Tein GSM64-9USS2 Street Advance Z Lowering Coilovers for 1990-2005 Miata NA/NB

Vehicle Fitment

• 1990-1998 Mazda Miata (NA6C, 1.6L, RWD)
• 1994-1998 Mazda Miata (NA8C, 1.8L, RWD)
• 1999-2005 Mazda Miata (NB8C, 1.8L, RWD)

Fitment Notes

• Uses OEM upper mounts -- not included; reuse factory mounts or purchase separately
• Replacement OEM-style upper mounts available separately for 1990-1997 NA models only
• Separate OEM upper mounts not currently available for 1998-2005 models
• EDFC compatible -- extension kit required; motor install location not confirmed
• 2-door body style only

Features

• 16-way damping force adjustment
• Advance Needle technology for wide-range, noticeable damping change
• Shortened shell case design for optimized damper stroke at lowered ride height
• ZT-coated non-welded threaded adjustment sleeve
• Twin-tube internal construction
• SAE9254 cold-formed no-sag springs with powder coat rust protection
• TEIN-green 2-layer, 1-bake powder coat shell case (Japanese patent #4347712)
• Full-length dust boots
• 1-piece aluminum spring seat with Delrin thrust washer
• High-performance wide-temperature-range damper oil
• Rebuildable/overhaul-eligible construction
• Made in Japan

Specifications

• Front Spring Rate: 392 lbs/in (7.0 kgf/mm)
• Rear Spring Rate: 336 lbs/in (6.0 kgf/mm)
• Front Spring Free Length: 175 mm | I.D.: Phi70 mm
• Rear Spring Free Length: 175 mm | I.D.: Phi70 mm
• Upper Mount: OEM (not included)
• Damping Adjustment: 16-way
• Internal Design: Twin-tube
• NA6C / NA8C (1990-1998) -- Front Lowering: -1.4" recommended / -3.0" to -0.5" adjustable range
• NA6C / NA8C (1990-1998) -- Rear Lowering: -1.2" recommended / -2.8" to +0.2" adjustable range
• NB8C (1999-2005) -- Front Lowering: -1.6" recommended / -3.9" to -1.3" adjustable range
• NB8C (1999-2005) -- Rear Lowering: -1.6" recommended / -3.7" to -0.7" adjustable range

Included Components

• 2x Front coilover assemblies (with springs)
• 2x Rear coilover assemblies (with springs)
• 1x Hardware kit

Product Description

The Tein GSM64-9USS2 Street Advance Z is a full coilover kit covering all first- and second-generation Mazda Miata platforms -- NA6C (1990-1998 1.6L), NA8C (1994-1998 1.8L), and NB8C (1999-2005 1.8L). Built in Japan and engineered specifically for each chassis, this kit delivers an aggressive lowered stance with meaningful performance gains through Tein's Advance Needle 16-way damping adjustment system, which provides a noticeably wider and more tactile range of damping force change compared to standard coilovers. The shortened shell case design ensures adequate damper stroke at reduced ride heights, maintaining reliable handling even at maximum drop settings. Drop heights differ by platform. NA6C and NA8C models achieve a recommended front drop of 1.4" and rear of 1.2", with an adjustable range of -3.0" to -0.5" front and -2.8" to +0.2" rear. NB8C models see a slightly deeper recommended drop of 1.6" front and 1.6" rear, with an adjustable range of -3.9" to -1.3" front and -3.7" to -0.7" rear. All four corners use SAE9254 cold-formed springs with a no-sag powder coat finish, rated at 392 lbs/in front and 336 lbs/in rear. The ZT-coated non-welded threaded sleeve allows smooth, precise ride height adjustment without corrosion concern. The Street Advance Z uses the vehicle's factory upper mounts, which must be reused from the existing struts and are not included in the kit. Replacement OEM-style upper mounts are available separately for 1990-1997 NA models only; separate mounts are not currently available for 1998-2005 applications. The system is EDFC compatible (extension kit required) and is fully rebuildable, supporting long-term ownership and track-day use alongside everyday street driving.