Prothane Rear Sway Bar Bushings – 1990–1997 Mazda Miata (NA) | 1/2” (12.7mm) | Red Polyurethane | 12-1109

Prothane red polyurethane rear sway bar bushings for the 1990–1997 Mazda Miata (NA chassis). Direct replacement for the factory rubber chassis-mount sway bar bushings on the NA’s rear anti-roll bar. 1/2” (12.7mm) inner diameter to match the factory NA rear sway bar diameter. Sold as a set — includes both rear sway bar chassis mount bushings.

Polyurethane vs. Factory Rubber — The Trade-Off

The NA Miata’s factory sway bar bushings are rubber — soft, compliant, and NVH-friendly, but prone to degradation over time. Aged rubber bushings crack, compress permanently, and allow the sway bar to shift in its mounts under cornering load — introducing slop into the rear suspension response and reducing the effectiveness of the rear anti-roll bar. Prothane’s polyurethane bushings address both issues:

• Durability: Polyurethane resists compression set, oil contamination, and UV degradation significantly better than rubber — maintains its shape and firmness over the life of the vehicle rather than gradually softening and deforming
• Response: Stiffer than rubber — reduces lateral movement of the sway bar in its mounts under cornering load, improving the immediacy of the rear anti-roll bar’s response. On an NA Miata used for autocross or track days, this translates to more consistent rear roll stiffness and improved turn-in feel
• NVH trade-off: Polyurethane is stiffer than rubber and transmits more road noise and vibration than factory rubber bushings. On a dedicated track or autocross NA this is not a concern; on a daily-driven street Miata it is an accepted trade-off. For a street-only build where NVH is a priority, OEM rubber replacements are an alternative

Key Features

• 1/2” (12.7mm) Inner Diameter: Matches the factory 1990–1997 NA Miata rear sway bar diameter. Confirm your rear sway bar diameter if running an aftermarket bar — aftermarket sway bars may use different diameters
• Rear Chassis Mount Bushings: These are the sway bar-to-chassis mount bushings — the bushings that hold the sway bar in its brackets on the body. Not end link bushings
• Red Polyurethane: Prothane’s standard red polyurethane formulation — also available in black (stealth) in a separate listing
• Prothane: The benchmark polyurethane suspension bushing brand — widely used in the NA Miata community for suspension refreshes and performance upgrades

Installation Note

Polyurethane sway bar bushings must be greased on installation — apply Prothane’s supplied or recommended polyurethane-compatible grease (silicone-based) to the inner bore of the bushing and the sway bar contact surface. Running polyurethane bushings dry will cause squeaking and accelerated wear. Do not use petroleum-based grease — it will degrade the polyurethane.

Fitment

• Mazda Miata NA (1990–1997) — rear sway bar, factory 1/2” diameter

Confirm rear sway bar diameter before ordering if running an aftermarket sway bar — this bushing is sized for the factory 1/2” NA rear bar. Must be greased with polyurethane-compatible (silicone) grease on installation — do not install dry. Not end link bushings — these are chassis mount bushings only.

Specifications

• Brand: Prothane
• Part Number: 12-1109
• Material: Red polyurethane
• Inner Diameter: 1/2” (12.7mm)
• Position: Rear sway bar chassis mount bushings
• Quantity: Set (both rear mounts)
• Application: Mazda Miata NA (1990–1997)
• Weight: 0.6 lbs