Spindle Nuts - Front and Rear

All 1990-2005 Mazda Miatas use the same front spindle nut (small-part#816-4233). There is some confusion with the rear spindle nuts. All 1.6 liter axle shafts use the small spindle nut like the fronts. All 2 piece 1.8 liter rear axles also use the small spindle nut. The one piece 1.8 liter rear axles use either the small (part# 816-4233) or the large (part# 816-4223) depending on the date of manufacture. Since many Spec Miatas have had axle changes, you need to know what size axle you have. The small nut has an 18mm thread while the large nut has a 22mm thread.

The simplest method to determine what size axle you have is to slide an open end wrench over the threaded portion of the axle. The small nut has an 18mm thread while the large nut has a 22mm thread. Please be aware it is very possible to have two different size axles on either side of the car.