and stock sways. Much, much better ride quality on rougher roads, though somewhat floaty for my tastes. Hard to have everything. Many folks have asked me why I did this ... 'cause, isn't "stiffer always better"? Well, no. Depends completely on the intended usage, road quality, driving style and how hard the car is pushed. My rationale: one , two , three . Hard decision to make, but worth it, IMO.
FM sways added back: Wanted to erase much of the floaty behavior. Overall, the body sway is nearly that of the GC/FM combination, though with much more dive and squat by comparison. I can live with this. Better-behaved through transitions; better control through harder cornering; better feel upon setting up a corner, and upon hard acceleration out of one.
Results So Far: With stock springs, adjustable shocks, slightly-stiffer anti-sway bars and various bracing, what I've got now is, for me, the best compromise to retain ride quality on all but the nastiest and broken roads, yet with enough control to support spirited driving and the occasional autox/track day. A bit more body sway than with the GC coilovers, but then my driving skills are at the point [from autox and track schools] where I can compensate and get nearly the same cornering grip and performance as with any of the above combinations. Tightened the 'nut' behind the wheel, so to speak.
Best thing is: This combination can work perfectly as a daily-driven vehicle, and yet still handle whatever track and autox work is tossed at it (for a weekender). Of course, hard track work can overpower this suspension. In that case, I'd surely go back to a stiffer coilover setup. But, on a dual-use, daily-driven car, this combination is, for me, hard to beat.
Shock Installation Tips -- This instruction page is a good resource for all of the steps needed for installing a set of Miata shocks.
Shock Settings -- KYB AGX 8-way
According to KYB, the shock's 8 settings are as follows:
* #2 is equal to factory
* #1 is slightly softer
* #4 is approx 15% firmer than #2
* #6 is approx 50% firmer than #4
* #8 is approx 30% firmer than #6
* 3/5/7 are in between the others
This is for the 8-way shock. Apparently, the 4-way shock suitable for 1999+ cars uses the 2/4/6/8 settings.
For daily driving, I find that 2F/2R or perhaps as firm as 2F/3R is suitable. Very good ride quality, yet sufficiently capable with the other suspension improvements to handle a reasonably spirited drive. If needing a bit more grip in the rear, I might drop the rear setting down a notch.
For mountain runs or special 'twisty' sessions with friends, I like to crank up the shocks to 4F/5R or 5F/5R. Noticeable boost in handling ability.
For autocross on a smooth surface, something between 5F/4R and 6F/7R seems to work well. On broken surfaces, same as for mountain runs. Obviously, it depends on the surface and the intended use. Generally speaking, softer = more grip, firmer = more resistance to undulations but possibly at the expense of less grip.
The KYB AGX is a remarkably flexible shock. Overall, I highly recommend it. Cushy as needed, capable enough for racing, easy to adjust. Not as smooth as Konis. Not quite as capable as a tuned Bilstein. But, overall, it's a decent adjustable shock that works well for a mixed street/autocross car. YMMV.
In comparison, I have also used Bilstein HD's on a previous car (1992 Honda Accord EX sedan). Loved the control but disliked the stiffness, as it seemed valved for a car that was 500 lbs heavier than the Honda. Have not had Bilsteins on the Miata.
Compression & Rebound -- Shock Differences
There are many differences between various shocks and the valving used to tune them to a specific car and its intended use. All I can say is this: I wish I had known about this great discussion on the Vortex forums regarding shock valving and damping characteristics, when I chose to dive into the suspension tweaking game. Great read, there.
Spring Stiffness -- Tuning for grip by adjusting the spring rates on Springs, Anti-Sway Bars.
There are many good discussions on Miata.net about the relative benefits of anti-sway bars. Some folks love them. Some hate them. No doubt, they can alter the behavior of the car and help in fine-tuning that famous balance the Miata is known for. Such as this one: Best-Gripping Sway Bar Setup
Overall spring stiffness is also an area where you can easily foul up the Miata's balance, or end up with an ox cart you're embarrassed to drive because the only one smiling is your dentist.
Picking Spring Rate, Sway Bars, Roll Stiffness, etc. This is a good overview of where the limits lay, with the Miata's suspension. Can there be too much of a good thing (stiffness)? Absolutely. Finding the balance is the key.
Suspension Bushings -- Polybush touring/comfort "blue"
Available by direct order from Polybush. The comfort/touring set is not a generally-stocked item. They quoted me a price and then shot a new run of the bushings. Purchased all 22 bushings in a complete set, nicely labeled. Cost a small fortune, but I think it was worth it.
Tightened everything up again, removing all of the slop that had developed with 80Kmi hard mountain driving. Exceptional upgrade while only minor hint of being stiffer than stock. More to the point -- it is definitely a more-capable suspension, now, able to handle what is thrown at it. Ride quality is often better than stock. No squeaks (installed with liquid soap, no grease, per the mfr's recommendation).
Got a loose suspension? Things not as solid and predictable as when new? Replacing the ball joints and stock rubber bushings with the comfort/blue polyurethane bushing set from Polybush made a world of difference. I did poly upgrades on two prior Hondas and knew the risks of going too stiff. For a daily-driven 96M, I did not want to go there.
Goals -- To get back to near-new ride quality, eliminate the float/play that had developed over time, provide longevity and handling gains beyond stock rubber bushings.
Mission accomplished. Polybush had to make a special run to make my set, as they don't typically stock this anymore. Great customer service. Answered all my questions in advance. Appreciated my hesitance to build a rattle-trap Miata that would raise my dental insurance premiums.
Big difference! All the play is gone, yet the ride quality is only a tad stiffer. Seemingly softer on straight-line and long sweepers; a bit stiffer in hard cornering. But, 'stiff' is not what comes to mind with the change, really. More-responsive, better road feel, with a tad more road noise sent to the driver. Overall, a great balance. On all but the roughest pavement, ride quality is often much better. It's certainly more capable, better able to deal with what comes. On the track, it's an amazing difference. I can now even feel the tread squirm on my street tires, whereas before it was buried in the general movement of the suspension. Strongly recommended.
Install Effort: Budget an entire weekend with a friend, get a couple extra dust boots for the ball joints, get pickle forks and air tools, get a good bushing press, and have a supply of Curad/Bactine on hand. For a newbie + assistant, this took 9hrs one day, plus 4.5hrs the next evening, then 4hrs the third evening (~35hrs w/two people); could likely do under 20hrs the second time around, or even < 15hrs if done with air tools on a lift. Not difficult; just a lot of work.
ROLL BAR -- Hard Dog M2 Sport DD
Some of the photos show earlier images with the twin-hoop style bar; now, it has a full (HDM2SDD) roll bar.
This nicely firmed up the handling of the car. Particularly over rougher sections of pavement, the suspension is working harder and the body less. Fewer creaks and shakes, better feel on the road, a bit more planted to the road. Tip: installing altered the suspension alignment somewhat, so realignment was necesary.
Brakes -- Rotors, Pads, Lines
April 2003 -- Slotted Brembo rotors, Axxis Ultimate pads, Goodridge braided steel lines. After 'bedding' the pads with 10 hard stops from 60-10mph then 2 hard stops from 80-10, the car sat (brakes off) overnight to cool. Being a newbie, this took me awhile to install. IMO, if you want a job done right, do it yourself and take your time.
May 2003 Update -- The brakes just keep getting better. Stronger braking power than the first two weeks, excellent first-brake strength, great pedal feel, no squeal/noises. Zero problems with water on the rotors/pads. Only downside is an abhorrent amount of dusting, but that can be cured with regular cleaning. (Glad I prepped and waxed the wheels before installation.) All in all, I love it.
July 2004 Update -- The brake performance is now decreasing, since the pads are nearing the end of the useful life. Got new pads coming, and caliper rebuild kits. Back to OEM pads, for me. While I enjoy the gain in performance, I'm no longer doing track/autox so regularly and probably don't need the boost. Plus, I'll not lament moving away from the tremendous dusting that the Axxis Ultimate pads have. Great, reliable performance; terrible dusting.
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Index of Pages: 1-Introduction , 2-Tires & Wheels , 3-Suspension , 4-Alignment , 5-Performance , 6-Exterior , 7-Interior , 8-Autocross & Track , 9-Adventures & Trips , 10-Paint Protection , 11-Maintenance , 12-Safety .
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