If your on a tight budget stick with the miata. The X is a money pit at the track.
I have begun to greatly increase my track time (thanks to a membership at a local countryclub style track) and I am planning on actually going to buy a miata to begin to learn more about driving itself, however of course I own a modified Evo so I'll be damned if I'm going to let it sit at home.
However, it's easy to spend over $700 on brakes alone for this car. My pads are newish EBC yellows that have only seen 2 track days and my rotors are slotted (f) brembo/ (r) girodisc.
Rotors: Do I need a slotted rotor? What is the best price point for rotors that you've seen? I plan on doing track days, however I'm not going to be running 10/10s constantly, I'll be more along the lines of learning how to drive to certain lap times. Learning how to control my speed and well... .I don't know enough yet to say what else I need to learn. Regardless, I will be using both the Evo and Miata to learn whatever I can.
Girodisc currently tops my list with their slotted and "bailout" rotors, it seems like I should go slotted, but not sure if it makes that much of a difference in driving (but it does on my wallet to the tune of $90)
Brake pads: I think I'll stick with EBC Yellows as I've driven them for a few months and find them perfect at track days as well as daily driving. Unless there's a really darn good reason to move to something else.
I will probably soon implement a ducting system to reduce overall wear and tear.
Tires: I would like to continue to Autocross and considering our car is so dang heavy I've heard that the Hankook Ventus RS-3 are a good tire for both autocross and track use as they hold heat better over time. remember I am aiming for a balance between price point/durability/performance
I'd rather save $20-$50 per tire over the long run than get .01 second.
I have 2 sets of wheels and currently run NT01 on my track wheels. They have maybe 10 more heat cycles. I would prefer to keep some type of DOT tire for my track wheels and a good street tire on my daily wheels.
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My "daily drive" is negligible since I work from home or travel 80% of the time. I spend maybe 8 days a month in the office. But that drive is only 10 miles round trip. Still, I would rather keep the car street friendly as I am affectionately referred to as the "Turbo Taxi" by my friends. Being the preferred carpool ride to parties/downtown etc.
Suspension coming as soon as I win some money off a scratch off or in 6-8 months. Whichever comes first.