XYZ Racing Top Sport Coilovers — Maserati BITURBO SI φ52 welding (PCD: 4X98) 1986-1991

The Biturbo SI’s rear-wheel-drive chassis and twin-turbo four/six-cylinder layout put real load through a suspension system that was never designed with modern damping technology in mind. XYZ Racing’s Top Sport coilover is built for owners running this Maserati hard on B-roads and the occasional track day, not just polishing it for shows.

On a car this light on electronic aids, spring rate and damping control do the job that stability systems handle on newer machinery. The Top Sport kit gives the Biturbo SI a suspension platform that reacts predictably when you lean on the front end mid-corner, instead of the wallow and dive that period-correct rubber bushes and tired dampers produce.

What this coilover does for your 1986-1991 Maserati Biturbo SI Φ52 Welding (pcd: 4×98)

Fitting this kit to a 1986-1991 Biturbo SI raises spring rate roughly 2kg/mm over the standard street setting, or increases damping force by 30-50% depending on where you set the adjuster. That extra control matters most when the twin-turbo boost comes in mid-corner and weight shifts hard onto the outside front wheel – the uprated spring rate resists dive and keeps the contact patch loaded evenly. Over broken UK B-road surfaces, the increased damping absorbs the impact of potholes and expansion joints without the harshness a straight spring-rate hike alone would introduce, so the car stays composed rather than skipping across bumps. Tyre traction improves because the suspension no longer unloads over rough sections, which on a turbocharged, rear-driven car translates directly into more usable power out of a corner. Ride height is also adjustable independently of spring preload, so you can correct the nose-down stance common on Biturbo cars fitted with tired factory springs.

About the Top Sport coilover

The Top Sport range is set up using data from XYZ Racing’s own track programme, tuned specifically for cars that see aggressive road driving and occasional circuit use rather than dedicated race duty. Spring rates and damping are lifted 30-50% (or roughly 2kg/mm) above the firm’s street-oriented settings, calibrated to soak up big hits – potholes, kerbs, broken tarmac – without transmitting the full shock into the chassis or unsettling the body. That control keeps the tyre in contact with the road through compressions and mid-corner bumps, which is where the stability gain actually comes from rather than from added grip alone. It’s a kit built around one job: staying composed on a track day one weekend and driving home comfortably enough the next morning.

Fitment for the Maserati Biturbo SI Φ52 Welding (pcd: 4×98) (1986-1991)

This kit is specced for the Maserati Biturbo SI Φ52 Welding variant (PCD 4×98), chassis code MS03, covering the 1986 to 1991 production years. Confirm your car matches this Φ52 welding/PCD 4×98 specification before ordering, as the Biturbo range ran multiple hub and PCD variants across this period.

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Configure your Top Sport setup for the Biturbo SI below and pick the spring rate and damping range that matches how you’ll actually drive it.