Suspension
The track Miata runs XIDA Race coilovers with 800lb front springs and 500lb rear springs. They’re not cheap, but there’s a reason that everyone else in the market compares themselves against Xidas. The car is stiff but compliant and handles great on smooth and rough tracks. I personally run about 5 clicks from full soft as a starting point and fine tune from there.
The car also has the matching, recommended Supermiata sway bar combo of a 1.125″ diameter .188″ wall Racing Beat front sway bar and Supermiata 14mm rear sway bar.
With the Extended Lower Ball Joints, the car runs the Supermiata dual duty alignment. With the moderate grip RS4 tires targeting 31-32psi hot, this produces even wear and temperatures on track.
Brakes
The later NB Miatas offered the larger Sport calipers. The fronts were replaced in 2018 and the rears more recently. GLoc sport pads are installed, with R10 compound up front and R8 in the rear. Motul RBF600 fluid works fine in the temperatures these produce, even on brake heavy tracks like Hallett and COTA, and I’ve never personally experienced fade with this setup. I also installed stainless steel brake lines from Supermiata.
Brake ducting on lower powered Miatas can be controversial. I installed the 2.5″ kit from Singulair and it seems to have done a great job in extending pad life while maintaining even rotor wear. The ducting has been routed from the factory fog light holes using the original hardware for a connection that’s both solid and more attractive than many.
Finally I’ve installed the proportioning valve from an ABS Miata. From the factory, the non-ABS Miatas have a great deal of front bias in heavy braking, whereas the ABS setup is a true 50/50 split (similar to using a proportioning valve wide open). With the pad compounds currently installed, this setup adds a lot of rear braking force while still keeping the car slightly front biased for safety.
Wheels and Hubs
Miata hubs are notorious wear items when you start doing crazy things like doubling the available grip per corner. BroFab hubs incorporate rock solid BMW front and MR2 rear hubs adapted to have the same exterior dimensions as the Miata originals, and with reasonable care should never need to be replaced again. All four have long ARP studs installed.
Koenig Dekagram 15×9 wheels (your choice of black or gold) with 225/45r15 Hankook RS4 tires. This has been a really good combination for me and provides serious grip in the dry, decent wet traction, and 20-25 hours of track use before wearing out. The wheel arches aren’t pulled or rolled and there is no rubbing; the factory wheel liners are still in place (other than where the brake ducts were run), which added ~2mph top speed vs. having them removed for clearance.
Bracing
This car does retain the heavy factory butterfly brace, and the frame rails are in good shape. Most of the additional stiffness comes from the Hard Dog bar and hardtop.
It also has Mazda Competition motor and differential mounts which firm everything up nicely without rattling you around when you’re not going 10 10ths on track.
The one additional stiffening mod that I made was to add Tivar 88 bushings from 5X Racing. These made a surprisingly noticeable difference to the way that the car feels.