Tech Tips: 2006–’15 Mazda MX-5

Keith Tanner
Flyin’ Miata
(800) FLY-MX5s

Handling is always where the biggest bang for the buck is, of course. The car’s pretty good for comfort as long as it’s on a good suspension.

My first suggestion on what to address on the 2006–’12 cars is shocks. They were poorly damped from the factory (even the Bilstein-equipped cars), and benefit strongly from a good aftermarket shock like a Koni or Tokico. The Bilstein cars starting in 2013 were much better. That’s the best bang for the buck for handling and ride quality. While you’re in there, a set of well-chosen springs will have a big effect–but a poorly specified set will really wreck the car. Obviously, I feel that Flyin’ Miata got it right. Sway bars from the RX-8 are a popular modification as well.

Next step is a really good suspension. As usual, there are lots of cheap or poorly thought-out pieces out there that limit suspension travel or just plain don’t work well. Our Fox setup really takes full advantage of the platform’s potential. It’s the only one I’ve tried that puts a clear gap between the capabilities of the NA/NB and the NC.

The best bang for the buck power adder is probably a 2.5-liter swap out of something like a Ranger. This is becoming more common. It’s not quite as easy as the 1.8 swap on the earlier Miatas, but it’s a torquey, long-stroke engine that’s available pretty cheap in junkyards.

Maintenance is the usual: good oil regularly changed. They’re modern Japanese cars, and they just keep working.

The big problem with putting the car on track is rollover protection. There are good options available for the soft top cars, but the power hardtop cars are a problem as the top design prevents any bar that’s taller than the fairly short factory hoops. We have a bar with an interchangeable main hoop that can be 7 inches taller than stock, but you have to have the top down when it’s in full track mode.

Autocrossing must-haves are good shocks. Then it gets into class rules, of course. The NC can carry a fair bit of tire; a 17×9 wheel with a 235 or 245 tire is a pretty quick option. The soft top cars have slightly more room under the fenders and are easier to roll.

Get the newest car possible. Manual trans cars got improved transmission internals in 2007 or 2008, and forged engine internals in 2009. Otherwise the changes were restricted to suspension tuning and various option packages. The big question is, of course, what roof. The PRHT is a guilty pleasure for cruising around, but the roll protection restrictions cannot be ignored.

Brian Goodwin
Goodwin Racing
(858) 775-2810

We consider the NC generation Miata a hot performance bargain. They are relatively cheap, and the supply of high-performance NC parts is greater than ever before. Early NC1 (2006–’08) examples in good shape start in the $5000 range, later NC2 (2009-up) in good shape start about $10,000.

If the customer is not into serious modification, then we suggest a 2009 or newer. Why? The 2009-up have a number of upgrades from the factory including a stronger and more reliable motor, stronger transmission, updated front suspension geometry, and a more aerodynamic nose. For fun in an NC2, just add suspension upgrades and good wheels and tires.

The serious hot rodders start with the NC1. The NC1 is like buying an empty computer case: You buy it cheap and bolt in all the good stuff. The NC1 stock 2.0-liter motors often failed relatively young and we have had numerous customers get an NC1 with failed motor on Craigslist for as little as $1400 and have it delivered by flatbed to us for 2.5-liter conversions, Ohlins coil-overs, complete stainless exhaust system, track-worthy cooling system, roll bar, etc.

Mazda’s corporate 2.5-liter motors are an easy install into the NC. The 2.5 was the high-volume motor that Mazda put in every other vehicle they made from Mazda3 through their various SUVs. As a result of that volume, the 2.5 motor is actually less expensive to buy brand new than a replacement 2.0-liter, making the upgrade an easy choice. (The 2.5 is also readily available used and cheap in local yards under the Mazda and Ford labels.) The 2.5 install can be done with all factory smog equipment for those seeking a street-legal Miata with more torque than the factory ever intended, and it can be built as a track toy tuned on E85 and making over 200 horsepower normally aspirated, or far beyond 300 horsepower with boost.

The NC chassis did not get much respect when new because it derived from the relatively heavy big bones of the larger RX-8, but those big bones means an NC does not twist into a pretzel when you run it with 200 to 300 horsepower.

Cooling upgrades are an NC priority. As these cars age, the factory plastic overflow tank is a common failure point because the plastic gets brittle and cracks. The NC relies on the plastic expansion tank to be a pressurized part of the cooling system, so when that tank cracks, the cooling system loses pressure and the engine overheats. We get a regular supply of NC arriving on flat beds with failed motors due to this simple plastic tank failure. We offer an upgraded aluminum expansion tank to cure the issue.

For those building for track use, we also suggest our new triple-pass radiator and oil cooler, particularly important for track customers, 2.5-liter conversion customers, and any customer contemplating boost.

Shopping for an NC? Pull the oil cap and keep walking if you see sludge that reveals a lack of regular oil changes. A filthy engine bay also equates to lack of maintenance–just move along to another NC as there are plenty available. Check engine and trans and diff for oil leaks along with the underside condition generally–lowered cars often show a lot of speed bump damage. Check the color of brake fluid. Check if the a/c blows cold. Check interior and exterior top condition–replacement top installation is best left to professionals if you care about the results looking taut.

A 235/40R17 tire fits in stock fenders on 17×8- to 17×9-inch wheels with offset of 48 to 50mm. With fender rolling, you can go up to 255/40R17 on 17×9 for STR class autocross and track days. We have fit 17×10 in fully rolled fenders with 255mm tires, up to 285/30R18 and more with our fender flares.

The cheap brake upgrade is factory RX-8 brakes, which bolt into NC–but they are heavy! We worked with Wilwood on a front/rear combo of 12.88-inch brakes that saves 10 pounds of unsprung weight at the front, and matched 12.88 rear setup that includes dedicated lightweight rear parking brake caliper. The balance and confidence the full setup provides in late-brake passing on track days will put a big, silly grin on any face.

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View comments on the GRM forums
bmw88rider SuperDork
7/24/17 3:16 p.m.

You can it a good amount of brake under there with just the 17" Tires. Betty has the Fox Sport package on there and I love it. I just removed the rear sway bar because it really wasn't needed with the setup. I have her under 2800LB fully loaded out option wise and an LS3 under the bonnet. It even has the 8.8" Rear which is heavier than the GM one.

You can see even with 245 on there, there is plenty of room with fender rolls and a flare. Realistically, you can go to 255 easy and 275 if you worked your magic some.

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