Suspension and Shocks
By Miq Millman
|Last updated: 12 September, 1995
Suspension / shocks / upgrades:
Shocks control the cars bouncing. In the extreme cases they can also
effect how much the car moves in turns as well as in relation to how the
road travels. Generally it is not expected to have a shock so stiff that
it doubles in function as an anti-sway bar. The shock should be stiff
enough to keep the vehicle from oscillating after hitting a bump.
What is Jounce?
Jounce is when the shock is un-compressed (the secondand further time
after the initial compression). Many shocks out there (the stock Miata
shocks for example) do _not_ compensate for this, or even adjust it.
What is rebound?
This is the subsequent compression of the shock absorber and the only
movement that most simple shocks are capabile of controlling. It is an
easier mechanism to control, infact usually just putting a stiffer medium
in the compression chamber will suffice.
When are my shocks bad?
When your Miata's back end starts to bounce like a pogo-stick after going
over a speed bump or one side of the car starts to make a clanking noise
as the suspension travels through its range until it hits the bump stops.
This is generally a good time to replace the shocks.
If you decide that some racing application venue is your cup of tea, then
no matter the condition of the stock setup, you will want to replace them.
Adjustable shocks allow you to change the stiffness of the shock to suit
various needs. If you don't care that the dime you just drove over is
heads or tails, let alone the make up of the dropped pocket change in the
street, than likely you can get away with some racer's old stock setup.
Likely you will find slightly used stock components with less than 1000
miles on them. However, taking a Miata to 8/10's or more of its
mechanical capabilities it not the place where you test out the structural
regidity and constitution of the door panels as they scrape on the ground
in that tight sweeper turn.
GAB vs. Koni vs. Tokiko
These are the tree major suppliers of shocks for the Miata. They all have
their benefits and limitaions.
GAB is the only manufacturer to make a shock that adjusts for both rebound
and jounce. As well, their 8 way adjustables have a range that is just a
tad stiffer than stock to making you wonder if the shocks are actually
moving at all and aren't just red chucks of aluminum stuffed into the
cavity. The adjustment can be done while the car is sitting in a parking
lot with no tools at all, the knobs are just infront of the lower pickup
points. The major limitations of GAB are two fold, their price (close to
$600+ retail) and the lack of availability. (only available though a
company called Wingz in the Bay Area (510) California)
Koni is the widest accecpted choice for the serious auto crosser, they
have the benefit of having adjustable spring perches, which in a
non-competitive modus are a boon since you can change the ride height.
Unfortunantly in the Solo II world, the perches are just a tad off so you
end up with a car that rides about 1/3 to 3/4" higher than before.
Adjustment isn't as easily done as the GAB, the shocks have to accessed
from the top, which is a bit of a reach for the rears.
Tokiko is gaining popularity, probably because they weren't available the
first three years of Miata production. They price similar to the Koni's
at about $440 for a set, and are also adjustable from the tops of the
shock. There have been models of Tokiko in the past that had the
adjustment wrench break off. Likely this is no longer a real concern.
The 5 way adjustments are all stiffer than the stock setting. As an added
bonus, the Tokiko setup seems to drop the ride height about 1/4".
"R" package Bilsteins
These are non adjustable, stiffer than stock, and seem to be just ok as a
performance shock. Hot shoes are replacing them with Koni's in the Solo
II autocross world.
Or What's missing from my Miata?
In 1992 Mazda added a "track bar" that tied in the inner points of the
rear suspension. This can easily be retrofitted to the earlier cars.
Supposedly it reduces a shimmey effect felt at 65 mph. Putting this item
will slightly reduce the options your Miata might have for cat-back
With the 1994 model change, a number of chassis braces were added to
stiffen up the beloved ragtop. It was rumored that most if not all of
these items were originally taken off the earlier cars to cut costs. The
side brace between the seatbelt mounts is the least noticed change that
was made. It was added to improve side impact resistance and not make the
vehicle feel tauter.
The other suspension braces in 1994+ models tied the outer points of the
lower suspension and are duplicated buy a couple of manufacturers.
Notable in their infamy, Wiz Performance braces require a new four wheel
alignment becuase they tie into the bolts used for alignment; Racing Beat,
makers of the best braces are difficult to reach at times and
occaisionally are out of stock.
What extras can I add?
Shock tower braces are open to debate for being useful. It is my
humble opionion that the stiffer your suspension is, the more you will
see gained from this brace. Oh, and it does look nifty spaning across
the engine compartment.
A plug for rollbars
If you can handle the limited use of the rear window and the horrors of
taking a dremel to the sheet metal in your Miata, a four point rollbar
will do wonders to the stiffness and responsiveness. As well the piece
of mind offereed by knowing that should bad things happen, you are
To cut or not to cut, that is the question.
Cutting the springs is an old trick. It changes the geometry of the
spring stiffening up the constant K, and at the same time shortens the
overall length. There is no tried and true rhyme or reason to the
correlation between how much you lop off and the results. Thus it's
generally considered lucky if you get a good result. (i.e. try it if you
must, but if you mess up the springs, I don't know you, I never told you
to do this, don't come after me for the price of new stock springs)
Stiffer does not == lower.
The best performance spring would have a "progressive" stiffness. That
means that as the spring gets further compressed, the constant K (amount
of springiness) gets higher. Thus you can very easily get a stiffer, more
responsive spring on your Miata and not lower the car.
As well, you can get a spring that lowers the car and is very mushy and
From the performance aspect, you want to lower the car as much as feasible
because lowering the entire body lowers the center of mass, which in turn
lets the car take turns much better, and much faster. Bear in mind that
the Miata is already a low clearance vehicle, so you probably don't want
to go much farther than 1" or so.
For what its worth, my car is lowered 1 1/4" in the rear, 3/4" in the front.
It makes the car sit very level, canceling out the tail high look that
stock Miata's sometimes have.
SoloII CS recommendations
Just about everyone that does well in Solo II CS has the large (15/16")
front bar from Rod Millen or its resellers.
When is too much too much? (adjustable endlinks)
Stiffening up the front too much can cause the outside rear end to lift.
Since the Miata has the power going to the rear wheels, this makes for
nifty wheelspin. Wheelspin may look cool at the stop light drags, but it
makes for a slow transition. In addition to wheelspin, too much front bar
will make the car understeer (as you take that turn too fast the front end
smacks into the outside barrier first, as opposed to oversteer where the
rear end smacks into the outside barrier first).
The counter for too much front bar is to add a rear bar as well to get it
really really stiff. (Oversteer plus understeer equals neutral handling??)
Bushing material is pretty simple. You have stock mushy rubber. You have
slightly harder squeeky urethane. You have custom made super stiff
bushings made out of Delrin or aluminum.
The stiffer the bushing, the better the job your suspension bars will be
able to do. The stiffer the bushing the more harder the job your
suspension bars will be able to do. No I didn't just repeat myself. If
the bars do a better job that's great. If they work harder, then that
means more wear and tear on the the car. That's no so great.
As is most things in life, your car's suspension is a series of trade
offs. Decide what you want to do, then make the choices offered.
The total suspension package.
My suggestions to make a not necessarily CS legal, well handling Miata:
GAB shocks (the adjustability and Jouce control give these a long life)
Eibach springs (lowers car 1") not legal for CS Solo II
Racing Beat Adjustable anti-sway bars (set to middle hole in rear, front
hole in front) (rear not legal for CS Solo II)
Racing Beat lower suspension braces (not legal in CS Solo II)
A good agressive alignment (see Tip #3)
Sticky rubber on stock rims (Dunlop SP8000 in 195/55/14 is current fave)
Do all the above, you can easily see 1.1 lateral G's on a skip pad.
Miq Millman firstname.lastname@example.org 503 642 6139 (Aloha site)
AL4-55 Intel, 5200 NE Elam Young Parkway, Hillsboro, OR 97124-6497
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