KYB 551118 Suspension Strut - Rear

KYB Gas-a-Just Rear Strut for MX-5 Miata

KYB Gas-a-Just 551118 is a rear suspension strut built as an OE-style monotube replacement for the Mazda MX-5 Miata. It is engineered to restore original handling response while adding the firmer control expected from a high-pressure monotube design.

The KYB Gas-a-Just line is focused on vehicles that see harder use, including towing, heavier wheels and tires, and more demanding driving conditions. For the Mazda MX-5 Miata, this rear strut helps maintain steering response, suspension control, and the operation of vehicle safety systems as the chassis was designed to perform.

• OE monotube replacement for rear suspension service
• High-pressure monotube design separates gas and oil for consistent response
• Air-free hydraulic piston and valve area for control and responsiveness
• Triple chrome plated piston rod helps reduce seal wear
• Built for vehicles with heavier tires, wheels, or increased load demands
• Rear application for 2006-2015 Mazda MX-5 Miata, excluding run-flat tire setups

Product Details and Fitment

Fits 2006-2015 Mazda MX-5 Miata, rear. Part number 551118 is a direct-fit suspension strut for the rear position and is listed as a recommended OEM replacement for this application. This part cross-references Monroe Shocks & Struts 72496 for the same application.

Gas-a-Just monotube construction uses a floating piston and high-pressure nitrogen gas chamber to keep the oil and gas separated. That layout supports fade-resistant operation and quicker reaction to suspension movement, which is useful when the MX-5 Miata is driven with more aggressive inputs or fitted with larger, heavier wheels and tires. Part number 551118 is also referenced by Mazda OE numbers N12128700 and NE5128700C.

What This Strut Helps Address

• Excessive rear bounce or reduced damping control
• Loose or delayed rear suspension response
• Handling changes after shock or strut wear
• Reduced steering feel from worn suspension components
• Seal wear concerns associated with fluid leakage

Installation Notes and Tips

Verify rear-position fitment before installation and confirm the vehicle is not equipped with run-flat tires, since this application excludes them. Match the strut to the correct side and inspect related suspension components, mounts, and fasteners during service. Compressed length is 14.44 inches, extended length is 21.33 inches, and stroke length is 6.89 inches.

Quality Assurance

KYB designs the Gas-a-Just line as an OE monotube replacement to restore factory handling characteristics with a performance-oriented damping response. The monotube layout, high gas pressure, and chrome piston rod construction are used to support consistent operation and reduced seal wear in demanding suspension service.