FM springs are well known for providing a good balance of street ability and track performance. Their combination of ride height - giving the suspension room to work - and spring rate means your Miata will ride and handle better than you would expect from a set of performance springs.
There's more going on than you think, though. See that section with the tighter coils? Those are designed to act as a secondary spring, keeping the spring from going loose under full droop. While these rates might sound high compared to some other springs on the market, they are stiff enough to keep your car off the bumpstops. Softer springs will often give a worse ride because they allow you to blow through your suspension travel and end up on the stops. We've specified a powdercoat with a high zinc content for extra corrosion resistance, too.
How much will they lower your car? We can't tell you, because Mazda changed the ride height of Miatas over the years. However, if you measure from the center of the wheel to the fender lip, you can compare your car to the final result. It's not a huge drop but once you drive the car you'll appreciate how well it works.
Specifications for the NC Front springs: 300 lb/in Rear springs: 196 lb/in Front ride height: 13.5" Rear ride height: 13"
About the shocks:
The Koni Sport shocks have adjustable rebound so you can crank them up when you're feeling frisky on the autocross course. They come with a lifetime warranty.