The MX-5 is Imperfect and Needs Some Modifications! by BestCS

By diyauto
( 1 )

10 minute read

The MX-5 is Imperfect and Needs Some Modifications! 

Compliments of BestCS @


The MX-5 is Imperfect and Needs Some Modifications!

Of course, you know that I love all of you, so I write this piece in order to aid you in your search for happiness (and world peace too!). Also note that I have tried all of my great tips. Anything that I haven't I'll point out. I'll also suggest some ideas from reading posts.

The absolute very best modification will only cost you $5. Go to Lowes and pick up a can of high temperature BBQ paint and paint that muffler! You can do it on the car, but you'll get a better job removing it. It's only two bolts and some mojo and it's off.

The next mod is free and it involves doing nothing. Don't replace the stock tips on the muffler with those 3" chrome cans. What I'm saying is leave the stock tips alone. Dual pipes on a 4-cylinder car is ridiculous, and it screams, "I wish I had bought a V8!" Bringing attention to the tips just increases the volume of the lament. BTW, the stock muffler turns out to be a very good one. It's quiet, and it doesn't have any drone. The best characterization is it has a kind of sewing machine quality or sound about it.

The NC has the worst suspension I have ever encountered on a "sports" car. Anyone who thinks it's OK has never owned a real sports car. The problem isn't the front but the rear. When I first started driving the car, I couldn't believe the crashing sound from the rear going over bumps. I looked underneath to see if it had springs! Well it did, and I had to learn to slow down for bumps in the road something I had never done before! What was happening was the car was bottoming out hitting the bump stops.

What I did next was really stupid. I installed the Eibach Pro-Kit Springs that made the situation worse! Now the car was banging around in the rear running over pebbles! Also I didn't like the amount the car was lowered. It looked kind of cartoonish. I believe the right thing to have done at this point would have been to replace the shocks. I had on order a set of Tokico Red which are adjustable (more later). Another idea would have been to order a set of Konis since they too are adjustable plus lower the car a bit (0.5"->0.75"). If you do replace the shocks, get adjustable ones. The reason is more than just being able to adjust the damping. Shocks wear and the adjustments can compensate for it increasing their lifetime. One technical note at this point - the shocks only damp the springs which might have helped with the bouncy motion of the body. I'm not sure exactly what the outcome of replacing the shocks would have been without doing it myself.

I want to point out that I'm talking about improving the handling, look, and ride comfort on my STREET RIDE. After a good deal of reading and research at the forum and the various vendors, I discovered the stock spring rates (Sports Pkg) were adequate, and the problem was the damping of the Bilsteins. I still wanted a lowered look, but with one exception, the available springs lower the car too much and may be too stiff. The one exception is the RB springs which lower the car about 0.5" and increases the spring rate by 25%. However, these aren't recommend for the PRHT. If coupled with the Konis, the car will be lowered an additional 0.5"-> 0.75" which might be too low. As the NC gets older, vendors might start offering a better selection of them? So at this point, I'm experimenting with the RB springs. A full report will be out soon!

Besides the Konis or Tokico Reds (in combination with various spring), you might consider a set of coilovers, but I don't recommend them. They're an extreme and unnecessay solution to a problem that can be solved much cheaper. However, I installed a set just to experiment due to TR offering a set of Eibach Multipro R1 Coilovers (same as MS?) for a grand. Hence, I cancelled the Reds. Incidentally when you go to adjust them, try setting the adjustment in the middle between soft and hard. Then head towards soft or hard depending on your tastes or derriere. Note - from fender lip to ground F/R 25.5"/25.875" (my stock ride height with 215/45/17 is 27"). You may have a problem with coilovers due to stiffness (high spring and damping rates). On a track, this may be fine, but for normal driving, they may not soak up the bumps and pot holes giving a hasher ride compared to a standard suspension. Another problem is the minimum drop may be too much. I went full soft on the Eibachs, and the ride was well controlled and comfortable. The handling difference compared to stock was like night and day. The car cornered flatly and the stock sways were fine. Unfortunately, the left front coilover failed (dropped the car too much), and they went back to Eibach. BTW, don't torque the critical bolts unless the full weight of the car is on the wheels and after the ride height is adjusted.

Also, if you can't do your own mechanical work, don't modify your car. The main reason is labor is just too expensive. Also a true scientist would investigate each mod thoroughly to see exactly what effect it had on the car's performance. This means doing one at a time. Of course, the piecemeal approach is more time consuming but may save you money in the long run, i.e., you may reach a point where you are entirely happy (well probably not)?

Now returning to the mufflers, I got lucky and picked up an unused RS Race for a very nice price. I also got a Greddy Ti-C muffler too:

It is very similar to the Race except it has that fart can look that the teenage devotees of Hondas love. Both have an insert to reduce noise. The RS with insert is significantly louder than the Greddy. Greddy says less than 94 DB (insert removed), however, the sound or tone is what's important. The Greddy with insert has a rich deep masculine sound, and when you stick your foot in it, a pleasant purr while the RS has a lot more attitude. The RS will be an excellent way to punish your neighbors around midnite while they won't even notice the Greddy. The RS has a kind of raw raspy sound. It doesn't have the warm friendly of tone the Greddy. The Greddy doesn't have any drone, but the RS has a lot of it. I think what makes the difference between the two is the size of the cannisters. Also the Greddy is JDM (and more expensive), so it tailored to the tastes of the home country of the MX-5. Anyway, I've always found outstanding quality in JDM products. BTW, I got the Ti-C here:

Now, we come to the subject of wheels. My advice is don't get too extreme with things like weight, offset, tire section width, or rim size. I don't believe unsprung weight is a big factor on a street ride, but it makes sense to keep tire-wheel weight close to stock, 38#s. With too much offset (affecting scrub radius) and a wide section width (changing shape of contact patch), the steering effort will increase. Also 18" rims are a poor choice is you live in an area like I do where the pot holes are big enough to swallow a tank! Remember the shorter the sidewall the closer to the pavement and damage!

A good wheel deserves a fine tire, and there is only one I can recommend - the General Exclaim UHP. It's cheap, light weight, wears well, handles great, gives a comfortable ride, and easily available. Get it in 215/45/17. The price & weight (18#s) is the same as the 205/45/17. The section width only increases 10mm, but it greatly adds to the appearance of the car. BTW, some of you get rims and tires so big that they're practically touching each other which looks really goofy!

I found these alignment specs worked well:

Camber -1 all corners
Toe-in 0.0625 inch all corners
Castor 5->6

Love your transmission, and it'll do the same for you. Whatever gear oil you put in it (& the 3rd member too), it doesn't matter if it's dino or synthetic as long as it meet the proper specs. Miata transmissions have a long history of being somewhat cantakerous when cold. They also can be notchy. However, it you take it easy in your movements through the various gears, you'll discover a smoothness and fluidity to your shifts with practice. Remember you are the student and the transmission is the master. The Japanese way is to be humble and cooperative while the transmission instructs you in its mysterious ways! Finally change the hydraulic fluid every couple of years or better yet put a synthetic in.

Finally, the last subject is CAI or cold air intakes! I examined the stock airbox, and it appears to be a well designed unit. From the air box, a tube runs out to the nose of the car and makes a 90 degree bend. After the bend, there is a tube to suck air out of the nose. This air is as cool as it is going to get, because fresh air entering the front of the car. Also the engine sucks air in, so I don't see any advantage to a ram air effect locating the air pickup point down lower. However, a CAI might make more noise than the stock unit, but one could acheive that with a K&N filter. But there has always been debate over the effectiveness of it in regard to providing the engine with "clean" air. I don't believe it would do any harm, and most owners would have sold the car before it did. Anyway, I stuck one in. BTW, save a couple of bucks and order the K&N panel filter online directly from K&N:

Saddly I won't be buying FI in any form. They'd have to be plug & play before I'd pay. The reasons are simple. My life is way too busy and complicated enough to be annoyed with all the rigamarole involved in the care and feeding of one. I will make a prediction though. If any mfg wants to sell them, he had better make sure they are user friendly.

Happy trails pardners!