Tips and Tricks
The Battery: It's hard to find most auto part stores won't have them in stock, however they're generaly available at the dealership. They're also available on the web at Miata specific sites but I'm guessing that shipping charges for a car battery would be a bit high. Also... The Miata ignition system cranks a bit slower by nature than most others so don't be alarmed when it doesn't crank as fast as you're used to.
Spark plug wires: The original equipment spark plug wires often don't last longer than 40,000 miles or so, one of the few weak points of the Miata. The most frequent symptom of this is hesitation upon acceleration. Aftermarket wires are available that will last much longer and provide a better spark from a number of firms such as Magnecore, Accel, upgraded NGK (oem is supplied by NGK) and others.
Aftermarket horn: A very popular upgrade since the factory horn isn't very loud and some will say sick sounding. If you replace the horn (which many of us have and are glad we did), be aware that aftermarket horns may blow the fuse that controls them... and this same fuse also controls the brake lights.. Replace the fuse with the next step up in amperage. There are two fuse boxes, the one with this fuse is under the hood. See the owners manual for details.
Shocks: The factory shocks generally start getting weak around 40-50,000 miles. This will lead to degraded ride and handling (which you may or may not notice since it's so gradual). But... will also lead to uneven tire wear and unevenly worn tires can be noisy and a safety issue. Aftermarket shocks are MUCH superior to Mazda brand shocks in longevity, handling, ride and price! Koni, KYB, Bilstein, Tokico are among the most popular firms offering good options.
Tire pressure: Don't run too much air pressure! Miatas have the best balance of ride and handling with cold air pressure between 26 and 30psi for street use. Start in that range, move the psi up or down a bit until you like the feel.
Wheels: Aftermarket wheels are a very popular upgrade, many of us are running them. When shopping for aftermarket wheels watch out for too much weight! The Miata has a wonderful and nimble driving feel and part of the reason is that the suspension is very sensitive (much more so than other cars). As such, wheels that are much heavier than stock will degrade ride quality, handling feel and braking. In extreme instances acceleration will suffer too. The reason behind this is that unsprung weight (the weight that is below the suspension) take considerably more energy to move than weight that is above the suspension. This same principle applies to tires but they generally vary much less in weight than wheels do.
How much do Mazda factory wheels weigh? Check out Miata.net, click on the Garage link on the home page, then look for the wheel weight link.
Winter Driving: A Miata with regular or all season tires is nearly helpless in snow, almost to the point of being dangerous. On the other hand, a Miata with a set of four snow tires (do NOT install them on the rear only) is better than many front wheel drive cars running all season tires. The difference is dramatic.
Radiator: Watch the color: Many Miatas come from the factory with a radiator having a plastic top (and bottom too but the top is what you can readily see). When they're new the plastic is black. As the plastic ages it will become brittle and less able to take the heat and pressure. If yours is several years old and starting to turn a brownish or greenish color it's getting weak and it's only a matter of time before it cracks or bursts. Consider replacing it if you see this color change, if it fails while you’re out and about or on a road trip it can be most inconvenient. Factory replacement radiators will work fine (until they get old and brittle). There are also higher quality aftermarket radiators available that are more durable and have a higher cooling capacity (a cooler engine is a happier engine).
Coolant: The 50/50 mix of water and antifreeze that is very popular today may not be the best for your Miata, check the owner’s manual and you’ll most likely find that the recommended mix is leaner (less antifreeze and more water). A leaner coolant mix actually cools better since water transfers heat more efficiently than antifreeze.